JP3373624B2 - Liquid 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 "liquid developing device" for developing an electrostatic latent image. The present invention can be suitably applied not only to analog and digital electronic copying machines, but also to 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 photoconductor, a "developing solution in which toner is dispersed in a dispersion medium" is applied to a developing roller. There is a liquid developing method in which the electrostatic latent image is visualized by the toner while being held on the peripheral surface and supplied to the surface of the latent image carrier. One of the developing methods is the developing roller peripheral surface and the latent image in the developing section. A method is known in which development is performed by reducing the thickness of the developer film formed on the peripheral surface of the developing roller from the distance from the surface of the carrier, that is, the developing gap (JP-A-55-143565). .
This developing system is hereinafter referred to as "non-contact liquid developing system".

In the non-contact liquid developing system, there is a gap between the developing solution film formed on the peripheral surface of the developing roller and the surface of the latent image carrier, and when the charges forming the electrostatic latent image reach the developing section, Due to the action of the electric field due to the electric charges, the developer film projects so as to "extend" toward the electric 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 by using a developing roller having a smooth peripheral surface, the developed image has a so-called "white spot" or " It has been found that a crushed state (a state in which a fine portion of the image is uniformly black so that the fine image cannot be discriminated) appears, and a good visible image cannot be obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and effectively solves the problems such as white spots and crushing in the non-contact liquid developing system,
It is an object of the present invention to provide a novel liquid developing device capable of obtaining an extremely good visible image.

[0006]

The liquid developing apparatus of the present invention "provides a liquid phase developer held by a developing member to a latent image carrier to visualize an electrostatic latent image formed on the latent image carrier. And a developer supply unit and a developer removing unit.

The "developing member" is formed in the shape of a roll or an endless belt, and the peripheral surface of the liquid is disposed in proximity to the surface of the latent image bearing member at a predetermined developing portion with a developing gap therebetween and held. It is a member that brings the phase developer to the developing section by rotation. The “developer supply unit” is a unit that supplies the liquid phase developer to the developing member. "Developer removing means"
It is a means for removing the excess liquid phase developer from the developing member supplied with the liquid phase developer.

The developing member is a conductive "support substrate".
A "developer retaining layer" which is formed in a layer on the supporting substrate and retains the liquid-phase developer in an impregnated state, and has elasticity, and the above-mentioned developer retaining layer having fine holes perforated at high density And a thin "flexible liquid-permeable film layer" formed on the layer. The developer removing unit is configured such that the liquid-phase developer supplied by the developer supplying unit is "flexible in developing member". The excess liquid-phase developer is removed so that the liquid-permeable film layer is retained on the inner side of the surface. In the development section,
Liquid phase development held on the developing member by the action of the electrostatic latent image
A polarized state is generated in the agent, and this polarized state causes flexible communication.
While extruding the liquid film layer toward the latent image carrier,
A part of the phase developer passes through minute holes, and a flexible liquid flow fill
It exudes to the surface side of the flexible layer, and the surface of the flexible liquid-permeable film layer
The surface of the latent image carrier substantially in contact with the surface of the latent image carrier.
A latent image carrier on which an electrostatic latent image is formed by exposing the liquid-phase developer
The electrostatic latent image is visualized by touching the surface.

As the material of the developer holding layer, paper materials, especially "Japanese paper" can be preferably used in addition to general sponge-like materials. As the flexible liquid-permeable film layer, various plastic films such as polyester-based, nylon-based, polyolefin-based, polystyrene-based, vinyl chloride-based, acrylic acid-derivative-based, ethylene / vinyl alcohol-based, polycarbonate-based copolymers, etc. Alternatively, a rubber film or the like can be used.

As the liquid phase developer, "a developer in which toner is dispersed in a dispersion medium", that is, a conventionally known developer for electrophotography can be used (Claim 2). It is also possible to use "printing ink" (claim 3). Further, a "developing bias voltage having a polarity opposite to that of the electrostatic latent image" can be applied to the supporting substrate of the developing member (claim 4).

The size of the "developing gap" between the peripheral surface of the developing member and the latent image carrier is 400 μm or less, preferably 100 μm or less. As a developer removing means,
In addition to using a "squeeze roller" described later in connection with the embodiments, a doctor blade or a scraper can be used.

The "rotational direction of the developing member" may be the same direction or the opposite direction to the moving direction of the latent image carrier surface in the developing section. In addition to "photoconductive photoconductor" as latent image carrier, "dielectric thin layer is formed on conductive substrate"
It is possible to use a material (which can form an electrostatic latent image by position-selective charging with a multi-needle electrode or the like).

The "printing ink" that can be used as the liquid developer is an emulsion ink, a water-based ink,
Oily ink or the like can be used. "Emulsion ink" is
Approximately 1 oil phase in which pigment is uniformly dispersed in non-drying oil or non-volatile oil
So-called W in which about 90 to 50% of the water phase is emulsified in 0 to 50%
A / O type or a so-called O / W type in which an oil phase in which a pigment is uniformly dispersed is emulsified in an aqueous phase may be used.

[0014]

In the conventional "non-contact liquid developing method", the reason why the above "white spots" and the like occur is considered as follows. FIG. 4 illustrates the state of the developing unit as an explanatory diagram.
An electrostatic latent image is formed on the latent image carrier 1 by a positive charge (denoted by a + sign), and in the developing unit, the developing roller 2
When the liquid-phase developer 3 held in the form of a thin film on the peripheral surface of the latent image carrier 1 approaches the peripheral surface of the latent image carrier 1, the liquid-phase developer 3 moves toward the electrostatic latent image charge as shown in the figure. It projects so as to extend and adheres to the peripheral surface of the photoconductor to visualize the electrostatic latent image.

That is, when the liquid-phase developer is a developer in which toner is dispersed in a dispersion medium, the toner is electrically charged in the dispersion medium toward the latent image carrier due to an electric field generated by electrostatic latent image charges. Electrophoresis, and "a kind of polarization state due to bias of toner charge" is generated in the thickness direction of the liquid-phase developer film. The electric force exerted on the toner by the electrostatic latent image deforms the liquid-phase developer film to project it toward the electrostatic latent image.

When the liquid-phase developer is a printing ink, the "polarized state generated in the liquid-phase developer" by the electric field due to the electrostatic latent image deforms the liquid-phase developer film, It is projected toward the electrostatic latent image.

When the liquid-phase developer 3 is projected so as to extend toward a part of the electrostatic latent image charge, the liquid-phase developer is unlikely to be formed in the vicinity of this projecting portion. That is, as shown in the drawing, when one protrusion 3A is formed on the liquid-phase developer 3, the surface of the liquid-phase developer film around the protrusion 3A is recessed 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-phase developer film in the “recessed portion”, the pressure becomes low, and the liquid-phase developer 3 around the projection 3A is drawn toward the projection 3A.

The projection 3A continues to grow by taking in the liquid-phase developer 3 thus attracted, but since the liquid-phase developer 3 is strongly attracted to the projection 3A side in a portion in the immediate vicinity of the projection 3A, another projection is formed. Therefore, in the visible image obtained as a result of development, a so-called "white spot" portion is generated around the portion visualized by the protrusion 3A, or the electrostatic latent image is a so-called "solid portion". In some cases, white voids appear in a mottled pattern, resulting in uneven development.

Further, in a fine portion of the image, an excessive liquid phase developer adheres to cause "crushing" of the image. Note that FIG. 4 shows a state immediately before the protrusion 3A comes into contact with the surface of the latent image carrier 1.

FIG. 3 is a diagram for explaining the principle of liquid development according to the present invention. Reference numeral 1 is a latent image carrier, reference numeral 5
Indicates a developing member, and reference numeral 3 indicates a liquid phase developer, respectively. The developing member 5 includes a developer holding layer 5 on a conductive support substrate 50.
1 is formed in layers, and a thin flexible liquid-permeable film layer 52 is further formed thereon.

As shown in FIG. 3A, the flexible liquid-permeable film layer 52 is composed of a thin flexible film which is formed by forming high density with fine holes on one surface. The phase developer 3 is the flexible liquid-permeable film layer 52 in the developing member 5.
Is held on the inner side of the surface. That is, as shown in an enlarged explanatory view in FIG. 3D, the liquid-phase developer 3 is held in the developer holding layer 51 in an “impregnated state” and each minute amount of the flexible liquid-passing film 52. It is held so as to fill the hole 520.

As shown in FIG. 3B, when an electrostatic latent image (indicated by a + sign) is present in the developing portion, the developer held on the developing member 5 is subjected to the above-mentioned "polarized state (liquid phase development)". When the material is a developing solution, a pseudo-polarized state which is selected depending on the bias of the toner charge) occurs, and this polarized state deforms the liquid-phase developer 3.

As the liquid developer 3 is deformed, the liquid developer 3 shown in FIG.
As shown in (b), while extruding the flexible liquid-permeable film layer 52 toward the latent image carrier 1, a part thereof bleeds to the surface side of the flexible liquid-permeable film layer 52 through fine holes. put out. In this state, the exuded liquid-phase developer 3 comes into contact with the surface of the latent image carrier on which the electrostatic latent image is formed, and the electrostatic latent image is visualized.
At this time, the surface of the flexible liquid-permeable film layer 52 is in “substantial contact state” with the surface of the latent image carrier 1, so that “extra large protrusion” of the liquid-phase developer 3 is formed. There is no room, and the liquid-phase developer 3 is evenly supplied to the entire electrostatic latent image. Therefore, uneven development such as "white spot" does not occur.

In the case of an electrostatic latent image having a high resolution,
The deformation of the flexible liquid-permeable film layer 52 is suppressed to a small level, the bleeding of the liquid-phase developer is limited, and the excess liquid-phase developer 3 does not adhere to the latent image carrier 1. "Collapse" does not occur.

Of course, the liquid phase developer does not come into contact with the portion having no electrostatic latent image charge, and only the electrostatic latent image charge is effectively visualized as shown in FIG. 3 (c).

The deformation of the flexible liquid-permeable film layer (due to the extrusion of the liquid phase developer) is allowed by the elasticity of the developer holding layer that supports this film layer.

[0027]

EXAMPLES Specific examples will be described below. In FIG. 1, a "photoconductive photoconductor" as a latent image carrier shown by reference numeral 10 is formed in a drum shape and rotates in the arrow direction,
Charging means and exposure means (not shown) (such as an original image exposure method for irradiating an original optical image or a writing method using a light beam)
Then, an electrostatic latent image is formed, and the electrostatic latent image is visualized by the liquid developing device. The visible image is transferred onto the transfer paper by a transfer unit (not shown).

The "liquid-phase developer" used in this embodiment is a developer 16 for electrophotography in which toner is dispersed in a dispersion medium (ISOPER: trade name). Is also an embodiment of the invention described in claim 2, and the visible image formed on the photoconductor 10 is a "toner image".

In the embodiment of FIG. 1, reference numeral 12 is a developing member, reference numeral 13 is a squeeze roller, reference numeral 14 is a doctor blade, and reference numeral 15 is a developer tank as a "developer supply means". The developing member 12 is provided with a developer holding layer 122 on the peripheral surface of a metal roller 121 having a smooth peripheral surface, and the surface thereof is covered with a thin flexible liquid-permeable film layer 123 so as to be "rolled". The lower peripheral surface is immersed in the developer 16 in the developer tank 15.

The peripheral surface of the developing member 12 is a peripheral surface of the photosensitive member 1 through an extremely small developing gap of "30 μm or less" in the absence of an electrostatic latent image by an appropriate spacer means. It is deployed in close proximity to.

In this example, the developing member 12 was prepared as follows. A thickness of 0.5 mm washi was used as a base, and a copolyester film having a thickness of 20 μm was provided on the base.
Fine holes of φ were formed with a thermal head at an area density of “16 × 16” per square millimeter, and this was formed on the peripheral surface of the metal roller 121, and the copolyester film layer side was the front surface side. It wound so that it became a developing member.

The Japanese paper as the base is the developer holding layer 1
22 and the copolyester film constitutes the flexible liquid-permeable film layer 123. The flexible liquid-permeable film layer has a thickness of about 5 to 100 μm, and the fine holes have a diameter of 3
It is preferably about 0 to 100 μm.

At the time of development, the developing member 12 and the squeeze roller 13 are rotated in the arrow direction. The developing solution 16 is supplied to the developing member 12 in the developing solution tank 15, is held in the developer holding layer 122 in an impregnated state, and fills the fine holes of the flexible liquid-permeable film layer 123. Retained on the surface.

The squeeze roller 13 rotates in the direction of the arrow in the state of being close to the peripheral surface of the developing member 12 to remove the excess developer 16 from the peripheral surface of the developing member, so that the developer passes through the flexible liquid-permeable film layer 123. So that it is held inside the surface of. The developer adhering to the squeeze roller 13 is removed from the peripheral surface of the squeeze roller 13 by the doctor blade 14.

The developing solution 16 held in the developing member 12 in this manner is brought to the developing portion as the developing member 12 rotates, and is placed on the photoreceptor 10 as described with reference to FIG. Visualize the electrostatic latent image. According to the experiment, it was possible to obtain a good visible image without white spots or fine image collapse.

FIG. 2 shows another embodiment. In order to avoid confusion, the same reference numerals as those in FIG. 1 are used in FIG.

The difference from the embodiment shown in FIG. 1 is that, in this embodiment, the developing member 17 is formed as an "endless belt", and is stored in an ink tank 19 which is a developer supplying means. The obtained liquid phase developer is the W / O type emulsion ink 20.

The developing member 17 includes a metal endless belt 171 having a thickness of 0.1 mm, a fine hole of 30 .mu.m.phi. The film having a surface density of 16 × 16 per square millimeter ”is wound so that the side of the copolyester film is the front side. The Japanese paper, which is the base of the master paper for stencil printing, is the developer retaining layer 172, and the perforated copolymerized polyester film is the flexible liquid-permeable film layer 173.
Is doing.

At the time of development, the developing member 17 and the squeeze roller 13 are rotated in the arrow direction. The emulsion ink 20 is supplied to the developing member 17 in the ink tank 19, is held in the developer holding layer 172 in an impregnated state, fills the minute holes of the flexible liquid-permeable film layer 173, and further has its surface. Is retained.

The squeeze roller 13 rotates in the direction of the arrow in the state of being close to the peripheral surface of the developing member 17, and removes the excess ink 20 from the peripheral surface of the developing member 17, so that the ink which is the liquid phase developer is flexible. The liquid passing film layer 173 is held inside the surface of the liquid passing film layer 173. The developer adhering to the squeeze roller 13 is removed from the peripheral surface of the squeeze roller 13 by the doctor blade 14.

The emulsion ink 20 held on the developing member 17 as described above is brought to the developing portion as the developing member 17 rotates and, as described with reference to FIG. Visualize the electric latent image. According to the experiment, it was possible to obtain a good visible image without white spots or fine image collapse.

In the embodiment shown in FIGS. 1 and 2, when a developing bias having a polarity opposite to that of the electrostatic latent image is applied to the conductive supporting substrate by the voltage power source 100, the visible image " The "image density" is further improved.

The developing bias voltage has the function of promoting the deformation of the liquid-phase developer and the deformation of the flexible liquid-permeable film layer, so that the development is favorably performed even in a weak electrostatic latent image electric field. is there. Further, when the liquid-phase developer is a developer in which toner is dispersed in a dispersion medium, the polarity of the developing bias voltage is the same as the polarity of the toner, so that the toner in the retained developer does not develop. Since the toner gathers on the surface side of the member to increase the toner density, it contributes more effectively to increasing the density of the visible image.

[0044]

As described above, according to the present invention, a new liquid developing device can be provided. Since the liquid developing device of the invention according to claims 1 to 3 is configured as described above, "developing unevenness" due to white spots and the like, which is a problem in the conventional non-contact liquid developing system, and " Good development can be performed without development failure such as "crush".

Further, since the invention according to claim 4 has the above-mentioned constitution, in addition to the above effects of the invention according to claims 1 to 3, it is possible to effectively improve the density of the visible image. it can.

[Brief description of 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 claims 1 and 3;

FIG. 3 is a diagram for explaining the operation of the invention.

FIG. 4 is a diagram for explaining a problem in a conventional non-contact developing method.

[Explanation of symbols]

10 latent image carrier 12 Development member 16 Developer (liquid developer) 13 Squeeze Roller 14 doctor blade

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshiyuki Araseki Yoshiyuki Araseki, Tohoku Ricoh Co., Ltd., No. 3, Tomei Ricoh Co., Ltd., Shinmei-do, Nakameisei, Shibata-cho, Shibata-gun, Miyagi Prefecture (56) Reference JP-A-1-237581 (JP, A) ) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/10

Claims (4)

(57) [Claims] 1. A device for supplying a liquid-phase developer held by a developing member to a latent image carrier to visualize an electrostatic latent image formed on the latent image carrier, which is in the form of a roll or an endless belt. A developing member having a peripheral surface formed in a predetermined developing portion and disposed in proximity to the surface of the latent image carrier with a developing gap, and holding the held liquid-phase developer to the developing portion by rotation; The developing member has a developer supplying means for supplying the liquid phase developer to the developing member, and a developer removing means for removing the excess liquid phase developer from the developing member supplied with the liquid phase developer. , A conductive support base, a developer holding layer which is formed on the support base in a layered state and holds the liquid phase developer in an impregnated state, and an elastic developer holding layer, and fine holes are densely formed all over the surface. A thin flexible liquid-permeable film layer formed on the developer holding layer The developer removing unit is configured such that the liquid-phase developer supplied by the developer supplying unit is held on the inner side of the surface of the flexible liquid-permeable film layer in the developing member. The residual liquid phase developer is removed, and in the developing section , the above-mentioned development is performed by the action of the electrostatic latent image.
A polarized state is generated in the liquid phase developer held by the member,
Latent image on the flexible liquid-permeable film layer depending on the polarization state of
While extruding toward the body, part of the liquid phase developer,
Bleeding to the surface side of the flexible liquid-permeable film layer through minute holes
Of the latent image on the surface of the flexible liquid-permeable film layer.
The above-mentioned exudation in a state of being substantially in contact with the surface of the holding body
Liquid developer on the surface of the latent image carrier on which the electrostatic latent image is formed.
A liquid developing device, which is brought into contact to visualize the electrostatic latent image . 2. The liquid developing apparatus according to claim 1, wherein the liquid phase developer is a developing solution in which toner is dispersed in a dispersion medium. 3. The liquid developing apparatus according to claim 1, wherein the liquid phase developer is a printing ink. 4. The liquid developing apparatus according to claim 1, 2 or 3, wherein a developing bias voltage having a polarity opposite to that of the electrostatic latent image is applied to the supporting base of the developing member.