JP3806135B2 - Liquid developing electrophotographic apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid development electrophotographic apparatus using a liquid toner having a high viscosity and a high concentration, and in particular, a liquid development electrophotography in which development is performed after an oil layer having a low solid content concentration is formed on the surface of a toner layer on a development roller. Relates to the device.

  FIG. 4 shows the entire configuration of a conventionally known liquid developing type electrophotographic apparatus (see, for example, Patent Document 1). The illustrated photosensitive drum 10 is charged by a charging device 21 and then exposed by an exposure device 22 to form an electrostatic latent image. The prewetting device 23 applies a silicone oil having a viscosity of about 2.5 cSt to the surface of the photosensitive drum 10 with a thickness of 4 to 5 μm.

  The developing device 24 is provided in association with yellow / magenta / cyan / black, and has a high viscosity and high concentration liquid toner exhibiting non-volatility with a toner viscosity of 400 to 4000 mPa · S and a carrier viscosity of 20 cSt. Used as a developer. The developing roller is in contact with the photoreceptor to supply a liquid developer so as to maintain a two-layer structure with the prewetting liquid film on the photoreceptor, and an electric field generated between the photoreceptor and the photoreceptor. Accordingly, toner particles of the liquid developer are adhered to the photoconductor.

  The developer is supplied to the developing roller by being transported while being thinly extended from the toner reservoir by the developer applying means, thereby forming a toner layer having a thickness of 2 to 3 μm on the developing roller. The The developer application means is composed of a plurality of rotating rollers connected to each other, and the supplied liquid developer is conveyed while being applied to the surface while being stretched by the rotation roller, and is rotated at the final stage in contact with the developing roller. A liquid developer film applied to the surface of the roller is applied to the contact surface of the developing roller.

  The intermediate transfer roller 15 is biased to about −800 V and transfers the toner attached to the photosensitive drum 10 in the order of, for example, yellow, magenta, cyan, and black according to the electric field between the intermediate transfer roller 15 and the photosensitive drum 10. The pressure roller 19 fixes the toner of the intermediate transfer roller 15 melted by the heating device 28 to the printing medium. The heating device 28 partially heats the surface of the intermediate transfer roller 15 at a position before contacting the pressure roller 19. In the figure, 26 is a blade for scraping off residual toner, and 27 is a static eliminating device.

  In such a developing device using high-viscosity and high-concentration liquid toner, in order to suppress the fogging in the non-image area caused by the viscous adhesion of the toner fluid, it is formed on the image support before the development. In addition, a prewetting process for applying an insulating liquid in advance is required.

  It is also known to apply a voltage between the supply applicator roller and the developing roller in order to form a highly viscous toner in a uniform toner thin layer on the developing roller. Furthermore, it has been proposed to create an aggregated state of toner particles by applying an electric field on the developing roller (see Patent Document 2).

  However, when high-viscosity and high-concentration liquid toner is used, the stress due to the viscosity of the toner liquid is very large compared to the force that causes the toner particles to move due to electrostatic force, and the toner is transported and separated at the developing unit Since the disturbance of the layer sometimes generated is large, there is a problem that the uniformity of the layer formation is poor, the uniformity of the image is deteriorated, and the fog is likely to occur. Even if the bias is applied to make the toner collect in the developing roller side in the electric field nip, the toner is disturbed by the liquid viscous force at the separation portion at the exit of the nip thereafter.

In addition, when a higher electric field is applied, it is possible to form a toner aggregation state that is strong enough to overcome the viscous force. However, as a result of the aggregation degree being too high, the toner is fixed on the developing roller and the development density decreases. There are problems such as problems such as failure to collect the development residual toner.
JP 11-174852 A JP-A-9-62109

  The present invention has been made in view of such circumstances, and has a configuration in which a liquid toner having a high viscosity and a high concentration is used. An electric field is applied in advance to the toner layer on the developing roller, and the surface of the toner layer is applied. Forming an oil layer with a low solid content concentration, and providing a uniform and transparent oil layer on the surface layer without giving toner aggregation more than necessary and without disturbing the toner layer due to liquid viscosity. Then, an object is to obtain an image with high image quality by developing the toner layer in contact with the image support.

  Another object of the present invention is to perform a more effective development by uniformly applying a thin toner layer before the member to which an electric field is applied.

  The liquid developing electrophotographic apparatus of the present invention uses a high-viscosity liquid toner as a liquid developer, contacts the image support on which an electrostatic latent image is formed, supplies the liquid developer, and the image support. And a developer support that forms toner images by adhering the toner particles of the liquid developer to the image support in accordance with the electric field generated between them. Means for transporting and coating the liquid toner in a uniform thin layer on the developer support and a conductive blade in contact with the liquid toner layer on the developer support are provided. The conductive blade applies a voltage to the conductive blade to move the toner particles contained in the liquid toner to the lower layer side of the toner layer on the developer support so that the toner particles are sparse on the surface layer of the toner layer. Without regulating the liquid toner having a carrier liquid layer with a low solid content concentration formed in such a state, the liquid toner is allowed to pass between the conductive blade and the developer support, and the solid content concentration on the developer support is reduced. The low carrier liquid layer is developed in direct contact with the image support.

  The present invention provides a conductive blade in contact with a liquid toner layer on a developer support, and a voltage is applied to the conductive blade so that the toner particles contained in the liquid toner are removed from the developer support. The conductive blade moves to the lower layer side of the upper toner layer and does not regulate liquid toner having a carrier liquid layer with a low solid content concentration formed in a state where toner particles are sparse in the surface layer of the toner layer. The toner particles contained in the liquid toner are sparsely formed on the surface of the uniform thin layered toner layer on the developer support. The toner layer is not disturbed more than necessary, and the toner layer is not disturbed by the liquid viscous force, and a uniform and transparent oil layer can be formed on the surface layer portion. By developing while contacting the layer to an image support, it is possible to obtain a high image quality image.

  Therefore, the present invention also makes it possible to construct a small apparatus that does not require a prewetting system.

  Further, according to the present invention, it is possible to perform more effective development by uniformly applying a thin toner layer before the member to which an electric field is applied.

  Hereinafter, the present invention will be described in detail according to embodiments. In the present invention, non-volatile high-viscosity and high-concentration liquid toner is used as the liquid developer, but the liquid toner disperses solid particles made of pigment and resin in a liquid carrier (oil). It has been made. In particular, a liquid toner using a silicone oil having a viscosity of 2.5 cSt to 1000 cSt as a carrier agent and having a solid component ratio of 5% to 40% is desirable.

  FIG. 1 is a diagram for explaining the operation of the developing device which is a feature of the present invention. A developing roller 40 in contact with the photosensitive member, that is, the image support, which can be configured as a drum or a belt, and two applicator rollers 41 and 42 for supplying a developing solution thereto are shown.

  The developing roller 40 contacts the image support to supply the liquid developer, and adheres the positively charged toner particles of the liquid developer to the surface of the image support in accordance with the electric field between the image support and the image bearing member. It is a roller to make it. The applicator roller 41 widely spreads the liquid developer supplied to the nip portion between the applicator roller 42 and applies it to the surface of the developing roller 40 in a uniform and thin layer.

On the developing roller 40, there is provided a conductive blade that comes into contact with the liquid toner layer formed in a uniform and thin layer. This conductive blade is made of a conductive rubber material having a volume resistivity of 10 ³ Ωcm or more and 10 ⁸ Ωcm or less. Such a conductive blade has an appropriate elasticity and is sufficient to pass a predetermined amount of liquid toner having a predetermined viscosity, for example, 1 μm to 50 μm, for example, 50 cSt to 5000 cSt. With appropriate pressure, the blade end surface can be brought into contact with the developing roller in the forward direction as shown in the figure.

  A voltage is applied to the conductive blade. For example, a voltage having the same polarity as the toner polarity, for example, a bias voltage of +1300 V can be applied to the developing bias voltage of +450 V applied to the developing roller 40. Due to this bias voltage, toner particles move on the developing roller after the bias is applied near the surface of the developing roller, that is, to the lower layer side of the toner layer, and as a result, the carrier liquid moves to the surface side of the toner layer. become. In other words, a state in which the toner particles contained in the liquid toner are sparse is formed on the surface of the toner layer on the developing roller.

  It is desirable to develop the toner particles offset by the bias voltage applied to the conductive blade in this way before returning. That is, it is desirable that the conductive blade is disposed as close as possible to the development position, for example, at a position of 1 second or less, preferably 0.1 second or less in time.

  When the toner layer on the developing roller is in contact with the image support and is developed, the toner particles on the surface side of the toner layer on the developing roller are in direct contact with the image support. Is a sparse carrier liquid.

  As described above in the description of the prior art, in order to suppress the fogging in the non-image area caused by the viscous adhesion of the toner fluid, an insulating liquid (preliminary liquid) is preliminarily formed on the image support before development. Wet liquid) can be applied in advance. However, in the present invention, as described above, the toner liquid on the surface side of the toner layer on the developing roller is a sparse carrier liquid that comes into direct contact with the image support. In order to fulfill the function of the prior art prewetting liquid, the present invention does not necessarily require the prewetting liquid.

  FIG. 2 is a view for explaining the operation of the developing device, which is a feature of the present invention, different from FIG. In FIG. 2, the leveling blade is attached before the position where the conductive blade is disposed. This leveling blade is intended to make the toner thin layer uniform. For example, an insulating urethane rubber is used to allow liquid toner to pass before reaching the conductive blade due to its elasticity and contact pressure. The toner can be limited to a predetermined amount and formed in a uniform layer.

  FIG. 3 is a diagram for explaining the operation of the developing device, which is another feature of the present invention, different from FIGS. 1 and 2. In FIG. 3, a patterned roller for conveying and supplying liquid toner onto the developing roller is brought into contact with the preceding stage of the developing roller. A conductive blade is brought into contact with the toner layer supplied from the patterned roller onto the developing roller. The patterned roller is a roller having a very fine pattern on the surface. For example, a roller that can be used for gravure printing or an anilox roller made by Asahi roller can be used. By using such a patterned roller, a certain amount of liquid toner can be conveyed.

It is a figure for demonstrating the effect | action of the developing device which is the characteristics of this invention. It is a figure for demonstrating the effect | action of the developing device which is the characteristics of this invention different from FIG. FIG. 4 is a diagram for explaining the operation of the developing device, which is another feature of the present invention, different from those in FIGS. 1 and 2. 1 is a diagram illustrating an overall configuration of a conventionally known liquid developing type electrophotographic apparatus.

Explanation of symbols

10 Photoconductor (Drum)
15 Intermediate transfer member (roller)
19 Pressure roller 21 Charging device 22 Exposure device 23 Prewetting device 24 Development device 26 Blade 27 Static elimination device 28 Heating device

Claims (6)

Using high-viscosity liquid toner as a liquid developer, the liquid developer is supplied in contact with the image support on which an electrostatic latent image is formed, and an electric field generated between the image support and the image support is generated. Accordingly, in a liquid development electrophotographic apparatus including a developer support that forms toner images by attaching toner particles of the liquid developer to the image support.
Means for transporting and applying liquid toner in a uniform thin layer on the developer support; and a conductive blade in contact with the liquid toner layer on the developer support;
The conductive blade applies a voltage to the conductive blade to move the toner particles contained in the liquid toner to the lower layer side of the toner layer on the developer support so that the toner particles are sparse on the surface layer of the toner layer. The liquid toner having a carrier liquid layer with a low solid content concentration formed in a state of becoming a non-regulating liquid toner is allowed to pass between the conductive blade and the developer support, and the solid on the developer support A liquid developing electrophotographic apparatus comprising: developing a carrier liquid layer having a low concentration in direct contact with the image support. 2. The liquid developing electrophotographic apparatus according to claim 1, wherein a voltage having the same polarity as the toner polarity is applied to the conductive blade, and the conductive blade is disposed as close as possible to the developing position. The liquid developing electrophotographic apparatus according to claim 1, wherein a leveling blade for uniformizing the toner thin layer is mounted in a stage preceding the position where the conductive blade is disposed. A toner layer supplied from the patterned roller onto the developer support by contacting a patterned roller for transporting and supplying the liquid toner onto the developer support in front of the developer support. The liquid developing electrophotographic apparatus according to claim 1, wherein the conductive blade is in contact with the liquid developing electrophotographic apparatus. The liquid developing electrophotographic apparatus according to claim 1, wherein the conductive blade is a conductive rubber material having a volume resistivity of 10 ³ Ωcm to 10 ⁸ Ωcm. 2. The liquid developing electrophotographic apparatus according to claim 1, wherein a silicone oil having a viscosity of 2.5 cSt to 1000 cSt is used as the liquid toner, and a solid component ratio is 5% to 40%.

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