JP5513958B2 - Wet development equipment - Google Patents

Description

  The present invention relates to a wet developing apparatus for use in a wet electrophotographic printing machine to visualize an electrostatic latent image formed on a photosensitive drum with a liquid toner.

  In this type of conventional wet developing apparatus, a voltage that becomes a developing bias is applied to the developing roller by applying a voltage from the power supply unit to the anilox roller. Then, a positive voltage is applied to the anilox roller and the developing roller by the bias voltage, and a thin film of a uniform toner layer is formed on the developing roller while appropriately controlling the input voltage (printed reference). 1). The film thickness on the surface of the developing roller at this time has a great influence on the print quality such as print density and stability of print quality.

JP 2009-192920 A

  In the conventional wet developing apparatus, when the roller bias is changed to control the film thickness on the surface of the developing roller, the potential difference between the anilox roller to which the roller bias is applied and the developing roller is small. As a result, as the printing speed increases and due to the physical properties of the developer, the image density decreases, the dot reproducibility decreases, streaks and unevenness, and the traces of cells on the surface of the anilox roller appear on the image surface. There is a problem that it is difficult to control the print density in terms of print quality such as image reproducibility and stability of print quality during continuous printing.

  The present invention has been made in order to solve the above-described problems. By increasing the potential difference of the toner particles on the surface of the anilox roller with respect to the developing roller, the printing speed is increased and the property of the developer is changed. It is an object of the present invention to provide a wet developing apparatus in a wet electrophotographic printing machine that enables printing with the quality as described above.

In order to achieve the above object, a developing device according to the present invention forms an electrostatic latent image on the surface of a photosensitive drum by exposure, and the electrostatic particles are formed by the toner particles in the liquid toner by a developing roller of a wet developing device. A wet electrophotographic printing machine that visualizes a latent image into a toner image and prints the image on paper by transferring the toner image onto the paper.
The liquid toner supply path in the wet developing apparatus includes a developing roller for supplying the liquid toner to the photosensitive drum, and an anilox roller that is partly immersed in the liquid toner and is in contact with the developing roller at the same peripheral speed. At the same time, a doctor blade that controls the pumping amount of the liquid toner is brought into contact with the surface of the anilox roller,
Between the rolling contact portion of the anilox roller with the doctor blade and the rolling contact portion of the developing roller, a toner charging charger is provided on the surface not immersed in the liquid toner ,
A corona charger is provided on the surface between the rolling contact portion of the developing roller with the anilox roller and the rotation portion of the rolling contact portion with the photosensitive drum,
The toner charge on the anilox roller is increased by adjusting the output of the toner charging charger and controlling the bias voltage applied to the anilox roller .

Then Te the wet developing device odor, was used in the helical type A two screen roller.

  According to the wet developing apparatus used in the wet electrophotographic printing machine according to the present invention, the toner charging charger is provided on the surface of the anilox roller that is in contact with the developing roller and supplies liquid toner to the developing roller. The toner particle potential on the surface of the anilox roller can be made higher than that on the developing roller, thereby promoting the electrical movement of the toner particles on the surface of the anilox roller, and the control accuracy is also improved in the amount of movement. This has improved the print density and print quality stability unprecedented, and has improved the response to high speeds.

  Further, since the corona charger is provided on the surface between the rotation portion of the contact portion of the developing roller with the anilox roller and the contact portion of the photosensitive drum, the liquid on the surface of the development roller supplied from the anilox roller is provided. The toner particles of the toner can be charged to agglomerate the toner particles on the surface of the developing roller, and the agglomerated toner particles can develop the latent image on the surface of the photosensitive drum, thereby improving high speed. be able to.

  In addition, the supply path of the liquid toner from the tank to the photosensitive drum can be a simple configuration with two rollers, an anilox roller and a developing roller, so that the manufacturing cost of the developing device is low. In addition, since it can be installed in a small space, it is possible to obtain an effect in terms of workability and maintainability as well as an economical effect and easy handling with a small and simple configuration.

  As described above, according to the wet developing apparatus of the present invention, although it has a simple configuration, in high-speed printing, it is possible to produce printed products with stable quality without unevenness in density and image, and also in terms of functionality. High effect can be obtained. In addition, the number of mechanical adjustment parts is reduced, and the adjustment work is easy, and the quality control is facilitated because the print quality is mainly adjusted electrically.

  According to the present invention, the helical type roller is used as the anilox roller of the wet developing device, so that the toner particles on the surface of the anilox roller are favorably moved to the developing roller surface. In combination with the charging from the toner charging charger to the anilox roller surface, it is possible to prevent the occurrence of unevenness in the printed image.

1 is an explanatory view schematically showing a wet electrophotographic printing apparatus in which a plurality of wet electrophotographic printing machines using a wet developing apparatus according to the present invention are arranged in a vertical direction. It is explanatory drawing which shows schematically the wet developing apparatus which concerns on this invention. It is an expanded view of the surface of a helical type anilox roller.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a wet electrophotographic printing apparatus 1 in which a plurality of (four) wet electrophotographic printing machines 1a, 1b, 1c, and 1d using a wet developing device are arranged in the vertical direction. In this wet electrophotographic printing apparatus 1, the continuous paper 2 is passed through the lower wet electrophotographic printer 1a from the lower wet electrophotographic printer 1a through the upper wet electrophotographic printers 1b, 1c, 1d. Color printing is implemented.

  Since each of the wet electrophotographic printers 1a to 1d has the same configuration, the lowermost wet electrophotographic printer 1a will be described below.

  In the figure, 3 is a photosensitive drum, 4 is a transfer roller that is in contact with the photosensitive drum 3, and 5 is a backup roller that is in contact with the transfer roller 4, and the paper 2 is passed between the rollers 4 and 5. It is like that. Reference numeral 6 denotes a wet developing device in which the developing roller 7 is in rolling contact with the photosensitive drum 3. The wet developing device 6 uses a liquid toner (developer) obtained by dispersing toner particles in a carrier liquid.

  The photosensitive drum 3 is rotationally driven in a direction indicated by an arrow at a constant speed during image formation by a driving unit such as a motor (not shown). During this time, the surface of the photosensitive drum 3 is uniformly charged in the dark by a charging device. Subsequently, an original light image is irradiated and formed by the exposure device, whereby an electrostatic latent image is formed on the surface of the photosensitive drum 3. Thereafter, when the electrostatic latent image passes through the developing area, the electrostatic latent image is visualized (developed) by the wet developing device 6, and a toner image is formed on the surface of the photosensitive drum 3. ing. The toner image formed on the surface of the photosensitive drum 3 is a bias applied through the transfer roller in the transfer region after removing a part of the carrier liquid, which is a liquid toner image component, by a carrier liquid removing device (not shown) Primary transfer is performed on the surface of the transfer roller 4 by the charge and the nip pressure between the rollers. The toner image primarily transferred to the transfer roller 4 is given an electric field that does not peel off the toner image on the surface of the transfer roller 4. The toner image on the transfer roller 4 is secondarily transferred onto the paper 2 by the bias applied through the backup roller 5 and the nip pressure between the rollers in the secondary transfer region.

  The sheet 2 on which the toner image has been secondarily transferred is discharged to the outside as a printed matter after the toner image is fixed by a fixing device (dryer) (not shown).

  On the other hand, after the primary transfer, the residual potential remaining on the surface of the photosensitive drum 3 is removed by the static eliminator. Residual toner remaining on the surface of the photosensitive drum 3 after the primary transfer is removed by a photosensitive cleaner to prepare for the next image formation.

  FIG. 2 is an enlarged view of the wet developing device 6. In this drawing, the wet developing device 6 includes a developing roller 7 that is in contact with the photosensitive drum 3, a tank 8 that stores liquid toner, and a tank 8 inside. And an anilox roller (supply roller) 9 that is in contact with the developing roller 7 and supplies the liquid toner in the tank 8 to the developing roller 7. The liquid toner supplied from the anilox roller 9 to the developing roller 7 is supplied from the developing roller 7 to the photosensitive drum 3. A developing roller cleaner 10 is in rolling contact with the developing roller 7. The anilox roller 9 is of a helical type whose surface shape is a helical shape as shown in FIG.

  In the wet developing device 6, the developing roller 7 and the anilox roller 9 are configured to rotate at the same speed in the same circumferential direction at the rolling contact portion. Further, the tip of the doctor blade 11 is brought into contact with the surface upstream of the rolling contact portion of the anilox roller 9 that is partially immersed in the liquid toner with the developing roller 7, and the anilox roller is contacted by the doctor blade 11. Excess liquid toner other than the liquid toner in the recessed cells formed on the surface of the ink 9 is scraped off.

  Further, in the rotation direction of the anilox roller 9, the toner charging is performed so as to face the surface of the anilox roller 9 between the doctor blade contact portion that contacts the doctor blade 11 and the developing roller contact portion that contacts the developing roller 7. The toner charger 12 is provided for positively charging the toner particles of the liquid toner stored in the cell of the anilox roller 9 and transported in a fixed amount by the toner charging charger 12.

  Further, in the rotation direction of the developing roller 7, the corona charger is opposed to the surface of the developing roller 7 between the photosensitive drum rolling contact portion that is in contact with the photosensitive drum 3 and the anilox roller rolling contact portion that is in contact with the anilox roller 9. 13 is provided to charge the surface of the developing roller 7 with the corona charger 13 so that the toner particles on the surface of the developing roller 7 moved from the anilox roller 9 are aggregated.

  As an example of the wet developing apparatus according to the present invention, a transfer roller 4 for transferring a toner image on the surface of the photosensitive drum 3 to the paper 2 is shown between the photosensitive drum 3 and the paper 2. However, without using the transfer roller 4, the surface of the photosensitive drum 3 may be directly brought into contact with the backup roller 5 to directly transfer the toner image on the surface of the photosensitive drum 3 to the paper 2. Needless to say.

  In the above configuration, the liquid toner pumped up from the tank 8 and stored in the cell on the surface of the anilox roller 9 is scraped off by the doctor blade 11 and is then applied to the portion facing the developing roller 3. In the meantime, a positive charge is applied by the toner charging charger 12, and the positive potential of the toner particles in the liquid toner is increased.

  The toner particles of the liquid toner on the surface of the anilox roller 9 move to the surface of the developing roller 7 by rolling contact with the developing roller 7, and are then aggregated by charges from a corona charge 13 provided on the developing roller 7. In this state, it is moved to the surface of the photosensitive drum 3 to form a toner image on the surface of the photosensitive drum 3.

  At this time, a bias voltage is applied to each of the photosensitive drum 3, the developing roller 7, and the anilox roller 9. For example, a voltage of about 50V is applied to the photosensitive drum 3, and a voltage of 300 to 350V is applied to each of the anilox roller 9 and the developing roller 7. Has been. The toner charging charger 12 provided on the anilox roller 9 is applied with a potential of 550 to 1000 V, preferably 550 to 650 V, and further applied to the developing roller 7 by the corona charger 13. A voltage of 1200 to 1800 V, preferably 1500 V is applied as electricity.

  In the above, when there is no charging from the toner charging charger 12 to the anilox roller 9, the cohesive force of the toner particles on the surface of the anilox roller 6 is weak, and the transfer of the toner particles to the developing roller 7 is uneven. As a result, the print quality deteriorates due to density unevenness and streaks. Further, if this exceeds 1000 V and the applied amount to the toner particles becomes too high, the dislocation property of the toner particles to the developing roller 7 is deteriorated, resulting in a problem that the density is lowered due to a decrease in the dislocation amount of the toner particles.

  By being configured as described above, on the surface of the anilox roller 9, the toner particles on the surface of the anilox roller 9 are charged by the toner charging charger 12, and the output adjustment of the toner charging charger 12 is performed. By controlling the bias voltage to the anilox roller 9 to increase the charge of the toner particles on the anilox roller 9, the electrical movement of the toner particles from the anilox roller 9 to the developing roller 7 is promoted, and the anilox roller 9 The toner particles are transferred from the toner to the developing roller 7 satisfactorily. At the same time, the toner particles on the surface of the developing roller 7 are agglomerated by applying a voltage to the developing roller 7 by the corona charger 13, so that the control accuracy of the movement amount of the toner particles from the developing roller 7 to the transfer roller is increased. It is possible to increase the stability of print density and print quality, which is unprecedented, and to improve high-speed compatibility.

  In addition to the helical type employed in the present invention, the cell shape (pattern) on the surface of the anilox roller 9 includes a honeycomb type and a diamond type, and streaks are also generated in the developed image depending on the cell shape on the surface of the anilox roller 9. In the test data of the inventors of the present invention, the surface cell shape is determined by the helical type anilox roller and the charger for charging the toner on the anilox roller surface. It was confirmed that the combination with the voltage application is the optimum configuration for preventing the generation of streaks and unevenness in the printed image.

  DESCRIPTION OF SYMBOLS 1 ... Wet electrophotographic printing apparatus, 1a, 1b, 1c, 1d ... Wet electrophotographic printing machine, 2 ... Paper, 3 ... Photosensitive drum, 4 ... Transfer roller, 5 ... Backup roller, 6 ... Wet developing device, 7 ... Developing roller, 8 ... tank, 9 ... Anilox roller, 10 ... Developing roller cleaner, 11 ... Doctor blade, 12 ... Toner charger, 13 ... Corona charger.

Claims (2)

An electrostatic latent image is formed on the surface of the photosensitive drum by exposure, and the electrostatic latent image is visualized as a toner image by toner particles in the liquid toner by a developing roller of a wet developing device. Wet electrophotographic printing machine that prints images on paper by transferring,
The liquid toner supply path in the wet developing apparatus includes a developing roller for supplying the liquid toner to the photosensitive drum, and an anilox roller that is partly immersed in the liquid toner and is in contact with the developing roller at the same peripheral speed. At the same time, a doctor blade that controls the pumping amount of the liquid toner is brought into contact with the surface of the anilox roller,
Between the rolling contact portion of the anilox roller with the doctor blade and the rolling contact portion of the developing roller, a toner charging charger is provided on the surface not immersed in the liquid toner ,
A corona charger is provided on the surface between the rolling contact portion of the developing roller with the anilox roller and the rotation portion of the rolling contact portion with the photosensitive drum,
A wet developing apparatus in a wet electrophotographic printer, wherein the charge of toner particles on the anilox roller is increased by adjusting the output of the toner charging charger and controlling the bias voltage to the anilox roller.   2. The wet developing apparatus in a wet electrophotographic printing machine according to claim 1, wherein the anilox roller is of a helical type.

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