JP2006243050A - Liquid developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developing device bringing a developing roller and an anilox roller into contact with each other under constant pressure, accurately regulating the width of a nip between a developing roller and the anilox roller, and forming an appropriately thin layer of liquid developer, thereby preventing a fault in image quality. <P>SOLUTION: Non-pattern parts UP are provided on the surfaces of both ends of the anilox roller 53. The diameter of each of the non-pattern parts UP is made larger than the diameter of a pattern part P. The developing roller 52 and the anilox roller 53 are disposed in contact with each other via each non-pattern part UP by pressing force applied by a pressing means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid developing device employed in a copying machine, a facsimile machine, a printer, and the like.

  A conventional general liquid developing apparatus is a liquid developer in which an electrostatic latent image formed on an image carrier such as a photosensitive member (for example, a photosensitive drum) is dispersed in toner in an insulating liquid (carrier liquid). Thus, development is performed. That is, the liquid developing device includes a developing roller having an elastic layer on the surface, an anilox roller (coating roller) that applies the thin liquid developer to the developing roller, and an amount of the liquid developer on the anilox roller. A doctor blade that regulates and thins the layer and a developer storage tank for storing a liquid developer are provided. Then, the liquid developer pumped up from the developer storage tank is supplied to the anilox roller, the amount thereof is regulated by the doctor blade, the layer is thinned, and then applied to the developing roller. The developing roller supplies the thin liquid developer to the image carrier and develops the electrostatic latent image formed on the image carrier with the supplied liquid developer.

  By the way, in such a liquid developing device, when forming a thin layer of the liquid developer, as described above, the amount of the liquid developer on the anilox roller is regulated by the doctor blade to make the layer thin. Yes. When the liquid developer is thinned as described above, it is necessary to keep the nip width between the anilox roller and the developing roller uniform. For this reason, methods for regulating the nip width have been proposed in the past.

  As a method for regulating the nip width, for example, a technique has been proposed in which a gap roller is interposed between the shafts of the anilox roller and the developing roller and the nip width between the two rollers is regulated by contact between the gap roller and the shaft.

  However, since the gap roller is interposed between the roller shafts in the above-described prior art, the tolerances of the three components of the gap roller, the anilox roller shaft, and the developing roller shaft are accumulated, resulting in large variations in accuracy. Therefore, there is a risk of forming a non-uniform thin layer on the developing roller. Such a non-uniform thin layer causes image disturbance.

  By the way, the surface of the anilox roller is formed with a pattern portion in which a large number of concave portions are uniformly arranged. As a method for regulating the nip width, the developing roller is directly applied to the pattern portion (anilox roller). A method of regulating the pitch between the two rollers (between the central axes of the two rollers) by contacting them can be considered.

  However, if the gap between the pitches is regulated by this method, due to the shake of both rollers that are rotationally driven during development, the pattern portion of the anilox roller can vary where the surface pressure becomes lower and higher, Where the surface pressure is low, the nip width becomes small, which is not preferable. The roller runout is caused by the eccentricity of the rotation axis of the anilox roller or the developing roller due to tolerance. Therefore, when the contact pressure of both rollers is increased in order to increase the surface pressure of the portion where the surface pressure is low, this time, the surface pressure further increases at the portion where the surface pressure increases due to variations in the surface pressure. Since the nip width is increased as described above, there is a problem that the liquid developer accumulates on the upstream side in the rotation direction of both rollers at the contact portion between both rollers, or a non-uniform thin layer is generated.

  An object of the present invention is to form a thin layer of an appropriate liquid developer by allowing a developing roller and an anilox roller to be brought into contact with each other at a constant pressure and accurately controlling a nip width between the developing roller and the anilox roller. As a result, an object of the present invention is to provide a liquid developing apparatus that can eliminate image quality defects.

  In order to solve the above-mentioned problems, the invention described in claim 1 is characterized in that a liquid developer is supplied to an image carrier that carries an electrostatic latent image, a developing roller having an elastic layer on the surface, and a plurality of rollers on the surface. In a liquid developing apparatus including an anilox roller that includes a pattern portion formed of a concave portion, and that supplies a liquid developer to the pattern portion on the surface and supplies the liquid developer to the developing roller, on both end surfaces of the anilox roller, A non-pattern part not provided with the concave part is provided, the diameter of the non-pattern part is made larger than the diameter of the pattern part, and the non-pattern part is made to contact each other by contact pressure of the developing roller and the anilox roller by a biasing means The gist of the present invention is a liquid developing device characterized in that the liquid developer is brought into contact with each other.

  According to a second aspect of the present invention, in the first aspect, the anilox roller and the developing roller are rotated in the counter direction at a contact point.

    According to the first aspect of the present invention, since the non-pattern portion is made larger than the diameter of the pattern portion so that the non-pattern portion of the anilox roller and the developing roller are in contact with each other, the gap roller is not used. Accumulation is only for the anilox roller and the developing roller, and the accumulation of tolerances can be reduced. The biasing means can contact both rollers with a constant pressure (contact pressure), and even if the rotation shaft of the anilox roller or the developing roller has roller runout due to eccentricity due to tolerance, There is no variation in surface pressure between the developing roller and the pattern portion. For this reason, since the accumulation of the tolerance is reduced and the variation in the surface pressure is eliminated, the nip width between the developing roller and the anilox roller can be regulated with high accuracy, and the liquid development on the developing roller can be controlled. A thin layer of the agent can be formed uniformly. As a result, image quality defects can be eliminated.

  According to the second aspect of the present invention, in the liquid developing device of the type in which the anilox roller and the developing roller are rotated in the counter direction at the contact point, the non-pattern portion provided at both ends of the anilox roller and the developing roller are directly It becomes the structure which contacts. Further, in claim 2, the developing roller is brought into contact with the pattern portion so as not to restrict the pitch between the two rollers (between the central axes). Therefore, the recesses forming the pattern portion of the elastic layer are bitten. Can be eliminated. For this reason, it is not necessary to increase the torque as compared with the case where the pattern portion and the developing roller come into contact with each other and the pitch between the rollers (between the central axes) is regulated.

Hereinafter, an embodiment mounted on an image forming apparatus mounted with a liquid developing apparatus of the present invention will be described with reference to FIGS. First, the outline of the liquid image forming apparatus 10 will be briefly described.
The liquid image forming apparatus can be used in a copying machine, a facsimile machine, a printer, and the like.

  The liquid image forming apparatus 10 includes a photosensitive drum 20 as an image carrier, a main charging device 30, an LPH (LED PRINT HEAD) 40, a liquid developing device 50, a cleaning device 60, a static elimination lamp 70, and the like, and a housing (not shown). It is assembled to. The photosensitive drum 20 is an amorphous silicon drum and is charged by the main charging device 30 so that the dark potential at the developing position is about 300V. The LPH 40 irradiates the surface of the charged photosensitive drum 20 with light corresponding to image information, whereby an electrostatic latent image is formed on the surface of the photosensitive drum 20.

  The liquid developing device 50 uses the liquid developer A composed of toner and carrier liquid with stirring and mixing so as to have a predetermined concentration, and the developing roller 52 uses the developer to statically irradiate the portion of the photosensitive drum 20 irradiated with light. The toner image is formed on the photosensitive drum 20 by applying to the electrostatic latent image. The dark potential of the photosensitive drum 20 is set to 300V, the developing bias is set to 200V, and the post-exposure potential is set to 20V.

  The toner image obtained by developing the electrostatic latent image formed as described above is transferred to an intermediate transfer member (both not shown) such as paper or an intermediate transfer belt as a recording medium. The liquid developer A that has not been transferred onto the photosensitive drum 20 is scraped off by the cleaning device 60 in the next process. The photosensitive drum 20 is neutralized by a neutralizing lamp 70 in order to reduce the residual potential on the surface and make it uniform, and thereafter, it is prepared for the next series of processes. Note that the potential setting for image formation in this way varies optimally depending on the characteristics of the photosensitive drum 20, the performance of the toner, and the environment.

  The liquid developing device 50 includes a storage tank 51 that stores the liquid developer A. Inside the storage tank 51, a developing roller 52, an anilox roller 53, a pumping roller 54, a pair of agitation screws 57, a doctor blade 83, and a cleaning device 80 are provided. The developing roller 52, the anilox roller 53, the pumping roller 54, and the stirring screw 57 are rotationally driven by a drive motor (not shown) through a drive transmission mechanism including a gear train and the like. The developing roller 52 and the anilox roller 53 are rotated in the direction indicated by the arrow in FIG. 1 by the rotational drive of the drive motor (not shown). That is, in the present embodiment, as shown in FIG. 1, the developing roller 52 and the anilox roller 53 have a contact point (a contact portion of a non-pattern portion UP where the developing roller 52 and the anilox roller 53 are in direct contact with each other). In FIG. 2, the rotation is made in the same direction.

  In this embodiment, the surface of the developing roller 52 has a low hardness elastic layer. As the surface hardness of the elastic layer of the developing roller 52, for example, Asker C 40 to 70 degrees is preferable. The elastic layer can be formed of, for example, silicon rubber. If the hardness of the elastic layer is too low (that is, too soft), such as less than 40 degrees Asker C, the elastic layer contacts the pattern portion P of the anilox roller 53 with a high contact pressure, and the developing roller 52 Hinders good transfer of a thin layer of liquid developer A to For this reason, the image quality deteriorates, and the cleaning blade which is the cleaning device 80 easily bites into the elastic layer and is not durable and is not preferable. Further, if the hardness of the elastic layer exceeds 70 ° Asker C, the elastic deformation of the elastic layer is insufficient, so that the light contact with the pattern portion P of the anilox roller 53 cannot be performed, and the liquid developer A is transferred. This is not preferable because it cannot be performed.

Further, the thickness of the elastic layer is set to allow the deformation so that the developing roller 52 can be brought into light contact with the pattern portion P when the developing roller 52 comes into contact with the non-pattern portion UP and elastically deforms.
The liquid developer A is adjusted so that the toner is dispersed at a high concentration in a carrier liquid made of a nonpolar insulating liquid such as silicone oil. The stirring screw 57 circulates and stirs the liquid developer A. The pumping roller 54 is partially immersed in the liquid developer A and is not shown in FIG. 1 but is spaced apart from the pattern portion P of the anilox roller 53 so as to have a minute gap. Then, the liquid developer A drawn up at the time of rotation is applied to the pattern portion P of the anilox roller 53. Note that the length in the longitudinal direction of the pumping roller 54 is shorter than the length L of the pattern portion P of the anilox roller 53 by several millimeters and shorter than the doctor blade 83.

  The surface excluding both end portions of the anilox roller 53 is a pattern portion P that becomes a coating region for the developing roller 52. In the pattern portion P, as shown in FIG. 3, a large number of recesses 58 are uniformly engraved (note that only a part of the recesses 58 is shown in FIG. 2). The shape of the concave portion 58 that is a single shape is an inverted quadrangular pyramid in the present embodiment, but is not limited to this shape. For example, a large number of fine recesses such as a square recess and an inverted quadrangular recess may be formed on the pattern portion P of the anilox roller 53 uniformly.

  The length of the doctor blade 83 in the longitudinal direction is slightly longer than the length of the pattern portion P. The doctor blade 83 is formed of a rubber blade-like member as an elastic body, and is in contact with the pattern portion P in the trail direction with respect to the rotation direction of the anilox roller 53 on the upstream side of the developing roller 52. (See FIGS. 1 and 2). The doctor blade 83 is not limited to being made entirely of rubber, and at least the edge portion that contacts the anilox roller 53 may be formed of an elastic body.

  The diameter of the anilox roller 53 (here, the diameter of the pattern portion described later) and the diameter of the developing roller 52 are in the range of 20 to 100 mm. Of these, 20 to 30 mm is particularly suitable for general consumer office equipment, and 50 to 100 mm is preferred for commercial printing machines and the like. In the case of the general consumer, the thin layer of the liquid developer A has a layer thickness of 4 to 10 μm when measured and thinned by the doctor blade 83.

  Both end portions of the anilox roller 53 are non-pattern portions UP that do not include the recess 58, and the surface thereof has a circular shape in cross section and a smooth curved surface in the circumferential direction. In FIG. 2, only one non-pattern part UP is shown.

  Further, the diameter Dup of the non-pattern part UP is made larger than the diameter Dp of the pattern part P. The degree of the size is determined according to the hardness of the elastic layer on the surface of the developing roller 52 and the size of the diameter of the anilox roller 53.

  In the present embodiment, the diameter Dup of the non-pattern part UP is Dp <Dup <1.2 × Dp. As described above, when the surface hardness of the elastic layer of the developing roller 52 is 40 to 70 degrees Asker C and the diameter of the anilox roller 53 is 20 to 100 mm, the diameter Dup of the non-pattern portion UP is preferably in the above range.

  Note that the hardness of the elastic layer of the developing roller 52 is 40 to 70 degrees as described above, and the relationship between the diameter Dup of the non-pattern portion UP and the diameter Dp of the pattern portion P is the above relationship. It is possible to do the following. That is, when the developing roller 52 is brought into contact with the non-pattern portion UP by an urging means described later, the elastic layer of the developing roller 52 in contact with the non-pattern portion UP is directed in the radial direction of the developing roller 52. By contracting, the elastic layer facing the pattern portion P can lightly contact the pattern portion P.

  When the diameter Dup of the non-pattern portion UP is 1.2 × Dp or more, the pattern portion P is not affected by the elastic deformation of the elastic layer of the developing roller 52 regardless of the numerical value in the hardness range of the developing roller 52. Since it cannot contact, it is not preferable.

  The liquid developer A pumped up by the pumping roller 54 as described above is transferred to the surface of the pattern portion P of the anilox roller 53, and the plurality of recesses 58 and the tips thereof are in the trail direction with respect to the rotation direction of the anilox roller 53. The doctor blade 83 abutted is weighed and thinned.

  The anilox roller 53 applies a measured amount of the liquid developer A onto the developing roller 52, thereby forming a thin layer of the liquid developer A on the developing roller 52. In the development area on the photosensitive drum 20, the electrostatic latent image is developed by the liquid developer A. Further, after development, the liquid developer A remaining on the developing roller 52 is removed from the developing roller 52 by the cleaning device 80.

Here, the support structure of the anilox roller 53 will be described with reference to FIG.
The rotating shaft 53a of the anilox roller 53 is rotatably supported via a bearing 100 with respect to the side wall 51a of the storage tank 51 as shown in FIG.

  A guide groove 102 is formed in a pair of side walls 51a (only one side wall 51a is shown in FIG. 4) facing each other above the position where the bearing 100 is disposed (in FIG. 4, For convenience of explanation, only one guide groove 102 is shown). As shown in FIG. 4, each guide groove 102 is arranged such that its center line L passes through the rotation center of the rotation shaft 53 a of the anilox roller 53. An upper end of the guide groove 102 is a top portion 103. A bearing 104 is fitted in the guide groove 102 so as to be slidable along the center line L through the sliding body 105 and so as not to be detached. Both ends of the rotating shaft 52a of the developing roller 52 are rotatably supported by the bearings 104, respectively.

  A pressing spring 110 as an urging means is disposed between the sliding body 105 and the top portion 103. In the present embodiment, the pressing spring 110 as the urging means is constituted by a coil spring, but the urging means may be constituted by a leaf spring or a rubber material. The developing roller 52 is brought into contact with the anilox roller 53 with a constant contact pressure via the sliding body 105 and the bearing 104 by the urging force (that is, spring force) of the pressing spring 110. . The biasing force (that is, spring force) is such that when the developing roller 52 contacts the anilox roller 53 by the biasing force, the elastic layer of the developing roller 52 that contacts the non-pattern portion UP is in the radial direction of the developing roller 52. The elastic layer that opposes the pattern portion P has a force that allows the pattern portion P to come into light contact with each other. This urging force may be set according to the degree of elastic deformation (that is, hardness) of the elastic layer and the difference in diameter between the non-pattern part UP and the pattern part P.

  In the liquid developing device 50 configured as described above, when a drive motor (not shown) is driven during development, the scooping roller 54 is rotated in the direction of the arrow shown in FIG. Then, the liquid developer A is pumped up by the pumping roller 54 rotating from the storage tank 51 and applied to the rotating anilox roller 53. The liquid developer A on the anilox roller 53 is measured and thinned by the concave portion 58 of the pattern portion P and the doctor blade 83 and then applied to the developing roller 52. The developing roller 52 supplies the thinned liquid developer A to the photosensitive drum 20, and develops the electrostatic latent image formed on the photosensitive drum 20 with the supplied liquid developer A.

  With the above-described configuration, in the liquid developing device 50 of the present embodiment, the non-pattern portion UP is made larger than the diameter of the pattern portion P so that the non-pattern portion UP of the anilox roller 53 and the developing roller 52 are in contact with each other. The gap roller is not used. For this reason, the accumulation of tolerance is only the amount of the anilox roller 53 and the developing roller 52, and the accumulation of tolerance can be reduced.

  Then, both rollers can be brought into contact with each other with a constant contact pressure by the 110 pressing spring 110, and the roller shafts 53a and 52a of the anilox roller 53 and the developing roller 52 are not shaken due to eccentricity due to tolerance. However, there is no variation in the surface pressure between the developing roller 52 and the pattern portion P. For this reason, since the accumulation of the tolerance is reduced and the variation in the surface pressure is eliminated, the nip width between the developing roller 52 and the anilox roller 53 can be regulated with high accuracy. In addition, a thin layer of the liquid developer A can be formed uniformly. As a result, image quality defects can be eliminated.

In addition, this invention is not limited to the said embodiment, You may implement | achieve as follows.
In the liquid developing device, the anilox roller and the developing roller include a type that rotates in the same direction and a type that rotates in the counter direction at the contact point as in the above-described embodiment. In a liquid developing device of the type in which the anilox roller and the developing roller are rotated in the counter direction with each other, the pattern portion and the developing roller are brought into direct contact with each other to regulate the pitch between the rollers (between the central axes). There is a problem that the elastic layer of the roller tends to bite into the concave portion of the pattern portion, causing torque increase of both rollers. On the other hand, when the contact pressure between the two rollers is lowered, contact failure occurs and the liquid developer becomes transfer failure, causing image quality failure.

  Therefore, in order to deal with this problem, in another embodiment, the liquid developing device is configured to rotate in the counter direction at the contact point between the anilox roller 53 and the developing roller 52 in the configuration of the embodiment.

  In this embodiment, when the developing roller 52 comes into contact with the pattern portion P, the pitch between the anilox roller 53 and the developing roller 52 (between the central axes) is not restricted. Therefore, even in a liquid developing device of the type in which the anilox roller 53 and the developing roller 52 are rotated in the counter direction with each other at the contact point, the non-pattern part UP provided at both ends of the anilox roller 53 and the developing roller 52 are It becomes the structure which contacts directly. For this reason, it is possible to eliminate the biting of the concave portions 58 constituting the pattern portion P of the elastic layer, so that the pattern portion P and the developing roller 52 come into contact with each other and the pitch between the anilox roller 53 and the developing roller 52 (the central axis). It is not necessary to increase the torque as compared with the case of regulating the interval.

  Further, in the present embodiment, when the developing roller 52 and the anilox roller 53 are rotated in the counter direction at the contact point, the developing roller 52 and the pattern portion P of the anilox roller 53 are in light contact with each other and the same at the contact point. Since the speed of separating from each other is faster than when rotating in the direction, the occurrence of riblets can be suppressed.

Here, suppression of riblets will be described.
When the developing roller 52 and the anilox roller 53 are rotated in directions opposite to each other (counter direction), a speed profile of a thin layer liquid developer existing between both rollers will be considered. In the speed profile of the liquid developer, there are two directions toward the rotation direction A of the developing roller 52 and the rotation direction B of the anilox roller 53. The speed of the liquid developer toward the rotation direction B increases as it approaches the surface of the developing roller 52, and the speed of the liquid developer toward the rotation direction B increases as it approaches the anilox roller 53. Then, in the thin layer, there is a zero speed point that does not go in both directions in the intermediate portion, and the liquid developer undergoes shear deformation separation at the zero speed point. Due to this shear deformation separation, when both rollers rotate in the counter direction at the contact point, the viscosity of the liquid developer is reduced, the fluidity of the liquid developer is improved, and the occurrence of riblets is suppressed.

  In addition, when rotating in the same direction at the contact point of both rollers, the liquid developer that has passed through the contact point and formed a thin layer at the contact point is transferred to each roller by the adhesive force of the liquid. It is attached to the wire and pulled to cause breakage separation, and a riblet (short raindrop) pattern is formed. It is known that riblets are likely to occur when the separation speed between rollers is slow.

  In the above-described embodiment, the developing roller 52 is pressed against the anilox roller 53 by the pressing spring 110. Conversely, the anilox roller 53 is pressed against the developing roller 52 by the urging unit to maintain a certain level. The contact pressure may be applied.

1 is a schematic view of a liquid image forming apparatus including a liquid developing apparatus according to a first embodiment embodying the present invention. FIG. 3 is a perspective view of a main part showing a contact state between a developing roller 52 and an anilox roller 53. The principal part perspective view of the anilox roller surface. FIG. 3 is an explanatory diagram of bearing portions of the developing roller 52 and the anilox roller 53.

Explanation of symbols

20 ... Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 50 ... Liquid developing device 52 ... Developing roller 53 ... Anilox roller 58 ... Recessed part 110 ... Pressing spring (biasing means)
A ... Liquid developer P ... Pattern part UP ... Non-pattern part

Claims (2)

A liquid developer is supplied to an image carrier that carries an electrostatic latent image, and a developing roller having an elastic layer on the surface and a pattern portion including a plurality of recesses on the surface are provided. In a liquid developing device including an anilox roller that is carried on and supplied to the developing roller,
Provided on the surface of both end portions of the anilox roller is a non-pattern portion not provided with the recess, and the diameter of the non-pattern portion is larger than the diameter of the pattern portion,
A liquid developing apparatus, wherein the developing roller and the anilox roller are brought into contact with each other through the non-pattern portion by a biasing force of a biasing means.   The liquid developing apparatus according to claim 1, wherein the anilox roller and the developing roller are rotated in a counter direction at a contact point.

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