JPH10254257A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoide deterioration in printing quality and to enable an excellent transfer in a wider paper range, by changing process conditions in accordance with the surface 10-points average roughness of a recording material. SOLUTION: At the time of transferring a toner image to the recording material 6 from a photoreceptor 2, on which the toner image is formed with a liqiud developer being made so that toner grains are dispersed in a liquid carrier, the process conditions are changed according to the surface 10-points average roughness Rz of the recording material 6. The recording material 6 whose smoothenss is high is in a state where the gap between the surfaces of the photoreceptor and the recording material is filled with the liqiud carrier (a), but in the recording material 6 whose smoothness is low, the gap remains without being filled with the liquid carrier, to prevent the electrophoresis of the toner grains (b). In such a case, squeeze gaps of each color or the rotational speed of a squeeze roller is varied according to the surface 10-piece average roughness Rz of the recording material 6. In a mat system coating sheet for instance, the squeezing gap is widened or the circumferential speed of the squeezing roller is reduced to make the amount of the liquid carrier on the photoreceptor large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus and an image forming method using a liquid developer in which toner particles are dispersed in a liquid carrier.

[0002]

2. Description of the Related Art In an electrophotographic apparatus employing a wet developing method disclosed in Japanese Patent Application Laid-Open No. 2-43567, an electrostatic latent image formed on a photoreceptor surface is formed by dispersing toner particles in a liquid carrier. After developing with a liquid developer, a wet toner image is obtained, the toner image is transferred onto a recording material by electrophoresis, and then heated and fixed.

On the other hand, when a color image is formed, a leading end of a sheet-like recording material is gripped around a transfer drum with a gripper and wound around a transfer drum as described in, for example, Japanese Patent Application Laid-Open No. 62-279361. There is also a method in which the toner images of each color are sequentially transferred onto a recording material by contact rotation.

[0004] The average particle size of the toner particles used in the wet development method is about 7 to 7 in the dry development method.
In most cases, it is as small as 2 μm or less compared with 10 μm. Therefore, the wet developing method has an advantage that the resolution is excellent and a high-quality color image can be obtained. As the liquid carrier, a hydrocarbon-based insulating solvent such as Isopar (registered trademark) of Exxon is often used.

As described above, in the wet developing method, the toner particles electrophores in the liquid carrier, so that the liquid carrier needs to be appropriately filled between the photosensitive member surface and the recording material during transfer.

For example, in the specification of Japanese Patent Application Laid-Open No. 8-160775, a developing solution amount control means for controlling the amount of the developing solution, the excess developing solution is removed from the surface of the photosensitive drum by the rigidity of the recording paper. It is disclosed that the rotation speed of the squeeze roller is controlled.

[0007]

However, even when the rigidity of the recording paper is the same, different printing results may be obtained even if the process conditions are the same if the recording paper surface has different smoothness. For example, a gloss-coated paper having a very high smoothness and a mat-coated paper having a low smoothness generally have the same rice basis weight (g per 1 m ² ), and both recording papers have the same transfer condition under the same transfer condition. Satisfactory print quality has not been obtained. In other words, when an image having a solid portion and a single dot portion is printed, the matte coated paper can be transferred uniformly on the glossy coated paper under the optimal transfer condition in which the dot shape becomes a perfect perfect circle. When the transfer is performed to non-uniform transfer, a part of the solid part may be unevenly printed (fading). On the other hand, when the transfer is performed to the gloss-based coated paper under the optimal transfer condition for the mat-based coated paper, the dot shape is changed in the recording paper conveyance direction. A phenomenon was found in which a so-called "tadpole" shape was tailed in the opposite direction, and the reproducibility of the highlight portion (low image density region) was significantly reduced.

In the printing industry, gloss-based coated paper is recognized as glossy paper on both white paper and printed surface, and mat-based coated paper is recognized as glossy paper on both white paper and printed surface. I have. For example, Nippon Kikai Paper Co., Ltd., “Guidebook for Paper and Printing,” published on 1994.5, p.4-
The stock list on p.5 is referred to.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and an image forming method capable of maintaining good print quality for a long time even if the surface shape of a recording material is different.

Another object of the present invention is to provide an image forming apparatus and an image forming method capable of easily performing multiple transfer with good print quality even if the surface shape of the recording material is different.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, according to the present invention, a recording material is formed from an image carrier on which a toner image is formed using a liquid developer in which toner particles are dispersed in a liquid carrier. An image forming apparatus that transfers the toner image to the image forming apparatus, wherein the image forming apparatus includes a process condition changing unit that changes a process condition according to a surface ten-point average roughness Rz of the recording material. Is done.

According to a preferred aspect of the present invention, the image forming apparatus is characterized in that the process condition changing means is a means for changing a maximum pressure P at a nip between the image carrier and the recording material. Is provided.

According to a preferred embodiment of the present invention, the image forming apparatus includes a transfer member for holding a recording material for receiving a toner image transferred on the image carrier, and at least a part of the surface of the transfer member. Has an elastic body, and the process condition changing means changes the hardness of the elastic body and / or the amount of deformation of the elastic body in the nip portion between the image carrier and the recording material. An image forming apparatus is provided.

According to another aspect of the present invention, the toner image is transferred from an image carrier having a toner image formed on a surface thereof to a recording material using a liquid developer in which toner particles are dispersed in a liquid carrier. A thickness d (μm) of a white background liquid carrier layer on the image carrier before transfer to the recording material, and a maximum pressure at a nip portion between the image carrier and the recording material. P (g / cm ² ) and the surface ten-point average roughness Rz (μm) of the recording material satisfy the relationship of 0.8 ≦ (d × log ₁₀ P) /Rz≦3.0. An image forming apparatus is provided.

According to another aspect of the present invention, there is provided a liquid container.
Toner using a liquid developer with toner particles dispersed in the rear.
-The toner is transferred from the image carrier, on which an image is formed on the surface, to the recording material.
An image forming apparatus for transferring an image, wherein
The thickness of the liquid carrier layer on the white background portion on the image carrier before the transfer
d (μm) at the nip between the image carrier and the recording material.
Maximum pressure P (g / cm^Two) And the average of ten points on the surface of the recording material
An image forming apparatus is characterized in that the roughness Rz (μm) satisfies the relationship of 1.2 ≦ (d × log10P) /Rz≦2.0.
Be done According to another aspect of the present invention, there is provided a liquid carrier.
Image using a liquid developer in which toner particles are dispersed
Is formed on the surface of the image carrier, and from the image carrier surface
Transfer where the recording material that receives the transfer of the toner image is held on the surface
An image forming apparatus comprising: a drum;
The drum has a transfer drum body and at least part of its surface
A surface member detachable from the transfer drum body including
And the surface ten-point average roughness Rz of the recording material and / or
Also changes the surface member according to the thickness of the recording material.
An image forming apparatus is provided.

According to another aspect of the present invention, there is provided an image carrier on which a toner image is formed by using a liquid developer in which toner particles are dispersed in a liquid carrier; An image forming apparatus comprising: a transfer drum on which a recording material for receiving an image is held, the surface of the transfer drum having an elastic body,
The transfer drum is detachable from the image forming apparatus, and the transfer drum is changed according to the surface ten-point average roughness Rz of the recording material and / or the thickness of the recording material. An image forming apparatus is provided.

According to another aspect of the present invention, the toner image is transferred from an image carrier having a toner image formed on a surface thereof to a recording material using a liquid developer in which toner particles are dispersed in a liquid carrier. An image forming apparatus, comprising: a process condition changing unit that changes a process condition when the recording material is gloss-coated paper or matte-coated paper. Is done.

According to a preferred aspect of the present invention, a toner image is formed on one or more image carriers a plurality of times.
An image forming apparatus is provided, wherein the toner image is multiply transferred to the recording material from at least two image carriers to form a color image on the recording material.

According to another aspect of the present invention, the toner image is transferred from an image carrier having a toner image formed on a surface thereof to a recording material using a liquid developer in which toner particles are dispersed in a liquid carrier. An image forming method, wherein the process conditions are changed according to the surface ten-point average roughness Rz of the recording material.

The surface shape of the recording material according to the first aspect of the present invention is defined by a surface ten-point average roughness,
For example, measure the surface roughness curve using a Keyence Corporation surface profile measuring microscope VF-7500, and extract only the reference length from the roughness curve in the direction of the average line as described in JIS B0601. The average height (distance) of the highest to fifth peaks and the height (distance) of the lowest to fifth valleys measured in the direction of the vertical magnification from the average line of the extracted portion Is obtained by calculating the sum of the average value and the average value, and expressing this value in micrometers (μm).

The average particle diameter of the toner particles used in the wet development method is about 7 to about 7 in the dry development method.
It is extremely small, usually 2 μm or less, for 1010 μm. As described above, in the wet development method, the toner particles electrophoreses in the liquid carrier, so that the liquid carrier needs to be appropriately filled between the photosensitive member surface and the recording material during transfer. As compared with the dry developing method, the toner particle diameter in the wet developing method is small, so that the toner thickness of the wet toner image is very thin as easily inferred from the toner particle diameter. Very sensitive to FIG. 2 (a)
2B, a recording material having a high degree of smoothness under the same transfer conditions, for example, a transfer area on a recording paper (FIG. 2A) and a recording material having a low degree of smoothness, for example, a transfer area on a recording paper (FIG. 2).
(B)) schematically shows the state. In the case of recording paper having a high degree of smoothness, the gap between the photoreceptor surface and the recording paper surface is in a state of being filled with a liquid carrier, and the toner particles are satisfactorily transferred from the photoreceptor side to the recording paper by electrophoresis. In the case of recording paper having low smoothness, the gap between the surface of the photoreceptor and the surface of the recording paper is not completely filled with the liquid carrier, and a gap remains, which hinders electrophoresis of toner particles. If the surface member of the transfer drum is an elastic body, the elastic body is easily deformed, and the contact area with the photoconductor as the image carrier becomes large. This is preferable because the difficult range is widened.

In the present invention, the average particle size of the toner particles is determined by using a measuring device (for example, SA-CP3 manufactured by Shimadzu Corporation) that uses a centrifugal sedimentation method known as a general measuring method in the art. It is evaluated by the volume average particle size of the particles.

In the present invention, as the process conditions changed according to the recording material, for example, changes in the amount of liquid carrier in the transfer area or the pressure contact force between the recording material and the image carrier in the transfer area are used. Can be In the present invention, as a means for adjusting the amount of the liquid carrier on the image carrier, for example, in the case of a squeeze roller, a change in the gap between the squeeze roller and the image carrier, or the rotation speed and rotation direction of the squeeze roller is used. Can be As a means for changing the pressing force between the recording material and the image carrier, a change in the material hardness of the surface member or the amount of deformation is used.

As the liquid developer suitably used in the present invention, for example, colored particles (toner particles) containing a pigment and a resin as main components are contained in a carrier liquid (liquid carrier) of petroleum hydrocarbon in a concentration of 0.1. ~ 20wt% dispersed,
For electrostatic transfer to a recording material, it is preferable that the volume resistivity of the carrier liquid is 10 ¹⁴ or more and the dielectric constant is in the range of 1.0 to 3.5. When the volume resistivity of the carrier liquid is 10 ¹⁴ or less, a good electric field is not applied to the colored particles, and transfer failure may occur. In consideration of the movement of the colored particles in the transfer area, the kinematic viscosity of the carrier liquid is preferably 4 × 10 ⁻⁶ m ² / s or less in the operating temperature range. Considering the removal of the liquid, the squeezing property is reduced at an extremely low viscosity, so that the viscosity is preferably 1 × 10 ⁻⁶ m ² / s or more.
Note that those having a small change in viscosity in the operating temperature range are preferable.

[0025]

An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the electrophotographic printer 1 includes a latent image forming unit 27, a developing unit 8, a cleaning unit 28, a fixing unit 26, a pre-transfer charger 17 and an auxiliary squeezing unit 29, a mist collecting unit 30, And a latent image forming means 27 is irradiated with light for exposure from the exposure means. The exposing means may, for example, have a resolution of 800 dpi (minimum dot formation interval of about 12
7 / 4000mm) laser scanning exposure system. As the exposure system, various types such as an LED array can be used. The image binarization means binarizes the image using amplitude modulation screening for modulating continuous tone data with the size of halftone dots, frequency modulation screening for modulating the number of halftone dots per unit area, or the like. Further, a device having a dot modulation function of further modulating the two types of screening and the size of each dot by the irradiation time or intensity of the laser beam may be used.

The latent image forming means 27 includes the photosensitive member 2 and the charge removing means 16.
And a primary charger 7 and a photoconductor (image carrier) 2
The surface is cleaned by the cleaning means 28 prior to the removal of the residual charges.

The photosensitive member 2 is formed by forming a photosensitive layer made of an organic photoconductive material on the surface of a cylindrical drum, and an electrostatic latent image is formed on the surface of the photosensitive member 2 by light irradiated from the exposure means. . The charge removing means 16 is composed of a small-sized incandescent lamp and a red filter for cutting short-wavelength light, and irradiates the surface of the photosensitive drum 2 with light to remove residual charges.
The primary charger 7 is a corona charger that uniformly charges the surface of the photoreceptor 2 with ions generated by corona discharge.

The developing means 8 has a first developing unit 8a to a fourth developing unit 8d, which are integrally moved in a horizontal direction indicated by an arrow in the drawing, which is a tangential direction of the photosensitive member 2, by a driving means (not shown). You. Each developing unit contains, for example, a liquid developer of yellow, magenta, cyan, and black, respectively. The liquid developer is a hydrocarbon solvent, for example, Isopar G, H, L, M
(Trade name of Exxon Chemical Co., Ltd.) in which toner particles in which pigments such as yellow, magenta, cyan, and black are mixed in a resin are dispersed.

By the way, since an electrophotographic printer for printing a multicolor toner image uses a plurality of developers, it is needless to say that it is preferable to prevent color mixture between the developers. In this embodiment, as described below, the main squeeze rollers 14a to 14d are arranged for each developing unit, and the removed liquid developer is reused. On the other hand, the auxiliary squeeze roller 29 removes excess developer from each color toner image developed on the photoreceptor 2 by one roller, so that the removed liquid developer is mixed with each color. It is discarded because it cannot be reused. For this reason, in order to reduce waste of the liquid developer and to reduce the cost, it is necessary to remove excess liquid developer from the photoconductor 2 as much as possible before the removal of the liquid developer by the auxiliary squeeze roller 29. desirable. However, depending on the type of the recording material and the surface roughness, it may be preferable to leave an appropriate amount of the liquid developer. Therefore, it is preferable to determine the conditions in consideration of this point.

According to this embodiment, by minimizing the surplus liquid developer on the surface of the photoreceptor 2 within a range that does not hinder the transfer to the recording material, the color mixture of the liquid developer and the dot-shaped toner image To minimize the occurrence of fattening. One of them is that when switching between developing units,
The operation of removing the excess liquid developer is started in the vicinity of the leading end of the developed image on the surface of the photoconductor 2 in the rotation direction or at a position in front of this part. That is, before the toner image reaches the vicinity of the squeeze unit 29, the operation of removing the surplus developer is started. Further, the operation of removing the surplus liquid developer is finished behind the rear end of the image in the rotation direction of the photoconductor 2.

As another method, the rotation axis of the main squeeze roller may be positioned higher than that of the developing roller, or the outer diameter of the main squeeze roller may be larger than that of the developing roller. That is, the first developing unit 8a of the developing unit 8
In, a developing roller 13a and a main squeeze roller 14a are disposed in parallel in a liquid developer liquid tank 25a. A liquid developer is supplied to the liquid tank 25a from the first developing unit 8a. As shown in FIG. 7, the developing roller 13a and the main squeeze roller 14a are separated by a predetermined distance (h and D in the figure) in the vertical and horizontal directions when the developing unit 8 is at the standby position on the right side of the photoconductor 2. The body 2 is disposed so as to face the rotation axis of the body 2 in parallel. The rollers 13a and 14a are disposed in a liquid tank 25a so as to be vertically movable so as to enable the developing means 8 to move in the horizontal direction, and are urged upward by a spring (not shown). When the developing means 8 is switched, the developing roller 13a comes close to the photoconductor 2 and is attached to both ends of the roller. The developing roller 13a and the photoconductor 2 are each urged by a spring (not shown) by a roller (not shown). The gap is maintained. Then, the developing unit 8 is pushed down with the horizontal movement. Therefore, the main squeeze roller 14a
Is the developing roller 13 in the front of the moving direction when the developing unit is switched.
It approaches the photoconductor 2 at a predetermined distance above a. When the first developing unit 8a is switched to the developing position of the photoconductor 2,
The rollers 13a and 14a are in contact with the photoconductor 2 with a slight gap therebetween, and are urged by springs (not shown) attached to both ends, and are brought into contact with the photoconductor, for example, 50 to 10 by rollers (not shown).
It is configured to keep a gap of 0 μm. Positioning with such a predetermined narrow gap is referred to herein as “proximity”.

Here, as shown in FIG.
h is the distance between the centers of the a and the main squeeze roller 14a in the up-down direction, v is the moving speed associated with switching of the developing means 8,
V, the radius of the photoconductor 2 is R, the radius of the developing roller 13a is rd, the radius of the squeeze roller 14a is rs, and the photosensitive drums when the rollers 13a and 14a are close to the photoconductor 2 respectively. The angles of approach to the vertical axis passing through the center of the body 2 are ωd and ωs.

At this time, the proximity angle ω between the rollers 13a and 14a
d and ωs are respectively given by the following equations.

Ωd = cos ⁻¹ {(R−hd) / (R + rd)} (1) ωs = cos ⁻¹ {(R−hd−h) / (R + rs)} (2) Further, assuming that the time from when the developing roller 13a approaches the photoconductor 2 until the main squeeze roller 14a approaches is T, the rotation angle of the photoconductor 2 during that time is θ. (Radians), θ = VT / R from VT = Rθ. Here, T = D / v (t).

At this time, by satisfying ωs−ωd> 0, it is possible to expedite the start of the removal of the excess liquid developer and increase the removal efficiency, and more preferably, to remove the excess liquid developer as much as possible. , Ωs−ωd ≧ 0. That is, the center distance h is preferably set to satisfy the following equation.

Cos ^-1 {(R−hd−h) / (R + rs)}> VT / R + cos ⁻¹ {(R−hd) / (R + rd)} (3) The other developing unit 8b To 8d are the first developing unit 8a
Therefore, the same reference numerals are given to the corresponding components in the figure, and the detailed description is omitted.

Here, the developing means 8 is arranged at a standby position to the right of the photosensitive member 2 in an initial position before the start of development. During development, the developing units 8a to 8d are sequentially moved by the driving unit to the latent image forming unit 27 in this order, and each of the static units formed on the basis of the color-separated print information, as described later. Electrostatic latent images are sequentially formed, and after completion of the development of the four colors, the image is returned to the standby position. Further, each liquid developer is supplied only when the electrophotographic printer 1 is used, and usually, the liquid developer does not enter the liquid tank of the developing unit.

The main squeeze rollers 14a to 14d are made of a metal roller or an insulating synthetic resin on the surface of the metal roller.
A thin film made of ceramic or the like is formed, is electrically connected to the auxiliary squeeze roller 29 as shown in the figure, is electrically held in a float state, and is grounded via a capacitor 24.

Incidentally, a squeeze bias may be applied to the main squeeze rollers 14a to 14d and the auxiliary squeeze roller 29 by a separate power source. The squeeze bias voltage is preferably set to a value that does not cause a white background stain on an obtained image and does not deprive the image area of the toner when the surplus developer is removed. That is, it is preferable to set a value between the potential of the non-picture area and the potential of the image area. Even when the squeeze roller is a float, as long as the potential is within the above range, when the squeeze roller is attached to the non-picture area, the squeeze roller has an action of attracting the toner particles by the attractive force of the electric field. On the other hand, it can be further compressed against the image area by the repulsive force of the electric field. White background stains are particularly harmful because they have the effect of increasing the optical density more than ideal, as is the case with other dot-shaped toner images, and especially when frequency modulation screening is used, such white background stains should be reduced as much as possible. Gives the desired result.

By the way, the effect of removing the white background stain is more effective when the difference between the potential of the squeeze roller and the potential of the non-picture area is larger than the difference between the bias potential of the developing roller and the potential of the non-picture area. is there. That is, the potential of the squeeze roller is close to the potential of the picture area, and the toner particles are more easily attracted.

As a specific potential, for example, in the case of electrophotography by the reversal developing method, if the surface potential of the non-picture area on the photoreceptor is set to -600 V and the surface potential of the print area is set to -100 V, When a bias voltage of -400 V is applied to the roller, a bias voltage of -400 V or an absolute value or less is applied to the main or auxiliary squeeze roller, or the potential of the squeeze roller is included in the range in most cases. To be When the squeeze roller and the developing roller are set to the same potential, both power supplies may be shared. When the potential difference between the two is fixed, a voltage stabilizing means such as a constant voltage diode may be inserted between the two.

On the other hand, the effect of compressing the toner image is more effective when the difference between the potential of the squeeze roller and the potential of the non-picture area is smaller than the difference between the bias potential of the developing roller and the potential of the non-picture area. It is a target. That is, the electric potential of the squeeze roller is close to the electric potential of the non-picture area, which can exert a stronger repulsive force on the toner particles. As described above, it is necessary to determine the potential of the squeeze roller with respect to the potential of the developing roller depending on which of the action of removing the white background stain and the action of compressing the toner image is important. In the case where a set (main squeeze roller and auxiliary squeeze roller) is provided, it is possible to sufficiently remove the white background dirt with the squeeze roller on the upstream side and compress the toner image with the squeeze roller on the downstream side. Also, when the developing bias of the developing roller is at a potential between the picture area and the non-picture area, there is a case where no white background stain is generated. In this case, even when a single squeeze roller is provided, The potential of the toner image may be further increased by bringing the potential closer to the potential of the non-picture area. The removal of the white background stain or the compression of the toner image need not be performed by a squeeze roller, and can be realized by separately providing a roller having no squeeze effect but having a stabilized potential or a stationary surface. good. The compression effect can also be achieved by the pre-transfer charger 17 as described later.

In this embodiment, the squeeze roller is used exclusively as a means for removing the excess liquid developer.
In addition, an air knife effect such as blowing air to the surface of the photosensitive drum may be used, or a heating means using hot air may be used. In areas where a large amount of excess developer remains,
The surplus developing solution may be stopped by utilizing the “corona squeeze effect” by the corona discharger such as the pre-transfer charger 17.

The other developing units 25b to 25d are configured in the same manner as the first developing unit 25a, and a detailed description will be omitted.

In FIG. 1, a transfer drum 3, which is a transfer member for holding a recording material, has a cylindrical shape made of a conductive element such as aluminum, and its surface member is formed of an elastic body 1 made of a polymer material. I have. As shown in FIGS. 3 and 4, spacers 5 are attached to the entire periphery of the transfer drum 3 near both ends in the axial direction. Since the surface of the spacer 5 is brought into contact with the surface of the photoconductor 2 serving as an image carrier, the respective axes of the photoconductor 2 and the transfer drum 3 can maintain a parallel positional relationship. Thereby, the distribution of the maximum deformation amount of the elastic body 1 in the nip portion in the axial direction of the transfer drum can be made uniform. Here, the length from the center of the transfer drum to the surface of the spacer is 100 mm, and the distance from the center of the transfer drum to the surface of the elastic body is, for example, 100.1 mm to 10 mm.
It is 0.5mm long. In the nip portion, the elastic body 1 on the surface of the transfer drum 3 shrinks by the amount of protrusion from the spacer 5 in the radial direction of the transfer drum 3, and the amount of deformation is uniformly regulated over the entire surface of the transfer drum 3. Accordingly, the pressure of the elastic body 1 pressing the recording material 6 from the back surface of the recording material 6 is also uniform over the entire surface of the recording material 6, so that a uniform transfer of the toner image from the photoconductor 2 to the recording material 6 can be realized.

When a rubber material is used as the elastic body, a plasticizer is usually added to reduce the hardness. However, the plasticizer migrates onto the toner or the photoreceptor, causing a filming phenomenon in which a thin film layer is formed on the photoreceptor surface, or adversely affecting the photoreceptor characteristics, resulting in a decrease in image density. . Also, when lowering the hardness by lowering the crosslink density without adding a plasticizer like silicone rubber,
Low molecular weight components such as oil inside rubber may leach to the surface and adhere to the photoreceptor, resulting in the same adverse effect as a plasticizer. On the other hand, if it is made of a polymer and further has a porous structure, for example, the bubble diameter is 200 to 300.
By increasing the thickness to about μm, the hardness can be easily reduced without adversely affecting the photoreceptor and the image quality. Examples of such a material include nitrile rubber, urethane rubber, chloroprene rubber, and the like, which are resistant to hydrocarbon solvents used in embodiments described later.

The average particle size of the toner particles of the liquid developer used in this embodiment is 1. cyan, magenta and yellow.
FIG. 8 shows good transfer conditions of 0 μm and black of 1.2 μm (measured by a centrifugal sedimentation method with SA-CP3 manufactured by Shimadzu Corporation) using a magenta developer. The relationship between the maximum pressure of the nip and the amount of the liquid carrier in the nip between the photoconductor 2 and the transfer drum 3 is as follows.
It is preferably in the region shown in FIG. The surface ten-point average roughness of the gloss coated paper obtained a value of about 2 μm from the result of measurement with the Keyence Corporation surface profile measuring microscope VF-7500. On the other hand, in the case of the mat type coated paper and the high quality paper, the conditions for obtaining a surface ten-point average roughness of 5 μm or more from the same measurement and obtaining good transfer are as shown in FIG. It was found that there was an optimal transfer condition in an area different from.

In the case of a color printer, for example, in which a toner image is superimposed on a recording material, the recording material does not contain a liquid carrier before the transfer of the first color toner image, whereas At the time of transfer after the color tone, the surface of the recording material is also in a state where the liquid carrier is attached. Therefore, it is more preferable to change the transfer conditions. Specifically, the amount of liquid carrier for the second and subsequent colors is reduced compared to the first color, or
By lowering the maximum pressure in the transfer nip portion for the second and subsequent colors as compared to the color, better transfer is possible.

Here, as a method of measuring the pressure, a rigid plate (for example, stainless steel having a thickness of 4 mm) of the same size as the underlay material is placed on the underlay material (for example, 100 mm × 100 mm), and A method is conceivable in which a weight having a known mass is placed on the underlay material, and the displacement of the underlay material in the thickness direction at that time is measured using a displacement meter or the like. From this measurement result, the relationship between the amount of deformation of the underlay material and the pressure is obtained, and the maximum pressure is determined by determining the maximum deformation amount of the underlay material at the nip portion. As a method of measuring the liquid carrier amount, for example, a sheet is wound around a transfer drum and fixed,
A print sequence is executed for a pattern having only a white background (in the case of reversal development, the print sequence is executed by blocking laser light). A method of measuring the weight of the paper before and after the printing sequence, taking the change as the amount of liquid carrier absorbed by the paper, and approximating this to the amount of liquid carrier in the nip portion, or the like can be considered. Further, the thickness of the liquid carrier layer in a white background portion on the photoreceptor before transfer can be obtained by dividing the above-mentioned liquid carrier amount by the sheet area and the specific gravity. That is, for example, when the liquid carrier amount on the vertical axis of FIG. 8 is 100 (mg / A3 size) and the specific gravity is 0.76 (g / cm ³ ), the liquid carrier layer thickness becomes about 1
μm. Similarly, liquid carrier amount is 300 (mg / A3 size)
Corresponds to a liquid carrier layer thickness of about 3 μm.

By further studying, the thickness d (μm) of the white background liquid carrier layer on the image carrier before the transfer to the recording material and the nip portion between the image carrier and the recording material will be described. It was confirmed from experiments that the relationship between the maximum pressure P (g / cm2) and the surface ten-point average roughness Rz (μm) of the recording material was good in a specific state. That is, good transfer can be performed when the following relationship is satisfied.

0.8 ≦ (d × log ₁₀ P) / Rz ≦ 3 For example, by setting P to 100 g / cm 2, the thickness d (μm) of the white background liquid carrier layer on the image carrier before transfer is set. When the transfer is performed by using the parameter as a parameter, at least Rz is 1.7.
For gross coated paper of μm to 2.7 μm, d × log
_{When 10} P was in the range of 2.3 to 5, good transfer was surely performed. Even if it exceeds this range, it is considered that favorable results can be obtained in a range satisfying the above relational expression. When the value of d × log ₁₀ P is larger than the range of this relational expression, a tailing phenomenon in which a dot portion flows occurs, and conversely, d × log ₁₀ P
When the value was small, a part of the solid portion was blurred. It has been confirmed that the above relational expression holds even when P is changed, and that the same holds true for mat type coated paper having an Rz of 6.3 to 6.7 μm. In addition,
More preferably, it is preferable that 1.2 ≦ (d × log ₁₀ P) / Rz ≦ 2.

Further, this elastic body 1 is attached to an aluminum sheet (thickness 0.225 mm) as an elastic body attaching sheet 23 as shown in FIGS. Fixed. Therefore, since it is easy to replace the paper according to the surface smoothness of the paper, for example, separate elastic body mounting sheets 23 are prepared for the gloss-coated paper and the mat-coated paper, and compared with the gloss-coated paper. When printing on matt coated paper,
The pressure for pressing 6 against photoconductor 2 may be increased. If the material hardness of the elastic body 1 is known, the amount of deformation of the elastic body 1 at the nip portion (the amount of protrusion from the spacer 5) can be determined to uniquely determine the force with which the elastic body 1 presses the paper from the back surface of the paper. It is determined. Therefore, the pressure at which the recording material 6 is pressed against the photoconductor 2 at the nip can also be adjusted. That is, by changing the material hardness or the deformation amount of the elastic body 1 in accordance with the surface roughness of the recording material, an optimal pressing pressure can be realized. In addition, even if the amount of protrusion from the spacer 5 is the same, the amount of deformation of the elastic body 1 varies depending on the thickness of the recording material 6.
The material hardness or deformation of the elastic body 1 may be changed according to the thickness of the recording material 6. In the configuration of FIG. 4, if the elastic body 1 on the surface of the transfer drum 3 is further covered with a member such as a PET film that does not pass through the liquid carrier, the liquid is not absorbed by the elastic body 1 in the wet development method, so that the transfer drum 3Easy cleaning of the surface layer.

Further, for example, the elastic body 1 may be formed integrally with the transfer drum 3, and the entire transfer drum 3 may be replaced according to the surface roughness and thickness of the recording material.

The fixing means 26 comprises a rubber roller having a thickness of 2 mm coated on a hollow aluminum core made of aluminum and the outermost layer of which is coated with a silicone resin having a thickness of 100 μm. A pair of heat rollers composed of a structure containing a lamp is used.

Next, a full-color printer according to an embodiment of the present invention will be described with reference to FIG. A toner image created by image data separated into four colors of yellow, magenta, cyan, and black is developed with toner of each color in this order, and is superimposed on a recording material 6 held on a transfer drum 3. After the black transfer, the transfer roller 3 is separated from the transfer drum 3 by the separation claw 15, and the heat rollers 11 and 12 are separated.
Is fixed.

The primary charger 7 uniformly charges the surface of the photoconductor 2. The surface material of the photoconductor 2 includes amorphous silicon, selenium, and organic photoconductor (OPC: Organic Photocon
ductor) and the like, but in this embodiment, OPC is used. The charged surface of the photoreceptor 2 is first exposed by an exposure device (not shown) to an optical pattern corresponding to the image data of the first toner image with a laser beam, and corresponds to the image data of the first toner image. An electrostatic latent image is formed. In this embodiment, a reversal developing method is used in which the absolute value of the surface potential of the latent image forming section is lower than that of the non-latent image forming section.

Next, the developing means 8 disposed on the right side of the photoreceptor 2 is moved horizontally in the direction of arrow C by a driving means (not shown) to correspond to the image data of the first toner image formed on the photoreceptor 2. The developed electrostatic latent image is developed by the first developing unit 8a in the developing means 8. At this time, the developing roller 13
a contacts the photoconductor 2 to supply the developer to the photoconductor 2, and the developed toner image moves counterclockwise by the rotation of the photoconductor 2. Then, the squeeze roller 14a approaches the photosensitive member 2 in front of the front end of the developed toner image, and starts removing excess developer. In FIG. 1, the developing roller 13a rotates clockwise, and the squeeze roller 14a rotates counterclockwise. The squeeze roller 14a is urged by a spring (not shown), and is contacted with the photoreceptor 2 by rollers (not shown) attached to both ends of the roller. A certain gap is maintained. In the present embodiment, the peripheral speed of each developing roller is the peripheral speed of the photoconductor 2 (160 mm / s).
0.5 to 3 times the gap with the photoconductor 2 is 100 to 200 μm,
2-5 times and 50-100μm for squeeze roller respectively
It is. In the measurement of the liquid carrier amount as described above,
The first color toner image transfer process condition was set at 250 mg per A3 size sheet, and the other color transfer process conditions were set at 200 mg per A3 size sheet. Specifically, for example, the squeeze gap of the first color toner is 100 μm.
m, and the squeeze gap of the other colors was 75 μm. A wide variety of papers can be realized by changing the squeeze gap of each color or changing the rotation speed of the squeeze roller according to the ten-point average roughness of the surface of the recording material. Specifically, in the case of matt-coated paper and high-quality paper, the amount of liquid carrier on the photoreceptor is increased by increasing the squeeze gap or decreasing the peripheral speed of the squeeze roller compared to the case of gloss-coated paper. Larger and better transfer can be realized.

On the other hand, before the development of the first toner image is started, the leading end of the recording material 6 sent from the recording material tray 19 by a conveying roller (not shown) is gripped by the gripper 20 of the transfer drum 3, and When the paper 20 passes the position of the recording material pressing roller 18, the recording material pressing roller 18, which has been separated from the transfer drum 3, is pressed against the transfer drum 3 by a separation mechanism (not shown), and presses the recording material 6 against the transfer drum 3. It is wound around the transfer drum 3 in order from the top and held. Immediately before the rear end of the recording material 6 reaches the position of the recording material pressing roller 18, the recording material pressing roller 18 is separated from the transfer drum 3, and the gripper 21 grips the rear end of the recording material 6.

The first toner image developed on the photosensitive member 2 is transferred onto the recording material 6 on the surface of the transfer drum 3. Here, when the recording material 6 is held on the transfer drum 3 and the transfer drum 3 is rotated once, the development of the first latent image is started.
When the transfer speed of the recording material 6 to the recording material 6 and the transfer process speed are different, the speed is changed after holding the sheet on the transfer drum 3, and the transfer of the photosensitive drum 2 and the transfer drum 3 separated by a separation mechanism (not shown) is performed. This is preferable because it allows time to complete the pressing operation.

Immediately before the transfer, the surface of the photoconductor 2 is charged to the same polarity as the charge polarity of the toner image together with the toner image developed by the pre-transfer charger 17. Due to this pre-transfer charging, the toner image is pressed against the photoconductor 2 by the electric field force, and the attraction force between the photoconductor 2 and the toner image is increased, so that the toner image flows and thickens in the process of transferring the toner image to the recording material 6 When a transfer electric field is formed from the surface of the photoconductor 2 to the surface of the transfer drum 3, a repulsive force acts between the surface of the photoconductor 2 and the toner particles, and the effect can also be obtained as a transfer bias unit. . The transfer of the toner image from the photoconductor 2 to the recording material 6 is performed by forming an electric field between the photoconductor 2 and the transfer drum 3 and moving the toner in the liquid carrier in the nip portion by the electric field force. It is more preferable to apply a bias having a polarity opposite to that of the surface of the photoconductor 2 to the transfer drum for the purpose of forming an electric field because the transfer rate increases. Further, by changing the value of the reverse polarity bias according to the recording material, it is possible to set optimal transfer conditions.

Although the untransferred toner slightly remains on the photoreceptor 2, it is cleaned and removed by the cleaning roller 9 and the cleaning blade 31. Further, the electrostatic latent image is also erased by the static elimination means 16 disposed downstream of the cleaning roller 9, for example, the static elimination lamp as in this embodiment, and the next second development is started.

At the time of forming the second toner image, the developing unit 8 moves by one developing unit in the horizontal direction indicated by the arrow C,
The second toner image developing device 8b is disposed at a position facing the photoconductor 2. A magenta image is developed on the photoconductor 2 in the same process as the first toner image, and is transferred onto the recording material 6 so as to overlap the first toner image already existing on the recording material 6.

The above process further comprises a third toner image,
This is repeated for the fourth toner image. As for the order of forming toner images on the recording material 6, for example, yellow, magenta, cyan, and black toner images are superimposed in this order to form a four-color full-color image. This color order is preferable because the mixing of the other color toner into the yellow toner can be minimized.

On the other hand, it is preferable that the color order is black, cyan, magenta, and yellow because a toner layer having high transparency is superposed on the recording material and the color reproduction range is expanded. The color order of cyan, magenta, yellow, and black is preferable because the color reproduction range of the cyan, magenta, and yellow color overlapping portions is widened in a state where the mixing of other color toners with the yellow toner is reduced.

During the transfer of the last toner image, the recording material
Immediately before the top of 6 comes to the position of the peeling claw 15, the gripper 20 on the surface of the transfer drum 3 is released, and at the same time, the peeling claw 15 is pressed against the transfer drum 3 and slips under the top of the recording material 6, and the recording material 6 is separated from the transfer drum 3. Here, the recording material 6 can be peeled off by rotating the transfer drum once after the black development is completed. This is more preferable because mechanical vibrations and the like accompanying the separation of the recording material do not affect the transfer of the last toner image. After the rear end of the recording material 6 has passed the transfer position (nip), the gripper 21 at the rear end of the recording material 6
Is released. Thereafter, when the rear end of the recording material 6 passes through the transfer drum cleaning member 10, the separated transfer drum cleaning member 10 is pressed against the transfer drum 3, and the surface of the transfer drum 3 is rotated during one rotation of the transfer drum 3. At least toner particles are removed from the developer attached to the elastic body 1. While the transfer drum 3 is being cleaned, the developing unit 8 returns to the original position. When the cleaning is completed, the transfer drum cleaning member 10 is separated, and the leading end of the next recording material 6 is gripped by the gripper 20.

The heat rollers 11 and 12 are rollers enclosing a heat source (not shown) such as a halogen lamp. As shown in FIG. 1, the heat rollers 11 and 12 rotate in the directions of arrows E and F, and are arranged to face each other. ing. When the recording material 6 approaches the heat rollers 11 and 12, the heat roller 11 and the heat roller 12 are pressed against each other by a pressing mechanism (not shown), and the recording material 6 is conveyed between the heat rollers 11 and 12 while the toner image is conveyed. Is fixed on the transfer material. At this time, the liquid carrier adhering to the paper is
It is heated at 12 and becomes steam. This vapor or what is further atomized here is called mist, but in the present invention, this mist generated mainly in the fixing process is sucked,
A recovery device 30 is provided.

In the case of using the wet developing method, it is necessary to supply sufficient heat to evaporate the liquid carrier in the fixing process in order for the recording material 6 to absorb the liquid carrier 4. In this case, if the distance from the peeling position of the recording material 6 to the heat rollers 11 and 12 is longer than the length of the maximum recording material 6 in the process direction, the speed of the photoconductor 2 and the transfer drum 3 are not changed. Can be fixed at low speed. On the other hand, if the distance from the peeling position of the recording material 6 to the heat rollers 11 and 12 is shorter than the length of the maximum recording material 6 in the process direction for the purpose of downsizing the device, etc. At the end, the photosensitive member 2 and the transfer drum 3 are separated by a separating mechanism (not shown), and sufficient heat can be provided to the recording material by making the fixing process speed lower than the developing / transfer process speed. In this case, the photoconductor
Although it is possible to reduce the speed without separating the transfer drum 2 and the transfer drum 3, it is more preferable to separate the transfer drum 3 to prevent deterioration of the surface of the photoconductor 2 due to a change in speed.

When the recording material on which the toner image has been transferred immediately after the transfer is inserted into the nip portion between the heat rollers 11 and 12, a phenomenon that the toner image flows downstream in the transport direction may occur.
By allowing the liquid carrier contained in the toner image to penetrate into the recording material after a waiting time until the toner is inserted into the heat roller after the transfer, more stable fixing is possible. Since the permeation speed and amount differ according to the thickness of the recording material (US basis weight), the standby time is changed according to the thickness. Specifically, the rice basis weight is 80 g /
In the case of a thin recording material of m ² or less, it is preferable to make the standby time longer.

The diameter of the photosensitive member 2 and the diameter of the transfer drum 3 preferably have an integer ratio. In this embodiment, the diameter of the photosensitive member 2 is 100 mm, and the diameter of the transfer drum 3 is 200 mm. This is because unevenness due to the unevenness of the surface of each of the photoreceptor 2 and the transfer drum 3 and the resistivity of the surface of the transfer drum 3 are generated in one color in exactly the same place on one screen. Thus, as in the conventional case, unevenness in the shade of each color occurs at different places, thereby preventing a change in tint. Further, since the maximum size of the recording material 6 is A3 (419 mm × 297 mm), the circumference of the transfer drum 3 is longer than the length of the recording material 6, and the nip portion of the nip portion in the squeeze transition period immediately after the start of development for each color. Liquid carrier 4
However, the transfer drum 3 transfers the excessive amount of liquid to an area where the transfer drum 3 does not hold the recording material 6,
Good print quality can always be maintained.

In the present embodiment, a drum-shaped transfer drum is used as a transfer member for holding a recording material. However, the present invention is not limited to a transfer drum, but may be applied to another type of transfer member such as a so-called transfer belt. Is also applicable.

Further, the concept of the present invention provides a similar effect even in a so-called tandem type image forming apparatus having a plurality of photosensitive members, and changes the transfer condition of the first color and the transfer conditions thereafter. Alternatively, by changing the transfer condition of each color according to the surface roughness of the recording material, a very good transfer state can be maintained for all colors, and a high-speed image forming apparatus with a wide variety of papers can be realized.

Further, by providing a sensor such as a gloss meter that can easily monitor the surface smoothness at a paper transport system or a paper standby position such as a drawer, it is possible to automatically change the transfer conditions. . Alternatively, a function may be provided for notifying the user when the recording material does not meet the transfer conditions set from the sensor output.

Further, in an electrophotographic apparatus using an intermediate transfer member, the elastic body of the present invention can be used as a structural material of the intermediate transfer member, and can be used for the maximum pressure of the nip portion between the photosensitive member and the intermediate transfer member and the liquid carrier. Good primary transfer can be performed while maintaining an appropriate amount.

[0074]

As is apparent from the above description, according to the image forming apparatus of the present invention, deterioration in print quality can be avoided by changing the process conditions according to the surface ten-point average roughness of the recording material. And good transfer is possible over a wider range of paper.

Further, good transfer can be achieved in multiple transfer in which a toner image is superimposed on a recording material.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of an electrophotographic apparatus according to the present invention.

FIG. 2 is a schematic diagram of a transfer area of a photoconductor and a transfer drum.

FIG. 3 is a side view when a spacer is attached to the surface of the transfer drum.

FIG. 4 is a cross-sectional view when a spacer is attached to the surface of the transfer drum.

FIG. 5 is an elastic body attached to an aluminum sheet for attachment to a transfer drum.

FIG. 6 is a diagram showing how to attach an elastic body to a transfer drum.

FIG. 7 is a diagram showing an arrangement interval in a vertical direction between a developing roller and a main squeeze roller of the developing unit.

FIG. 8 shows a pressure for pressing the recording material from the back surface of the recording material,
FIG. 4 is a diagram illustrating a preferable relationship between the amount of liquid carrier in a nip portion between a photoconductor and a transfer drum in a case of gloss-coated paper and a case of mat-coated paper.

[Explanation of symbols]

 1: elastic body 2: photoreceptor 3: transfer drum 4: liquid carrier 4a: liquid carrier that has passed between the photoreceptor and the recording material 4b: excess liquid carrier 5: spacer 6: recording material 7: primary charger 8: Developing means 8a: First developing unit 8b: Second developing unit 8c: Third developing unit 8d: Fourth developing unit 9: Cleaning roller 10: Transfer drum cleaning member 11, 12: Heat roller 13a, 13b, 13c, 13d: developing roller 14a, 14b, 14c, 14d: main squeeze roller 15: peeling claw 16: discharging means 17: pre-transfer charger 18: recording material pressing roller 19: recording material tray 20, 21: gripper 22: screw 23: Elastic body mounting sheet 24: condenser 25a, 25b, 25c, 25d: liquid tank 26: fixing means 27: latent image forming means 2 : Cleaning means 29: Auxiliary squeeze means 30: mist recovery means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/11 G03G 15/10 116

Claims (10)

[Claims] 1. An image forming apparatus for transferring a toner image from an image carrier having a toner image formed on a surface thereof to a recording material using a liquid developer in which toner particles are dispersed in a liquid carrier, wherein the recording is performed. An image forming apparatus comprising: a process condition changing unit that changes a process condition according to a surface ten-point average roughness Rz of a material. 2. An image forming apparatus according to claim 1, wherein said process condition changing means is a means for changing a maximum pressure P at a nip portion between said image bearing member and said recording material. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus includes a transfer member that holds a recording material that receives a transfer of a toner image on the image carrier. At least a part of the surface of the recording medium has an elastic body, and the process condition changing means changes the hardness of the elastic body and / or the deformation amount of the elastic body in a nip portion between the image carrier and the recording material. An image forming apparatus, comprising: 4. An image forming apparatus for transferring a toner image from an image carrier having a toner image formed on a surface thereof to a recording material by using a liquid developer in which toner particles are dispersed in a liquid carrier, wherein the recording is carried out. The thickness d (μm) of the white background liquid carrier layer on the image carrier before transfer to the material, the maximum pressure P (g / cm ² ) at the nip between the image carrier and the recording material, An image forming apparatus, wherein a ten-point average roughness Rz (μm) of a recording material satisfies the relationship of 0.8 ≦ (d × log ₁₀ P) / Rz ≦ 3. 5. An image forming apparatus for transferring a toner image from an image carrier having a toner image formed on a surface thereof to a recording material by using a liquid developer in which toner particles are dispersed in a liquid carrier, wherein The thickness d (μm) of the white background liquid carrier layer on the image carrier before transfer to the material, the maximum pressure P (g / cm ² ) at the nip between the image carrier and the recording material, An image forming apparatus, wherein a surface ten-point average roughness Rz (μm) of a recording material satisfies a relationship of 1.2 ≦ (d × log10P) / Rz ≦ 2. 6. An image carrier on which a toner image is formed on a surface using a liquid developer in which toner particles are dispersed in a liquid carrier, and a recording material receiving a transfer of the toner image from the surface of the image carrier is provided on the surface. An image forming apparatus comprising: a transfer drum that is held, wherein the transfer drum includes a transfer drum main body and a surface member that is detachable from the transfer drum main body including at least a part of a surface including an elastic body; An image forming apparatus, wherein the surface member is changed according to the surface ten-point average roughness Rz of the recording material and / or the thickness of the recording material. 7. An image carrier on which a toner image is formed on a surface using a liquid developer in which toner particles are dispersed in a liquid carrier, and a recording material receiving a transfer of the toner image from the surface of the image carrier is provided on the surface. An image forming apparatus comprising: a transfer drum that is held; at least a part of a surface of the transfer drum has an elastic body; and the transfer drum is detachable from the image forming apparatus. An image forming apparatus, wherein the transfer drum is changed according to a surface ten-point average roughness Rz of a recording material and / or a thickness of the recording material. 8. An image forming apparatus for transferring a toner image from an image carrier on which a toner image is formed on a surface to a recording material using a liquid developer in which toner particles are dispersed in a liquid carrier, wherein the recording is performed. An image forming apparatus comprising: a process condition changing unit that changes a process condition for a case where a material is a gloss-based coated paper or a mat-based coated paper. 9. A toner image is formed on one or more image carriers a plurality of times, and the toner image is multiplex-transferred onto the recording material from the one or more image carriers to form a color image on the recording material. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed. 10. An image forming method for transferring a toner image from an image carrier having a toner image formed on a surface thereof to a recording material using a liquid developer in which toner particles are dispersed in a liquid carrier, wherein the recording is performed. An image forming method, wherein process conditions are changed in accordance with the surface ten-point average roughness Rz of a material.