JP2005321513A - Liquid development electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid development electrophotographic apparatus with which high image quality, high density, and a wide dynamic range can be ensured by superimposing thin layers of the same color and the development and multi-value area gradation of each thin layer can be realized. <P>SOLUTION: The liquid development electrophotographic apparatus carries out development by superimposing thin layers of the same color, thereby ensuring high image quality, high density, and a wide dynamic range. In the liquid development electrophotographic apparatus, a prescribed number of image forming units are disposed in order along a transfer body, each image forming unit having around its photoreceptor a photoreceptor discharger, charger, exposure device, and development mechanism. The image forming units have a developing process for varying development density and obtain prescribed image density by superimposing thin layers of different densities of the same color. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid developing electrophotographic apparatus, and more particularly to a liquid developing electrophotographic apparatus that develops the same color of a thin layer several times to ensure high image quality, high density, and a wide dynamic range.

  In a liquid developing electrophotographic apparatus, as a method for ensuring image density, there is an increase in the toner layer thickness of the developing support (developing roller) or an increase in the toner solid content ratio. Also, the supply amount can be increased by speeding up the rotation of the toner supply roller or applying a bias between the toner supply roller and the development support.

Further, as a method for securing the image density, the supply of liquid toner to the developing roller as a developing support is stretched by a plurality of linked rollers to form a toner layer (see Patent Document 1).

  Further, as a method for ensuring the image density, a predetermined toner layer thickness is obtained by controlling the number of rotations of the last stage roller in a plurality of connecting rollers that convey toner (see Patent Document 2).

Further, in order to obtain a uniform toner layer with a simple structure, a patterned roller (anilox roller) is disposed as a toner supply roller in front of the development support (development roller) to supply a certain amount of toner. (See Patent Document 3).

  However, when a high-viscosity and high-concentration liquid toner is used, the toner layer thickness on the developing support (developing roller) is large even when the conventional toner supply method is used (when the toner viscosity is 100 cSt, the toner layer When the thickness is approximately 5 μm or more), riblets (fluctuations, ribs) generated during liquid layer separation at the nip exit between the developing support (developing roller) and the photosensitive member become prominent. That is, when a high-resolution image equivalent to 1200 dpi is printed, the dots and fine lines are disturbed.

  FIG. 12 shows a conceptual diagram of the toner layer splitting, and an example of the toner layer thickness and a fine line image. In FIG. 12, as can be seen from the conceptual diagram of toner layer thickness and separation, when the toner layer thickness is thick, the pressure in the toner layer in the roller nip increases and is greatly stretched at the nip outlet where it is opened. However, when the toner layer thickness is thin, the pressure in the toner layer is small and the amount of toner to be stretched is small. Further, when the toner layer thickness is reduced, the amount of toner is inevitably insufficient and the image density is often not satisfied. When the solid content ratio is increased in order to ensure the density, toner fog (background stain) is likely to occur due to the reduction of the rear layer (pre-wet layer) with the latent image support in the non-image area. In addition, it is necessary to make the solid content ratio 20 wt% or less under the above conditions.

To solve these problems, the dry toner development method using dry toner is used, but the latent image potential and development bias of the photoconductor are adjusted by superimposing low density development and high density development of the same color. A technique realized by doing this is known (see Patent Document 4). This achieves high image quality, high density, and a wide dynamic range.
JP-A-11-065289 Japanese Patent Laid-Open No. 11-258916 JP 2001-324876 A JP-A-5-127485

  As described above, the conventional techniques have the following problems.

  In the prior art, it seems that the method disclosed in Patent Document 4 can be realized even in a liquid toner developing system using liquid toner. However, due to the phenomenon unique to liquid development, high-quality images can be obtained even if superposition of low-density development and high-density development of the same color is achieved by adjusting the latent image potential and development bias of the photoreceptor. I can't. The “phenomenon peculiar to liquid development” referred to here is as follows.

  In the dry toner development method, if the development electric field strength is weakened, the probability that toner particles are developed is lowered, the total amount of development can be lowered, and the density can be lowered. At this time, the developed toner particles and the toner particles remaining on the development support (development roller) without being developed are independent of each other, and do not cause deterioration in image quality.

  On the other hand, in the liquid toner developing system, the generation of riblets (fluctuations and ribs) cannot be suppressed unless an electric field strength that can overcome the pressure in the toner layer is applied. In general, under the condition where the developing electric field strength is weakened so that the developing efficiency of the toner is lowered, the electric field strength cannot overcome the pressure in the toner layer, and a remarkable riblet (fluctuation, rib) is generated. That is, when the developing electric field intensity is lowered to adjust the density, the image quality is deteriorated at the same time.

  FIG. 13 shows an example thereof. In FIG. 13, the development bias 300V (non-100% development) is compared with the development bias 500V (100% development). As can be seen from FIG. 13, the development via is varied to perform non-100% development. If done, noticeable riblets (fluctuations, ribs) are generated and the image quality is disturbed.

  Under such circumstances, the so-called area gradation method is generally adopted as the density expression in the liquid toner developing method. In this system, in order to ensure sufficient gradation, if the gradation pattern (screen cell) is enlarged, the apparent image resolution is lowered. In addition, problems such as noticeable image graininess occur. Therefore, it has been difficult to achieve both a sufficient dynamic range (gradation) and high resolution.

  An object of the present invention is to provide a liquid developing electrophotographic apparatus that realizes thin layer development and multi-value area gradation by overlapping the same color of a thin layer a plurality of times to ensure high image quality, high density, and a wide dynamic range. Is to provide.

  In order to solve the above problems, the present invention takes the following means.

  The liquid developing electrophotographic apparatus of the present invention develops the same color of a thin layer a plurality of times and develops the same color of the thin layer a plurality of times in a liquid developing electrophotographic apparatus that ensures high image quality, high density, and a wide dynamic range. The toner layer thickness at the time of development at the time of overlapping is appropriately changed.

  That is, in the liquid developing electrophotographic apparatus of the present invention, a developing device in which a predetermined number of each of a photosensitive member static elimination device, a charging device, an exposure device, and a developing mechanism are sequentially formed around the photosensitive member is disposed on the image carrier. The developing device includes a developing process for changing the developing density, and a predetermined image density is obtained by overlapping the same color of the thin layer a plurality of times at different densities each time.

In addition, the liquid development electrophotographic apparatus of the present invention has a plurality of times of development, and at each development,
By configuring so that the image density at the K-th development is 2 ^K−1 / (2 ^N −1) times the target solid density (K = 1, 2, 3,..., N), Even with only the tonal method, a wider dynamic range and detailed gradation expression can be realized with a smaller number of developments.

According to this method, the toner layer thickness at each development can be suppressed to 2 ^K-1 / (2 ^N -1) times at the maximum.

  FIG. 7 shows the developing layer thickness at each development when the toner layer thickness necessary for obtaining a predetermined image density is developed a plurality of times. In FIG. 7, when the toner layer thickness of 7.5 μm necessary for obtaining a predetermined image density is performed twice by the number of development divisions, the first development layer thickness is 2.5 μm, and the second development layer thickness is 5. 0 μm. Further, when the toner layer thickness of 8.4 μm necessary for obtaining a predetermined image density is performed with three development divisions, the first development layer thickness is 1.2 μm, and the second development layer thickness is 2.4 μm. The third developing layer thickness is 4.8 μm.

Further, by setting the image density at the time of the K-th development as described above, ^2N gradation expression can be realized with only 100% development by the combination of the respective overlays. That is, as a highly viscous liquid development, multi-tone expression can be efficiently performed while maintaining the best image quality.

  FIG. 8 shows a specific example of gradation expression. For example, FIG. 8A shows a case where a toner layer thickness of 7.5 μm necessary for obtaining a predetermined image density is divided into two (doubled), and the first development and the second development. It is possible to express four gradations by a combination of the above. FIG. 8B shows a case where the toner layer thickness of 8.4 μm necessary for obtaining a predetermined image density is divided into three times (three times), and the first development and the second development. It is possible to express 8 gradations by combining with the third development.

  According to the present invention, the following effects can be expected.

  According to the liquid development electrophotographic apparatus of the present invention, each thin layer development and multi-value area gradation can be realized, thereby obtaining an effect of efficiently ensuring high image quality, high density, and a wide dynamic range. .

That is, in a liquid developing electrophotographic apparatus that employs a developing method in which a thin layer of the same color is developed N times for one original image, the image density at the K-th development is a target solid density,
The image forming apparatus includes a developing process that is 2 ^K−1 / (2 ^N −1) times (K = 1, 2, 3,..., N). As a result, multi-tone area gradation expression can be efficiently performed with a small number of developments, and high image quality, high density, and a wide dynamic range can be ensured.

  FIG. 11 shows an example of image quality when four-tone screening is performed as a specific example when multi-tone screening is performed according to the present invention. In the figure, image quality example 1 is an original image showing density gradation, and image quality example 2 is an image quality example when the original image is subjected to general binary screening. The image quality example 3 shows an image quality example when the four-value screening according to the embodiment of the present invention is performed. An image quality example 3-a shows an image quality example when screening for the first plate (0.33 times density) development is performed. An image quality example 3-b shows an image quality example when the second plate (0.67 times density) development is screened. The comparison of the area gradation expression, as is apparent from the comparison between the image quality example 2 and the image quality example 3, can greatly improve the gradation expression power without changing the size of the screen cell. It is possible to ensure image quality, high density, and a wide dynamic range.

Needless to say, the above discussion is valid even when the toner layer thickness during development is kept constant and the solid content ratio is changed.
In addition, by appropriately changing both the toner layer thickness and the solid content ratio, the total image density (toner solid content layer thickness) at the time of development is the target solid density,
If it is adjusted to 2 ^K−1 / (2 ^N −1) times (K = 1, 2, 3,..., N), the implementation requirement of the present invention is satisfied.

  The best mode for carrying out the present invention will be described with reference to FIGS.

  In the following description, the expression “transfer body” is used as the image carrier on the next stage of the photoconductor, but this may be a so-called intermediate transfer body for once color superimposition, or a final print medium. May be. In the case of an intermediate transfer body, it is considered that it is mainly used for multi-color printing. On the other hand, in the case of the final print medium, it seems that it is mainly used in monochromatic printing. Further, the transfer body may be heated by applying a transfer bias as required.

  In the example shown in FIG. 1 and FIG. 2, in the case of adopting a development method in which a thin layer of the same color is developed twice, the number of developments in which the photosensitive member and the development process associated therewith are performed around the transfer member. An example is shown in which only the minutes are arranged. 1 shows a state before the toner attached to the photosensitive member is transferred to the transfer member, and FIG. 2 shows a case where the toner attached to the photosensitive member is transferred to the transfer member.

  The liquid developing electrophotographic apparatus of the present invention has a developing mechanism comprising a photosensitive member neutralizing device 1, a charging device 2, an exposing device 3, a toner supply roller 4 and a developing roller 5 as a developing support around a photosensitive member 6. The image forming units 10a and 10b, which are developing devices of the same color, in which the cleaning mechanism 7 is sequentially formed, are arranged around the transfer body 11 that is the next stage image carrier. Although not shown, two image forming units 10 are provided in association with yellow / magenta / cyan / black, and two image forming units 10 are arranged around the transfer body 11.

  Note that the number of image forming units 10 is not limited to two, and N thin image forming units 10 are arranged around the transfer body 11 when developing the same color thin layer N times.

  The photoconductor neutralizing device 1 neutralizes the photoconductor 6. The charging device 2 charges the photoreceptor 6. The exposure device 3 forms an electrostatic latent image on the photosensitive member 6 by exposing the photosensitive member 6 using laser light or LED light emission. The toner supply roller 4 conveys the liquid developer while thinly extending from the toner reservoir and supplies the toner to the developing roller 5 in order to adhere the toner particles of the liquid developer to the photoreceptor 6. The developing roller 5 forms a toner layer having a predetermined toner layer thickness, and supplies the toner to the photosensitive member 6 according to the electric field between the developing roller 5 and adheres the toner to the exposed portion of the photosensitive member.

  For example, when the toner layer thickness 7.5 μm necessary for obtaining a predetermined image density shown in FIG. 8A is divided twice (doubled), the image forming unit 10a performs the first development. As the layer thickness, a toner layer having a toner layer thickness of 2.5 μm is formed on the developing roller 5a by transporting the liquid developer while thinly extending from the toner reservoir using the toner supply roller 4a. Is attached to the exposed portion of the photoreceptor 6a.

  In addition, the image forming unit 10b has a toner layer thickness of 5.0 μm on the developing roller 5b by transporting the liquid developer from the toner reservoir while thinly using the toner supply roller 4b as the second developing layer thickness. A toner layer having a thickness is formed, and the toner is attached to the exposed portion of the photoreceptor 6b. The cleaning mechanism 7 removes toner and pre-wet liquid remaining on the photoreceptor 6.

  In FIG. 2, the transfer body 11 transfers the toner attached to the photoreceptors 6a and 6b according to the electric field between the photoreceptors 6a and 6b. For example, when obtaining a toner layer thickness of 7.5 μm, the transfer body 11 first transfers toner having a toner layer thickness of 2.5 μm attached to the photoreceptor 6a as the first development, Subsequently, as the second development, toner having a thickness of 5.0 μm and the same color toner layer attached to the photoreceptor 6b is transferred. Subsequently, the toners of other colors attached to other photoconductors (not shown) are sequentially transferred twice.

  In the example shown in FIGS. 3 and 4, in the case of adopting a development method in which a thin layer of the same color is developed twice, the development process associated with the image forming unit is performed around the photosensitive member for the number of times of development. Only an example of arrangement is shown. 3 shows a state before the toner attached to the photosensitive member is transferred to the transfer member, and FIG. 4 shows a case where the toner attached to the photosensitive member is transferred to the transfer member.

  In the liquid developing electrophotographic apparatus of the present invention, a developing mechanism comprising a photosensitive member neutralizing device 1, a charging device 2, an exposing device 3, a toner supply roller 4 and a developing roller 5 as a developing support is provided around the photosensitive member 6. Two image forming units 10 formed one by one in sequence are arranged around the transfer body 11 which is the next stage image carrier in association with yellow / magenta / cyan / black.

  Note that the image forming unit 10 is not limited to two developing mechanisms including the photosensitive member neutralizing device 1, the charging device 2, the exposure device 3, and the toner supply roller 4 and the developing roller 5. Are developed N times, and N developing mechanisms each including a photoreceptor neutralizing device 1, a charging device 2, an exposure device 3, a toner supply roller 4 and a developing roller 5 are arranged around the photoreceptor 6. become.

  For example, in the case where the toner layer thickness 7.5 μm necessary for obtaining a predetermined image density shown in FIG. 8A is divided twice (doubled), the image forming unit 10 As the first development, the toner supply roller 4a is used to convey the liquid developer while being thinly extended from the toner reservoir, so that the development layer 5a has a toner layer thickness of 2.5 μm as the first development layer thickness. By forming a toner layer and supplying the toner to the photoconductor 6 according to the electric field between the photoconductor 6 and the toner, the toner adheres to the exposed portion of the photoconductor 6. Further, the toner having a toner layer thickness of 2.5 μm attached to the photosensitive member 6 is transferred to the transfer member 11.

  Next, as the second development, the toner supply roller 4b is used to convey the liquid developer while being thinly extended from the toner reservoir, thereby allowing the development roller 5b to have a toner layer thickness of 5.0 μm as the second development layer thickness. A toner layer having a thickness is formed, and the toner is supplied to the photoconductor 6 according to the electric field between the photoconductor 6 and the toner is attached to the exposed portion of the photoconductor 6. Further, the toner having a toner layer thickness of 5.0 μm attached to the photosensitive member 6 is transferred to the transfer member 11.

  Then, the cleaning mechanism 7 removes the toner and pre-wet liquid remaining on the photoreceptor 6. Subsequently, toners of other colors attached to other photosensitive members (not shown) are sequentially transferred.

  In the multiple development shown in FIGS. 1 to 4, when obtaining the predetermined image density by overlapping the same color of the thin layer multiple times at different densities each time, the toner layer thicknesses at the multiple development are made constant to each other. A development process configured to change the toner solid content ratio during development may be provided.

  For example, in the example shown in FIG. 1 and FIG. 2, the toner layer is applied to the developing roller 5a using the toner supply roller 4a as the first development from each toner reservoir storing the same color liquid developer having different toner solid content ratios. And supplying the toner to the photoconductor 6a according to the electric field between the photoconductor 6a and the toner adheres to the exposed portion of the photoconductor 6a. Next, as the second development, a toner layer having a different image density at the time of development is formed on the developing roller 5b using the toner supply roller 4b, and the toner is exposed in accordance with the electric field between the photosensitive member 6b. By supplying the toner to the body 6b, the toner adheres to the exposed portion of the photoreceptor 6b.

  The transfer body 11 transfers toner having different image densities during development attached to the photoconductors 6a and 6b according to the electric field between the photoconductors 6a and 6b. For example, the transfer body 11 first transfers the toner attached to the photoreceptor 6a as the first development, and then the image density of the same color attached to the photoreceptor 6b as the second development. Transfer different toner.

  It is also possible to provide a development process configured such that both the toner layer thickness and the toner solid content ratio are different when obtaining the predetermined image density by overlapping the same color of the thin layer multiple times at different densities each time. .

  The example of the multiple development shown in FIGS. 1 to 4 also has an advantage that the time required for image formation is not significantly increased compared to the single development.

  In the example shown in FIG. 5 and FIG. 6, in the case of adopting a development method in which a thin layer of the same color is developed N times, the mechanical basic configuration is almost the same as that of one development, but the photoconductor is the Nth time. And a mechanism for contacting the transfer body at every development (rotation). The cleaning mechanism is provided with a mechanism for contacting and retracting the photosensitive member in conjunction with the contact and retraction.

  As a result, when the same color thin layer is developed N times, the development results for N-1 times are superimposed on the photoconductor, and transferred to the transfer body at the time of the Nth development. Become. Note that this method requires means for changing the image density for each rotation.

  5 and 6, FIGS. 5 (a) and 6 (a) show a state before the toner that is superimposed and attached on the photosensitive member is transferred to the transfer member, and FIG. 5 (b) and FIG. 6 (b) shows a case where toners superimposed and attached on the photoreceptor are collectively transferred to the transfer body during the N-th development.

  The liquid developing electrophotographic apparatus of the present invention has a developing mechanism comprising a photosensitive member neutralizing device 1, a charging device 2, an exposing device 3, a toner supply roller 4 and a developing roller 5 as a developing support around a photosensitive member 6. The image forming unit 10 in which the cleaning mechanism 7 is sequentially formed is arranged for each color corresponding to yellow / magenta / cyan / black around the transfer body 11 which is the next image carrier.

  For example, in the case where the toner layer thickness 8.4 μm necessary for obtaining a predetermined image density is divided into three times (three times overlapping) as shown in FIG. Each time it is developed, it contacts the transfer body 11, and when retracted, the cleaning mechanism 7 is also interlocked and retracted. That is, the image of the next round is superimposed on the photoreceptor 6 on the image of the previous round.

  Further, the image forming unit 10 is provided with means for changing the developing density by changing the toner layer thickness for each turn, and the means will be described below.

  In FIG. 5, as means for changing the developing density by changing the toner layer thickness for each turn, the peripheral speed ratio between the photosensitive member 6 and the developing roller 5 is changed, or the developing roller 5 and the toner supply roller 4 are Means for changing the peripheral speed ratio are provided.

FIG. 9 shows an example of the relationship between the peripheral speed ratio between the developing roller 5 and the photosensitive member 6 and the toner print density (the peripheral speed between the developing roller 5 and the toner supply roller 4 is constant).
In FIG. 9, in the difference in the peripheral speed between the developing roller peripheral speed and the photosensitive member peripheral speed, the toner layer attached to the photosensitive member 6 becomes thicker as the developing roller peripheral speed is higher than the photosensitive member peripheral speed. Increase the development density.
On the other hand, as the developing roller peripheral speed is lower than the photosensitive member peripheral speed, the thickness of the toner layer deposited on the photosensitive member 6 is reduced and the developing density is lowered.
As described above, the peripheral speed ratio between the photosensitive member 6 and the developing roller 5 is changed, or the peripheral speed ratio between the developing roller 5 and the toner supply roller 4 is changed to change the toner layer thickness for each rotation. The development density is changed.

Further, when the peripheral speed ratio between the developing roller 5 and the toner supply roller 4 is changed, substantially the same result can be obtained. (Because the toner is a non-Newtonian fluid and an electric field is present, it does not match the so-called liquid lubrication theory.) The peripheral speed of the developing roller 5 and the photosensitive member 6 is constant.
That is, in the speed difference between the developing roller peripheral speed and the toner supply roller peripheral speed, as the developing roller peripheral speed is higher than the toner supply roller peripheral speed, the thickness of the toner layer attached to the developing roller 5 becomes thinner. Reduce development density.
On the other hand, as the developing roller peripheral speed is lower than the toner supply roller peripheral speed, the thickness of the toner layer attached to the developing roller 5 is increased and the developing density is increased.

  In FIG. 6, as a means for changing the development density by changing the toner layer thickness for each turn, a bias is applied to the toner supply roller 4 independently of the development roller 5, and the potential difference between the toner supply roller 4 and the development roller 5. Thus, there is provided means for controlling the toner supply amount to the developing roller 5.

FIG. 10 shows an example of the potential difference between the toner supply roller and the developing roller and the toner layer thickness. In FIG. 10, as the potential difference between the toner supply roller potential and the developing roller potential is negative and the negative potential difference is large, the thickness of the toner layer attached to the developing roller 5 is reduced and the developing density is lowered.
On the other hand, as the potential difference between the toner supply roller potential and the developing roller potential is positive and the positive potential difference is larger, the thickness of the toner layer attached to the developing roller 5 is thicker and the developing density is increased.
As described above, by changing the potential difference between the toner supply roller 4 and the developing roller 5, the toner layer thickness is changed for each turn to change the developing density.

  The example of the multiple development shown in FIGS. 5 and 6 also has an advantage of minimizing the size of the apparatus.

As described above, the liquid developing electrophotographic apparatus of the present invention is a liquid developing electrophotographic apparatus that employs a developing method in which a thin layer of the same color is developed N times for one original image. The image density at the time of the second development is the target solid density,
The developing process is 2 ^K-1 / (2 ^N -1) times (K = 1, 2, 3,..., N). As a result, multi-tone area gradation expression can be efficiently performed with a small number of developments, and high image quality, high density, and a wide dynamic range can be ensured.

  Further, in the liquid developing electrophotographic apparatus described above, when the same color thin layer is developed twice on one original image, the image density at the time of one development is α times the target solid density. Also, it is possible to express four gradations by providing a developing process in which the image density during the other development is (1−α) times (0.05 ≦ α <0.5) the target solid density.

It is explanatory drawing by Example 1 of this invention. It is explanatory drawing by Example 1 of this invention. It is explanatory drawing by Example 2 of this invention. It is explanatory drawing by Example 2 of this invention. It is explanatory drawing by Example 3 of this invention. It is explanatory drawing by Example 3 of this invention. The developing layer thickness at each development is shown when developing the toner layer thickness necessary for obtaining a predetermined image density a plurality of times according to the embodiment of the present invention. It is explanatory drawing which shows the specific example of the gradation expression by the Example of this invention. 9 shows an example of the relationship between the peripheral speed ratio and the toner print density according to Embodiment 3 of the present invention. It is a figure which shows the example of the electrical potential difference between toner supply roller-developing roller and toner layer thickness by Example 3 of this invention. It is explanatory drawing by the Example of this invention. It is a figure which shows the conceptual diagram of a toner layer division | segmentation, the toner layer thickness, and the example of a thin line image. It is a figure which shows the example which causes image quality degradation simultaneously when developing electric field intensity | strength is lowered in order to adjust a density | concentration.

Explanation of symbols

1: Photoconductor neutralization device 2: Charging device 3: Exposure device 4: Toner supply roller 5: Development roller 6: Photoconductor 7: Cleaning mechanism 10: Image forming unit 11: Transfer body

Claims (7)

In a liquid developing electrophotographic apparatus,
Around the photosensitive member, a developing device in which a predetermined number of photosensitive member static elimination devices, charging devices, exposure devices, and developing mechanisms are sequentially formed is disposed on the image carrier,
The developing device includes a developing process for changing the developing density, and obtains a predetermined image density by overlapping the same color of the thin layer multiple times at different densities each time.
A liquid developing electrophotographic apparatus characterized by the above. In the liquid developing electrophotographic apparatus,
Around the photoconductor, a plurality of image forming units of the same color in which a photoconductor neutralizing device, a charging device, an exposure device, and a developing mechanism are sequentially formed are arranged around the transfer body, which is the next image carrier,
A developing process configured such that a toner layer thickness and / or a solid content supplied to a developing support provided in each developing mechanism is different;
The liquid developing electrophotographic apparatus according to claim 1, wherein: In the liquid developing electrophotographic apparatus,
An image forming unit in which a plurality of photosensitive member static elimination devices, charging devices, exposure devices, and developing mechanisms are sequentially formed around the photosensitive member is arranged for each color around the transfer member, which is the next image carrier,
A developing process configured such that a toner layer thickness and / or a solid content supplied to a developing support provided in each developing mechanism is different;
The liquid developing electrophotographic apparatus according to claim 1, wherein: In the liquid developing electrophotographic apparatus,
An image forming unit in which a photosensitive member neutralizing device, a charging device, an exposure device, and a developing mechanism are sequentially formed around the photosensitive member is arranged around the transfer member, which is the next-stage image carrier, for each color.
The photosensitive member contacts the transfer member at every N-th development, and is retracted in conjunction with the cleaning mechanism at the time of retraction, so that the image of the next rotation can be superimposed on the photosensitive member on the previous rotation image. And a developing process including means for changing the peripheral speed ratio of the photosensitive member and the developing roller or the developing roller and the toner supply roller as the means for changing the developing density for each turn.
The liquid developing electrophotographic apparatus according to claim 1, wherein: In the liquid developing electrophotographic apparatus,
An image forming unit in which a photosensitive member neutralizing device, a charging device, an exposure device, and a developing mechanism are sequentially formed around the photosensitive member is arranged around the transfer member, which is the next-stage image carrier, for each color.
The photosensitive member contacts the transfer member at every N-th development, and is retracted in conjunction with the cleaning mechanism when retracted, so that the image of the next rotation can be superimposed on the photosensitive member on the image of the previous rotation. And a developing process comprising means for independently applying a bias to a toner supply roller for supplying the developing toner to the developing support and changing the value as means for changing the developing density for each revolution.
The liquid developing electrophotographic apparatus according to claim 1, wherein: In the liquid developing electrophotographic apparatus,
When developing a single original image with a thin layer of the same color superimposed N times, the image density at the K-th development is 2 ^K−1 / (2 ^N −1) times the target solid density (K = 1, 2, 3,..., N)
The liquid developing electrophotographic apparatus according to claim 1, 2, 3, 4 or 5. In the liquid developing electrophotographic apparatus,
When developing a thin layer of the same color twice on a single document image,
The image density at the time of one development is α times the target solid density,
A development process in which the image density during development on the other side is (1−α) times the target solid density (0.05 ≦ α <0.5);
The liquid developing electrophotographic apparatus according to claim 1, 2, 3, 4 or 5.

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