JP2010253807A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an image with high quality to be formed by suppressing bleeding and beading without requiring the special surface treatment of an intermediate transferring body in an intermediate transferring system which performs image formation by density gradation by mixing liquids delivered from recording heads. <P>SOLUTION: In a state that a bridge of a liquid column LP based on an ink 15 is formed between a nozzle 13 of the recording head and the intermediate transferring body 20 such an electric potential that can electrolyze water included in the bridge is applied by electric power 30 to form an aggregate 14 of the ink, and to form an ink dot 16 in which the aggregate 14 is a main component on the surface of the intermediate transferring body 20. Thereafter, a density adjusting liquid is added to the same position where the ink dot 16 is formed on the intermediate transferring body 20 and mixed therewith to form the image. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for forming an image on a recording material by forming an image on an intermediate transfer body by an ink jet method and transferring the image to the recording material (recording medium).

In general, ink jet printers use inks of four colors, cyan, magenta, yellow, and black. As a method of expressing gradation, area gradation that reproduces gradation with a colored area in a unit area has been used.
As another method for expressing the gradation, there is a density gradation that expresses the gradation by the difference in ink density. Comparing the two, the area gray scale requires a larger area for expressing pixel data having the same information amount, and the resolution decreases. Further, in the area gradation, the area of the recording medium surface becomes larger than the ink coloring area in the low density region, so that the graininess becomes conspicuous.
As a method for compensating for the defects of area gradation, there is a method of improving color reproducibility by adding intermediate colors (light cyan, light magenta, etc.) in addition to four colors of cyan, magenta, yellow, and black. Although this method has improved the image quality, the only way to further improve the image quality is to increase the type of ink, which is not practical.

In view of this, there has been proposed a method of controlling the ink density on the recording medium by mixing a plurality of liquids having different densities after being ejected from the recording head.
For example, Patent Document 1 proposes a method in which ink droplets of two types of density are ejected from nozzles and mixed on recording paper to obtain a necessary gradation density.
However, in this method, since the phenomenon that the recording paper absorbs ink occurs at the same time, it is difficult to obtain a desired density on the paper surface.
Therefore, instead of mixing the liquid on the recording paper as in Patent Document 1, it is considered that the liquid needs to be mixed and applied on the recording paper by some means.

In Japanese Patent Laid-Open No. 2004-228688, a configuration in which the discharge ports are concentric so that the ink discharged from the discharge ports lands on the discharge target surface of the ink so that the inks mix with each other when they collide with each other. Proposed.
This method has the merit that ink is mixed immediately before applying it to paper, but if all of the flight path, timing, and speed of ink discharged from each nozzle are not accurate, collision between liquid enemies will not occur, In order to produce a desired color, the volume of each ink droplet must be finely controlled and must be ejected accurately, and such control is very difficult and impractical with current technology.
On the other hand, a method using an intermediate transfer method in which a liquid is mixed on an intermediate transfer member and transferred onto a recording sheet has been proposed.
In general, the intermediate transfer method is not easily influenced by the type of recording paper, and the ink jet head is not close to the recording paper, so there is an advantage that the head is not contaminated by dust on the recording paper. In order to improve transferability, the surface is often water-repellent to improve the transferability. There is a problem that a phenomenon called beading in which ink that is landed after ink that has landed in advance is attracted and ink droplets are gathered occurs and the image quality is deteriorated.

  In Patent Document 3, in order to solve such a problem, ink and a transparent liquid are applied to a parent ink region of an intermediate transfer member having a plurality of parent ink regions surrounded by an ink repellent region, and transferred to a recording member. A method has been proposed.

  In the method disclosed in Patent Document 3, since the ink and the liquid are contained in the parent ink region, bleeding and beading are improved, but it is difficult to put it to practical use from the viewpoint of durability of the surface-treated region.

The present invention has been made in view of such circumstances, and an object thereof is to provide an apparatus and an image forming method for forming a high-quality image by an inkjet method.
Specifically, in an intermediate transfer method that forms an image with density gradation by mixing liquid ejected from a recording head, bleeding and beading are suppressed without requiring special surface treatment of the intermediate transfer member. An object is to provide an image forming apparatus and an image forming method capable of forming a high-quality image.

  In order to achieve the above object, according to the present invention, the mixed solution is agglomerated on the intermediate transfer member, thereby increasing the independence of each pixel and suppressing liquid mixing between the pixels.

  Specifically, according to the first aspect of the present invention, it is possible to temporarily form a plurality of recording heads having nozzles for discharging liquid and a bridge of liquid columns made of the liquid between the nozzles. Water contained in the bridge of the liquid column is electrically connected between the liquid and the conductive surface, and an intermediate transfer body having a conductive surface capable of forming an image by discharging the liquid. Formed in the intermediate transfer body, a potential applying means for applying a potential that can be decomposed, a step of applying a plurality of types of liquid to the same location on the intermediate transfer body, and mixing these liquids. And an image forming apparatus characterized by having transfer means for transferring the image to a recording medium.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the liquid to be mixed is a conductive ink and a density adjusting liquid.
According to a first aspect of the present invention, in the image forming apparatus according to the second aspect, the density adjusting liquid is transparent or has the same color as the color of the recording medium.
According to a third aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the total amount of liquid applied to each pixel on the intermediate transfer member is made constant.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the ink is applied prior to the density adjusting liquid.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the second to fifth aspects, a pigment is dispersed in the ink by an anionic dispersant.
The invention according to claim 7 is the image forming apparatus according to claim 5 or 6, wherein the liquid to be mixed is
(PH-7 of the ink) × (pH-7 of the concentration adjusting liquid)> 0
It satisfies the following conditions.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the second to sixth aspects, the image forming apparatus further includes a potential applying unit that applies a potential to the density adjusting liquid. The potential applied to the ink and the potential applied to the concentration adjusting liquid have opposite signs.

The invention according to claim 9 is an image forming method in which a liquid is ejected from a nozzle of a recording head, an image is formed on the surface of the intermediate transfer member, and the image is transferred to a recording medium. The liquid column bridge made of the liquid is temporarily formed between the liquid surface and the conductive surface, and the liquid column bridge is formed between the liquid and the conductive surface. An electric potential capable of electrolyzing water contained in the bridge is applied, and a liquid of a different type from the liquid is applied to the same portion of the intermediate transfer body to which the liquid has adhered to form an image. It is characterized by that.
According to a tenth aspect of the present invention, in the image forming method according to the ninth aspect, the liquid to be mixed is a conductive ink and a density adjusting liquid.

According to the present invention, by mixing a plurality of liquids on the intermediate transfer member, the liquids can be mixed without considering the absorption of the liquid unlike the case of the recording medium. By controlling the discharged liquid to temporarily form a bridge of the liquid column between the recording head and the intermediate transfer member, at the moment when the solution contacts the intermediate transfer member, the vicinity of the interface with the intermediate transfer member Ions that produce an aggregating effect in the solution are efficiently generated, and the solute can be efficiently aggregated simultaneously with the landing liquid.
As a result, the color and density of the colored region in one pixel of the intermediate transfer body can be controlled on the spot without causing the blur between adjacent solution dots, and a high-quality image can be formed.
Further, the color material density of the colored region on the intermediate transfer member can be lowered by mixing the ink and the density adjusting liquid. Therefore, by controlling the amount of liquid to be mixed, gradations such as cyan, magenta, yellow, and black can be expressed by the density on the recording medium, and a high-quality image can be formed.

Further, since the density adjusting liquid is transparent or has the same color as the color of the recording medium, it can function as a density adjusting liquid for ink of any color, and only one type of density adjusting liquid is required.
In addition, by making the total amount of liquid applied to each pixel on the intermediate transfer body constant, the colored area on the intermediate transfer body can be made constant, and by changing the ratio of the applied liquid, density control is possible. It becomes.
In addition, by applying the ink onto the intermediate transfer body prior to the density adjustment liquid, the density adjustment liquid is applied to the ink image that has already been applied to the intermediate transfer body, so that the coloring member spreads and the order is reversed. Compared to certain cases, the image quality is high.
Further, by using an ink in which a pigment is dispersed with an anionic dispersant, the degree of freedom of the ink is increased and an image can be formed at a low cost.
Further, by using a combination of an ink and a concentration adjusting solution that satisfies (ink pH-7) × (density adjusting solution pH-7)> 0, aggregation of colored members already applied to the intermediate transfer member is achieved. By loosening the degree, the colored member can be efficiently spread.
In addition, by setting the potential applied to the ink and the potential applied to the density adjusting liquid to opposite signs, the degree of aggregation of the colored member already applied to the intermediate transfer member can be relaxed and the colored member can be efficiently expanded.

FIG. 2 is a schematic diagram illustrating a configuration of a recording head of an image forming apparatus according to an embodiment of the present invention and a relationship with an intermediate transfer member. It is a control block diagram. It is a schematic diagram which shows the process of ink dot formation. FIG. 3 is a schematic diagram illustrating an ink aggregation phenomenon. It is a schematic diagram which shows the process in which a density | concentration adjustment liquid is provided and a density | concentration is made low. FIG. 4 is a schematic diagram illustrating a configuration of a recording head that discharges a concentration adjusting liquid. It is a schematic diagram which shows the process in which an alkaline density | concentration adjustment liquid is provided and a density | concentration is made low. It is a schematic diagram which shows the process in which a density | concentration adjustment liquid is charged to reverse polarity and a density | concentration is made low. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus. It is a schematic block diagram which shows the other example of an image forming apparatus.

Embodiments of the present invention will be described below with reference to the drawings.
First, based on FIG. 1, the configuration of a recording head of an image forming apparatus (inkjet printer; the overall configuration will be described later) according to the present embodiment will be described.
The recording head 10 includes a nozzle plate 11 having nozzles 13, an ink chamber 12, conductive ink 15 containing water as a liquid contained in the ink chamber 12, and ink that discharges the ink 15 from the nozzle 13. It comprises a piezoelectric element 50 (see FIG. 2) as discharge means.

The ink 15 uses an ink in which a pigment is dispersed with an anionic dispersant, and uses four colors of cyan, magenta, yellow, and black. In the present embodiment, the piezoelectric element is used as the ink discharging means as described above. Ink is discharged from the nozzle 13 in accordance with the voltage pulse applied to the piezoelectric element 50 and is made to fly to the intermediate transfer body 20. .
When it is desired to lower the color material density in the intermediate transfer body 20, a density adjusting liquid is applied to the same position by the same method and mixed on the intermediate transfer body. Also, various colors of ink can be created by mixing cyan, magenta, yellow, and black and appropriately changing the ratio of the amounts of these inks.
Here, a colorless and transparent liquid is used as the concentration adjusting liquid. The degree of colorless and transparent mentioned here is such that it can be recognized as colorless and transparent with the naked eye. The concentration adjusting liquid does not necessarily need to be colorless and transparent, and light ink or the like can be used. However, if it is transparent or the same color as the color of the recording medium (generally white), the ink of any color can be used. It can function as a concentration adjusting liquid.

When each ink is ejected, it is necessary to form a liquid column that temporarily becomes a bridge state between the nozzle 13 and the intermediate transfer member. From the ease of forming such a liquid column state, The gap with the surface of the intermediate transfer member 20 is preferably very close.
However, if the distance is too close, it becomes difficult to maintain the gap between the surface of the moving intermediate transfer member 20 and the nozzle plate 11, so the gap distance is preferably about 50 μm to 200 μm, and in this embodiment, it is set to 100 μm.
A factor that affects the formation of the liquid column as well as the gap distance is a voltage pulse applied to the piezoelectric element, and is largely a peak voltage and a pulse width. In this embodiment, a driving pulse is applied so that the liquid column formation time is several tens of μs. In order to apply electrochemical energy to the liquid column formed in this way, it is necessary to pass an electric current between the ink interposed in the vicinity of the nozzle 13 and the intermediate transfer member 20. In order to flow current effectively, it is preferable that both the nozzle plate 11 and the intermediate transfer member 20 have high conductivity. In this embodiment, the recording plate (commercial inkjet printer) in which the nozzle plate 11 is made of metal. GX5000 (manufactured by Ricoh) was used, and the intermediate transfer member 20 was a silicone rubber in which carbon was dispersed.

Although not shown, the intermediate transfer member 20 has a structure in which a silicone rubber layer having a volume resistivity of about 5 Ω · cm is formed on an aluminum base with a thickness of 0.2 mm.
Then, when a liquid column that bridges the nozzle plate 11 and the intermediate transfer member 20 is formed, a power source 30 is connected as a potential applying means so that a current can flow in the liquid column. The potential is set so that the surface of the transfer body 20 becomes an anode.

  As shown in FIG. 2, the recording head 10 is controlled by a control means 60 as a microcomputer. The control means 60 controls the piezoelectric element 50 via the head drive circuit 52. ON / OFF of voltage application by the power supply 30 is performed via a power switch 54.

Next, a specific ink dot formation process will be described based on FIG. 1, FIG. 3, and FIG. FIG. 1 shows an initial state, and an ink meniscus is formed at the nozzle 13 site.
The power supply 30 is in a voltage application state, and is always in a voltage application state in the subsequent processes. FIG. 2A is a schematic diagram showing a state in which a liquid column is being formed by applying an appropriate drive pulse to the piezoelectric element 50. At this time, a very small amount of induced current flows in the power supply 30 as the charged liquid column tip moves, but this current does not contribute to the effect of the process of the present invention.
FIG. 2B is a schematic diagram showing a state in which the liquid column tip has landed on the surface of the intermediate transfer body 20 to form a bridge-shaped liquid column LP. A large current begins to flow simultaneously with the liquid landing on the surface of the intermediate transfer member 20 at the tip of the liquid column.

Very initially, it is assumed that a charging current for forming an electric double layer at the interface between the intermediate transfer member 20 and the liquid flows, and after the electric double layer is sufficiently formed, an oxidation reaction starts at the interface. . The oxidation in this embodiment is mainly performed on water molecules, and a lot of hydrogen ions are generated in a local ink region near the interface.
As a result, an ink aggregation phenomenon appears. The schematic diagram of this state is shown in FIGS. Due to this phenomenon, the ink in the vicinity of the interface aggregates to form an aggregate 14 as shown in FIG. Thereafter, the liquid column LP is divided according to the drive pulse to the piezoelectric element 50, and as shown in FIG. 3C, ink dots 16 mainly composed of the aggregates 14 are formed on the surface of the intermediate transfer body 20. The
By repeating such ink dot formation, it is possible to fundamentally solve the problem that different ink dots mix and spread. That is, the ink dot 16 maintains the independent region property as one pixel by the cohesive force, thereby suppressing bleeding and beading.

The degree of aggregation of the aggregate 14 can be controlled according to the degree of oxidation reaction. Specifically, it can be appropriately controlled by the drive pulse to the piezoelectric element, the voltage applied by the power supply 30, the physical properties of the ink itself, and the like. It is.
When it is desired to reduce the density of the image, as shown in FIG. 5, the color adjustment liquid 17 is applied to the ink dots 16 formed on the intermediate transfer body 20 at the same position (same location), so that the color It can be expected that the material spreads on the intermediate transfer member 20 and the density decreases.
As shown in FIG. 6, the discharge of the colorless concentration adjusting liquid 17 as a liquid different in kind from the ink 15 is performed by a recording head 10 </ b> T as a concentration adjusting liquid discharging unit having the same configuration as the recording head 10. The control of the recording head 10T is performed by the control means 60 in the same manner as the recording head 10.

However, there is a concern that the ink does not spread efficiently only by applying the concentration adjusting liquid to the once aggregated ink (see the rightmost diagram in FIG. 5).
As a countermeasure, the colored member can be efficiently spread by loosening the degree of aggregation of the colored member by making the concentration adjusting liquid 17 alkaline (see FIG. 7).
As another countermeasure, as shown in FIG. 8, a power supply 31 as a potential applying means is connected between the nozzle plate 11T for concentration adjusting liquid and the intermediate transfer member 20, and the applied voltage is a sign opposite to that of the power supply 30. By doing so, it becomes possible to loosen the degree of aggregation of the colored member and to efficiently spread the colored member.

Next, an embodiment in which the effect of the above process is confirmed will be described.
[Example 1]
The following were prepared as a concentration adjusting liquid and a recording liquid.
<Concentration adjustment solution>
・ Diethylene glycol: 20.0% by mass
・ Distilled water: remaining amount
<Black recording liquid>
-Sulfonic acid group-bonded carbon black pigment dispersion (CAB-O-JET-200, solid content 20% by mass, manufactured by Cabot Specialty Chemicals Inc.): 35.0% by mass
2-pyrrolidone: 10.0% by mass
・ Glycerin: 14.0% by mass
Propylene glycol monobutyl ether: 0.9% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.
<Yellow recording liquid>
-Sulfonic acid group-bonded yellow pigment dispersion (CAB-O-JET-270Y, solid content 10 mass%, manufactured by Cabot Specialty Chemicals Inc.): 40.0 mass%
・ Triethylene glycol: 15.0 mass%
・ Glycerin: 25.0% by mass
Propylene glycol monobutyl ether: 6.0% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.
<Magenta recording liquid>
-Sulfonic acid group-bonded magenta pigment dispersion (CAB-O-JET-260M, solid content 10% by mass, manufactured by Cabot Specialty Chemicals, Inc.): 40.0% by mass
・ Diethylene glycol: 20.0% by mass
Propylene glycol monobutyl ether: 3.0% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.
<Cyan recording liquid>
-Sulfonic acid group-bonded cyan pigment dispersion (CAB-O-JET-250C, solid content 10% by mass, manufactured by Cabot Specialty Chemicals Inc.): 40.0% by mass
・ Ethylene glycol: 4.0% by mass
Triethylene glycol: 14.0% by mass
Propylene glycol monobutyl ether: 6.0% by mass
・ Sodium dehydroacetate: 0.1% by mass
-Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5 mass% aqueous solution of lithium hydroxide, and pressure filtration was performed with a membrane filter having an average pore diameter of 0.8 µm.

FIG. 9 shows an example of a configuration diagram of an image forming apparatus for realizing the image forming method of the present invention. The drum 20 as an intermediate transfer member is formed by forming a silicone rubber layer having a volume resistivity of about 5 Ω · cm on the outer periphery of an aluminum base tube with a thickness of 0.2 mm, and the outer peripheral linear velocity is 50 mm / s counterclockwise. Is driven to rotate.
Around the drum 20 is a line type recording head (commercial inkjet printer GX5000, manufactured by Ricoh) 10Y, 10M, 10C which is separated from the surface of the drum 20 with a gap distance of about 100 μm and the nozzle plate 11 is made of metal. 10K, 10T are arranged. These recording heads have the same configuration as the recording head 10 shown in FIG.
The yellow ink is used for the recording head 10Y, the magenta ink is used for the recording head 10M, the cyan ink is used for the recording head 10C, and the black ink is used for the recording head 10K. 10T is filled with the concentration adjusting liquid 17 by a supply means (not shown).

For the recording heads 10Y, 10M, 10C, and 10K, a power source 30 capable of supplying a sufficient current is connected between each metal nozzle plate 11 and the drum 20. The voltage of the power supply 30 can be arbitrarily changed by a voltage changing means (control means 60) (not shown).
Based on the ink dot formation process described with reference to FIGS. 1 and 3, the control means 60 can form ink dots of an arbitrary pattern made of the density adjusting liquid and each color ink on the surface of the drum 20.
Further, a pressure roller 70 for nipping and pressure-conveying the paper S as a recording medium and an initialization unit 80 for initializing the surface of the drum 20 are provided. The sheet S is fed at a predetermined timing by a sheet feeding unit (not shown) (including a registration roller pair).

The pressure roller 70 is provided with a rubber layer having a thickness of 5 mm as a surface layer for securing a paper conveying force with respect to a metal core. In the initialization means 80, a fluororubber cleaning blade is in contact with the drum 20 in order to remove ink components and the like adhering to the surface of the drum 20.
The power supply means (control means 60) maintains a potential difference between the conductive nozzle plate of each recording head 10 and the drum 20, so that the drum 20 side becomes an anode.
A mirror-reversed image was formed on the intermediate transfer member by using the density adjusting liquid and each color ink to set the potential difference between the conductive nozzle plate of each recording head 10 except 10T and the drum 20 to 120V.
Subsequently, an image is obtained by performing adhesive transfer on plain paper as the paper S.

As an evaluation method of the present embodiment, an image obtained by applying one drop of magenta ink on the intermediate transfer body 20 using the recording head 10M and an image obtained by applying one drop of magenta ink on the intermediate transfer body 20 using the recording head 10M. The images after the density adjustment liquid was applied to the same position using the recording head 10T and the images after adhesive transfer to plain paper were compared.
As a result, it was confirmed that the latter had a larger colored area and a lower density than the former, and the gradation could be expressed by the pigment concentration.

[Example 2]
The following was prepared as a concentration adjusting solution.
<Concentration adjustment solution>
・ Diethylene glycol: 20.0% by mass
Distilled water: remaining amount Subsequently, the pH was adjusted to 9.1 with a 5% by mass aqueous solution of lithium hydroxide.
The other conditions are the same as in Example 1. Therefore, the relationship between the ink and the density adjusting liquid satisfies the following conditions.
(PH-7 of ink) × (pH-7 of concentration adjusting solution)> 0
The image obtained by applying one drop of magenta ink on the intermediate transfer body 20 using the recording head 10M and then applying the density adjusting liquid to the same position using the recording head 10T was compared with the image obtained by reducing the density in Example 1. However, the image created this time had less uneven colored areas.
This is considered to be an effect due to the moderate remelting of the aggregated dots. Therefore, it can be said that a high-quality image was formed by the present Example 2.

[Example 3]
The following was prepared as a concentration adjusting solution.
<Concentration adjustment solution>
・ Diethylene glycol: 20.0% by mass
・ Lithium chloride: 0.1% by mass
Distilled water: remaining amount FIG. 10 shows an example of a configuration diagram of an image forming apparatus corresponding to the third embodiment. In addition to the configuration of the first embodiment (FIG. 9), a power source 31 capable of supplying a sufficient current is connected between the metal nozzle plate of the recording head 10T and the drum 20.
The voltage of the power supply 31 can be arbitrarily changed by the voltage changing means (control means 60), but the voltage sign is set opposite to that of the power supply 30. A potential difference of 60 V is maintained between the conductive nozzle plate of each recording head 10T and the drum 20 by the power supply means (control means 60) so that the drum 20 side becomes the cathode. Other conditions are the same as in the first embodiment.
Similar to Example 2, an image obtained by applying one drop of magenta ink to the intermediate transfer member using the recording head 10M and then applying the density adjusting liquid to the same position using the recording head 10T, and a lower density in Example 2 were used. When these images were compared, an image equivalent to the image created in Example 2 was obtained. This is also considered to be an effect due to the moderate remelting of the aggregated dots as in the previous case.

In the above-described embodiment (including the examples), the intermediate transfer member is exemplified as a plate and a drum. However, the intermediate transfer member is not limited to this and may be an endless belt or a sheet.
The inkjet head is not limited to the fixed full line type, and may be a shuttle type that can move in the main scanning direction on the recording medium.
Further, the ink ejection method may be a shape deformation element method other than the piezoelectric element, or other means such as a heater method. The applicable ink set can be applied to general commercially available inks although the effect of the invention is large or small.
Further, the number of mixed droplets of ink and density adjusting liquid is not limited to one drop, and the ratio of ink and density adjusting liquid is not limited to 1: 1.

DESCRIPTION OF SYMBOLS 10 Recording head 13 Nozzle 15 Ink as liquid 17 Concentration adjustment liquid 20 Intermediate transfer body 30, 31 Power supply as potential application means 70 Pressure roller as transfer means S Paper as recording medium

JP-A-6-305163 JP 2008-188803 A JP 2007-196667 A

Claims (10)

A plurality of recording heads having nozzles for discharging liquid;
An intermediate transfer member having a conductive surface capable of temporarily forming a bridge of a liquid column made of the liquid between the nozzle and capable of forming an image by discharging the liquid;
A potential applying means for applying a potential capable of electrolyzing water contained in the bridge of the liquid column between the liquid and the conductive surface;
Mixing these liquids by applying a plurality of types of liquids to the same location on the intermediate transfer member; and
An image forming apparatus comprising: a transfer unit that transfers an image formed on the intermediate transfer member to a recording medium. The image forming apparatus according to claim 1.
An image forming apparatus, wherein the liquid to be mixed is a conductive ink and a density adjusting liquid. The image forming apparatus according to claim 2.
An image forming apparatus, wherein the density adjusting liquid is transparent or has the same color as that of a recording medium. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus characterized in that a total amount of liquid applied to each pixel on the intermediate transfer member is made constant. In the image forming apparatus according to any one of claims 2 to 4,
An image forming apparatus, wherein the ink is applied prior to the density adjusting liquid. In the image forming apparatus according to any one of claims 2 to 5,
An image forming apparatus, wherein the ink has a pigment dispersed by an anionic dispersant. The image forming apparatus according to claim 5 or 6,
The liquid to be mixed is
(PH-7 of the ink) × (pH-7 of the concentration adjusting liquid)> 0
An image forming apparatus characterized by satisfying the following condition. The image forming apparatus according to any one of claims 2 to 6,
It has a potential applying means for applying a potential to the concentration adjusting liquid, and the potential applied to the ink and the potential applied to the concentration adjusting liquid have opposite signs with respect to the intermediate transfer member. An image forming apparatus. In an image forming method in which liquid is ejected from a nozzle of a recording head, an image is formed on the surface of an intermediate transfer member, and the image is transferred to a recording medium.
Temporarily forming a bridge of a liquid column made of the liquid between the nozzle and the conductive surface of the intermediate transfer member;
In a state where a bridge of the liquid column is formed, a potential capable of electrolyzing water contained in the bridge is applied between the liquid and the conductive surface,
An image forming method, wherein an image is formed by applying and mixing a liquid of a different type from the liquid at the same location of the intermediate transfer body to which the liquid has adhered. The image forming method according to claim 9.
An image forming method, wherein the liquid to be mixed is a conductive ink and a density adjusting liquid.

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