JP2012252140A - Wet-type image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet-type image forming apparatus capable of measuring image density with high accuracy.SOLUTION: An image density measuring part 17 comprises: a carrier liquid applying roller 34; a measurement body 35; a cleaning device 33; a density detection sensor 31; and a voltage supply device 36 for controlling bias. Carrier liquid is applied to a photoreceptor 1 using the carrier liquid applying roller 34. A patch image reaches a nip area between the photoreceptor 1 and the measurement body 35 and then is transferred to the measurement body 35. When the patch image is transferred to the measurement body 35, carrier liquid is supplied and the patch image is transferred from the photoreceptor 1 to the measurement body 35.

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and relates to a wet image forming apparatus that forms a toner image using a wet liquid developer.

  In an electrophotographic image forming apparatus, an electrostatic latent image is developed on a photosensitive member with toner using a developing device. Then, for example, the electrostatic latent image developed on the photoconductor is transferred to a recording sheet to form an image. In the transfer process of such an image forming apparatus, an electrostatic transfer method is generally employed.

  When transferring a toner image onto a sheet, which is a transfer target, a voltage is applied from the back side of the sheet placed so as to face the photoreceptor by a transfer roller or the like, and an electric field is formed between the photoreceptor and the recording sheet. Thus, the toner image is electrostatically attracted to the recording paper by this electric field.

  Thereafter, the transferred toner image is fixed on the recording paper by pressure fixing with a fixing device.

  On the other hand, in recent years, in an image forming apparatus that requires higher image quality and higher resolution, such as an office printer for mass printing or an on-demand printing apparatus, a liquid developer that has a small toner particle diameter and is less likely to cause toner image disturbance. There is known a wet developing apparatus using the above. This wet developing apparatus has the advantages that the average particle diameter of the toner is as small as 0.1 to 2 μm, so that a high-resolution image can be obtained, and a uniform image can be obtained because of its high fluidity because of the liquid. ing.

  In this wet image forming apparatus, it is possible to adjust image quality such as image density by changing image forming conditions including various elements including a bias potential applied to each part of the apparatus. In addition, the image density of the toner image may be different due to changes in the surrounding environment of the apparatus such as individual differences of the apparatus, changes with time, temperature and humidity.

  Therefore, a density control technique for controlling the image density by adjusting an image forming condition that affects the image density among the above elements has been proposed.

  In general, an optical detection method is used to detect the toner amount of a patch image, and the result is fed back to the developing device.

  For example, a patch image (detection pattern) having a plurality of density gradations is formed outside the image forming area, and this is read by an optical detection method to determine whether the toner is within the reference toner amount range.

  In an on-demand printing apparatus that requires high image quality, stability, and the like, it is necessary to carry out such a detection process in detail and stabilize the image density.

  In this regard, according to Patent Document 1, there is proposed a method of providing a transfer unit to transfer a patch image formed on an image carrier and measuring the image density of the patch image.

Japanese Patent No. 3767838

  However, in the method of measuring the image density by transferring the patch image to the transfer means, the patch image is transferred in a state where granular unevenness has occurred unless there is an appropriate amount of carrier liquid at the time of transfer, and the accuracy is high. There is a problem that the image density cannot be measured.

  The present invention has been made to solve the above problems, and an object thereof is to provide a wet image forming apparatus capable of measuring an image density with high accuracy.

  A wet image forming apparatus according to an aspect of the present invention is a wet image forming apparatus that forms a toner image on an image carrier using a liquid developer in which toner is dispersed in a carrier liquid, and an image pattern on the image carrier. An image forming unit for forming the image forming unit, a measurement body provided in contact with the image carrier and for transferring a density detection image pattern formed on the image carrier, and a density detection transferred to the measurement body. Carrier liquid is supplied to the nip area where the image carrier and the measuring body are contacted when detecting the density of the image pattern and detecting the density of the density control unit for controlling the density and the density of the image pattern for density detection. Carrier liquid replenishing means.

  Preferably, the measurement body removes excess carrier liquid in the image pattern formed on the image carrier, except when detecting the density of the image pattern for density detection.

  Preferably, the apparatus further includes a cleaning device that is provided in contact with the measurement body and removes the image pattern for density detection.

  Preferably, at least a part of the measurement body is provided in a hollow shape made of a light transmitting member, and the concentration control unit receives a light emitting unit that emits light and light provided to face the light emitting unit. One of the light emitting part and the light receiving part is disposed within the hollow shape of the measuring body.

  The wet image forming apparatus according to the present invention is provided with a measuring body for transferring an image pattern for density detection formed on the image carrier, and when detecting the density of the image pattern for density detection, Carrier liquid replenishing means is provided for supplying the carrier liquid to the nip region in contact with the measurement body. With this configuration, since the carrier liquid is supplied to the nip region between the image bearing member and the measuring member, it is possible to measure the image density with high accuracy by suppressing density unevenness during transfer.

It is a schematic block diagram which shows an example of the wet image forming apparatus according to Embodiment 1 of this invention. It is a schematic block diagram which shows an example of another wet image forming apparatus according to embodiment of this invention. It is a figure explaining another structure of an image density measurement part. It is a figure explaining the example of the measurement body 35 according to embodiment of this invention. It is a figure explaining the example of the carrier liquid application roller 34 according to embodiment of this invention.

  FIG. 1 is a schematic configuration diagram showing an example of a wet image forming apparatus according to the first embodiment of the present invention.

  Referring to FIG. 1, the wet image forming apparatus according to the first embodiment of the present invention is provided with a photoreceptor 1 that is a drum-shaped image carrier, and around the photoreceptor 1 in the rotation direction indicated by an arrow. A developing roller 24, an image density measuring unit 17, a transfer roller 11, a cleaning blade 121, a charging device 141, and an exposure device 151 are disposed in order.

  The surface of the photoreceptor 1 is uniformly charged to a predetermined surface potential by the charging device 141. Thereafter, image information is exposed by the exposure device 151 to form an electrostatic latent image on the surface of the photoreceptor 1. Next, the electrostatic latent image on the photoreceptor 1 is developed with a liquid developer containing toner particles and a carrier liquid by the developing roller 24 of the developing device, and a toner image is formed on the surface of the photoreceptor 1. At this time, not only toner particles but also a carrier liquid as a dispersion medium adheres to the surface of the photoreceptor 1.

  Then, the toner image formed on the surface of the photoreceptor 1 is conveyed to a transfer portion that is a portion facing the transfer roller 11. In the transfer portion, the transferred member 10 is conveyed in the direction of the arrow (direction d), and the toner particles on the photosensitive member 1 are transferred to the transferred member by the force of the voltage having the opposite polarity to the toner particles applied to the transfer roller 11. 10 is transferred. Then, the member 10 to which the toner particles are transferred is conveyed to a fixing unit (not shown) to fix the toner image.

  On the other hand, a cleaning blade 121 is provided on the photosensitive member 1 after passing through the transfer portion, and collects transfer residual toner particles and dispersion medium remaining on the photosensitive member 1. The photoreceptor 1 from which the toner particles and the dispersion medium have been collected is exposed by an eraser lamp (not shown), and the latent image potential is cancelled. By repeating these steps, images are printed one after another.

  Here, the liquid developer includes, as main components, an insulating liquid that is a carrier liquid, toner particles that develop an electrostatic latent image, and a dispersant that disperses the toner particles.

  The carrier liquid can be used without particular limitation as long as it is generally used for an electrophotographic liquid developer. For example, as the carrier liquid, an isoparaffin-based isopar (G, H, L, M, etc.) can be used. (Exxon Mobile), IP solvent (1620, 2028, 2835, etc.) (Idemitsu Kosan) and paraffinic Moresco White (P-40, P-70, P-120) (Matsumura Oil Research Institute). it can. It is also possible to use silicon oil or mineral oil.

  The toner particles are mainly composed of a resin and a pigment or dye for coloring. The resin has a function of uniformly dispersing pigments and dyes in the resin and a function as a binder when fixing on a recording sheet.

  The toner particles can be used without any particular limitation as long as they are generally used for electrophotographic liquid developers. As the toner binder resin, for example, a thermoplastic resin such as polystyrene resin, styrene acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, or polyurethane resin can be used. It is also possible to use a mixture of a plurality of these resins.

  Also, commercially available pigments and dyes used for coloring the toner can be used. For example, carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, etc. can be used as the pigment. Solvent red 27, acid blue 9, or the like can be used as the dye.

  As a method for adjusting the liquid developer, it can be adjusted based on a commonly used technique. For example, the binder resin and the pigment are melt-kneaded using a pressure kneader, a roller mill or the like at a predetermined blending ratio and uniformly dispersed, and the obtained dispersion is finely pulverized by, for example, a jet mill. By classifying the obtained fine powder with, for example, an air classifier, a colored toner having a desired particle diameter can be obtained. The obtained toner particles are mixed with an insulating liquid as a carrier liquid at a predetermined blending ratio. This mixture can be uniformly dispersed by a dispersing means such as a ball mill to obtain a liquid developer.

  The average particle diameter of the toner can be 0.1 μm to 5 μm because the wet image forming method is adopted. If the particle size is less than 0.1 μm, the developability is greatly reduced, and if the particle size is larger than 5 μm, the image quality is lowered.

  The ratio of the toner particle mass to the liquid developer mass is suitably about 10 to 50%.

  If it is less than 10%, the toner particles are likely to settle, and there is a problem with the stability over time during long-term storage, and it is necessary to supply a large amount of liquid developer in order to obtain the required image density. The carrier liquid adhering to the recording paper is increased, and there is a possibility that the vapor processing when dried at the time of fixing becomes a problem. On the other hand, when it exceeds 50%, the viscosity of the liquid developer becomes too high, and it may be difficult to handle in production.

  The viscosity of the liquid developer is preferably from 0.1 mPa · s to 10,000 mPa · s at 25 ° C. If it exceeds 10,000 mPa · s, it becomes difficult to handle the liquid developer such as stirring and feeding, and the load on the apparatus for supplying a uniform liquid developer may increase.

Next, an outline of the configuration of the developing device will be described.
The developing device includes a developing roller 24 that is in pressure contact with the photoreceptor 1, a developing tank 5 that stores a liquid developer 6 containing toner and a carrier liquid, and a part of the developing tank 5 that is immersed in the liquid developer. A pumping roller 22 that pumps up the liquid, a regulating member 23 that regulates and measures the thickness of the liquid developer pumped up by the pumping roller 22, and a supply roller 21 that supplies the liquid developer pumped up by the pumping roller 22 to the developing roller 24. Including.

  It is assumed that the pumping roller 22 and the supply roller 21 adjacent to each other rotate in the same direction in the contact area. Further, the pumping roller 22 is rotated following the supply roller 21. In this example, the pumping roller 22 is shown rotating in the direction of the rotation direction f. Moreover, the case where the supply roller 21 rotates in the direction of the rotation direction e is shown.

  Further, it is assumed that the supply roller 21 and the developing roller 24 adjacent to each other rotate in opposite directions in the contact area. By setting the opposite direction, the liquid developer from the supply roller 21 to the developing roller 24 can be efficiently supplied. In addition, the thin layer of the developing roller 24 can be made uniform. At the time of image formation, in this example, the supply roller 21 is rotated in the direction of the rotation direction e, and the developing roller 24 is rotated in the direction of the rotation direction b.

  In this example, although not shown, a driving mechanism (driving unit) for rotating the supply roller 21 and the developing roller 24 is provided, and a driving mechanism for rotating the pumping roller 22 is provided. It is assumed that it is not done.

  The amount of liquid developer may be accurately regulated by using a metal roller (anilox roller) having a concave portion on the surface thereof as the pumping roller 22.

  A charging device 26 and a cleaning blade 25 are provided around the developing roller 24. Then, a predetermined amount of liquid developer is supplied to the developing roller 24 as described above, and a charge is given to the toner contained in the liquid developer on the developing roller 24 by the charging device 26. Thereafter, the charged toner conveyed to the photoreceptor 1 by the developing roller 24 develops the image portion on the photoreceptor 1. In this example, the photoconductor 1 is shown rotating in the direction of the rotation a.

Each roller or the like has a cylindrical shape, and a cross-sectional portion thereof is shown in this example.
The cleaning blade 25 may be a rubber body or a rigid body. Examples of the rubber body include urethane rubber, NBR rubber, and fluorine rubber. In the case of a rigid body, resins such as polypropylene, ABS, and polycarbonate, and metals such as aluminum, anodized, SUS, and brass can be used.

  The configuration shown in FIG. 1 is a configuration of a wet image forming apparatus capable of forming a single color (for example, black) image. Next, a wet image forming apparatus capable of forming a plurality of colors (colors) will be described.

  FIG. 2 is a schematic configuration diagram showing an example of another wet image forming apparatus according to the embodiment of the present invention.

  Referring to FIG. 2, the wet image forming apparatus according to the first embodiment of the present invention includes a yellow photoconductor 1Y, a magenta photoconductor 1M, a cyan photoconductor 1C, and a black photoconductor 1K. Arranged. Further, intermediate transfer members 40Y, 40M, 40C, and 40K provided so as to come into contact with the respective photosensitive members are provided. Further, transfer rollers 111Y to 111K are provided to face the intermediate transfer members 40Y, 40M, 40C, and 40K, respectively.

  Further, a developing roller 24 of the developing device, an intermediate transfer member 40, a cleaning blade 121, a charging device 141, and an exposure device 151 are provided corresponding to each photoconductor 1.

  Further, as described above, the developing device is partially immersed in the developing roller 24 in pressure contact with the photosensitive member 1, the developing tank 5 storing the liquid developer containing the toner and the carrier liquid, and the developing tank 5. A pumping roller 22 that pumps up the liquid developer, a regulating member 23 that regulates and measures the thickness of the liquid developer pumped up by the pumping roller 22, and a liquid developer pumped up by the pumping roller 22 is supplied to the developing roller 24. And supply roller 21.

  The toner image developed by each photoconductor 1 is transferred to the intermediate transfer body 40. Then, the toner images of the respective colors transferred to the intermediate transfer body 40 are conveyed to a transfer portion that is a portion facing the transfer roller 111. In the transfer unit, the recording medium is conveyed in the direction of the arrow, and the toner image on the intermediate transfer body 40 is transferred to the recording medium by the transfer roller 111. Then, the toner image is fixed by being conveyed to a fixing unit (not shown). Color image formation is possible by this method.

  In this configuration as well, the case where the image density measuring unit 17 is provided in each photoconductor 1 is shown.

  Although the case where the image density measuring unit 17 is provided on the photosensitive member 1 will be described here, an image density measuring unit 18 may be provided instead of the image density measuring unit 17 as shown in the drawing. .

  In other words, the image density measuring unit 18 may be provided in the intermediate transfer body 40.

  Here, the symbols Y, M, C, and K attached to the symbols indicate yellow, magenta, cyan, and black, respectively.

  In the following, the description will be made using the configuration of FIG. 1 for the sake of simplicity, but the present invention is not limited to FIG. 1 and can be similarly applied to the configuration of FIG.

  Referring to FIG. 1 again, the wet image forming apparatus according to the present embodiment forms an electrostatic latent image of a patch image by exposure device 151 when measuring the image density. The developing roller 24 of the developing device develops the electrostatic latent image of the patch image. Then, a patch image, which is a developed toner image, is measured by the image density measuring unit 17, and control for adjusting the image density based on the measurement result is executed. For the patch image, for example, data having a halftone density is used. The patch image can be formed between a normal toner image and the next normal toner image. It is possible to efficiently control the image density by this method.

  The image density measurement unit 17 includes a carrier liquid application roller 34, a measurement body 35, a cleaning device 33, a density detection sensor 31, and a voltage supply device 36 that controls a bias.

  In this example, the patch image is transferred to the measuring body 35, and the image density of the transferred patch image is measured.

  First, a carrier liquid is applied to the photoreceptor 1 using the carrier liquid application roller 34. The carrier liquid applied to the photosensitive member 1 is supplied to the nip region between the measuring member 35 and the photosensitive member 1.

  Although a liquid having a viscosity and specific gravity different from that of the carrier liquid can be used, it is preferable to use a liquid equivalent to the carrier liquid.

  The patch image reaches the nip region between the photoconductor 1 and the measurement body 35 and is transferred to the measurement body 35. The transfer method may be adhesive transfer or pressure transfer, but it is preferable to use a bias in order to execute transfer with high transfer efficiency. An appropriate bias for moving the patch image to the measuring body 35 is applied by the voltage supply device 36.

  The density detection sensor 31 is an optical sensor having a light emitting unit that emits light and a light receiving unit that receives light. By irradiating light to the measurement target from the light emitting unit and detecting transmitted light by the light receiving unit. This is a sensor for detecting the optical density of an object to be measured.

  In this example, the patch image is irradiated with light from the light emitting portion of the density detection sensor 31. The measuring body 35 is formed of a transparent material such as conductive plastic that transmits the emitted light, hard glass, or synthetic resin. The light emitted from the light emitting unit passes through the transparent measuring body 35, and the light reaches the light receiving unit provided inside the measuring body 35. If there is no toner particle and only the carrier liquid, 100% of the light emitted by the light emitting part is received by the light receiving part.

  The toner amount is detected based on the signal received by the light receiving unit. Specifically, the toner amount is detected by measuring how much of the light emitted by the light emitting unit is received.

  Then, a reference value for detecting the toner amount of the patch image is provided in advance, and it is determined whether or not the toner amount is appropriate based on whether or not the detected toner amount has reached the reference value.

  When it is determined that the toner amount is not appropriate, particularly when it is determined that the toner amount is smaller than the reference, the amount of liquid developer in the developing process is increased. For example, controlling the peripheral speed ratio of the drawing roller 22, the supply roller 21, and the developing roller 24 can be mentioned. If this method is employed, the amount of liquid developer delivered to the developing roller 24 is proportional to the peripheral speed ratio between the pumping roller 22 and the supply roller 21, so that the image density can be controlled according to the reference. . Note that the present invention is not limited to this method, and the image density may be adjusted by developing the developing roller 24 using the photosensitive member 1 or adjusting the electric field in the subsequent transfer process. It is also possible to adjust the image density by increasing the toner density in a toner density adjusting tank (not shown).

  In this example, when the patch image is transferred to the measuring body 35, the carrier liquid is replenished and transferred from the photoconductor 1 as the image bearing member to the measuring body 35, so that the transfer is performed without causing unevenness of the grain (darkness unevenness). It is possible to make it. That is, the density detection sensor 31 can detect a highly accurate value, that is, an image density.

  The patch image transferred to the measurement body 35 is removed by the cleaning device 33.

  In this example, a description will be given of a blade-shaped cleaning device, but the form of the cleaning device is not particularly limited to this, and an appropriate one may be selected according to need. Good. Further, the recovered carrier liquid and the toner particles of the patch image can be reused to reduce the running cost.

FIG. 3 is a diagram illustrating another configuration of the image density measurement unit.
Referring to FIG. 3A, the position of carrier liquid application roller 34 is different here. Further, the rotation direction of the photoreceptor 1 is different.

  Specifically, a configuration in which the carrier liquid is applied to the measurement body 35 is shown instead of a configuration in which the carrier liquid is applied to the photosensitive member 1. Even in this configuration, the coated area of the measuring body 35 reaches the nip area between the measuring body 35 and the photosensitive member 1 by rotation, so that the carrier liquid can be supplied to the area.

  With reference to FIG. 3B, the contact position of the carrier liquid application roller 34 with respect to the photoreceptor 1 is set higher than the contact position of the measurement body 35 provided on the downstream side in the rotation direction of the photoreceptor 1. Thus, the case where the carrier liquid replenished in the nip region between the photosensitive member 1 and the measuring member 35 is a liquid reservoir is shown. Even in this configuration, sufficient carrier liquid can be supplied to the nip region.

  Referring to FIG. 3C, the difference is that the density detection sensor 31 is replaced with a density detection sensor 32 as compared with the configuration of FIG. Specifically, the density detection sensor 32 is a sensor for detecting a reflective optical density. It is possible to measure similarly also in the said structure. For example, it can be used when the measuring body 35 is not formed of a transmissive material.

  Referring to FIG. 3D, here, a case where an endless belt is used as the measuring body 35 is shown. For example, the endless belt can also be formed of a transmissive material that can transmit light.

  The timing of generating the patch image and measuring the toner amount can be performed immediately before the start of the printing operation, but may be measured for each sheet between toner images or for each predetermined number of sheets. Alternatively, the toner amount may be measured, or the measurement timing of the toner amount may be determined by a combination thereof.

FIG. 4 is a diagram illustrating an example of measurement body 35 according to the embodiment of the present invention.
With reference to FIG. 4, the length of the measuring body 35 in the axial direction needs to be at least long enough to transfer a patch image, which is a solid image, to the measuring body 35.

  Referring to FIG. 4A, here, a configuration in which a measuring body 35 is provided in accordance with the axial length of the photoreceptor 1 is shown. The case where the patch image is provided in the image forming area is shown.

  Referring to FIG. 4B, here, a case where a patch image is provided outside an image forming area where a normal toner image is formed is shown. A measuring body 35 having an axial length for transferring a patch image formed outside the image forming area is provided. With this configuration, it is not necessary to provide the measurement bodies 35 corresponding to all areas of the photoconductor 1, and the configuration is simplified.

  In FIG. 4B, the configuration in which the patch image is created outside the image forming area has been described. However, the configuration is not particularly limited thereto, and a configuration in which the patch image is provided in the image forming area may be used. In this case, even in this case, a region where a patch image is formed is set in advance, and the measurement body 35 is provided so as to correspond to the region.

  In the above description, the measurement body 35 has been described as being used for transferring the patch image formed on the photoreceptor 1 and measuring the image density of the patch image. In some cases, it can be used as a squeeze roller. That is, it is possible to improve the image quality by removing excess carrier liquid contained in the toner image and adjusting the amount of carrier liquid in the toner image.

  Specifically, by applying a bias voltage that attracts toner particles in the liquid developer to the photoreceptor 1 and setting the pressure to an appropriate value, the carrier liquid amount is adjusted to prevent the toner image from being disturbed. It is possible.

  FIG. 5 is a diagram illustrating an example of the carrier liquid application roller 34 according to the embodiment of the present invention.

  Referring to FIG. 5, here, the length of the carrier liquid application roller 34 in the axial direction is not set to the same length as that of the photosensitive member 1, but in a region where a patch image is formed on the photosensitive member 1. Set to the corresponding axial length.

  With this configuration, the carrier liquid is not applied to the entire surface, but the carrier liquid is applied only to an area that affects the patch image, so that the carrier liquid can be efficiently supplied.

  In cases other than when a patch image is generated and the toner amount is measured, the carrier liquid application roller 34 is separated from the photoreceptor 1 by a separation mechanism (not shown). As a result, it is possible to suppress excessive supply of the carrier liquid.

(Example)
The toner amount was measured using the wet image forming apparatus of FIG. Specifically, a configuration equivalent to that in FIG. 3A was used as the configuration of the image density measurement unit. Moreover, the structure shown to FIG. 4 (A) was used for the length of the axial direction of the measurement body 35. FIG. The carrier liquid application roller 34 is a rubber roller and has the same configuration as that shown in FIG. After the power was turned on, a patch image was created. The toner amount of the patch image on the surface of the photoreceptor 1 was 1.5 g / m ² . The density is equivalent to a solid image during normal printing. The size of the patch image is 5 cm × 5 cm. The TC ratio of the patch image is 30%.

  The toner amount of the patch image on the surface of the photoreceptor 1 is measured by wiping a predetermined area of the surface of the photoreceptor 1 and volatilizing the carrier liquid with heat.

The carrier liquid application roller 34 applied the carrier liquid to the surface of the measurement body 35 at 4 g / m ² , entered the nip region between the photoconductor 1 and the measurement body 35, and transferred the patch image to the measurement body 35.

  Since the toner particles were charged to a positive polarity by the charging device 26, the measured body potential was applied at −400 V to the photosensitive body potential here.

  The residual toner on the photoconductor 1 was measured by wiping off the surface of the photoconductor 1 and volatilizing the carrier liquid component in the same manner as the measurement of the toner amount on the surface of the photoconductor 1. As a result, the toner amount was 0 g, and 100% transfer was confirmed.

The toner on the surface of the measurement body was measured with a transmission type measuring member. The toner amount was 1.5 g / m ² . It was confirmed that there was no difference between the actual toner amount and the detected toner amount.

  When the toner image on the surface of the transferred measurement object was confirmed with a 200 × microscope, the patch image (solid image) showed no unevenness in density.

(Comparative example)
Except for the step of supplying the carrier liquid, the amount of toner was measured in the same configuration as in the above-described example. The toner amount of the patch image on the surface of the photoreceptor 1 was 1.5 g / m ² .

Further, a measured body potential was applied to the photoreceptor potential at −400V.
When the toner on the surface of the measurement body was measured with a transmission type measurement member, the toner amount was 1.3 g / m ² .

Therefore, it was confirmed that there was a difference between the actual toner amount and the detected toner amount.
When the toner image on the surface of the transferred measurement object was confirmed with a 200-fold microscope, it was confirmed that the patch image (solid image) was transferred with uneven density.

  Therefore, it was confirmed that by supplying the carrier liquid to the patch image, it is possible to measure the image density with high accuracy while suppressing the uneven density.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 1C, 1K, 1M, 1Y photoconductor, 5 developing tank, 6 liquid developer, 10 member to be transferred, 11, 111Y to 111K transfer roller, 17, 18 image density measuring unit, 21 supply roller, 22 pumping roller, 23 regulating member, 24 developing roller, 25, 121 cleaning blade, 26, 141 charging device, 31, 32 density detection sensor, 33 cleaning device, 34 carrier liquid application roller, 35 measuring body, 36 voltage supply device, 40, 40Y, 40M, 40C, 40K intermediate transfer member, 151 exposure apparatus.

Claims (4)

A wet image forming apparatus for forming a toner image on an image carrier using a liquid developer in which toner is dispersed in a carrier liquid,
An image forming unit for forming an image pattern on the image carrier;
A measuring body provided in contact with the image carrier and for transferring an image pattern for density detection formed on the image carrier;
A density control unit that detects the density of the image pattern for density detection transferred to the measurement body and controls the density;
A wet-type image forming apparatus, comprising: a carrier liquid supply means for supplying a carrier liquid to a nip region where the image carrier and the measurement body are in contact with each other when detecting the density of the image pattern for density detection .   2. The wet image according to claim 1, wherein the measurement body removes excess carrier liquid in the image pattern formed on the image carrier except when detecting the density of the image pattern for density detection. Forming equipment.   The wet image forming apparatus according to claim 1, further comprising a cleaning device that is provided in contact with the measurement body and removes the density detection image pattern. At least a part of the measuring body is provided in a hollow shape made of a member that transmits light,
The concentration control unit includes a light emitting unit that emits light, and a light receiving unit that receives light provided to face the light emitting unit,
One of the said light emission part and the said light-receiving part is a wet image forming apparatus in any one of Claims 1-3 arrange | positioned in the hollow shape of the said measurement body.

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