JP2918918B2 - Wet development electrostatic recording device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an electrostatic recording type recording apparatus such as a PPC copier, a latent image printer, etc., and more particularly to developing a latent image using a liquid developer. And a wet development electrostatic recording apparatus.

[Prior Art] Techniques relating to a developer used in a wet development electrostatic recording apparatus include, for example, JP-A-52-17419 and JP-A-5-17419.
JP-A-180248 and JP-A-63-4249 are conventionally known.

In general, in a wet-type PPC copying machine, a colorant and a resin are mainly used as a developer in a carrier liquid composed of a petroleum aliphatic hydrocarbon solvent in order to obtain good image fixing properties. Is used. That is, as the petroleum-based aliphatic hydrocarbon solvent, for example, isoper E, G, H, L, K, M manufactured by Esso Standard
Also, Shell Zone 71, Solvesso 150 manufactured by Shell Sekiyu KK and the like are known. Other carrier liquids include cyclohexane, n-hexane, n-heptane, n-octane, isooctane, isododecane, ligroin and the like.

A liquid developer is prepared by kneading a colorant, a dispersing resin, and a small amount of other additives together with the carrier liquid by means of a ball mill, a Keddy mill, or the like to form a concentrated toner, and dispersing the concentrated toner in an appropriate amount of the carrier liquid. Can be.

Conventionally, in a wet type PPC copying machine, a developer is configured to be circulated in an image forming unit by a pump or the like.For example, untransferred toner not used for development is collected by a cleaning unit. The toner is re-dispersed by the cleaning foam roller, returned to the developing tank from the cleaning liquid collecting hole, and reused. By using such repetition, wasteful consumption of toner is eliminated, and a large amount of recording operation can be performed with a relatively small amount of developer.

[Problems to be Solved by the Invention] In the conventional wet-type PPC copying machine, there is a problem that the quality of a recorded image is deteriorated when a long-time copying process is performed or after the copying process is paused for a long time. was there. Specifically, an abnormal image in the form of white stripes appears on the copied solid black image. This is due to the circulation of the developer. That is, most of the untransferred toner of the cleaning unit and the toner adhered to the developing roller and scraped off by the scraper are returned to the original developer and are uniformly dispersed, but the remaining part of the toner is sludge-like. And stored in the unit. Sludge-like toner,
Normally, it is washed away by the circulating liquid flow and collected in the developing tank. However, after a long time, the sludge-like toner becomes a dead space in the unit (a weak portion of the liquid flow).
Deposited on If the copying operation is stopped for a long time, the sludge-like toner gradually dries during that time, and flake-like large particles (which do not contribute to development) which are difficult to re-disperse are generated. Since the size of these large particles (1 to 500 μ) is larger than the size of the toner particles (0.5 to 0.8 μ), the large particles are caught in the gap (100 to 150 μ) between the developing roller and the photoconductor, and an abnormal image (white stripes) is formed. ).

SUMMARY OF THE INVENTION An object of the present invention is to provide a wet developing electrostatic recording apparatus capable of preventing occurrence of such an abnormal image and obtaining a good recorded image for a long time.

Means for Solving the Problems In order to solve the above problems, in the present invention, a latent image forming mechanism for forming an electrostatic latent image corresponding to a recorded image; a developing mechanism for visualizing the electrostatic latent image; A first component composed of a petroleum-based aliphatic hydrocarbon and a silicone oil having a siloxane structure and having low evaporative properties with respect to the first component, wherein the content is 5 to 20%. A liquid developer formed by dispersing a toner containing a colorant and a resin as main components in the carrier liquid, and mixing the developer with the second component in the developing mechanism. A circulating mechanism; and a transfer unit for transferring the image visualized by the developing mechanism to a predetermined recording medium.

[Operation] That is, in the wet development electrostatic recording apparatus of the present invention, the first carrier made of petroleum aliphatic hydrocarbon is used as the carrier liquid of the developer.
A mixed solution of a component and a second component having a content of 5 to 20%, which is a silicone oil having a siloxane structure and having a low evaporating property with respect to the first component, is used.

For example, a silicone oil such as methylphenylpolysiloxane has a property that it is relatively difficult to evaporate. Therefore, by using this as one component of the carrier liquid of the developer, the toner becomes difficult to dry, large particles are prevented from being generated, and the above-mentioned white streak is not generated. However, this type of silicone oil has a drawback in that it has relatively poor fixability and a good recorded image cannot be obtained. In addition, the relatively high clay can cause trouble in the developer environmental mechanism.

In the present invention, the petroleum-based aliphatic hydrocarbon
Since a mixed solution of the component and a second component having a content of 5 to 20% and comprising a silicone oil having a siloxane structure and having low evaporating properties is used, good image fixability can be obtained by the first component. The drying of the toner is prevented by the second component. Therefore, a high-quality recorded image can be obtained over a long period of time.

[Embodiment] FIG. 1 shows an outline of the structure of mainly a mechanical section of a wet electrophotographic copying machine of one type embodying the present invention. Referring to FIG. 1, an optical scanning system 10 is provided above the copying machine, and an image forming unit 20 is provided below the optical scanning system. An original (not shown) is placed on the contact glass plate 12 and pressed by the pressure plate 11. The lower surface of the document, that is, the image surface, is exposed by the exposure lamp 13 of the optical scanning system 10.
The reflected light from the original is divided into the first mirror 14, the second mirror 15, the third
The light passes through the mirror 16, the lens unit 17, and the fourth mirror 18, and is imaged on the surface of the photosensitive drum 21 provided in the image forming unit 20.

In the optical scanning system 10, an exposure lamp 13 and a first mirror 14 are mounted on a first carriage (not shown), and a second mirror 15 and a third mirror 16 are mounted on a second carriage. The first carriage and the second carriage are respectively driven to scan at a constant speed in the direction of arrow A in the figure. The speed of the second carriage is half the speed of the first carriage. Accordingly, the original images on the contact glass plate 12 are sequentially scanned with the movement of the first carriage and the second carriage, and the read images are formed on the photosensitive drum 21.

On the other hand, in the image forming unit 20, the photosensitive drum
21 is driven to rotate at a constant speed in the direction of the arrow in the figure. After the surface of the photosensitive drum 21 is charged to a uniform potential by the main charger 22, it is exposed to image light by the optical scanning system 10. A latent image is formed. This electrostatic latent image is visualized when passing through the developing unit 60 located in the direction of travel of the photosensitive drum. That is, the toner in the developing unit 60 is attracted to the surface according to the potential distribution, and a toner image corresponding to the high / low potential is formed.

The paper feed mechanism 30 feeds one transfer paper (recording paper) to the surface of the photosensitive drum 21 at a predetermined timing synchronized with the formation of the toner image. The transfer sheet overlaps the toner image on the photosensitive drum 21 and moves with the rotation of the photosensitive drum. When the transfer sheet passes through the transfer charger 25, the toner image is transferred to the transfer sheet. The transfer paper on which the image has been transferred is separated from the photosensitive drum 21 by the separation unit 26, conveyed along a predetermined path, and heads toward the fixing unit 50. The fixing unit 50 fixes the image on the transfer paper to the transfer paper by applying pressure and heat. The transfer sheet on which the fixing is completed is discharged to a discharge tray through a discharge roller.

In the image forming unit 20, when the separation of the transfer paper is completed, the cleaning unit 70 cleans the toner and paper dust remaining on the surface of the photosensitive drum 21 to prepare for the next image formation.

A liquid developer is supplied from the developer supply mechanism 40 to each of the developing unit 60 and the cleaning unit 70. The developer supply mechanism 40 includes a tank 41 filled with developer therein, and the developer therein is supplied with a pump 45.
And supplied to the developing unit 60 and the cleaning unit 70 via the supply pipe 47. The tank 41 is provided with a developer container 42 containing a concentrated developer and a diluent container 43 containing a diluent. When the liquid level in the tank 41 drops below a predetermined value due to the consumption of the developer,
The mouth of the diluent container 43 is automatically opened, and the diluent is supplied into the tank. When the toner concentration in the developer in the tank 41 decreases, the solenoid device 44 is energized. When the solenoid device 44 is energized, the opening of the developer container 42 is opened, and the concentrated developer is supplied into the tank.

The details of the image forming unit 20 and the developer supply mechanism 40 are shown in FIG. Referring to FIG. 2, in the developing unit 60, a first developing roller 62, a second developing roller 63, and a squeeze roller 65 are rotatably supported. These rollers are conductors and are disposed very slightly away from the surface of the photosensitive drum 21. Rollers 62 and 63 are counterclockwise,
The rollers 65 are each driven to rotate clockwise. These rollers rotate when the photosensitive drum 21 is rotating, and stop when the photosensitive drum 21 stops.

The developer in the tank of the developer supply mechanism 40 passes through the pump 45 and the supply pump 47a, and is injected into the development unit from a supply port 61 provided above the development unit 60. Rollers 62, 63 and 65 have scrapers 64a, 64b and 64, respectively.
The free end of c is in contact. Scrapers 64a, 64b and 64c
Removes the developer adhering to the surface of each roller and keeps the developer flowing down from above. The developer remaining on each scraper wets the surface of the roller. The developer on the surfaces of the rollers 62 and 63 is attracted by the electric charge on the surface of the photosensitive drum 21 and moves to the photosensitive drum. Roller 65
Removes excess liquid on the surface of the photosensitive drum 21. The developer remaining below the inside of the developing unit 60 passes through the collecting pipe 48a from the outlet 66 by its own weight, and flows through the developer supplying mechanism 40.
Is collected in the tank 41.

In the cleaning unit 70, the surface of the sponge-shaped foam roller 73 and one end of the blade 76 are
, Which scrape off the remaining developer on the surface of the photosensitive drum 21. Further, the squeezing roller 74 arranged so as to press the foaming roller 73 is
The developer soaked is squeezed out. Further, the cleaning unit 70 has a supply pipe 47b from the developer supply mechanism 40.
Is supplied through the cleaning agent. The developer is supplied from a supply port 71 above the cleaning unit, discharged from a lower discharge port 75, and collected by a collection pipe 48b.
And returns to tank 41.

That is, the developer not actually used and remaining in the unit is charged between the tank 41 and the developing unit 60 and the tank 41.
Between the cleaning unit 70 and the cleaning unit 70 and is reused.

In FIG. 2, reference numeral 24 denotes an eraser, and reference numeral 27 denotes a static elimination lamp.

Incidentally, a part of the developer circulated in the developer supply mechanism 40 passes through the inside of the toner concentration detection unit 46. As shown in FIG. 4a, the toner concentration detecting unit 46 includes a light emitting element 46a and a light receiving element 46b opposed to each other with a slight gap (about 0.5 to 1.0 mm). Is configured to pass through. That is, the toner detection unit 46 constitutes a transmission type optical sensor, and detects a signal corresponding to the amount of light transmission of the developer as the toner density.

The toner density signal detected by the density detection unit 46 is
It is input to the density control unit 80. Concentration control unit 80
Refers to the input toner concentration at predetermined time intervals, and when it is lower than the predetermined concentration, energizes the solenoid device 44 for a predetermined time and opens the opening of the developer container 42 to open the internal concentrated developing The agent is supplied into the tank 41 in a fixed amount. With this control, the toner concentration of the developer in the tank 41 is maintained in a predetermined range.

FIG. 3 shows a specific configuration of the fixing unit 50 of FIG. Referring to FIG. 3, a fixing roller 51 and a pressure roller 53 are provided along a passage of the transfer paper 39.
At the center of the fixing roller 51, a heater 52 is incorporated. The pressure roller 53 is a pressure cam that receives the force of the pressure spring 55
The transfer paper 39 and the toner image 39a attached to the upper surface of the transfer paper 39 are pressed against the fixing roller 51 by receiving an upward force by 54.

By the way, the developer used in this type of wet copying machine is constituted by dispersing a colorant, a resin, and the like in a carrier liquid. As the carrier liquid, for example, Isopar H manufactured by Esso Standard Co., Ltd. Such petroleum aliphatic hydrocarbon solvents are used. Since this type of carrier liquid has a preferable fixing property, it is possible to record an image of high and low humidity by using it.

However, since this type of carrier liquid has a characteristic of relatively easily evaporating, the following inconvenience may occur.

(1) When the developer is circulated and reused as in this embodiment, the untransferred toner of the cleaning unit and the toner adhered to the developing roller and scraped off by the scraper are:
Most of the toner is returned to the original developer and is uniformly dispersed, while the remaining part of the toner is sludge-like and accumulates in the unit. The sludge-like toner is also usually washed away by the circulating liquid flow and collected in the developing tank, but after a long time, the sludge-like toner is transferred to a dead space (a weak part of the liquid flow) in the unit. accumulate. If the copying operation is stopped for a long time, the sludge-like toner gradually dries during that time, and flake-like large particles (which do not contribute to development) which are difficult to re-disperse are generated. The size of the large particles (1 to 500 μ) is the size of the toner particles (0.5 to
0.8 μ), so that it falls within the gap (100 to 150 μ) between the developing roller and the current optical member. In this case, when recording a solid black image, for example, as in a recorded image shown in an enlarged manner in FIG. 7, an image omission such as a white stripe occurs, and the quality of the recorded image deteriorates.

(2) For example, when moving a copying machine, it is necessary to remove the developer in the copying machine in advance so that the developer does not spill out. However, after moving the copying machine, if the developer is left without putting the developer in the developing tank, as shown in FIG. 4b, the developer remains in the gap between the light emitting element 46a and the light receiving element 46b of the toner detecting unit 46. The developer FLD dries,
Dirt adheres to the detection surface of the toner detection unit.
This stain is not easily removed even when the developer is injected,
The light receiving level of the toner detection unit is greatly attenuated.
As a result, the detected density of the toner detecting unit becomes much higher than normal, and if the density control is continued based on the erroneous detected density, the developer density is abnormally reduced and the recording density is lowered.

(3) In the case of a developer using petroleum-based aliphatic hydrocarbon, offset is likely to occur in the fixing process. That is, when a part of the toner image transferred on the transfer paper is reverse-transferred to the fixing roller or the pressure roller, the density of the recorded image is reduced or missing, or the toner attached to the roller is transferred again to the transfer paper. There is. In order to prevent this kind of offset, generally, as a material of the roller surface of the fixing device,
It is configured to use silicone rubber, which is unlikely to cause offset, and to constantly apply silicone oil to the roller surface. However, since silicone rubber has relatively low heat resistance and durability, parts must be replaced periodically depending on the degree of deterioration. In addition, the need to apply silicone oil inevitably complicates the structure of the fixing device.

In order to avoid the above-mentioned disadvantages, in this embodiment, a mixed solution of polymethylphenylsiloxane (silicone oil) and Isopar H (petroleum-based aliphatic hydrocarbon) is used as a carrier liquid for the developer. . That is, since polymethylphenylsiloxane has a low evaporating property as compared with petroleum-based aliphatic hydrocarbons, containing it makes it difficult for the developer to dry, and can prevent the toner from becoming flake-like particles. Adhesion of toner to the toner detection unit can also be prevented. Further, since it also contains a petroleum-based aliphatic hydrocarbon, it is possible to prevent the fixability of an image from deteriorating. Further, since silicone oil such as polymethylphenylsiloxane itself prevents the occurrence of offset in the fixing process, a material other than silicone rubber can be used for the fixing roller and the pressure roller, and the silicone oil is applied. Can also be omitted. In this embodiment, the fixing roller
The surface of 51 and the pressure rollers 53 and 54 (the inside is aluminum) is covered with Teflon (registered product of DuPont: trade name) with high heat resistance and durability, and the mechanism to apply silicone oil is fixed. It is omitted in the unit 50.

The effect of the improvement of the carrier liquid of the developer will be described below together with the results of experiments.

Experiment 1: In this example, an experiment was performed under the following conditions.

Copier: Wet copier CT-5085 Toner: Toner for CT5085 Transfer paper: Standard transfer paper Type6200 (all are manufactured by Ricoh Co., Ltd.) Developer: 100 of the above toners in each carrier liquid
Operating conditions: Using a manuscript with a black solid area of 15%, copy operation of 500 to 1000 sheets (A4 size) per day was continued for 22 days. The results are shown in Table 1.

Referring to Table 1, it can be seen that if at least 5% of polymethylphenylsiloxane is contained in the developer carrying liquid, a decrease in recording quality due to the generation of flake toner can be prevented. The reason that the occurrence of flaky toner can be prevented is that silicone oil having a siloxane structure such as polymethylphenylsiloxane has a sufficiently low evaporation property compared to petroleum-based aliphatic hydrocarbons, so that the sludge-toned toner dries. It is believed that it may have been previously redispersed in the carrier liquid.

With this realization, when tests A to E are used,
It was found that the load torque did not increase in the rotating parts such as the cleaning roller and the developing roller as compared with the case of the other carrier liquids because the toner was not fixed. Specifically, when the test liquids A to E were used, a reduction in the load torque of about 15% was observed in the cleaning section as compared with the conventional isoparaffin-based solvent. Further, the presence of toner that does not contribute to development is reduced, and the number of copies that can be made per unit weight of toner is increased.

FIG. 8a shows the evaporation characteristics of various mixing ratios of polymethylphenylsiloxane (Shin-Etsu Silicone: KF-58) and Isopar H, and FIG. 8b shows the evaporation characteristics of various grades of Isopar. Referring to each figure, it can be seen that the carrier liquid mixed with polymethylphenylsiloxane evaporates slower than that of Isopar H alone.

In addition, Isopar V is very difficult to evaporate, but has a very high viscosity compared to other grades (Isopar H is 1.13, Isopar H
Since V is 11.9), it is difficult to use it alone as a carrier liquid for a developer.

Referring to Table 1, 100% polymethylphenylsiloxane liquid may be used as the carrier liquid. However, in order to obtain good image fixability, petroleum aliphatic hydrocarbons are actually used. A more preferable result can be obtained.

Experiment 2: The toner detection unit 46 of the example was immersed in various types of developers and allowed to stand naturally in an environment of 25 ± 1 ° C. for 2 weeks, and the result was confirmed. Each developer was constituted by dispersing a toner for CT-5085 manufactured by Ricoh Co., Ltd. in a carrier liquid described later at a ratio of 100 g per one.

 The results of the experiment are shown in Table 2 below.

Referring to Table 2, the carrier liquids used in Experiment Nos. A7 to C8 have a favorable result in terms of sensor fouling because of their low evaporability. However, Isopar V has a very high viscosity compared to the others, so it is difficult to use it as a carrier liquid for the developer as it is.

Therefore, as in test liquids B1 to B3, Is having relatively low viscosity is used.
If the carrier liquid is a mixture of opar H and Isopar V, which has a high viscosity but low evaporability, the overall viscosity of the developer can be kept relatively low, and the sensor can be prevented from becoming dirty due to drying of the developer. can do.

In addition, silicone oils such as dimethylsiloxane and methylphenylsiloxane generally have lower volatility than petroleum-based aliphatic hydrocarbons.
In the case of ~ C8, a favorable result is obtained in preventing contamination of the sensor. However, in image recording such as a wet copying machine, the use of petroleum-based aliphatic hydrocarbons can provide favorable image fixing properties, so a mixture of silicone oil and petroleum-based aliphatic hydrocarbons such as C3 to C8 is used. It is desirable to use a carrier liquid.

Experiment 3: Occurrence of offset (toner transfer between transfer paper and roller) in the fixing process was measured at various fixing temperatures. The experimental conditions are as follows.

Roller surface material of the fixing section: PTFE (Polytetrafluoroethylene) and PFA (Per fluoralkoxy) of fluororesin Type of carrier liquid of developer A: Isopar H / Methylphenylpolysiloxane mixed liquid (2
0/80) B: Isopar H / Methylphenylpolysiloxane mixed solution (6
0/40) Only C: Isopar H (petroleum-based aliphatic hydrocarbon) was coated with silicone oil on the fixing roller. Under the above conditions, the results shown in FIG. 5 were obtained. Referring to FIG. 5, the carrier liquid of C causes a considerable offset even at a temperature as low as 110 ° C., so that a normal high-quality copy cannot be obtained as it is. That is, when the carrier liquid of C is used, a material (for example, silicone rubber) that is unlikely to cause offset must be coated on the roller surface of the fixing unit as in the related art. However, since silicone rubber has insufficient heat resistance and durability, it is necessary to periodically replace parts.

Referring to FIG. 5, it can be seen that the offset is improved by mixing methylphenylpolysiloxane with the carrier liquid. That is, when using a carrier liquid containing 80% methylphenylpolysiloxane,
Even at a temperature of 170 ° C., there is no occurrence of offset and a favorable copy can be obtained.

FIG. 6 shows the relationship between the mixing ratio of methylphenylpolysiloxane to the carrier liquid and the upper limit of the usable fixing temperature. For example, in the case of a copying machine used at a fixing temperature of 120 ° C., the occurrence of offset can be eliminated by including 50% or more of methylphenylpolysiloxane. As the fixing temperature increases, the content ratio of methylphenylpolysiloxane must be increased.

In this experiment, the measurement was performed under the same conditions as above except that the application of the silicone oil was stopped, and it was found that the upper limit of the usable fixing temperature was reduced by about 10 to 20 ° C. Therefore, when the content ratio of methylphenylpolysiloxane is sufficiently increased, no offset occurs even if the application of the silicone oil is omitted.

Fluorine-based resins such as PTFE and PFA have high heat resistance and durability, so if this material is used for the roller surface of the fixing unit, the roller is less likely to be damaged, and periodic replacement of parts is not required.

[Effects] As described above, according to the present invention, the first component (for example, Isop) composed of petroleum aliphatic hydrocarbon is used as the carrier liquid for the developer.
ar H) and a liquid mixture of a second component (for example, polymethylphenylsiloxane) having a content of 5 to 20%, which is a silicone oil having a siloxane structure and having low evaporative properties with respect to the first component. Is used, the first component maintains a favorable image fixing property, and the second component prevents flake-like toner from being generated in the developer (see Table 1). Quality images can be recorded. In addition, since no flake-like toner is generated, an increase in required driving torque in the rotary driving unit of the developing unit and the cleaning unit is prevented, and these can be driven with a low torque. Further, the number of copies that can be made per unit weight of toner is also improved.

[Brief description of the drawings]

FIG. 1 is a front view showing the structure of a main mechanism inside a type of wet copying machine embodying the present invention. FIG. 2 is an enlarged front view showing details of the image forming unit 20 of FIG. FIG. 3 is a front view and a perspective view showing the fixing unit 50 of FIG. 1, respectively. 4a and 4b are a perspective view and a front view, respectively, showing the configuration of the toner concentration detection unit 46 of FIG. 5 and 6 are graphs showing the results of Experiment 3. FIG. 7 is an enlarged plan view showing an example of a solid black image in which white stripes are generated by flaky toner. 8a and 8b are graphs showing measurement results of the evaporation characteristics of various liquids. 10: Optical scanning system, 10: Image forming unit 21: Photoreceptor drum (latent image forming mechanism) 22: Main charger 25: Transfer charger (transfer means) 30: Paper feed mechanism 40: Developer supply mechanism (circulation mechanism) 41 : Tank, 42: developer container 43: diluent container, 44: solenoid device 45: pump 46: toner concentration detecting unit 50: fixing unit 60: developing unit (developing mechanism) 61: supply port, 62: first developing roller 63: second developing roller, 65: squeeze roller 66: discharge port 70: cleaning unit, 71: supply port 73: foam roller, 75: discharge port 76: blade

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Kojima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Ichiro Tsuruoka 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Katsuhiro Echigo, inventor 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Mayumi Miyao, Inventor Mayumi Miyao 1-3-6, Nakamagome, Ota-ku, Tokyo Co., Ltd. Ricoh Company (56) References JP-A-50-80136 (JP, A) JP-A-63-26671 (JP, A) JP-A-1-148943 (JP, A) JP-B-41-6396 (JP, A) B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/10, 9/12

Claims (1)

(57) [Claims] A latent image forming mechanism that forms an electrostatic latent image corresponding to a recorded image; a developing mechanism that visualizes the electrostatic latent image; a developing mechanism that is disposed in the developing mechanism and that is made of a petroleum aliphatic hydrocarbon. A carrier liquid comprising a mixture of one component and a second component having a content of 5 to 20% and comprising a silicone oil having a siloxane structure and having low evaporability with respect to the first component, A liquid developer formed by dispersing a toner containing a colorant and a resin as main components; a circulating mechanism for circulating the developer in the developing mechanism; Transfer means for transferring the image to a recording medium of the above.