JP2000267524A - Image forming device - Google Patents

Abstract

(57) Abstract: An image forming apparatus is provided which suppresses the release of a developer solvent and recovers a solvent vapor efficiently and easily. SOLUTION: A means 20 for cooling and liquefying and recovering a solvent vapor of a liquid developer which is volatilized and generated in a wet electrophotographic apparatus.
The cooling temperature is controlled in consideration of the humidity in the environment in which the electrophotographic apparatus is used, and the temperature is set at a moderately high temperature from the lower limit temperature at which water in the atmosphere does not liquefy, thereby improving the recovery efficiency. Can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in an electrophotographic apparatus using a liquid developing technique.

[0002]

2. Description of the Related Art An electrophotographic apparatus using a liquid developer has an advantage which cannot be realized by a dry electrophotographic apparatus, and its value is recently being reconsidered. High image quality can be achieved by using a very fine toner of submicron size, sufficient image density can be obtained with a small amount of toner, and it is economical, and it can realize the same texture as printing (for example, offset printing). That the toner can be fixed on the paper at a relatively low temperature, thereby realizing energy saving;
These are the main advantages of wet electrophotography over the dry process.

[0003] On the other hand, the conventional liquid electrophotographic technology using liquid toner has some essential problems,
For that reason, it has long allowed the sole use of dry technology.

First, in order to develop an electrostatic latent image, a liquid developer using a high-resistance or insulating petroleum-based solvent as a carrier solvent must be used. The effect was a problem.

The second problem is that a large amount of solvent adheres to the latent image at the same time as the toner in the developing process, so that the excess solvent is squeezed after the development, and the excess toner floating in the solvent is removed. (1) It is necessary to have a process for surely collecting and removing the solvent vapor evaporated in the air in all processes including the transfer and fixing processes.

[0006] The third problem is an environmental problem due to the adhesion of a solvent to paper. In the electric field transfer of a liquid developer, a toner, which is a charged particle, moves in a solvent by a well-known electrophoretic phenomenon and is transferred to a sheet. Therefore, in electric field transfer, a predetermined amount of solvent must be interposed between the latent image holding member and the sheet, and as a result, a large amount of solvent adheres to the sheet after transfer. Part of the solvent is volatilized in the fixing step by heat and is discharged outside the apparatus, causing problems such as odor and adverse effects on humans due to inhalation of vapor. Further, the paper discharged outside the machine after fixing still contains a large amount of solvent, and when a user with an allergic nature touches this, dermatitis such as eczema may be caused.

In order to solve such a problem, a method has been proposed in which the latent image is temporarily transferred from a latent image holding member to an intermediate transfer medium and then transferred to a sheet. US Patent No. 5,148,
No. 222, 5, 166, 734, 5, 208, 63
No. 7 and the like disclose a method of transferring from a latent image holding member to an intermediate transfer medium by an electric field, and then transferring to a sheet by pressure (and heat). In these proposals, since the transfer to paper is performed by heat and pressure, the problem seen in the case of electric field transfer does not occur. Further, the solvent adhering to the intermediate transfer medium can be vaporized or sucked by heating or suction of air before pressure transfer to the sheet, so that the solvent adhering to the sheet can be significantly reduced. Such an improvement is possible because no solvent is required when transferring to paper by pressure.

However, even in these proposals, it is not practically possible to completely prevent the vaporization of the solvent vapor, and the solvent vapor fills the inside of the machine. In this case, it is not preferable to discharge the air inside the machine to the outside of the machine for the above-described reasons. Therefore, liquefaction and recovery of the solvent vapor in the machine are performed. For example, JP
In Japanese Patent No.-82835, the solvent vapor generated around the fixing section is sucked and introduced into another chamber, and the solvent mist atomized into droplets is further introduced into the liquefaction chamber for recovery. Japanese Patent Laid-Open No. 50-
In Japanese Patent No. 13055, a gas containing a solvent vapor is cooled by a cooling means. As a result, a mixed liquid of the solvent vapor and the water which is liquefied as a result is recovered, the solvent and the water are separated, and the solvent is reused.

[0009]

As described above, in a conventional electrophotographic apparatus using a liquid developing technique, a harmful solvent contained in a developer adheres to a sheet or is discharged outside the apparatus as vapor. There was a problem that it was easy to be done. In addition, when liquefying and recovering the solvent vapor, not only the solvent vapor but also the mixed water is cooled together, so that the cooling efficiency is poor and the cooling temperature needs to be lowered in order to increase the recovered solvent. As a result, not only the solvent but also water is mixed in the recovered liquid, and there is a problem that it is difficult to reuse the recovered liquid. Further, the system disclosed in JP-A-48-82835 has a disadvantage that the mist chamber is immediately heated by the solvent vapor, and the efficiency is reduced.

Accordingly, an object of the present invention is to provide an image forming apparatus which suppresses the release of a developer solvent and recovers a solvent vapor efficiently and easily.

[0011]

According to a first aspect of the present invention, a latent image forming means for forming an electrostatic latent image on a latent image holding member, and a developer is supplied to the electrostatic latent image to form a visible image. An electrophotographic apparatus having a developing means for converting the visible image onto an image carrier, wherein the solvent is liquefied and recovered by cooling a liquid developer carrier solvent vapor generated in the apparatus. In the image forming apparatus having the vapor liquefaction and recovery means, the image forming apparatus further includes means for detecting the air temperature outside the body or inside the body or both, and the cooling temperature of the carrier solvent vapor is outside the body detected by the temperature detection means or An image forming apparatus characterized by having a temperature equal to or higher than the air temperature in the body and having a means for controlling the cooling means, thereby minimizing the discharge of the solvent vapor of the liquid developer to the outside of the body, and Efficient solvent re-use It can be recovered in use and easy to state.

According to a second aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image on a latent image holding member, a developing means for supplying a developer to the electrostatic latent image to visualize the latent image, An electrophotographic apparatus having a transfer means for transferring the visible image onto an image carrier, comprising: a solvent vapor liquefaction and recovery means for liquefying and recovering by cooling a liquid developer carrier solvent vapor generated in the apparatus. The image forming apparatus further comprises means for detecting air temperature and humidity outside the machine or inside the machine or both,
The cooling temperature of the carrier solvent vapor is set to a temperature not exceeding the saturated vapor pressure of water when cooling is performed under the environment of the temperature and the humidity detected by the detection means, and the means for obtaining the cooling temperature is used. An image forming apparatus comprising: means for controlling the cooling unit.
As a result, discharge of the solvent vapor of the liquid developer to the outside of the machine can be suppressed to a minimum, and the solvent can be efficiently recovered in a state where it can be easily reused.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

FIG. 1 shows a first embodiment of the present invention.

The latent image holding member 1 is a photosensitive drum in which an organic or amorphous silicon photosensitive layer is provided on a conductive substrate. The latent image carrier 1 is uniformly charged by a well-known corona charger or scorotron charger 2-1 and then exposed to an image-modulated laser beam.
Upon receiving -1, an electrostatic latent image is formed on the surface. Thereafter, the electrostatic latent image is visualized by the developing device 4-1 containing the liquid developer.

The liquid developer or toner adhering to the electrostatic latent image may be directly transferred to a transfer step and transferred to a sheet by the transfer device 5, but here the second charger 2-2 and the second laser A second developing device 4 that forms a second electrostatic latent image by exposure 3-2 and stores a second developer of a different color from the liquid developer stored in the first developing device 4-1 This is developed by -2. Therefore, after the second development, a two-color toner image is formed on the latent image holding member 1.

Similarly, third and fourth developments are performed,
A full-color toner image is formed on the latent image holding member 1.

This toner image is transferred to a sheet by a transfer device 5, and may be transferred directly to the sheet or to a sheet 10 via an intermediate transfer medium 6 as illustrated in FIG. It may be transferred.

In the transfer from the latent image holding member 1 to the intermediate transfer medium 6 and the transfer from the intermediate transfer medium 6 to the paper 10, either the transfer by electric field or the transfer by pressure (and heat) is used. I can do it. Many liquid developers can generally be fixed on paper at room temperature,
The fixing by heat may be performed by heating the pressure roller 8 and the like. Such an image forming process is disclosed in, for example, US Pat. No. 5,570,173, and is a conventionally known process.

When such a process is realized, a well-known petroleum-based insulating solvent (for example, Isopar L and Norpar 12 (both are trade names) from Exxon) and the like are used as a liquid developer. Particles composed of dispersed charged particles (toner particles) are usually used, but other combinations may be used. When such a solvent is used, an organic solvent (solvent) vapor is generated by natural volatilization in any place where the liquid developer exists in the body. Further, the solvent of the liquid developer is removed from the latent image holding member 1, the intermediate transfer medium 6, the pressure roller 7, or the paper 9 by evaporating the solvent of the liquid developer intentionally and consequently by heat, regardless of the result. If so, a considerable amount of solvent vapor is continuously generated in the airframe.

First, a mixed gas mainly composed of solvent vapor and air is introduced from the solvent vapor recovery port 10 in FIG. 1 to the solvent vapor recovery / discharge system. Appropriate means such as a fan or a blower may be provided in the flow path (including the discharge path to the outside of the machine) of the mixed gas containing the solvent vapor in the machine. Further, it is preferable that the part where the solvent vapor is generated is kept as low volume and as tight as possible, and the solvent vapor recovery port 10 is located closer to the part where the solvent vapor is generated. Steam recovery efficiency is improved. Further, the solvent used is the above-mentioned petroleum insulating solvent (the specific gravity of the vapor with air as 1 is about 5.9), so that the solvent vapor tends to stay below, so that the solvent vapor recovery port is located below. Better to have. Further, a plurality of solvent vapor recovery ports may be prepared.

The gas mixture in the flow path is introduced into a liquefaction and recovery chamber 20 equipped with a cooling device. The cooling device 24 may be an air-cooling system using a fan or the like, a water-cooling system, or the like, in addition to the Peltier device, the compressor, and the like.

In the liquefaction and recovery chamber 20, the air containing the liquid developer carrier solvent vapor is cooled by an appropriate cooling means as described above, and the portion of the carrier solvent exceeding the saturated vapor pressure at the temperature in the liquefaction and recovery section is liquefied. And collect. However, if the cooling temperature here is not appropriate, the recovery efficiency will be poor. For example, in the case of an apparatus as disclosed in JP-A-48-82835, when the temperature outside the apparatus is high, or when the temperature inside the apparatus increases due to continuous operation of the apparatus, the temperature of the atomization chamber itself increases. In such cases, a sufficient recovery effect cannot be obtained. In addition, if it is cooled too much, or more specifically, if it is cooled to a temperature that exceeds the saturated vapor pressure of water, the water present in the air together with the solvent is recovered. Will be done. If the recovered solvent is mixed with water, a new separation mechanism between the solvent and water is needed to reuse it as a carrier solvent for the liquid developer. It also consumes wasteful energy.

As described above, the air in the liquefaction and recovery chamber 20 must be cooled to an appropriate temperature. For this purpose, a temperature measuring device 21 for measuring the temperature of the air (mixed gas) in the collection chamber 20 is provided so that the cooling temperature of the air containing the liquid developer carrier solvent vapor introduced into the liquefaction collection chamber 20 can be determined. It has become.

Further, a temperature measuring device 23 for measuring the room temperature outside the image forming apparatus is provided outside the image forming apparatus so that the ambient temperature of the use environment can be determined. The temperature measuring device can be placed in the image forming device. However, in this case, the temperature inside the image forming apparatus gradually increases due to the operation of the image forming apparatus. Therefore, when a device for measuring the ambient temperature is provided both inside and outside the device, the temperature inside the device is generally considered to be higher. If it is desired to perform measurement at a later time, it is necessary to grasp the driving situation before the measurement.

Generally, water exists in the atmosphere in a gaseous state. Water has a predetermined saturated vapor pressure under certain conditions.If the partial pressure of water exceeds the saturated vapor pressure, it cannot exist as a gas in the atmosphere. Condensation. The ratio of the partial pressure of water to the saturated vapor pressure is expressed as humidity. However, since this humidity cannot usually be 100%, the atmosphere at a certain temperature is once warmed and returned to the original temperature. The water contained in the atmosphere does not liquefy when returned. Therefore, if the cooling temperature in the cooling recovery unit is controlled to be equal to or slightly higher than the measured air temperature inside and outside the image forming apparatus, water is mixed in the carrier solvent recovered in the main recovery unit. However, it can be obtained in a state where it can be easily reused as a carrier solvent for a liquid developer. It is necessary to provide a control means 22 for the purpose of controlling the cooling temperature. Further, since the cooling unit is actively cooled, it is possible to suppress the cooling unit itself from having heat by continuous operation, and it is possible to efficiently recover the carrier solvent.

Further, it is clear that the more the carrier solvent vapor is cooled, the more it liquefies. Therefore, it is necessary to cool the carrier solvent vapor to a temperature not exceeding the saturated vapor pressure of water rather than cooling to room temperature as described in the preceding section. If this is achieved, the liquefied and recovered amount of the carrier solvent increases without water being liquefied, and the efficiency is further improved. As a second embodiment, shown in FIG.
To achieve this, the temperature and humidity in the atmosphere and atmosphere are measured, and the temperature at which water does not liquefy, that is, does not exceed the saturated vapor pressure of water, is determined. It is sufficient to cool with. In more detail, a temperature measuring unit 23 and a humidity measuring unit 24 capable of measuring the temperature and humidity of the atmospheric air are provided, and a calculating unit 26 for calculating an appropriate temperature not exceeding the saturated vapor pressure of water from respective information is provided. It is sufficient to provide a means 22 for controlling the carrier solvent vapor in the cooling and liquefaction apparatus to the required appropriate temperature. Of course, the temperature measuring means 21 for measuring the temperature of the carrier solvent vapor in the cooling liquefaction apparatus is required.

By appropriately returning the liquefied solvent to the toner container 28, it is possible to reuse the solvent without adding a special device for separating water.

The room temperature is 30 ° C. and the humidity is 80%.
At a saturated vapor pressure of 80 [° C.] of the carrier solvent vapor,
When the cooling unit cools down to 10 ° C., about 14 g of water per 1 kg of cooling gas comes out. However, even when cooling to a temperature of 30 ° C. at which water is not liquefied, 70% or more of the solvent can be recovered. Therefore, in consideration of solvent reuse, this method is more efficient.

[0030]

As described above, according to the present invention, in an electrophotographic apparatus using a liquid developer, when the carrier solvent vapor of the liquid developer generated in the body is cooled and liquefied, air due to excessive cooling is used. Water is prevented from being mixed into the liquefied solvent due to liquefaction of the water therein, and the liquefied solvent can be reused without separating the liquefied solvent and water. As a result, it is possible to provide an extremely efficient, economical, and high-performance image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a schematic sectional view illustrating a second embodiment of the image forming apparatus of the present invention.

FIG. 3 is a schematic sectional view illustrating solvent reuse according to the first embodiment of the image forming apparatus of the present invention.

FIG. 4 is a schematic sectional view illustrating solvent reuse according to a second embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image holder 2 Charger 4 Developing device 5 Transfer device 6 Intermediate transfer medium 10 Solvent vapor recovery port 20 Liquefaction recovery chamber 23 Temperature measuring means 24 Humidity measuring means

Claims (2)

[Claims] 1. A latent image forming means capable of forming a latent image on a latent image holding member, a developing means for supplying a developer to the latent image to visualize the latent image, and an image carrier for applying the visible image to the image carrier Transfer means for transferring on the top,
An image forming apparatus including a solvent vapor liquefying and collecting means for cooling and liquefying and recovering a liquid developer carrier solvent vapor generated inside a machine having the latent image forming means, the developing means and the transferring means therein, The apparatus further includes a temperature detection unit that detects an air temperature outside the body or inside the body, or both, and a temperature at which the liquid developer carrier solvent vapor is cooled is higher than a temperature detected by the temperature detection unit. An image forming apparatus controlled by: 2. A latent image forming means capable of forming a latent image on a latent image holding body, a developing means for supplying a developer to the latent image to visualize the latent image, and an image carrier for applying the visible image to the image carrier Transfer means for transferring on the top,
An image forming apparatus including a solvent vapor liquefying and collecting means for cooling and liquefying and recovering a liquid developer carrier solvent vapor generated inside a machine having the latent image forming means, the developing means and the transferring means therein, When a detecting means for detecting the temperature and humidity of the air outside and / or inside the apparatus is provided, and the liquid developer carrier solvent vapor is cooled under the environment of the temperature and humidity detected by the detecting means. An image forming apparatus, wherein a temperature at which the liquid developer carrier solvent vapor is cooled is controlled to a temperature not exceeding a saturated vapor pressure of water under the environment.