JP2829320B2 - Wet image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet image forming apparatus, and more particularly, to a carrier liquid of a developer used in the apparatus.

[Conventional technology]

2. Description of the Related Art In a wet image forming apparatus such as a wet electrophotographic copying machine, an electrostatic latent image is generally formed on the surface of an electrophotographic photoreceptor or an electrostatic recording medium, and this is used as a developer (a toner in which a toner is dispersed in a carrier liquid). ), The resulting toner image is transferred onto transfer paper, and then the transferred image is fixed to form an image. The conditions required for the carrier liquid of the developer used here are (1) high electric resistance (10 ¹⁴ Ωcm or more), (2) low dielectric constant (ε = 3 or less), 3) low dissolving power (dissolution parameter 7th), (4) harmless, (5) almost odorless and transparent, (6) low flammability and thermal And (7) fast drying. A carrier liquid that satisfies these requirements relatively well is an aliphatic hydrocarbon solvent. For this reason, this kind of solvent is widely used as a carrier liquid for a developer. Physical properties of typical commercially available aliphatic hydrocarbon solvents are as follows.

Among these varieties, especially for reasons (5) to (7), B
~ E varieties are used most often. This is because when the viscosity and boiling point of an aliphatic hydrocarbon solvent generally decrease,
Drying is fast, but the odor is strong.The higher the viscosity and boiling point, the weaker the odor but the drying is poor.In particular, if the drying is bad, a large load is applied to the fixing device, which may lead to an increase in the size of the device. Since it has an unpleasant odor that a large amount of power is required, it is used with a slightly better drying. In addition, even in terms of viscosity alone, in the roller squeezing method that is currently used as a squeezing means for scraping off excess solvent on the photoreceptor, it is necessary to obtain 2-3 squeezing performance in order to obtain good squeezing performance. It is necessary to have the following liquid viscosity, but if this liquid viscosity is large, a large amount of solvent will remain in the non-image area and the transfer paper will be wet,
Alternatively, there is a problem that the squeezing is not performed well and the image on the photosensitive member is disturbed.

However, apart from such poor drying properties and poor squeezing performance, the use of a high-viscosity and high-boiling solvent significantly reduces odors and reduces dirt in liquid parts due to drying and fixing. In addition, it is possible to prevent a decrease in reliability due to an increase in mechanical load and liquid clogging, and also to reduce a loss of liquid due to evaporation, thereby increasing a commercial value as a copying machine in an office.

Further, the present inventors have studied a silicone oil having a siloxane structure as a substitute for the aliphatic hydrocarbon-based solvent, and have almost satisfied the characteristics (especially odorless) required as a carrier liquid for a developer. It turned out to be possible. However, this silicone oil has the same other properties as the aliphatic hydrocarbon solvent due to the difference in viscosity and boiling point, and it is difficult to improve the reliability by preventing sticking while maintaining the drying property and squeeze performance. It was correct.

[Problems to be solved by the invention]

The object of the present invention is to use a mixture of a high-viscosity or high-boiling point solvent having a specific value or higher and a low-viscosity or low-boiling point solvent having a specific value or lower as a carrier liquid, thereby achieving good squeezing performance.
Accordingly, it is an object of the present invention to provide a wet image forming apparatus having improved reliability by preventing sticking while maintaining good image quality and drying property.

[Means for solving the problem]

The wet image forming apparatus according to the present invention includes a unit for forming an electrostatic latent image on the surface of an electrophotographic photosensitive member or an electrostatic recording member, and a unit for developing the latent image with a developer obtained by dispersing a toner in a carrier liquid. Means for transferring the obtained toner image on transfer paper,
And a means for fixing a transferred image, wherein at least one of the carrier liquids of the developer is a solvent having a viscosity of 4 cs or more or a boiling point of 250 ° C. or more, and at least one of the solvents is a liquid having a viscosity of 2.5 cs or more. It is characterized in that at least two types of mixed solvents with a solvent having a boiling point of 180 ° C. or less are used.

[Action]

The image forming method by the wet image forming apparatus of the present invention will be described with reference to the example of a wet electrophotographic copying machine shown in FIG. 1. First, the surface of a photosensitive drum 13 rotating as shown by an arrow is charged with a charger.
After being uniformly charged by 26, the charged surface is image-exposed (indicated by 27) by an exposure system (not shown) to form an electrostatic latent image. Next, the latent image is developed by being brought into contact with the developing solution supplied from the developing tank 44 to the developing rollers 30 and 31 through the developing solution supply pipe 43 to form a toner image. Further, excess developer adhering to the image surface is scraped off by a squeeze roller 33 which rotates in the opposite direction to the photosensitive member. The toner image from which the excess developer has been removed in this way is supplied to the paper tray 38.
Is transferred by the transfer charger 16 onto the transfer paper P conveyed at a predetermined timing between the transfer charger 16 and the photosensitive drum 13 by the paper feed roller 37,
After being separated by the rollers 12 and 15, the sheet enters the fixing section by the conveyor belt 17, where the transferred image is heated by the heating roller 1 (3 is a heater).
Then, the toner is thermally fixed by passing between the pressure roller 2 and is taken out as a copy. On the other hand, untransferred toner and the like on the photosensitive drum 13 are cleaned by the cleaning roller 20 and the cleaning blade 21, and the same image forming operation is started again. 25 is a static elimination lamp, 28 is an eraser, 34 and 35 are developing roller scrapers, 36 is a squeeze roller scraper,
42 is a developer pump, 46 is a developer collection tube, and 47 is a developer collection hole. When an electrostatic recording medium is used instead of the photoconductor, for example, a recording head is used as a latent image forming unit.

If the solvent used for the developer in the above image forming apparatus has a low viscosity and a low boiling point, a squeeze roller
Although the squeezing action and the fixing portion at 33 can be performed satisfactorily, the developing rollers 30, 31, the cleaning roller 20, the cleaning blade 21, and the photoreceptor 13 are stuck. In addition, there is a problem that the cleaning process before and after the image forming operation is required, or the amount of solvent consumed is increased due to evaporation from around each solution. Or, if the boiling point is high, there is no such a problem, but a squeezing defect and a fixing defect are caused.

The present invention has been made in view of this point. That is, as a result of studying a high-viscosity or high-boiling solvent that suppresses sticking and evaporation, the present inventors found it extremely difficult to stick and evaporate at a viscosity of 4 cs or more or a boiling point of 250 ° C. or more. It does not change when other solvents are mixed. On the other hand, if a low-viscosity or low-boiling-point solvent is selected as a counterpart of this mixture, the mixing ratio of each is x, y, the viscosity is η ₁ , η ₂ , and the viscosity of the mixture is η, xlogη ₁ + ylogη ₂ = (X + y) η The viscosity of the mixed liquid was determined by the relational expression, and it was found that a mixing ratio capable of maintaining the squeeze effect was obtained. Especially viscosity
If the solvent has a boiling point of not more than 2.5 cs or a boiling point of 180 ° C., the drying property itself is good, and the good drying property can be maintained by increasing the mixing ratio. Examples of such a high-viscosity or high-boiling solvent include aliphatic hydrocarbon-based Isopar V (manufactured by Esso Standard) and phenylmethylsiloxane of silicone oil. H (manufactured by Esso Standard Co., Ltd.) and cyclic dimethylsiloxane of silicone oil. The mixing ratio of the high-viscosity or high-boiling solvent to the low-viscosity or low-boiling solvent is 1: 1 by volume.
About 0.5 is appropriate.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Examples 1 to 4 A developer using a solvent shown in the following table as a carrier liquid was set in a wet electrophotographic copying machine shown in FIG. 1, and a copy test was performed. The results are shown in the same table.

As can be seen from this table, the combination of aliphatic hydrocarbon solvents is slightly inferior in odor, but the mixed solvent of the combination of the present invention is excellent in squeeze effect (image quality) and drying property, and hardly adheres. Did not.

〔The invention's effect〕

As described above, the wet image forming apparatus of the present invention uses a mixture of a high-viscosity or high-boiling solvent having a specific value or more and a low-viscosity or low-boiling solvent having a specific value or less in a carrier liquid of a developer.
It is possible to improve reliability by preventing sticking while maintaining a good squeezing effect, that is, image quality and drying property.

[Brief description of the drawings]

FIG. 1 is a schematic view of a wet electrophotographic copying machine which is an example of a wet image forming apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Fixing roller, 2 ... Pressure roller 3 ... Heater, 13 ... Photoconductor drum 16 ... Transfer charger, 26 ... Charger

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsuhiro Echigo 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Manabu Mochizuki 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (56) References JP-A-50-80136 (JP, A) JP-A-63-4249 (JP, A) JP-B-41-6396 (JP, B1) (58) Int.Cl. ⁶ , DB name) G03G 9/125

Claims (1)

(57) [Claims] A means for forming an electrostatic latent image on a surface of an electrophotographic photosensitive member or an electrostatic recording medium; a means for developing the latent image with a developer obtained by dispersing a toner in a carrier liquid; In a wet image forming apparatus having means for transferring the obtained toner image onto transfer paper and means for fixing the transferred image, at least one of the carrier liquids of the developer has a viscosity of 4 cs or more or a boiling point of 250 ° C. or more. One solvent and at least one is a viscosity
A wet image forming apparatus, wherein at least two kinds of solvents having a boiling point of 180 ° C. or less are used.