JPH05330033A - Ink jet recorder - Google Patents

Abstract

PURPOSE:To obtain a stably high quality image and prevent solvent vapor from being discharged to the environment in a transfer type ink jet printer employing a volatile ink solvent. CONSTITUTION:A transfer medium body 1 having a heater 10 is covered by a shielding member 11. An image of ink on the transfer medium body 1 is heated by the heater 10 so that an ink solvent evaporates. The exhaust gas including the ink solvent vapor passes through a heat exchanger 13 being maintained at a room temperature to be cooled so that the ink solvent is liquefied and removed from the exhaust gas to be collected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to a transfer type ink jet recording apparatus which forms an ink image on a transfer medium and then transfers the ink image onto a recording paper.

[0002]

2. Description of the Related Art In a direct type ink jet recording apparatus which directly ejects ink droplets on a recording sheet to form an ink image, the recording sheet and the recording head are arranged close to each other, and clogging of the ink jet head or the like due to unintended contact between the recording sheet and the recording head occurs. However, the transfer type ink jet recording apparatus does not cause these problems, and high reliability can be obtained. Further, the transfer type ink jet recording apparatus has a feature that high image quality can be obtained without depending on the paper quality (paper surface smoothness).

As inks used in these devices, there are known inks in which coloring materials are dissolved or dispersed in various aqueous and non-aqueous solvents.

In an apparatus using an aqueous solvent ink, water has a property of easily evaporating, and the nozzle portion of the recording head dries to cause nozzle clogging, resulting in malfunction. The apparatus used has an advantage that high reliability can be obtained because the ink solvent is difficult to dry.

In the ink jet recording apparatus, in order to eject the ink from the ink jet head as ink droplets, the ink must be a liquid having a sufficiently low viscosity and a viscosity of a certain value or less. Normally, the required discharge characteristics cannot be obtained unless the viscosity of the discharge is lower than at least 50 mPa · s. Therefore, the ink is ejected in a state where the coloring material is diluted with a large amount of solvent.

In the transfer type ink jet recording apparatus, it is necessary to remove the ink solvent on the transfer medium to concentrate the ink image. The reason is as follows.

An ink image formed on a transfer medium by ejecting ink, which is a low-viscosity liquid, is composed of droplets raised and attached by the surface tension of the ink on the transfer medium and deformed by an external force. It is in a state where it is easy to do. In the transfer process to the recording paper, when passing through the part where the transfer medium and the recording paper come into contact, the ink image is spread and deformed because it passes through a narrow gap, and an ink image of high image quality is obtained on the recording paper. I can't.

Further, when the liquid ink image is transferred onto the recording paper, it permeates along the fibers and the edges become unclear, so that high image quality cannot be obtained.

In order to prevent these problems, a configuration is known in which the ink image is heated on the transfer medium to evaporate the ink solvent and concentrate the ink image. The ink solvent removal process needs to be performed promptly between the ink droplet ejection process onto the transfer medium and the transfer process onto the recording medium. The ink image on the transfer medium is heated using a heater to promote evaporation. Such a configuration is known (for example, Japanese Laid-Open Patent Publication No. 3-16963).
4 gazette).

[0010]

In the prior art ink jet recording apparatus, in which the above-mentioned ink image is dried on the transfer medium and then transferred, the ink solvent contained in the ink when ejected from the recording head is on the recording medium. During the process, a large amount of ink solvent vapor is released because it is removed by the time the final ink image is obtained.

In the case of a non-aqueous solvent, most of the vapors are accompanied by an offensive odor, and when the vapor concentration in the atmosphere reaches a specific value or more, not only the discomfort due to the odor but also the health effect on the human body is caused. It is also flammable and explosive. For example, in the case of petroleum-based solvents, a vapor concentration of 200 to 300 ppm or more is not preferable. Therefore, it is necessary to prevent the generated steam from polluting the environment around the device.

Even in the case of a water-based ink containing water as a main solvent, it is also necessary to prevent the vapor of the ink solvent vapor from diffusing out of the apparatus when it contains a component that emits harmful vapor.

In order to prevent the release of the ink solvent vapor to the surrounding environment, the ink solvent vapor generating portion may be provided with a cover to shield it from the surroundings.

In this case, the ink solvent has a high vapor concentration over time in a limited space inside the shield member, and when cooled in a relatively low temperature portion inside the shield member, it is condensed and liquefied to form the ink solvent. It becomes droplets and adheres. Further, the exhaust gas containing the ink solvent vapor leaked from the shielding member is cooled in the apparatus, liquefied, and adheres to the inside of the machine.

The ink solvent droplets that have condensed on the transfer medium or that have condensed on various portions inside the shielding member drop on the transfer medium and adhere to the transfer medium. When the ink solvent droplets are nonuniformly adhered to the transfer medium, the ink image formed on the transfer medium becomes nonuniform in a dry state, and uneven transfer occurs in the image, so that a high-quality image cannot be obtained. Was.

The present invention solves this problem, and is to realize a transfer type ink jet recording apparatus which prevents emission of ink solvent vapor to the surrounding environment.

Still another object is to realize an ink jet recording apparatus capable of obtaining a high quality image by preventing uneven transfer from a transfer medium to recording paper.

[0018]

An ink jet recording apparatus of the present invention is provided with an ink jet recording head for ejecting ink droplets, a gap between the ink jet recording head and the recording head, and a heating means. An ink jet recording apparatus having a transfer medium maintained and a heat exchange unit maintained at a temperature equal to or lower than the transfer medium temperature, wherein the ink is an ink having a colorant dissolved or dispersed in a solvent having evaporation property. ,
The heating means heats the ink image on the transfer medium to evaporate the ink solvent, the ink solvent vapor is cooled by the heat exchange means, and part of the vapor is liquefied and recovered.

[0019]

According to the above method, the exhaust gas having a high ink solvent concentration is isolated inside the shielding member, and the steam is liquefied and recovered by the heat exchanger and then exhausted. Therefore, the ink vapor is not condensed or adhered on the transfer medium. Therefore, there is no contamination of the surrounding environment by the ink solvent vapor, and uneven transfer does not occur, and a high quality image can be stably obtained.

[0020]

EXAMPLES Examples of the present invention will be described.

FIG. 1 is a perspective view of the ink jet printer of the first embodiment.

An ink image is formed on a transfer drum 1, which is a transfer medium, by a recording head 2 having a plurality of nozzles. The recording head 2 is an inkjet recording head of a type using a piezoelectric element, and has a plurality of nozzles at predetermined intervals in the axial direction of the transfer drum 1.

The first paper feed roller 6 and the second paper feed roller 7 carry a recording paper 8 which is a recording medium. The recording paper 8 is pressed by the pressure roller 9 and comes into contact with the transfer drum 1.

The transfer drum 1 is constructed by providing an elastic layer 17 around the metal tube 16. The elastic layer 17 is preferably made of a material that easily peels off the ink image. The apparatus of this embodiment is made of silicone rubber.

The ink is a dispersion of colored particles as a coloring material in a dispersion medium. The colored particles are particles of ethylene cellulose resin in which Raven 1255 of Colombian Carbon Co. is dispersed as a pigment together with a dispersion stabilizer. The ink solvent that is a dispersion medium is a non-aqueous solvent, that is, a high resistance low dielectric constant aliphatic hydrocarbon solvent that is a petroleum solvent having a small vapor pressure at room temperature as shown in FIG. 3 (for example, Exxon Chemical Co., Ltd.). Manufactured by Isopar V) is used. It has a high saturated vapor pressure at high temperatures and evaporates more quickly in high temperature environments.

A heater 10 is provided as a heating means for heating the ink solvent on the transfer drum 1 in order to quickly evaporate the ink solvent. A shield member 11 for preventing the diffusion of the ink solvent vapor around the transfer drum 1 and a fan 12 for discharging the air inside the shield member 11 are provided. The heater 10 intermittently lights a rod-shaped halogen lamp to keep the transfer drum 1 at a predetermined temperature. The shielding member 11 of this embodiment is preferably made of a material having heat insulation properties,
In this embodiment, it is made of resin. The shape of the shielding member 11 needs to be a shape that effectively covers the periphery of the transfer drum 1 and at the same time that the outside air is supplied so that the generated solvent vapor is not diffused to the surroundings. The shielding member 11 of the apparatus of the example covers the transfer drum 1 and the members such as the recording head 2 arranged in the vicinity thereof, and also has a ventilation gap 64 in the lower part. As a result, the outside air is supplied to the periphery of the transfer drum 1, and the air flow is controlled so that the air contains the ink solvent vapor and flows out toward the fan 12 by the action of the fan 12. A heat exchanger 13 is arranged at an intermediate portion between the shielding member 11 and the fan 12.

As shown in the cross-sectional view of FIG. 2, the heat exchanger 13 includes a conduit 18 of a good heat conductor (here, aluminum) through which an air flow passes, and a fin 14 disposed inside the conduit 18, and the exhaust gas passing therethrough. (Air containing ink solvent vapor inside the shielding member 11) is cooled. The heat exchanger 13 is exposed to the ambient environment air and is maintained at about the ambient temperature. A recovery groove 15 for recovering the ink solvent liquid is provided at the bottom.
Further, the ink solvent is guided to the recovery container 19.

Next, the operation will be described.

In FIG. 1, the transfer drum 1 is used during the recording operation.
Is rotated at a constant speed in the direction of arrow A, while the recording paper 8 is conveyed in the direction of arrow B, ink droplets are selectively ejected from the nozzles of a predetermined recording head 2. In the above process, since the ink is kept in a low viscosity state by the ink solvent contained during ejection from the recording head 2, good ejection characteristics (ejection frequency, ejection speed, ink amount of ejected ink droplets) are obtained. A predetermined value can be realized, and further, characteristics that stably obtain these can be obtained. That is, the optimum viscosity can be adjusted according to the characteristics of the recording head 2.

Since the heater 10 maintains a predetermined temperature above the ambient temperature, the ink solvent quickly evaporates from the ink image on the transfer drum 1.

The air containing the ink solvent vapor is used as the heat exchanger 13.
And is discharged to the outside of the shielding member 11 as indicated by an arrow C.

Next, the transfer drum 1 comes into contact with the recording paper 8 and receives pressure to transfer the ink image onto the recording paper 8. The ink image on the transfer drum 1 has a high concentration of colored particles because the ink solvent is evaporated and removed, and the ink image on the transfer drum 1 is not crushed when passing through a small gap in the contact portion. The same shape can be maintained, and the ink can be transferred onto the recording paper 8 without seeping into the recording paper 8 to obtain a good ink image on the recording paper 8.

In the apparatus of this embodiment, the heat exchanger 13
Is kept at about room temperature, the air containing the ink solvent passing therethrough is cooled to about room temperature. As a result, as shown in the vapor pressure characteristics of the ink solvent in FIG.
The ink solvent vapor contained therein is cooled and the excess vapor undergoes a phase change from a gas to a liquid, is deposited as an ink solvent liquid inside the heat exchanger 13, and adheres to the fins 14 and the conduits 18. This ink solvent liquid flows down to the bottom of the heat exchanger 13 according to gravity, is guided to the recovery groove 15, and is recovered in the recovery container 19.

The transfer drum 1 is kept at a high temperature and does not fall below the temperature of the solvent vapor evaporated from the outer circumference. Therefore, the ink solvent does not adhere to the transfer drum 1 due to dew condensation. Further, the ink solvent that has condensed inside the shielding member 11 does not adhere to the transfer drum 1. Therefore, uneven transfer due to nonuniformity of the ink image dry state does not occur.
The second embodiment is shown in FIG.

This ink jet printer has a shielding member 1.
1 is composed of a good thermal conductor. The shielding member 11 has an exhaust hole 61 and a fin 62 for radiating heat on the upper part thereof, and the upper part temperature is kept at about room temperature, which has a function as a heat exchanger.
Further, the side wall of the shielding member 11 has a recovery groove 15. This is a material for receiving the ink solvent liquid obtained by liquefying the ink solvent vapor cooled on the upper and side walls of the shielding member 11 and guiding it to the outside of the shielding member 11 (not shown) in a recovery container. is there. The recovery groove 15 is provided with an inclination so that the ink solvent liquid flows down in a certain direction by gravity.

The ink solvent heated by the heater 10 evaporates, rises by natural convection together with the surrounding air, and is discharged from the exhaust hole 61 to the outside of the shielding member 11. At this time, since the shielding member 11 is kept at almost room temperature, the exhaust gas is cooled and the ink solvent is liquefied and guided to the recovery groove 15 to be recovered.

The configuration and operation other than the above are the same as those in the first embodiment, and the description thereof will be omitted.

As is apparent from the above description, the ink solvent used in the apparatus of the present invention is a solvent having a low vapor pressure at room temperature and having a characteristic that the vapor pressure increases with an increase in temperature. Furthermore, the saturated vapor concentration at room temperature is
It is desirable that the level does not cause environmental pollution. As such a solvent, in addition to a petroleum-based high resistance low dielectric constant aliphatic hydrocarbon solvent, silicone oil or the like can be used.

In the present embodiment, an example using a non-aqueous ink has been described. When water is used as the ink solvent, water vapor is not an environmental pollutant, but water is the main component of the solvent, and other solvents other than water are used. In the case of an ink containing a component, it is necessary to prevent the diffusion of the ink solvent vapor as in the case of the non-aqueous solvent ink, and the configuration of the present invention is effective even in an apparatus using the aqueous ink.

The recording head is kept at the temperature inside the shielding member. In order to prevent malfunction of the nozzle portion due to drying, it is desirable that the evaporation rate at this temperature be low. The ink solvent of this embodiment has a low saturated vapor pressure at room temperature and is quickly evaporated on the transfer medium kept at a high temperature to be removed from the ink image. Therefore, there is an effect that high reliability can be obtained by using an ink solvent that is hard to dry.

Since it can be further liquefied and recovered,
The waste liquid is easy to handle and easy to dispose of. It also has the effect that it can be reused as an ink solvent.

Furthermore, there is an effect that the ink vapor does not condense on the transfer medium kept at a high temperature, the transfer unevenness does not occur, and a high quality image can be stably obtained.

[0043]

According to the ink jet recording apparatus of the present invention,
The ink image on the transfer medium is heated and evaporated to be removed as a solvent vapor from the ink image, and the solvent vapor is cooled and liquefied and recovered in a liquid state.

Therefore, there is an effect that the ink vapor does not condense on the transfer medium kept at a high temperature, the transfer unevenness does not occur, and a high quality image can be stably obtained.
Further, the configuration of the present invention has an effect that it is possible to prevent the vapor discharge to the environment by cooling the ink solvent vapor by the heat exchanger and liquefying and recovering it.

[Brief description of drawings]

FIG. 1 is a perspective view of an inkjet printer according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a heat exchanger of the inkjet printer according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an example of vapor pressure characteristics of an ink solvent used in the inkjet recording apparatus of the present invention.

FIG. 4 is a perspective view of an inkjet printer according to a second embodiment of the present invention.

[Explanation of symbols]

 1: Transfer drum (transfer medium) 2: Recording head 8: Recording paper (recording medium) 9: Pressure roller 10: Heater 11: Shielding member 13: Heat exchanger 14: Fin 15: Recovery groove 19: Recovery container 61: Exhaust Hole 62: Heat dissipation fin 64: Ventilation gap

Claims (1)

[Claims] 1. An inkjet recording apparatus for transferring an ink image formed on a transfer medium with an ink obtained by dissolving or dispersing a coloring material in a solvent having an evaporative property onto a recording medium, which ejects ink droplets. A recording head, a transfer medium which is provided with a gap from the recording head, and which is provided with a heating means, the transfer medium being kept at a temperature not lower than the ambient environment temperature, and the heat exchange means being kept at a temperature not higher than the transfer medium temperature, An inkjet recording apparatus comprising: a shielding member that shields the transfer medium from the surroundings.