JPH05318714A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To obtain a transfer ink jet recording device capable of widening the material selection range of a transfer medium and obtaining high quality ink images on the recording medium with low transfer pressure. CONSTITUTION:An ink image is formed on the first image transfer medium 1 and then dried by the use of an electrification device 26 and a cleaner 27, following this. it is electrostatically image-transferred on the second image transfer medium 3 and, further, pressingly image-transferred on the recording paper 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording device. More specifically, the present invention relates to a transfer type inkjet recording apparatus that forms an ink image on a transfer medium and then transfers the ink image to the recording medium to obtain the ink image on the recording medium.

[0002]

2. Description of the Related Art In a transfer type ink jet printer, there is no unintentional contact between a recording paper and a recording head, and ink jet clogging due to adhesion of paper dust or the like is unlikely to occur.
Therefore, it has a feature that high reliability is obtained. A conventional transfer type inkjet printer is disclosed in Japanese Patent Laid-Open No.
No. 9-225958 and USP 4,538,156.
The configuration described in Japanese Patent Publication is known.

In these apparatuses, a recording head having a plurality of nozzles is provided on a cylindrical transfer medium with a gap therebetween. After the ink image is formed on the transfer medium by this recording head, the recording medium is brought into contact with the transfer medium, and the recording medium is pressed against the transfer medium from behind the recording medium to transfer the ink image onto the recording medium. The way to do is taken.

[0004]

However, in the above-mentioned conventional ink jet printer, the material selection range is narrow when selecting the material of the transfer medium, and it is difficult to obtain a high quality ink image on the recording paper. It had a problem that

That is, it is necessary for the transfer medium to satisfy the following two characteristics, and these two characteristics tend to conflict with each other.

(1) The ink droplets ejected from the ink jet recording head have the characteristic that high quality dots can be formed on the transfer medium. (Hereinafter, this property is referred to as dot forming property.) (2) It has a property that an ink image on a transfer medium can be transferred onto a recording paper at a low pressure without being left untransferred. (Hereinafter, this property is referred to as transferability.) The dot formability depends on the wettability between the transfer medium and the ink. If it is easy to wet, the ink droplets adhering to the transfer medium will form a thin ink film in a short time. Spread. For this reason, even if it is desired to form a dot image of a desired size, the dots will spread widely, and the characters, images, etc. formed by these dots cannot be accurately reproduced. On the other hand, if it is difficult to get wet, the ink droplets are repelled on the transfer medium, and a group of a plurality of adjacent ink droplets aggregate to form an ink droplet having the minimum surface area, so that the intended pattern cannot be obtained. In this case as well,
Images cannot be reproduced accurately.

On the other hand, transferability depends on the releasability of the transfer medium, and in general, a material having good releasability has poor wettability with ink. Therefore, it is difficult to obtain a transfer medium having both good dot-forming property and transfer property.

The present invention solves this problem, and an object of the present invention is to obtain a transfer type ink jet recording apparatus capable of widening the range of material selection of the transfer medium and forming a high quality ink image. It is another object of the present invention to obtain a transfer type inkjet recording device capable of transferring an ink image onto a recording medium with a low transfer pressure.

[0009]

An ink jet recording apparatus of the present invention includes an ink jet recording head that ejects ink droplets, a first transfer medium that rotates with respect to the ink jet recording head with a gap, and the first transfer medium. And a rotatable second transfer medium.

[0010]

According to the above method, the first dot having good dot forming property can be obtained.
When the material of each transfer medium is selected, the dot forming property and the transfer property can be separately selected by using the above transfer medium and the second transfer medium having a good transfer property. The selection range can be widened, and a high quality ink image can be obtained on the recording paper with a low transfer pressure.

[0011]

EXAMPLES Examples of the present invention will be described.

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

The recording head 2 scans on the image forming drum 1 which is the first transfer medium. The recording head 2 is an inkjet recording head of a type that uses a piezoelectric element, and has a plurality of nozzles at regular intervals in the axial direction of the image forming drum 1.

The ink is an emulsion in which colored particles are dispersed in a dispersion medium. The dispersion medium is a petroleum solvent, that is, a high resistance low dielectric constant aliphatic hydrocarbon solvent, and specifically, Isopar G manufactured by Exxon Chemical Co. is used. It has the property of being volatile. The colored particles are composed of two components, Raven 1255 manufactured by Columbian Carbon Co., Ltd., as a pigment, and ethyl cellulose as a resin. It is dispersed in the above dispersion medium. The colored particles are negatively charged in the dispersion medium.

The ink has a solid content concentration of 2 represented by the following definition so that the ink can be stably ejected from the recording head 2.
The dispersion medium of the ink is further added and diluted until it reaches 5 wt%.

Solid content concentration = (weight of colored particles) / (weight of colored particles + dispersion medium + weight of additive) The image forming drum 1 which is the first transfer medium is a metal base tube 16
An image forming layer 17 made of a polyimide resin layer that has been subjected to a conductivity treatment is laminated around the periphery of the. The image forming layer 17 needs to be made of a material that has appropriate wettability with ink and has good dot forming properties.

Further, a charging device 26 composed of a corotron is provided around the image forming drum 1. This deposits a negative charge on the imaging drum 1.

The cleaner device 27 has an absorbing roller 28, which is a sponge roller, and a metal rod 29 pressed against the absorbing roller 28. The absorbing roller 28 absorbs a dispersion medium of excess ink from the ink image on the image forming drum 1. Then, the metal rod 29 is compressed and pushed out to be stored in the container 30.

The transfer drum 3, which is the second transfer medium, is constructed by laminating an elastic layer 37 made of conductive silicone rubber around a metal tube 36. The elastic layer 37 has a good releasability of the ink image and can transfer the pressure to the recording medium at a low pressure. Further, since the elastic layer 37 has a characteristic that the surface of the elastic layer 37 is deformed according to the unevenness of the surface of the recording paper, the ink image on the transfer drum 3 is not affected by the smoothness of the recording medium. It can be faithfully transferred to the recording medium.

The image forming drum 1 and the transfer drum 3 are in contact with each other, and a voltage is applied between them by a power source 4.

Further, a pressure roller 9 is provided as a pressure applying means for pressing the recording paper 8 which is a recording medium toward the transfer drum 3.

Next, the operation will be described.

The rotation direction and movement direction of each member during operation are indicated by arrows A, B and C in FIG. 1, respectively.

The recording head 2 selectively ejects ink droplets from a plurality of nozzles to form an ink image on the image forming drum 1 rotating in the direction of arrow A in the figure. Then, the charging device 26 irradiates the same polarity as the charging polarity of the colored particles of the ink image formed on the image forming drum 1 to concentrate the colored particles in the ink image.

FIG. 2 shows the process of concentrating the colored particles in the ink image described above. That is, the ink droplet (ink image) immediately after being ejected onto the image forming drum 1 by the recording head 2 has the charged colored particles 6 as shown in FIG.
0 is uniformly dispersed in the ink droplets. Next, the ink droplet (ink image) after passing through the charging device 26 is shown in FIG.
As shown in (b), an electric charge 61 having the same polarity as that of the colored particles 60 is accumulated on the surface of the ink droplet, and both are electrostatically repulsed, and the colored particles 60 are deposited on the surface of the image forming drum 1.
Further, the ink dispersion medium 62 remaining in the upper part of the ink droplet in the supernatant is absorbed and removed by the cleaner device 27, and an ink image in which the concentration of the colored particles is increased is formed on the image forming drum 1.

The reason for increasing the density of the ink image is as follows. In order to eject the ink droplets from the recording head 2 while maintaining high reliability, the ink must be a low-viscosity liquid having a viscosity below a certain value. As a result, the ink solvent content increases. The ink image formed on the image forming drum 1 by ejecting the low-viscosity ink is composed of ink droplets that are raised and attached by the surface tension of the ink on the image forming drum 1, and are easily deformed by an external force. Is in a state. In this state, when the ink image passes through the portion where the transfer drum 3 and the image forming drum 1 are in contact with each other, the ink image is spread and deformed because it passes through the narrow gap. Therefore, a high quality image cannot be obtained on the transfer drum 3. In the configuration of this embodiment, in order to prevent this, the density of the ink image on the image forming drum 1 is increased before transfer. This allows the ink image on the image forming drum 1 to be faithfully transferred onto the transfer drum 3 without being deformed in the transfer process.

The resistance value of the image forming layer 17 of the image forming drum 1 can be set so as to have a relaxation time such that charges accumulated on the surface disappear without staying on the surface for a long time.

Next, the image forming drum 1 and the transfer drum 3 are brought into contact with each other, and an electric field is applied by the power source 4 to make the image forming drum 1
The upper ink image is electrostatically transferred onto the transfer drum 3. That is, the colored particles having a negative charge in the ink image move toward the transfer drum 3 to which a positive potential is applied, by receiving an electrostatic force. At this time, since the elastic layer 37 has conductivity, the electrostatic transfer electric field efficiently acts on the ink image.

Next, the recording paper 8 is passed through the abutting portion between the transfer drum 3 and the pressure roller 9 while narrowing the pressure, and the narrow pressure applied applies the ink image on the transfer drum 3 to the recording paper 8.
Transfer to.

In this apparatus, the ink image formed on the image forming drum 1 is electrostatically transferred to the transfer drum 3 by using the image forming drum 1 having a good dot forming property and the transfer drum 3 having a good transferring property. In addition, the pressure is transferred to the recording paper 8.

Since the ink image on the image forming drum 1 is electrostatically transferred to the transfer drum 3, the material of the image forming drum 1 does not need to be a material having good transferability, and a material having excellent dot forming property. You can choose from. Therefore, the range of selection of the material of the image forming drum 1 is widened, and a high quality ink image can be obtained on the image forming drum 1.

Further, the image forming drum 1 does not need to be an elastic body, and the gap between the image forming drum 1 and the recording head 2 can be accurately maintained at a minute value. As a result, the ink droplets ejected from the recording head 2 adhere to a predetermined position on the image forming drum 1 without being affected by the ejection direction and the ejection speed.

On the other hand, since the ink image transferred onto the transfer drum 3 is electrostatically adhered to the transfer drum 3, the material of the transfer drum 3 does not need to be a material having a good dot forming property, and recording It is possible to select from materials having excellent transferability to the paper 8. Therefore, in addition to widening the selection range of the material of the transfer drum 3, the ink image on the transfer drum 3 is transferred to the recording paper 8 at a low pressure without causing a transfer residue, and a high quality ink image is formed on the recording paper 8. Obtainable.

Since the elastic layer 37 of the transfer drum 3 has elasticity, high image quality can be obtained regardless of the smoothness of the surface of the recording paper 8.

Further, in this embodiment, the elastic layer 37 is made of silicone rubber having good releasability. The silicone rubber has a characteristic of absorbing a petroleum solvent, which is a dispersion medium of the ink of this embodiment, and swelling and deteriorating, but in the configuration of this embodiment, the dispersion medium of the ink is removed from the ink image on the image forming drum 1. Since the structure is such that the elastic layer 3 is removed and transferred onto the transfer drum 3, the elastic layer 3
The silicone rubber of 7 does not deteriorate.

FIG. 3 is a sectional view of the ink jet printer of the second embodiment.

Three sets of units including the image forming drum 1, the recording head 2, the charging device 26 and the cleaner device 5
1, 52, and 53, the unit 51 is yellow, the unit 52 is magenta, and the unit 53 is cyan, an ink image of each color is formed on each image forming drum 1 and electrostatically transferred to the transfer drum 3. It is a composition. The structure of each member is similar to that of the first embodiment, and the description thereof is omitted.

This configuration solves the above-mentioned problems of the prior art and has the following advantages.

(1) The contours of the ink images of the respective colors are not mixed and the contours are not unclear.

(2) The ink images of the respective colors are accurately superimposed.

Therefore, a multicolor high quality ink image can be formed. The reason is as follows.

In the conventional direct type ink jet recording apparatus in which ink droplets are directly ejected from the ink jet recording head onto the recording paper or in the conventional transfer type ink jet recording apparatus having a single transfer medium, the ink image of the first color is dried. In this state, the subsequent second-color ink image is formed on top of this, so that the color materials of the first-color ink image and the second-color ink image mix with the dispersion medium of the ink, and The outline of the ink image becomes unclear. However, in the configuration of this embodiment, the transfer medium is divided into two members, that is, the image forming drum 1 which is the first transfer medium and the transfer drum 3 which is the second transfer medium. The (yellow) ink image is transferred onto the transfer drum 3 in a dry state on the image forming drum 1. Then, the unit 52 transfers the second color (magenta in this embodiment) ink image to a dry state on the image forming drum 1 and transfers it to the transfer drum 3. Similarly, the ink image of the third color (cyan in this embodiment) is dried by the unit 53 and transferred to the transfer drum 3. That is, since the respective colors are sequentially superposed in a dry state to form a multicolor ink image, the contour is not obscured and a high quality color image can be obtained.

Further, in an apparatus having a structure in which the ink images of the respective colors are superposed on the recording paper, the recording paper absorbs the ink to cause a dimensional change, and the ink images of the respective colors cannot be superposed accurately. On the other hand, in the configuration of this embodiment, since the ink images of the respective colors are superposed on the transfer drum 3 and are transferred collectively onto the recording paper 8, the ink images of the respective colors can be superposed accurately. it can.

FIG. 4 shows a perspective view of the ink jet printer of the third embodiment.

The difference from the first embodiment is that the pressure roller 9 includes the heater 41 therein. The heater 41 is composed of a rod-shaped halogen lamp, and by intermittently turning on the halogen lamp, the pressure roller 9 is maintained at a predetermined temperature, and the ink image at the time of transfer is brought to a high temperature state. As a result, the transfer pressure can be reduced and the transfer strength can be improved.

In the structure of this embodiment, the image forming drum 1 is not in direct contact with the pressure roller 9 kept at a high temperature.
It never gets hot. Therefore, the image forming drum 1 and the members provided around the image forming drum 1 are not required to have heat resistance and the selection range of the constituent materials is wide.

[0047]

According to the ink jet recording apparatus of the present invention,
An ink image is formed on the first transfer medium having a good dot-forming property and transferred to a second transfer medium having a good transfer property,
Further, it can be faithfully transferred to the recording medium at a low pressure. Therefore,
When selecting the material of each transfer medium, the dot forming property and the transfer property can be selected separately, so that the selection range of the material of each transfer medium can be widened and a high quality ink image can be formed on the recording paper at a low transfer pressure. It has the effect that it can be obtained.

[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 illustrating the function of the charging device of the inkjet printer according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an inkjet printer according to a second embodiment of the present invention.

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

[Explanation of symbols]

 1: Image forming drum (first transfer medium) 2: Recording head 3: Transfer drum (second transfer medium) 8: Recording paper (recording medium) 9: Pressure roller 17: Image forming layer 26: Charging device 27: Cleaner device 37: Elastic layer

Claims (1)

[Claims] 1. An inkjet recording head that ejects ink droplets, a first transfer medium that rotates through a gap with respect to the inkjet recording head, and a rotatable first contact medium that is in contact with the first transfer medium. An ink jet recording apparatus comprising the second transfer medium.