JPH0640024A - Ink-jet recording method - Google Patents

Abstract

PURPOSE:To realize excellent discharge characteristics, and to obtain an image having high picture quality at low transfer pressure in a transfer type ink-jet recording device. CONSTITUTION:Ink images are formed onto a transfer drum 1 by ink droplets discharged by a recording head 2 under the state of low viscosity, a part of a vehicle is removed from the ink images on a transfer medium 1, proper viscous ink images composed of a coloring-material solid matter and the residual vehicle are formed, a transfer drum 1 and recording paper 8 are abutted, and the ink images are transferred onto recording paper 8 at pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises the steps of forming an image of an inkjet ink (hereinafter referred to as ink) on a transfer medium,
The present invention relates to a transfer type inkjet recording method for transferring an image on a recording medium to obtain an ink image on the recording medium.

[0002]

2. Description of the Related Art In contrast to a direct type ink jet recording apparatus which directly ejects ink droplets onto a recording sheet to form an ink image, a transfer type ink jet recording apparatus is caused by unintended contact between the recording sheet or paper dust and a recording head. It has features that nozzle clogging does not occur, high reliability is obtained, and high image quality is obtained without depending on paper quality (paper surface smoothness).
As a conventional transfer type ink jet recording apparatus, Japanese Patent Laid-Open No. 59-225958 and US Pat.
The configuration described in the specification No. 156 is known.
In these, a recording head having a plurality of nozzles is provided for a drum-shaped or belt-shaped transfer medium with a gap therebetween. After an ink image is formed on the transfer medium by the recording head, the recording medium, which is the recording medium, is brought into contact with and pressed against the transfer medium to transfer the ink image onto the recording medium.

[0003]

The above-mentioned conventional ink jet recording apparatus has a problem that a large pressure is required to faithfully transfer the ink image on the transfer medium to the recording medium. That is, the ink must be a sufficiently low-viscosity liquid having a viscosity of a certain value or less in order to be ejected from the inkjet head. Normally, the required ejection characteristics cannot be obtained unless the viscosity is at least lower than 50 mPa · s for ejection. The ink image formed on the transfer medium by ejecting the ink is composed of droplets of a low-viscosity liquid and easily penetrates into the recording medium. Further, when the image is transferred by being brought into contact with the recording paper, it passes through a narrow gap, so that it is spread and distorted. Therefore, when the recording medium is brought into contact with and pressed in the next step of transferring to the recording medium, the shape is distorted, and further, the edge soaked into the recording medium becomes unclear and the image quality is deteriorated.

On the other hand, in the method disclosed in JP-A-62-92849, the ink image on the transfer medium is dried and then transferred to the recording medium. According to this method, the ink image on the transfer medium is not easily deformed and does not soak into the recording medium. Therefore, the ink image on the transfer medium is faithfully transferred to the recording medium without deterioration of the image quality due to the pressure transfer, and a high quality image is obtained.

However, in this case, the ink image on the transfer medium is in a state close to a solid that has been dried, and unless a large pressure is applied, the adhesive force between the ink and the recording medium cannot be obtained, and good transfer characteristics are obtained. Therefore, it was necessary to configure so that a large pressure could be applied. Therefore, since the pressure required for transfer is large, there are drawbacks such as an increase in size of the device and an increase in cost due to the structure of the device.

The present invention addresses the above problems and solves the problems of the prior art. The purpose of the present invention is to realize good ejection characteristics when ejecting from an ink jet recording head onto a transfer medium. Further, it is another object of the present invention to provide an ink jet recording method in which transfer from a transfer medium to a recording medium can be performed with a small transfer pressure, and as a result, a high quality ink image can be obtained.

[0007]

The ink jet recording method of the present invention is an ink jet recording method in which an ink jet ink image is formed on a transfer medium surface and transferred to a recording medium to obtain an ink image on the recording medium. An inkjet ink composed of a vehicle, (b) a pigment dispersed in the vehicle, and a coloring material solid component made of a resin in which at least a part is dissolved is used. Forming an ink image on top,
(2) A part of the vehicle is removed from the ink image on the transfer medium, and the color material solid component relative to the vehicle on the transfer medium is expressed as the color material solid component weight / (color material solid component weight + vehicle weight) = It is characterized by comprising a step of forming an ink image in a weight ratio of 0.35 to 0.7 and (3) a step of transferring the ink image from the transfer medium to a recording medium.

[0008]

According to the above method, the ink has a low viscosity when ejected from the recording head, and good ejection characteristics can be obtained.
The ink image formed by this ink is transferred to the recording medium at a low pressure from the transfer medium because a part of the vehicle is removed on the transfer medium to form an appropriate viscous state capable of low pressure transfer. .

[0009]

EXAMPLES Examples of the present invention will be described.

FIG. 3 shows a perspective view of the ink jet recording apparatus of the present invention.

In this ink jet recording apparatus, an ink image is formed on the outer periphery of the transfer drum 1 which is a transfer medium, and thereafter, the recording paper 8 which is a recording medium is brought into contact with and pressed by a pressure roller 9, so that the recording paper is 8 is the structure to be transferred.

Around the transfer drum 1, a cleaner device 3 for removing the transfer residual ink and a drying device 4 for removing the vehicle that has permeated the transfer drum 1 are arranged.

The recording head 2 selectively ejects ink as ink droplets from a plurality of nozzles in accordance with a recording signal.

The transfer drum 1 is constructed by providing an elastic layer 17 around a metal tube 16. The elastic layer 17 has a layer thickness of 1 m.
m silicone rubber layer. Since the silicone rubber has good releasability and elasticity, it can transfer an ink image onto the recording paper by following the irregularities of the recording paper, and has suitable properties as a transfer medium for the transfer drum 1.

The drying device 4 is a metal roller having a heater lamp 6 formed of a rod-shaped halogen lamp inside, and the heater lamp 6 is intermittently turned on to maintain a predetermined temperature range of about 200.degree. The permeated vehicle is evaporated and removed, and the transfer drum 1 is kept in a dry state.

The recording operation will be described. Transfer drum 1
While rotating at a constant speed in the direction of arrow A, ink droplets are selectively ejected from the nozzles of the recording head 2 to form an ink image on the transfer drum 1. The ink image on the transfer drum 1 is applied with pressure on the contact portion between the transfer drum 1 and the pressure roller 9, passes through the recording paper 8, and is transferred onto the recording paper 8 by the applied pressure.

After the transfer step, the transfer drum 1 removes the transfer residual ink image by the cleaner device 3 located downstream of the pressure roller 9, and further evaporates and removes the vehicle penetrating the transfer drum 1 by the drying device 4. Prepare for the next image forming step.

The ink used in the ink jet recording apparatus of the present invention will be described. This ink is composed of a vehicle and a solid component of a coloring material. The vehicle is a non-polar insulating solvent. The coloring material solid component is composed of a pigment dispersed in a vehicle and a resin in which at least a part thereof is dissolved. The above-mentioned vehicle has a property of penetrating into the elastic layer 17 of the transfer drum 1 of this embodiment.

Such an ink can be obtained as an ink composition in which a vehicle is used as a dispersion medium and a pigment is dispersed in the dispersion medium. That is, in the method for producing an ink of the present invention, the resin is dissolved in the ink solvent component and then the pigment is dispersed using a ball mill or the like. At this time, a dispersion stabilizer may be appropriately added if necessary. Thereafter, an ink solvent component is further added so as to obtain a desired solid content of the coloring material, and if necessary, it may be obtained after filtering with a filter or the like.

An example of an ink constituted by using the above-mentioned ink composition will be briefly described together with a manufacturing method.

Ink Example 1 The method for producing the above ink is as follows.

To 50 parts by weight of Isopar L, 16 parts by weight of commercially available stearyl methacrylate and 2 parts by weight of acrylic acid were placed in a polymerization tube, heated at 60 ° C., and stirred for 24 hours to prepare a mixture of stearyl methacrylate having an average molecular weight (weight basis) of 16000 and acrylic acid. A copolymer resin solution is obtained and designated as solution A.

Next, 9 parts by weight of MA-100 manufactured by Mitsubishi Kasei Co., Ltd. was added to the solution A obtained in the above step, and the solution A was thoroughly permeated into the carbon black, and then the circulating horizontal mill (EI) was used.
GER ENGINEERING LIMITED bead mill) 0.9 mm beads were dispersed at 5000 rpm for 1 hour to obtain a dispersion B having an average particle diameter of 2 μm. Next, while stirring the dispersion B with a stirrer (HI-15 manufactured by Tokyo Rikaki Co., Ltd.), gradually add 2 parts of Exol D-130.
The target ink was obtained by adding 3 parts by weight.

An ink having a viscosity of 20 mPa · S at 20 ° C. and a shear rate of 26000 / s was obtained from the above composition.

The transfer characteristics of the ink image formed on the transfer drum 1 using this ink will be described. FIG. 1 shows the transfer characteristics of this ink.

In the graph of FIG. 1, the horizontal axis represents the elapsed time from the formation of the ink image on the transfer drum 1 to the transfer. This is the time from the time when the ink droplets adhere to the transfer medium to the time when the ink image on the transfer medium is transferred to the recording paper, and hereinafter, this is referred to as the concentration time. The elastic layer 17 on the transfer drum 1 is a silicone rubber having a thickness of 1 mm and has a characteristic of absorbing a vehicle. Therefore, the concentration time corresponds to the concentration state of the ink image on the transfer drum.
The vertical axis represents the pressure applied during transfer.

A shaded area U is an area where a high-quality transfer image can be obtained. Similarly, an area S is an area where image quality is deteriorated due to blurring or spread deformation on a recording sheet at the time of transfer, and an area V is image quality deterioration due to transfer residual. This is the area that can be seen. Area U
In the lower end region of, the part indicated by the broken line is transitional,
The behavior of the regions S and V is unstable.

The results show that, with the configuration of this embodiment, high quality transfer can be performed with a small transfer pressure P1 in a specific concentrated state. That is, the minimum transferable time T1 and the maximum transferable time T2 of the concentration time with respect to the transfer pressure P1.
Exists. If transferred at a time earlier than T1, the concentration of the ink image is insufficient and the image collapses, and a good transferred image cannot be obtained due to penetration. When the transfer is performed after passing T2, the drying is progressing, so that the required transfer pressure is large and the transfer residual occurs at the pressure P1. When the characteristics using the ink of this experiment are represented by typical numerical values, when T1 is about 2 seconds and T2 is 6 seconds, the transfer pressure P1 capable of high-quality transfer is 3 Kg / cm.
^{Was 2} . This was a pressure of 1/5 to 1/10 of the transfer pressure in the case of transferring after the drying has sufficiently progressed.

At this time, the ink image on the transfer medium at the time of transfer had a solid content concentration of 35 to 70%. In this state, the ink image is kept in a moderately viscous state.

The solid content concentration is represented by the following definition.

Solid content concentration = (coloring material solid component weight) / (coloring material solid component weight + vehicle weight) The relationship between the concentration time and the solid content concentration can be explained using still another experimental result of FIG. it can. As a result of the measurement, the absorption property of Isopar L of the silicone rubber having a thickness of 1 mm was 1.3 Kg / m ^{2 as} a saturated vehicle permeation amount. On the other hand, the amount of ink ejected from the ink jet recording head 2 is 0.06 μg per dot, which forms a dot having a diameter of 84 μm on the transfer drum 1.
It was 0.8E-3 Kg / m ² . Since the vehicle is 73% by weight in the ink, the amount of vehicle is 7.9E-3 Kg / m ² in the ink image portion. Since such an amount is a sufficiently small value with respect to the saturated vehicle permeation amount, the above-mentioned vehicle permeation is promptly performed in about 7 seconds. The vehicle residual amount corresponding to the appropriate solid content concentration of 35 to 70% is 1.25 to 5.4E-3 Kg / m ² , and the permeation amount of the vehicle that permeates the transfer medium is 2.5 to
It is 6.65E-3 Kg / m ² . The time required for this permeation (appropriate concentration time) is in the range of about 2 to 6 seconds from the figure. If the concentration time is greatly exceeded and a long concentration time passes, the penetration of the vehicle into the transfer drum 1 progresses, and most of the vehicle is removed from the ink image, so that the concentration exceeds the proper solid content concentration, and low pressure transfer cannot be performed. . In the ink jet recording apparatus of the present embodiment, the ink image on the transfer medium is transferred with a small transfer pressure by transferring the ink image in a state where the ink image is kept in a moderately viscous state in a state where the drying has not progressed sufficiently. , It is possible to perform high-quality transfer without impregnation or shape distortion.

When the weight ratio of the solid component of the coloring material to the vehicle is less than 0.35, image deletion occurs even when a low pressure is applied in the transfer step, and when it exceeds 0.7, the ink image is dried. And a large transfer pressure is required.

That is, in this apparatus, ink is ejected from the recording head 2 in a low viscosity state. Further, a part of the vehicle is removed from the ink image on the transfer drum 1. Transfer is performed in an appropriately low-viscosity state, and high-quality transfer is performed at low pressure.

In the ink jet method of this embodiment, recording is performed in the following steps.

(1) a step of forming an ink image on a transfer medium with ink droplets; (2) removing a vehicle from the ink image on the transfer medium, and
(Weight of solid material of coloring material + weight of vehicle) = 0.35-0.
A step of forming an ink image in a weight ratio of 7, and (3) a step of transferring the ink image from the transfer medium to a recording medium,
(4) Step of removing the ink solvent permeating component from the transfer medium If the step (2) is omitted among the above steps, when the ink image is not dried on the transfer medium, the ink penetrates into the recording paper and is deformed. And a high quality transferred image cannot be obtained. If the drying progresses too much, a large transfer pressure is required. (4)
If the process is omitted, the previous vehicle that remains in the transfer medium during continuous operation will affect the ink image drying characteristics on the transfer medium during subsequent image formation, requiring a longer time for drying than the initial state. However, stable transfer characteristics cannot be obtained.

In the apparatus of this embodiment, an ink image maintained in a viscous state controlled by the ink composition is formed on the transfer medium in the above step, and this is transferred, so that a high-quality image can be formed at low pressure. can get.

In the present embodiment, the vehicle is removed from the ink image on the transfer medium by absorption into the transfer medium, but this may be performed by evaporation of the vehicle.

Further, the time required for the ink image to reach an appropriate viscous state on the transfer medium differs depending on the composition of the ink and the speed of removal of the vehicle of the ink on the transfer medium. It is necessary to set the concentration time until transfer to an appropriate value according to this characteristic.

[0039]

According to the ink-jet ink and the ink-jet recording method of the present invention, the ink is in a low viscosity state when ejected from the recording head, good ejection characteristics are obtained, and an ink image formed by this ink is formed. A part of the ink solvent is quickly removed on the transfer medium, and an ink image in a moderately viscous state composed of the residual vehicle and the solid component of the coloring material is formed on the transfer medium. By pressure-transferring to the recording paper in this viscous state, it is possible to transfer a high-quality image to a recording medium with low pressure.

[Brief description of drawings]

FIG. 1 is a diagram illustrating transfer characteristics from a transfer medium to a recording medium.

FIG. 2 is a diagram showing ink solvent penetration characteristics into a transfer medium.

FIG. 3 is a perspective view of a mechanism of the inkjet recording apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 1 Transfer Drum (Transfer Medium) 2 Recording Head 4 Drying Device 6 Heater Lamp 8 Recording Paper (Recording Medium) 9 Pressure Roller

Claims (1)

[Claims] 1. An inkjet recording method for forming an inkjet ink image on a surface of a transfer medium and transferring the same to a recording medium to obtain an ink image on the recording medium, wherein (a) a vehicle and (b) a vehicle are used. (1) forming an ink image on the transfer medium with ink droplets, using an inkjet ink composed of a dispersed pigment and a coloring material solid component made of a resin in which at least a part is dissolved; ) A part of the vehicle is removed from the ink image on the transfer medium, and on the transfer medium, the solid content of the coloring material with respect to the vehicle is expressed as solid weight of coloring material / (weight of solid coloring material + weight of vehicle) = 0. An ink jet printer comprising: a step of forming an ink image in a weight ratio of 35 to 0.7; and (3) a step of transferring the ink image from the transfer medium to a recording medium. Recording method.