JPH0717066A - Hot-melt ink recorder of electrostatic attraction method - Google Patents

Abstract

PURPOSE:To provide a hot-melt ink recorder of an electrostatic attraction method wherein the quantity of flown ink is made stable and fixing strength is excellent and unevenness of ink and deterioration of an image are prevented without misdirection and dropout of a dot by providing an electroconductive layer on the surface of a middle transfer body to which hot-melt ink is flown and stuck. CONSTITUTION:Voltage pulses of voltage 3V and pulse width 1.5ms are impressed to a contact electrode synchronously with pulses impressed to the recording heads 1-4 in order to regulate the volume resistivity of hot-melt ink stuck on a middle transfer body 5 to <=10OMEGAm. Thereby ink is heated to 70 deg.C. A transfer means is constituted of a rear roll 6 being a pressure welding member and a local heating member 8 for transfer which is arranged oppositely thereto. An ink picture formed on a middle transfer body 5 is transferred and fixed on a recording medium 9. The local heating member 8 for transfer is constituted by bonding a contact electrode made of copper material of 1mmphi onto the elastic layer of rubber material formed in a metallic supporting member. The contact electrode touches the heat-generating layer of the position opposite to the rear roll 6 being the pressure welding member, so that the surface of a part is exposed from the protective heat-generating layer formed of a polyimide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording device used in a printer, a facsimile, or the like, and more specifically, hot melt ink that is heated and melted flies from a recording head by electrostatic attraction to form an ink image. The present invention relates to an electrostatic suction type hot melt ink recording apparatus.

[0002]

2. Description of the Related Art A hot-melt ink recording apparatus uses a pressure pulse system for causing a molten hot-melt ink filled in a recording head to fly by applying a pressure, or a method for ejecting the molten hot-melt ink due to a difference in a method of flying the ink. It is classified into an electrostatic suction method in which an electrostatic suction force is applied to the molten hot melt ink filled in to fly.

An example of the latter hot-melt ink recording apparatus using the electrostatic attraction method is, for example, Japanese Patent Laid-Open No.
No. 0-90775 is known, and an ink ejection substrate that ejects a heat-meltable ink that is heated by a plurality of electrodes arranged at one end into a liquid state, and an ink ejection substrate that faces the ink ejection substrate with a recording paper sandwiched therebetween. It consists of electrodes and an ink ejection control unit that selectively applies a voltage according to the image signal between them to generate an electrostatic attraction force. The heat-melting ink is ejected directly onto the recording paper for recording. A recording device for forming an image is disclosed. However, in the above apparatus, the ejected heat-melting ink is rapidly cooled and solidified when it adheres to the recording paper, and is solidified and swelled before sufficiently penetrating into the recording paper. Adheres on recording paper. As a result, the fixing strength to the recording paper is insufficient, the ink is easily peeled off, and ink loss or ink unevenness easily occurs.

In view of this, in Japanese Patent Laid-Open No. 56-113462, rapid cooling of the ink on the recording paper is performed by ejecting the melted ink toward the heated and heated recording paper by electrostatic attraction. In addition, the viscosity of the ink is increased to improve the adhesion and penetrability of the ink, thereby obtaining a sufficient fixing strength. Further, in Japanese Patent Laid-Open No. 63-205241, a platen around which a recording paper is wound is arranged so as to face a print head (recording head), and a heat-melting ink is ejected from the print head toward the recording paper by electrostatic attraction or the like. Then, the heat-melting ink attached to the recording paper is heated or / and pressed to obtain sufficient fixing strength of the ink on the recording paper. However, in these devices, the heat-melting ink needs to be directly jetted onto the recording paper, so that the voltage for generating the electrostatic attraction force is applied across the recording paper. The resistance value of the recording paper varies depending on the volume resistivity and thickness of the recording paper, and even if the same recording paper is used, the resistance value changes due to unevenness and humidity, etc. The value decreases), the generated electrostatic attraction force, and thus the amount of ejected ink is not constant, and as a result, the formed image is deteriorated due to uneven density.

Therefore, the present inventors have previously disclosed an ink jet recording apparatus in which not only sufficient fixing strength can be obtained, but also the amount of flying ink is stable. One is to cause a heat-melting ink in a heat-melting state to fly from a recording head to an intermediate transfer body by using electrostatic attraction force, etc., and to keep the ink adhering to the intermediate transfer body near a softening temperature of a recording medium. Is an ink jet recording apparatus (Japanese Patent Application No. 4-38789) that transfers under pressure heating to the other.
An inkjet recording method in which a heat-meltable ink in a heat-melted state is ejected from a recording head to an intermediate transfer body by using electrostatic attraction force, and the ink attached to the intermediate transfer body is pressure-transferred to a recording medium (Japanese Patent Application No. 4-314398). These eject ink once onto an intermediate transfer member and transfer it onto recording paper, thereby stabilizing the amount of ink flying irrespective of the recording paper or the like, and at the same time securing the fixing strength to the recording paper. However, in such a method using the intermediate transfer member, the advantages that the fixing strength is improved and the flying ink amount is stabilized are achieved, but the direction of the ink flying from the recording head to the intermediate transfer member is disturbed. There is a case where a so-called dot dropout phenomenon occurs, in which ink is attached at a position deviated from a predetermined position (a phenomenon of misdirection), or ink cannot be attached in some cases. The phenomenon of such misdirection and dot omission is that in the ink dots formed by flying from the recording head to the surface of the intermediate transfer body, it is difficult for the charge carried on the heat-meltable ink to escape during the electrostatic attraction, The heat-melting ink charged to the same polarity adheres on the intermediate transfer body, and as a result, an electrostatic repulsive force is generated against the ink flying from the recording head after that, which is a cause. This causes a problem that the position of the next dot shifts from a predetermined position or cannot be attached.

[0006]

Therefore, the present inventors have found that the flying ink amount is stable without depending on various factors such as the recording paper, and only sufficient fixing strength to the recording paper can be obtained. In addition, as a result of intensive research to develop an electrostatic suction type hot melt recording device that does not cause the problems of misdirection and dot drop mentioned above, as a result of providing a conductive layer on the surface of the intermediate transfer member, The inventors have found that the electrostatic charge can easily escape from the dots previously formed on the body to prevent misdirection and dot omission problems, and completed the present invention.

Therefore, the object of the present invention is to stabilize the amount of ink ejected and to be excellent in fixing strength, and to prevent problems such as misdirection and missing dots, and to prevent ink unevenness and image unevenness. An object is to provide a hot melt ink recording apparatus capable of forming an image without causing image deterioration.

[0008]

That is, the present invention is a heating member for filling hot-melt ink which is solid at room temperature and which melts when heated to lower the volume resistivity, and heat-melts it. A recording means having a recording medium, and an intermediate transfer member which is disposed so as to face the recording means and onto which the hot melt ink flies and adheres, and for transferring or transferring and fixing the hot melt ink adhered on the intermediate transfer member onto a transfer medium. An electrostatic suction type hot melt recording apparatus comprising a transfer means, wherein the intermediate transfer body is provided with a conductive layer on the surface thereof.

The recording means is composed of a plurality of or a single recording head having a heating member which is filled with hot melt ink and heats and melts the hot melt ink. When configuring a color image recording apparatus, for example, a plurality of recording heads for ejecting different color inks such as yellow, magenta, cyan, and black are arranged in parallel to face the intermediate transfer member, Different color inks may be superposed.
The hot-melt ink is heated by this heating member to a flying temperature that is a temperature higher than the melting point and melted, and when an electrostatic attraction force is applied, the hot-melt ink forms a string and flies toward the intermediate transfer body.

The intermediate transfer member to which the hot melt ink flying from the recording head due to the electrostatic attraction adheres has at least a conductive layer on its surface, and its shape has a function of holding and conveying the adhered ink. As long as it has a drum shape or a belt shape, it does not matter.

As the material of the conductive layer, a highly conductive material such as a conductive material in a metal or polymer such as stainless steel, aluminum or copper or a conductive resin in which a filler is dispersed can be used, and its thickness is It is preferably 0.01 μm to 1 mm. This is because when the thickness of the conductive layer is 0.01 μm or less, it is difficult to form a uniform thickness due to the influence of the unevenness of the other layers that form the intermediate transfer member, and the electric resistance increases, so it takes time to dissipate the electric charges. This is because the amount of heat that diffuses increases and the energy efficiency decreases when the above is exceeded. Further, when the conductive layer is formed of a metal or the like, it can be used as an intermediate transfer member by itself, so that it is excellent in manufacturing cost and reliability. Furthermore, when electric charges are easily accumulated in the conductive layer due to the small surface area of the conductive layer, etc., by providing a conductive path composed of a conductive brush, a conductive piece, etc. for grounding the conductive layer with a low resistance, The charge quickly escapes from there, and the accumulation of the charge does not occur, and misdirection of the next flying ink and dot omission can be prevented.

The time taken for the ink adhering to the intermediate transfer member to discharge the charges used for its flight becomes longer according to the relaxation time determined by the product of its dielectric constant and volume resistivity. Further, although the dielectric constant of the ink does not change significantly, the volume resistivity changes greatly depending on the type and temperature of the ink, and in the present invention, since the hot melt ink whose volume resistivity decreases when heated is used, the intermediate transfer By providing the heating means on the body to heat the ink, it is possible to discharge the charge from the previously attached ink as quickly as possible, and to reliably carry out the next ink flight.

As such a heating means, only a heater arranged inside the intermediate transfer body to heat the entire intermediate transfer body, or a position arranged inside the intermediate transfer body and facing the recording means of the intermediate transfer body is used. A recording local heating member for heating, a heating member provided inside the conductive layer of the intermediate transfer member and a heating member that is in contact with the heating layer and energizes the entire heating layer to generate heat,
Some of them include a heating layer provided inside the conductive layer of the intermediate transfer member, and a recording local heating member which is in contact with the heating layer and energizes only the position opposed to the recording means to generate heat. In order to suppress wasteful heat generation and prevent the temperature of the device from rising, it is advantageous that the heating range is narrow and the number of members is small.Therefore, the heating unit consisting of the final heating layer and the local heating member for recording is used according to the image information. It is recommended to control so that heat is generated only when necessary.

As a material for such a heat generating layer, for example, a conductive resin film in which a conductive filler such as carbon black, metal powder, conductive ceramic powder or the like is dispersed in a synthetic resin such as polyimide, polyaramid, or fluorine resin. Or conductive ceramic sheet etc., the thickness is usually 0.3 μm to 300 μm, and the volume resistivity is 10 ⁻⁴ Ω.
it is preferable of m~10 ⁰ Ω · m. Thickness 0.3 μm
If it is thinner than 300 μm, the resistance layer has a weak strength because the resistance layer has weak strength, and if it is thicker than 300 μm, the heat is diffused until it transmits sufficient heat to the conductive layer and heats up to an unnecessary portion, which lowers energy efficiency. When a problem occurs and the volume resistivity is lower than 10 ^-4 Ω · m, the resistance value is too low and heat is generated in other high resistance portions such as the contact portion between the heating member and the heat generating layer, resulting in poor efficiency. 10 ⁰ Ω · m problem that large power is required instantaneously for generating heat and higher occurs.

The local heating member for recording which heats up by energizing only the position of the heat generating layer facing the recording means is buried in the protective heat generating layer by exposing only the surface of the contact electrode, and further laminated on the supporting member. A protective heat generating layer is formed by adhering on the elastic layer, and the contact electrode is disposed under pressure on the conductive layer at a position where ink is attached. Then, a metal having a low contact resistance and high conductivity such as silver, gold, platinum, copper, or nickel is used for the contact electrode, a polyimide film is used for the protective heat generating layer, a rubber material is used for the elastic layer, and a supporting member is used. Uses a strong metal. In addition, if the above-mentioned conductive layer or conductive path is used as the counter electrode, the configuration becomes easy. The pulse width and voltage for heat generation are determined in consideration of the structure of the heat generating portion, the driving frequency of printing, and the like.

The transfer means is provided for transferring or transfer-fixing an image formed by the hot melt ink adhered on the intermediate transfer member onto a recording medium with sufficient fixing strength, and is a pressing member and / or a transfer heating member. Composed.

As the pressing member, a back roll made of silicon rubber (please teach), which is arranged to face the intermediate transfer member via the recording medium, can be used, and the pressing member alone ensures reliable transfer or transfer. When attempting fixing, the pressure applied is increased, which leads to an increase in the size and weight of the pressure member.
It is better to use a transfer heating member together to reduce the pressurizing pressure to reduce the size and weight.

If all or part of the above-mentioned heating means can be used as the transfer heating member, the structure can be simplified by using it as much as possible. That is, in the heating means, when a heater that heats the entire intermediate transfer member or a heating member that energizes the entire heat generation layer to generate heat is used as the heating means, those members may be arranged at positions facing the pressure member. Since the hot-melt ink can be warmed, the transfer heating member also serves as a heating means, and when a recording local heating member or the like for energizing the heating layer to generate heat is used as the heating means, the heating layer is energized to generate heat. It is only necessary to newly provide only the transfer local heating member. Further, in order to suppress wasteful heat generation and prevent the temperature of the apparatus from rising, it is preferable to use a heat generating layer and a transfer local heating member for energizing the layer, and energize according to image information. Furthermore, in order to reliably transfer or transfer-fix, the ink temperature at the time of transfer may be set to a temperature that softens below the ink melting point, and for that purpose, a temperature detection device may be provided to control the temperature.

The hot melt ink used in the present invention has a property of lowering the volume resistivity when heated. The volume resistivity is preferably at least 10 ⁹ Ωm or less, preferably 10 ⁷ or less at a temperature below the melting point.
It should be less than Ωm. In addition, the ink has a volume resistivity of 10 ¹⁰ Ωm or less so that sparks do not occur at the flight temperature, and a volume resistivity of 10 ³ Ωm or more so that the string is extended from the recording means. The viscosity is 50 cp or less and the surface tension is 50 dyn so that
It is required to have a characteristic of being not more than e / cm, that is, a solid having an appropriate hardness and exhibiting plastic flow that does not cause cracks by being rubbed or bent by an external force on the recording medium. As such a hot melt ink, there is one in which a dye of each color as a colorant, an antioxidant, a viscosity modifier, etc. are added to linear polyethylene.

In the recording medium used in the present invention, since the image formed on the intermediate transfer member is transferred or transfer-fixed by the transfer means, there is no particular limitation on the thickness or the material thereof.
Not only plain paper but also thick paper and film sheet can be used.

[0021]

In the present invention, the hot melt ink is ejected onto the intermediate transfer member to form an image on the intermediate transfer member, and the image is transferred or transfer-fixed onto the recording medium. Independently, stable ink flight is possible,
The ink is stably transferred or transfer-fixed to the recording medium, and since the conductive layer can be provided on the surface of the intermediate transfer member to remove the charge from the ink, deterioration of the image quality due to electrostatic repulsion between dots is prevented. Can be prevented.

Further, by providing a heating means for heating the hot melt ink on the intermediate transfer member, the ink flying from the recording means can be warmed, the relaxation time thereof can be shortened, and the charge can be discharged earlier. The charge of the adhered ink can be quickly eliminated, and the next ink can be more reliably ejected without causing problems such as misdirection and missing dots.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings. 1 to 3 show an electrostatic suction type color ink jet recording apparatus to which the method of the present invention is applied. This recording apparatus is solid at room temperature and melts when heated to generate a volume resistivity. Recording means 1 to 4 and a recording means 1 to 4 having a heating member for heating and melting the hot melt ink.
4 and the intermediate transfer member 5 to which the hot melt ink flies and adheres due to electrostatic attraction, and the hot melt ink adhered on the intermediate transfer member 5 is transferred onto the recording medium 9 or It is composed of transfer means 6 and 8 for transferring and fixing.

As shown in FIG. 1, the recording means 1 to 4 are composed of four recording heads 1 to 4 having a recording density of 300 spi. Each recording head 1 to 4 has four color black for color printing, Yellow, magenta, and cyan inks are filled, and a heating member 1a for melting the filled hot melt ink is provided, for example, as in the recording head 1 shown in FIG. Each of the recording heads 1 to 4 has a pulse wave high voltage of 1 KV and a pulse width of 1.0 according to an image signal from a host computer (not shown).
A pulse of ms is applied, and each ink is caused to fly on the intermediate transfer body 5 which is arranged opposite to each other.

As shown in FIGS. 2 and 3, the intermediate transfer member 5 is formed in a drum shape having a conductive layer 5a and a heat generating layer 5b, and the heat generating layer 5b has a volume resistivity of 10 .OMEGA.m. It is formed of polyimide to a thickness of 50 μm, and the conductive layer 5a has a thickness of 3 by vacuum deposition on the surface of the heat generating layer 5b.
It is formed by laminating 000Å aluminum. The distance between the recording heads 1 to 4 and the conductive layer 5a is 200 μm.
Set to.

Further, as a local heating member for energizing the heating layer 5b to generate heat, a recording local heating member 7 opposed to the recording heads 1 to 4 was placed in contact with the heating layer 5b. As shown in FIGS. 2 and 4, the recording local heating member 7 has a partial surface exposed from the protective heat generating layer 7e made of a polyimide film on the elastic layer 7f made of a rubber material formed on the metal supporting member 7g. As described above, the four contact electrodes 7a to 7d made of a copper material having a diameter of 1 mm, which are in contact with the heating layer 5b at the positions facing the four recording heads 1 to 4, are bonded. Then, the volume resistivity of the hot melt ink deposited on the intermediate transfer member 5 to below 10 ⁰ Ω · m, the voltage is synchronized with the pulse applied to the recording head 1 to 4 3V, pulse width 1.5ms Voltage pulse is applied to the contact electrodes 7a to 7d to heat the ink to 70 ° C.

As shown in FIG. 3, the transfer means comprises a back surface roll 6 which is a pressure contact member, and a local heating member 8 for transfer which is arranged to face it, and is formed on a recording medium 9 on the intermediate transfer member 5. The transferred ink image is transferred and fixed. The transfer local heating member 8 includes a protective heating layer 8 made of a polyimide film on a rubber elastic layer 8c formed on a metal supporting member 8d.
A contact electrode 8a made of a copper material having a diameter of 1 mm and in contact with the heat generating layer 5b at a position facing the pressure contact member 6 is bonded so that a part of the surface is exposed from b.

A cleaner 10 for removing residual ink, paper dust, foreign matters and dust on the surface of the intermediate transfer member 5 is arranged between the transfer means and the recording means.

The hot melt ink used in this example was prepared by adding straight-chain polyethylene as a main component and adding each color dye as a colorant, an antioxidant, a viscosity modifier, and the like. Has a melting point of 102 ° C and has a surface tension of 26 dyne /
cm (120 ° C). Further, when the volume resistivity of this ink was measured, as shown in FIG. 5, there was a temperature dependence in which the resistivity rapidly decreased as the temperature rose.

When an arbitrary 100 dots in the image formed on the intermediate transfer member were examined, the maximum misdirection was 70 μm when the local heating means for recording was not operated, and When the local heating means is operated, the maximum misdirection is 2 μm.
Therefore, it was not possible to discriminate even if the image was visually observed. Further, even if the humidity was changed, the image formed on the intermediate transfer member did not suffer from unevenness or ink loss.

Further, the pressure contact force of the back roll 6 is 3 kgf /
cm, and a voltage pulse having a voltage of 3 V and a pulse width of 0.5 ms according to the image information is applied to the contact electrode 8a,
When the temperature of the ink at the time of transfer was raised to 50 ° C and the image formed on the intermediate transfer member was transferred and fixed on the rough paper, an image with uniform surface property was obtained and even if the rough paper was folded. The fixed ink did not come off.

[0032]

[Comparative Example 1] An image was formed on the intermediate transfer member by using an apparatus different from that of the embodiment in that the surface of the intermediate transfer member was constituted by an insulating layer, and the flight situation was examined. The maximum value is 150 μm, and in addition,
There were points where ink did not adhere, and the diameter of the ink that adhered was extremely small.

[0033]

Comparative Example 2 Transfer fixing was performed on a recording medium without operating the local heating member for transfer. When compared with the image of the example,
Although an image similar to that of the example was obtained on the intermediate transfer member, the surface property was not good due to the ink swelling on the recording medium after the transfer, and there were many places that peeled off when bent.

[0034]

According to the present invention, ink is ejected onto an intermediate transfer member having a conductive layer on its surface, and the ink is transferred or transfer-fixed onto a recording paper, whereby electrostatic repulsion of ink ejected later is achieved. Image with stable flying ink amount and excellent fixing strength, without causing misdirection or missing dots, and without causing ink unevenness, image unevenness, or image deterioration. It is possible to realize a hot melt ink recording device capable of producing

[Brief description of drawings]

FIG. 1 is a hot melt ink recording apparatus used in an embodiment of the present invention.

FIG. 2 is an enlarged view of an ink flying portion of a hot melt ink recording apparatus used in an embodiment of the present invention.

FIG. 3 is an enlarged view of an ink transfer fixing portion of a hot melt ink recording apparatus used in an embodiment of the present invention.

FIG. 4 is a recording local heating member of a hot melt ink recording apparatus used in an embodiment of the present invention.

FIG. 5 is a temperature-dependent characteristic diagram of the volume resistivity of the hot melt ink used in the examples of the present invention.

[Explanation of Codes] 1-4: recording head (recording means), 5: intermediate transfer member, 5
a: conductive layer, 5b: heat generating layer (heating means), 6: back roll (transfer means), 7: recording local heating member (heating means), 8: transfer local heating member (transfer means).

Front page continuation (72) Inventor Kazuo Maruyama 2274 Hongo, Ebina City, Kanagawa Prefecture, inside Fuji Xerox Co., Ltd.

Claims (4)

[Claims] 1. A recording means, which is solid at room temperature, is filled with hot melt ink that melts when heated to lower the volume resistivity, and has a heating member for heating and melting it, and a recording means. An intermediate transfer member that is arranged so as to face each other, and onto which the hot melt ink flies and adheres;
In an electrostatic attraction type hot melt ink recording apparatus comprising a transfer means for transferring or transferring and fixing the hot melt ink adhered on the intermediate transfer member onto a recording medium, a conductive layer is formed on the surface of the intermediate transfer member. An electrostatic suction type hot melt ink recording apparatus, which is provided. 2. The electrostatic suction type hot melt ink recording apparatus according to claim 1, wherein the conductive layer has a thickness of 10 nm to 1 mm. 3. The electrostatic suction type hot melt ink recording apparatus according to claim 1, wherein the intermediate transfer member is provided with a heating means for heating the hot melt ink attached to the conductive layer. 4. The heating means locally energizes the heat generating layer disposed inside the conductive layer of the intermediate transfer member and the heat generating layer at a position facing the recording means and / or the transfer means to generate heat. An electrostatic suction type hot melt ink recording apparatus according to claim 3, comprising a local heating member.