JPH0834115A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To provide an ink jet recording device capable of improving image quality by forming dots of low height on an intermediate transfer body without using a heating means of the intermediate transfer body. CONSTITUTION:A record head 2 heats and melts a heat melting ink 1 and makes the ink fly to an intermediate transfer body 3 arranged oppositely in accordance with image information. On the surface of the intermediate transfer body 3, a heat conductive resistance layer 4 is provided. The heat of the heat melting ink 1 stuck to the surface of the intermediate transfer body 3 flows out to the intermediate transfer body 3 through the heat conductive resistance layer 4. At this time, heat radiation takes time due to the heat conductive resistance layer 4 and changing to a solid phase becomes slow. Thus, the heat melting ink 1 expands to the surface of the intermediate transfer body 3 until it is solidified and dots of low height are formed. The heat melting ink 1 stuck to the surface of the intermediate transfer body 3 is pressed and transferred to a record medium 5 for recording.

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 for forming an image by melting and flying a heat-meltable ink onto a recording medium such as paper.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Publication No. 56-113.
No. 462 and Japanese Patent Application Laid-Open No. 60-90775, solid heat-melting ink is heated and melted, and electrostatic attraction force corresponding to image information is applied from the recording head to the recording medium. 2. Description of the Related Art Ink jet recording apparatuses of a type that eject ink to record an image on a recording medium are known. According to such an ink jet recording apparatus, problems that occur when an ink that is liquid at room temperature is used, specifically, ink bleeding (feathering) phenomenon when recording on plain paper and ink on the recording head It is possible to effectively avoid the problem of recording operation failure due to the phenomenon of drying and solidification.

However, in the ink jet recording method using the heat-meltable ink, since the heat-meltable ink is immediately condensed when flying to the recording medium side, there is a phenomenon in which the heat-meltable ink forms dots on the recording medium. confirmed. Therefore, when the ink image on the recording medium is rubbed, the information of the heat-meltable ink is easily peeled off, and the fixing strength of the ink dot is likely to be insufficient.

Further, even if a color ink is printed on a recording medium made of a transparent film sheet such as an OHP sheet, the ink dots raised on the sheet diffuse the light, and the color is not developed neatly. there were.

Means for solving these problems are disclosed in, for example, Japanese Patent Laid-Open Nos. 4-358840 and 5-20.
As described in Japanese Patent Publication No. 0997, etc., a method utilizing an intermediate transfer member has been considered. According to this method
It is possible to melt and fly the ink to the intermediate transfer body, and further transfer the ink attached to the intermediate transfer body to the recording medium by applying pressure at a constant temperature to flatten the dots and increase the fixing strength. . However, in these methods, it is necessary to add heating means to the intermediate transfer member to precisely control the surface temperature of the intermediate transfer member. For this reason, the device has the drawbacks of being complicated, generating a large amount of heat, and consuming a large amount of power.

On the other hand, for example, Japanese Patent Laid-Open No. 4-2517
As disclosed in Japanese Patent Laid-Open No. 47-47, a method in which a film-shaped intermediate transfer member is used and only the transfer portion is heated,
As disclosed in JP-A-43053 and Japanese Patent Application No. 4-314398, a method of transferring ink dots to a recording medium only by pressure without heating the intermediate transfer body has been considered.

However, in these methods in which the ink is ejected to the intermediate transfer body that is not heated to the softening temperature of the ink, the ink is cooled and condensed at the moment when it adheres to the intermediate transfer body, so that the diameter is small. A phenomenon in which raised dots are formed occurs. The phenomenon that the height of the dot is high causes various problems.

The first problem is that in the dots in this state, the dots are not uniformly crushed, so that the dot shapes after transfer become uneven and the image is deteriorated. In particular, when it is necessary to superimpose dots of a plurality of colors on the intermediate transfer member, such as in color recording, the height of the dots for one color is approximately four times the area where the dots for four colors are stacked. It will be high. Therefore, in the portion where the dots of four colors are overlapped, the dots may fall during the transfer to be elongated and slender, which causes color misregistration. This color misregistration varies depending on the height of the dots, that is, the number of overlapping colors, and causes the image to be unevenly formed. The second problem is that the pressure for crushing the dots during transfer to the recording medium becomes large, so that the mechanical strength of the intermediate transfer member is also required, and
This is the point where the weight increases.

The above problems are common to the ink jet recording system using the heat-melting ink, regardless of the system of the recording head. However, in the ink jet recording device of the system utilizing electrostatic attraction, Another problem arises. That is, the third problem is that when recording is performed by superimposing multiple colors on the intermediate transfer body by using electrostatic attraction, the height of the ink dot is increased, so that the dots of the subsequent color are recorded. In doing so, there is a problem in that dots of the next color cannot be formed at a desired position due to electrical influence. If the ink is solidified while still having an electric charge, the repulsive force will work due to the effect of the residual charge of the same polarity, and the subsequent ink will not overlap the previous ink dot, even if the next ink is stacked on top of it. Will occur. Particularly, in the apparatus described in the above-mentioned Japanese Patent Laid-Open No. 2-43053, since the insulating layer is provided on the surface of the intermediate transfer member, such a problem occurs. For this reason, a method of providing a conductive layer on the surface of the intermediate transfer member, allowing the charge to escape to the conductive layer during recording, and reducing the residual charge after the ink is solidified is considered.

However, even if the residual charges of the ink dots are completely removed, the dielectric is sandwiched between the recording head and the intermediate transfer member, and the electric field strength in the space where the dots are present is , It is larger than the area without dots. For this reason, when an attempt is made to overlap the ink of the next color, a large force is applied to the ink from the electric field in the portion where the dot of the previous color is present, and the amount of ink of the subsequent dots increases. In an extreme case, the unevenness is recognized as an image unevenness, which is a serious problem when performing overprinting with multiple colors.

As described above, when multicolor overlapping recording is performed on the intermediate transfer member by utilizing the electrostatic attraction force, the dot height adversely affects the image, and this influence has a high dot height. The more noticeable it becomes.

As described above, in the method of ejecting the heat-meltable ink onto the intermediate transfer member, the phenomenon that the height of the recording dot is high is a common problem not depending on the method of the head.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a low-height dot is formed on an intermediate transfer member without using a heating means of the intermediate transfer member, and image quality is improved. It is an object of the present invention to provide an inkjet recording device capable of improving the above.

[0014]

According to a first aspect of the present invention, there is provided a recording head holding a heat-meltable ink, and an intermediate transfer member arranged to face the recording head. The heat-meltable ink is heated and melted, and the heat-meltable ink melted in accordance with image information is caused to fly and adhere to the intermediate transfer body, and the ink adhered to the intermediate transfer body is transferred to a recording medium and recorded. In the inkjet recording apparatus, the thermal conductivity λ is 11.
It is characterized in that a heat conduction resistance layer having a thickness of less than 6 W / (m · K) and a thickness of 10 μm or more is provided.

According to a second aspect of the present invention, there is provided a recording head which holds a heat-melting ink having conductivity in a heat-melting state, and an intermediate transfer member which is arranged to face the recording head. Ink is heated and melted, an electric field is formed between the recording head and the intermediate transfer member, and the thermally melted ink melted by electrostatic force is caused to fly and adhere to the intermediate transfer member according to image information. In an ink jet recording apparatus that transfers and records the heat-meltable ink adhered to the intermediate transfer member onto a recording medium, the surface of the intermediate transfer member has a thermal conductivity λ of 11.6 W / (m · K). Thermal conductive resistance layer with a thickness of 10 μm or more and a thickness of 1
It is characterized in that a conductive layer having a thickness of 0 μm or less is provided.

[0016]

In the ink jet recording apparatus using the intermediate transfer member of the present invention, when the heat-melted ink is ejected to the intermediate transfer member according to the image information by the recording head, a pattern corresponding to the image information is formed on the intermediate transfer member. Ink is retained. At this time, the amount of heat that the ink dot has is moved by the heat transfer by the surrounding air and the heat transfer from the contact surface with the intermediate transfer body, and the temperature of the ink dot approaches the ambient temperature and becomes solid when the temperature becomes equal to or lower than the melting point temperature. Changes to. If the temperature of the intermediate transfer body is equal to room temperature and the temperature of the ink is from several tens to several hundreds of degrees, the heat transfer to the intermediate transfer body is more than the heat transfer to the ambient air by natural convection. It is also clear from heat transfer engineering that is larger. Moreover, since the volume of the intermediate transfer body is very large compared to the volume of the ink dots, the temperature of the intermediate transfer body itself hardly changes.

Here, the thermal conductivity λ of the intermediate transfer member is high,
When the amount of heat transferred to the intermediate transfer body is large, the ink is rapidly cooled, and the ink near the surface of the intermediate transfer body is solidified and changes into a solid phase. This time is earlier than the time during which the ink spreads on the surface of the intermediate transfer member due to the surface tension γ (in the case of the recording method using the electrostatic attraction force, the force that also combines the pressure due to static electricity) acting on the interface between the ink and the solid wall. , The ink dots are solidified before being sufficiently spread to form high-height dots.

In the present invention, the surface of the intermediate transfer member is provided with a thermal conductive resistance layer having a thermal conductivity λ of less than 11.6 W / (m · K). In this way, when a thermal conductive resistance layer having a small thermal conductivity λ is provided on the surface portion of the intermediate transfer member, the amount of heat per unit time flowing out from the ink dot to the intermediate transfer member via the thermal conductive resistance layer is small, It takes time for the ink temperature to drop. Therefore, the surface tension γ acting on the interface between the ink and the solid wall (in the case of the recording method using the electrostatic attraction force, the force that also includes the pressure due to static electricity) makes it possible for the ink to spread over the surface of the intermediate transfer member. There is a margin, and the dots spread to the surface of the intermediate transfer member. Therefore, if the volume of the dots is the same, dots having a height lower than that in the case without the heat conduction resistance layer 5 are formed. Also, if the thickness of the heat conduction resistance layer is too thin, heat transfer is accelerated, so the thickness should be 1
By setting the thickness to 0 μm or more, a time longer than a predetermined time is secured.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of an embodiment of the ink jet recording apparatus of the present invention. In the figure, 1 is a heat-melting ink, 2 is a recording head, 3 is an intermediate transfer member, 4 is a heat conductive resistance layer, and 5 is a recording medium. The heat-meltable ink 1 is
The ink is a solid having an appropriate hardness at room temperature and melts into a liquid when heated in the recording head 2. The heat-meltable ink 1 is resistant to rubbing and bending on the recording medium 5, shows plastic flow at room temperature and does not crack due to external force, melts at a predetermined melting point, and records by an electrostatic suction method. When a head is used, it is appropriately selected and used in consideration of having a conductivity of about 10 ³ to 10 ⁹ Ωm in a molten state.

The recording head 2 holds the heat-meltable ink 1, and heats the heat-meltable ink 1 inside to melt it.
The intermediate transfer body 3 is arranged to face the recording head 2 and is caused to fly in accordance with image information. The recording head 2 includes a pulse-on-demand method using a piezoelectric element, an electrostatic attraction method in which ink is ejected by electrostatic attraction force, and a thermal static method in which ink is ejected by a combination of electrostatic attraction force and thermal energy. Various methods such as an electric suction method and a static control method in which ink is raised by electrostatic attraction or the like and the raised ink is ejected by an air flow can be used. However, the recording head 2 needs to include at least a head heating unit that heats the heat-meltable ink to a melting temperature or higher when the ink is flying.

The heat transfer resistance layer 4 is disposed on the surface of the intermediate transfer member 3, and the intermediate transfer member 3 is disposed so as to face the recording head 2 at a predetermined interval. In FIG. 1, the intermediate transfer member 3 has a drum shape, but the function of holding and transporting the heat-meltable ink 1 melted and jetted from the recording head 2 and the heat-meltable ink 1 that is retained and transported is pressed onto the recording medium 5. As long as it has a function of transferring, it is not limited to a drum shape, a belt shape, etc.
It may have any configuration. Further, at least the surface layer of the intermediate transfer body has a property of not allowing the softened ink to penetrate into the intermediate transfer body, and it is necessary to hold the softened ink near the surface of the intermediate transfer body. for that reason,
When the heat conduction resistance layer 4 has such a property, it is possible to use the heat conduction resistance layer 4 on the surface, and when it does not have such a property, the heat conduction resistance layer 4 can be used on the surface. You may form the very thin surface layer which has such a property.

The thermal conductive resistance layer 4 provided on the intermediate transfer member 3 is
It is formed of a material having a thermal conductivity λ smaller than 11.6 W / (m · K). Examples of the material having such a thermal conductivity λ are materials other than metals, for example, resins such as polyethylene terephthalate, polycarbonate, acrylic resin, silicone rubber, synthetic rubber such as ethylene / propylene / diene / monomer, and natural rubber. Various materials such as ceramics, glass, and the like can be used. Furthermore, these can be used in combination, and glass fiber, cotton,
It may be formed by layering wool or the like, or may be made porous and have a gas such as air or nitrogen trapped inside.
If the thickness of the heat conduction resistance layer 4 is 10 μm or more,
It is possible to favorably delay the conduction of heat from the heat-meltable ink 1.

The position where the heat conduction resistance layer 4 is provided is suitable on the surface of the intermediate transfer member or in the vicinity of the surface.
Furthermore, a protective layer or a resin layer or the like may be provided on the surface as a liquid repellent layer for improving the releasability at the time of transferring the heat-meltable ink 1 as described above.

When recording is performed using an electrostatic attraction type recording head, it is necessary to dispose a conductor layer such as a metal as a counter electrode at least inside or on the surface of the intermediate transfer member. When placing the conductor layer inside the intermediate transfer member,
The conductor layer may have any thickness. When a conductive layer is used on the surface of the intermediate transfer member, the thickness of the conductive layer is preferably about 10 μm or less so that the effect of the heat conductive resistance layer is not impaired. Need to be configured. It was confirmed that when the thickness of the conductive layer is 10 μm or more, the conductive layer itself takes away the heat quantity of the ink dots, and the function of the heat conductive resistance layer located thereunder cannot be fulfilled.

An outline of the operation in one embodiment of the ink jet recording apparatus of the present invention will be described. FIG. 2 is an explanatory diagram showing an example of the shape of the ink dots immediately before contact with the intermediate transfer member, and FIG. 3 is an explanatory diagram of the spread of the ink dots attached on the intermediate transfer member. As described in FIG. 1, the recording head 2 holds the hot-melt ink 1. Inside the recording head 2, the heat-meltable ink 1 is heated and melted, and is made to fly to the intermediate transfer body 3 which is arranged oppositely according to image information. The temperature of the hot-melt ink 1 at this time is approximately several tens to one hundred and several tens of degrees although it depends on the characteristics of the ink.

The tip shape of the ink dot flying from the recording head 2 has a shape close to a sphere due to the surface tension immediately before reaching and contacting the intermediate transfer member. When the droplets fly in the air, the heat-meltable ink 1 has a drop shape close to a sphere or a cylinder, as shown in FIG. In the case where the liquid column (thread) moves to the intermediate transfer body 3, the liquid is moved between the recording head 2 and the intermediate transfer body 3 as shown in FIG. It has a shape.

In any case, at the moment when the heat-meltable ink 1 comes into contact with the surface of the intermediate transfer body 3, the intermediate transfer body 3 is driven by the kinetic energy of the ink dot and the tension acting on the surface of the intermediate transfer body 3. Spreads along the surface of the. Also,
In the case of the recording method using the electrostatic attraction force, since the heat-meltable ink 1 has conductivity, pressure due to static electricity is generated,
The hot melt ink 1 spreads to the surface of the intermediate transfer body 3 by acting together with the surface tension.

From the time when the heat-meltable ink 1 comes into contact with the surface of the intermediate transfer body 3, the amount of heat of the heat-meltable ink 1 starts to move to the intermediate transfer body 3, and the temperature of the ink dot is the temperature of the intermediate transfer body 3. Approaching temperature. At this time, the heat quantity of the ink dots moves due to heat transfer by the ambient air and heat transfer from the contact surface with the intermediate transfer body, but the temperature of the intermediate transfer body 3 is equal to room temperature, and the heat melting property is high. When the temperature of the ink 1 is about several tens to several hundreds of degrees, the heat transfer to the intermediate transfer body 3 is larger than the heat transfer to the surrounding air by natural convection. Further, since the volume of the intermediate transfer body 3 is very large as compared with the volume of the ink dots attached to the intermediate transfer body 3, the temperature of the intermediate transfer body 3 itself hardly changes. Therefore, the temperature of the ink dot approaches the ambient temperature, and when the temperature of the ink dot falls below the melting point temperature, the phase of the ink dot changes to solid.

As described above, the heat-meltable ink 1 spreads along the surface of the intermediate transfer body 3 from the time when it contacts the surface of the intermediate transfer body 3. At this time, the thermal conductivity λ of the intermediate transfer member 3
Is high and the amount of heat transferred to the intermediate transfer body is large, as shown in FIG. 3 (A), the heat-meltable ink 1 is rapidly cooled and solidified from the vicinity of the surface of the intermediate transfer body 3 to form a solid phase. Changes to. The time required for this change to the solid phase is the surface tension γ that acts on the surfaces of the heat-meltable ink 1 and the intermediate transfer member 3 (in the case of the recording method using electrostatic attraction, the force including the pressure due to static electricity). Therefore, if the heat-meltable ink 1 is earlier than the time when it spreads on the surface of the intermediate transfer member 3, the ink dots are solidified before sufficiently spreading, and high-height dots are formed.

When the heat conductive resistance layer 4 is provided on the surface of the intermediate transfer member 3 as in the present invention, the amount of heat per unit time flowing out from the ink dot to the intermediate transfer member 3 through the heat conductive resistance layer 4. Becomes smaller. Therefore, it takes time for the temperature of the ink to drop, and the change to the solid phase becomes slow.
As a result, the heat-melting ink 1 and the intermediate transfer member 3 are subjected to surface tension γ (in the case of the recording method using electrostatic attraction force, a force including static pressure due to static electricity) which acts on the surface of the heat-melting ink 1. There is a margin time to spread to the surface of the transfer body 3, and as shown in FIG. 3B, the dots spread to a surface of the intermediate transfer body having a larger area than that in the case of FIG. Low dots will be formed.

In this way, the heat-meltable ink 1 that has flown from the recording head 2 to the intermediate transfer body 3 is solidified on its surface to form ink dots. And the intermediate transfer member 3
Along with the rotation, the image formed by the ink dots having the pattern corresponding to the image information is formed on the surface of the intermediate transfer body 3.
Further, as the intermediate transfer body 3 rotates, the heat-meltable ink 1 attached to the intermediate transfer body 3 moves toward the pressure contact portion with the recording medium 5. Then, in the pressure contact portion, the heat-meltable ink 1
Is pressed against the recording medium 5 and transferred, whereby recording is performed.

FIG. 4 is a graph showing the relationship between the thickness of the heat conductive resistance layer and the height of the ink dots for each material, and FIG. 5 is an explanatory view of the relationship between the material of the heat conductive resistance layer and the height of the ink dots. Is. Actually, as the intermediate transfer member 3, various materials were arranged on the surface of the counter electrode made of copper, and ink was attached to the surface, and the height of the dot was examined. Room temperature at this time is 20
C., and the heat-meltable ink 1 is heated above its melting point to adhere to the surface of the heat conductive resistance layer. FIG. 4 shows the height of dots when ink dots having an average diameter of 80 μm are formed. The symbols in FIG. 4 are different depending on the material used for the heat conduction resistance layer. In FIG. 5, x is used when the dot height is 60% or more of the dot diameter, Δ is used when the dot height is 30 to 60%, and ◯ is used when the dot height is less than 30%. If the dot height exceeds 60%, dot collapse or the like will occur at the time of transfer to the recording medium, and image disturbance after transfer will be remarkable. Further, since the dots cannot be completely crushed, problems such as improper fixing occur. When the dot height is in the range of 30 to 60%, the irregularity of the dot is slightly recognized, but when some colors are overlapped, the flying ink may be affected, and the image is slightly deteriorated. To do. If it is 30% or less, no problem in image quality such as image distortion is observed with the naked eye. Even if the weight at the time of transfer is relatively small, all dots are flattened, and sufficient fixing strength can be obtained.

As a result of measuring the height of the formed ink dots, as shown in FIGS. 4 and 5, the heat conductive resistance layer was made of metal,
That is, the thermal conductivity λ of copper, aluminum, stainless steel, etc. is 11.6 W / (m · K) (= 10 kcal / m
-H.degree. C.) or higher, the dot height was distributed in a region of 60% or more of the dot diameter, regardless of the thickness of the thermal conductive resistance layer. However, other materials, such as glass, resins such as polycarbonate and polyethylene terephthalate, rubbers such as silicone rubber, cloth, wool, wood, cork, paper, etc. 11.6 W / (mK) It can be seen that when the size is smaller, the height of the ink dots is distributed in a low region of 60% or less, and it is possible to suppress the height of the ink dots to be lower than that when a metal is used as the heat conduction resistance layer. At this time, the thickness of the heat conduction resistance layer is 10
It was confirmed that the height of the ink dot is 30 to 60% when the thickness is less than μm, and the good ink dot height is 30% or less when the thickness is greater than 10 μm. That is, the thermal conductivity resistance layer has a thermal conductivity λ of 11.6 W / (m · K).
A substance smaller than (= 10 kcal / m · h · ° C) may be used. Further, in the case of recording such as color recording in which dots are overlapped, it is desirable that the thickness is 10 μm or more in order to improve image quality.

Hereinafter, some specific examples will be described. FIG. 6 is a schematic configuration diagram showing a first specific example in one embodiment of the inkjet recording apparatus of the present invention. In the figure, the same parts as those in FIG. 6 is a conductive layer, 7 is a back roll, 8 is a cleaner, 1
Reference numeral 1 is a black recording head, 12 is a yellow recording head, 13 is a magenta recording head, and 14 is a cyan recording head. FIG. 6 shows an example of a color inkjet recording apparatus using four colors.

A four-color recording head for color printing, specifically, a black recording head 11, a yellow recording head 12, a magenta recording head 13, and a cyan recording head 14 face the intermediate transfer member 3. And they are installed side by side. Then, the four-color recording heads 11 to 14 cause ink to fly onto the intermediate transfer body 3 in accordance with the image of each color component in accordance with an image signal from a host computer (not shown). Then, the ink dots of the respective colors are superposed on the intermediate transfer body 3.

A thermal conductive resistance layer 4 is provided on the surface of the intermediate transfer member 3, and a thin conductive layer 6 is provided on the surface thereof. The conductive layer 6 releases the electric charge of the ink adhering to the surface, and acts so as not to obstruct the superposition of ink dots. Further, it is formed very thin so as not to interfere with the function of the heat conduction resistance layer 4.

The back roll 7 conveys the recording medium 5 and presses the recording medium 5 against the intermediate transfer member 3. The ink on the intermediate transfer body 3 is pressure-transferred onto the recording medium 5 by the contact pressure between the back surface roll 7 and the intermediate transfer body 3. As a result, a color image is formed on the recording medium 5. The cleaner 8 removes residual ink, paper dust, foreign matter, and dust on the surface of the intermediate transfer body 15.

FIG. 7 is a block diagram showing an example of the recording head,
FIG. 8 is an explanatory diagram of an example of a printing state of the recording head.
In the figure, 21 is an ink chamber, 22 is a head heater, 23 is a flexible substrate, 24 is an orifice, 25 is a control electrode,
26 is a pixel drive board, 31 is powder ink, 32 is melted ink, 33 is an ink thread, and 34 is an ink dot.

In the example shown in FIGS. 7 and 8, the powder ink 31 is supplied to the recording head 2 by a powder ink supply device (not shown).
It is supplied to the ink chamber 21 inside. The powder ink 31 can be prepared, for example, by using linear polyethylene as a main component and adding each color dye as a colorant, an antioxidant, a viscosity modifier, and the like. As a result of differential thermal analysis (DTA), the melting point of this ink had an endotherm from 100 ° C to 104 ° C, and the peak was 102 ° C. The surface tension during melting was 0.026 N / m (120 ° C). The physical properties of the ink used in this example are shown below. Oxidized polyethylene wax 98% by weight Black dye PEW BLACK (manufactured by Mitsui Toatsu Co., Ltd.) 2% by weight A major feature of this ink is that it has a property of plastically flowing even after being solidified at room temperature, and when it is pressed, it is used as a recording medium. It is possible to crush without destroying the ink dots once formed on the. In addition to polyethylene, fatty acid metal salts, carnauba wax, and wax can be used as the main component of the ink.

The head heater 22 is a thick film resistor formed on a flexible substrate 23 made of polyimide, and is energized by a head heater driving circuit (not shown) during standby of the recording apparatus and during printing operation. The powder ink 31 is heated to its melting point or higher to produce the molten ink 32.

On the other hand, an orifice 24 is formed in the flexible substrate 23. The flexible substrate 23 can be made of, for example, photosensitive polyimide, and the orifice 24 can be formed by a photosensitive polyimide developing process. A liquid-repellent layer (not shown) is formed on the surface of the flexible substrate 23 facing the intermediate transfer body 3, and the molten ink 32 is washed away by the power and surface tension of the molten ink 32 to the outside of the recording head 2. Are prevented. The liquid-repellent layer can be formed of, for example, a fluororesin thin film, and the critical surface energy determined by measuring the contact angle was 0.015 N / m.

A control electrode 25 is provided on the surface opposite to the flexible substrate 23 (the surface inside the recording head 2). A large number of the above-mentioned orifices 24 and control electrodes 25 are arranged at the desired dot intervals of the recording device over the maximum width of the recording medium, and operate in parallel to improve the printing speed. Further, one control electrode 25 is provided so as to communicate with one orifice 24 and is processed into a shape surrounding the circular orifice 24. The control electrode 25 can be formed, for example, by adhering a copper foil to the flexible substrate 23 with an epoxy resin adhesive and applying a photoetching process.

Further, the control electrode 25 is the pixel drive board 2
It is pressure-contacted to 6 via an anisotropic conductive film. Here, the pixel drive board 26 drives a large number of control electrodes 25 with a high voltage (for example, a voltage of about 400V).
The pixel drive board 26 is, for example, a high breakdown voltage drive element array formed by a thin film transistor (TFT) technique on a glass substrate and a shift register for serial-parallel conversion of image data.

On the other hand, as shown in FIG.
Can be formed from, for example, an aluminum metal roll, and the heat conduction resistance layer 4 can be provided on the surface thereof, and the conductive layer 6 can be further provided on the surface thereof. The heat conduction resistance layer 4 is, for example, polyethylene having a thickness of 500 μm.
It can be made of terephthalate (PET). The conductive layer 6 may be made of stainless steel having a thickness of 5 μm, for example. The critical surface energy of the intermediate transfer member 3 having such a configuration is 0.05 N / in contact angle measurement.
It was m or more. In addition, the intermediate transfer member 3 has a -1K
A bias pulse of about V is applied.

Under such a structure, when a pulse signal of +400 V corresponding to image information is applied to the control electrode 25 by the pixel drive boat 26, the molten ink 32 facing the orifice 24 receives Coulomb force. The ink is ejected from the orifice 24 and flies toward the intermediate transfer body 3 while forming the ink string 33. The melted ink adhered to the intermediate transfer member 3 by the ink string 33 is gradually dissipated by the heat conductive resistance layer 4, so that the melted ink is sufficiently spread on the surface and then solidified. Therefore, the ink dots 34 having a low height are formed on the intermediate transfer body 3.

The inks of the respective colors ejected from the respective recording heads adhere to the intermediate transfer body 3 in an overlapping manner.
At this time, subtractive color mixing is performed on the intermediate transfer member 3. Since the intermediate transfer body 3 has an accurate feed amount and a constant environment is set by the pressurizing means, the size of the intermediate transfer body 3 is less likely to change due to disturbance such as expansion and contraction due to environmental changes than paper or the like. Therefore, in the case of forming a color image, the registration of each color (registration) is significantly easier than the case of subtractive color mixing on paper, and moreover, can be performed with high accuracy.

FIG. 9 is an illustration of an example of transfer fixing from the intermediate transfer body 3 to the recording medium 5. In the figure, 27 is a steel roll, 28 is a coating, and 35 is an ink dot. For example,
The recording medium 5 such as plain paper is fed between the intermediate transfer body 3 and the back roll 6 by a paper feeding device (not shown).
The back roll 6 is formed by coating the surface of a steel roll 27 with, for example, a coating 28 of polyacetal resin or the like. The back surface roll 6 presses the recording medium 5 against the intermediate transfer body 3 from the back surface side.

The image formed on the surface of the intermediate transfer body 3 by the recording head 2 is transferred from the intermediate transfer body 3 to the recording medium 5. At this time, the ink dots 34 that have solidified on the intermediate transfer body 3 are crushed and spread by the pressing force of the back surface roll 6, and substantially flat ink dots 35 are formed on the recording medium 5. . The ink dots 35 formed in this manner have excellent fixability and can form an ink image having excellent color developability even on, for example, a transparent film sheet.

As described above, when the critical surface energy of the intermediate transfer member 3 is 0.05 N / m or more, it is possible to transfer an image to the recording medium 5 having the same critical surface energy as follows. It is thought that it is due to the following reasons. That is, the ink dots 35 that have undergone plastic flow due to the pressure applied during transfer partially enter between the fibers of the recording medium and are mechanically and firmly bonded to the recording medium 5, while the linear polyethylene ink is separated. Since the moldability is high, ink dots do not substantially remain on the intermediate transfer body 3 having a smooth image receiving surface.

Further, since the transfer rate from the intermediate transfer body 3 to the recording medium 5 is substantially 100%, it is not necessary to clean the transfer residual ink. However, the recording medium 5 may often cause fibers, dust, and the like to adhere to the intermediate transfer body 3. Since the gap between the recording head 2 of each color and the intermediate transfer member 3 is about several tens of μm to several hundreds of μm, it is not preferable to send the intermediate transfer member 3 to the printing position with relatively large dust adhering thereto. Therefore, in the configuration shown in FIG. 6, the cleaner 8 that traps these large dust particles of several tens of μm or more is provided.

According to the above-mentioned first specific example, the height of the ink dots formed on the intermediate transfer member 3 was about ¼ of the diameter of the ink dots of 80 μm. Without the conventional heat conduction resistance layer 4, the height of the ink dot was about ⅔ of the diameter. As described above, in the ink jet recording apparatus of the present invention, it is possible to obtain ink dots having a smaller swelling than the conventional one. Also, when four colors were overlaid, the height of the ink dot was almost the same as the diameter. These ink dots are recorded on the recording medium 5
Since it is crushed by the pressure transfer to and fixed as the flat ink dots 35 on the recording medium, it is possible to form an ink image having excellent color developability on the recording medium.

FIG. 10 is a schematic block diagram showing a second specific example of an embodiment of the ink jet recording apparatus of the present invention. In the figure, the same parts as in FIG. Reference numeral 9 is a heat conductive resistance layer having conductivity. In the second specific example, as shown in FIG. 10, a heat conductive resistance layer 9 having conductivity is used on the surface of the intermediate transfer member 3. With this heat conductive resistance layer 9 having conductivity,
At the same time as forming a flat dot, the charge is prevented from remaining on the dot. This effect prevents the residual electric charges of the dots from adversely affecting the electric field when the dots of the second and subsequent colors are overlapped.

The heat-conductive resistance layer 9 having conductivity can be formed, for example, by dispersing 10% by weight of carbon particles inside polyimide. The total thickness of the heat conductive resistance layer 9 having conductivity can be set to, for example, about 500 μm. Further, the volume resistivity can be set to 10 Ωm or less, and it has sufficient conductivity. Further, the thermal conductivity λ can be about 0.12 W / (m · K).

Thermal conductive resistance layer 9 having such conductivity
When an image was recorded using the intermediate transfer member 3 having a surface on the same condition as in the first specific example, the ink dots attached to the intermediate transfer member were not immediately cooled, and Spreads along and is about 1/5 of the diameter of the ink dot
Ink dots of high height were formed. Further, when the second, third, and fourth color ink dots were overlapped from this dot, they were nicely overlapped on each dot, and the outer shape of the dot was almost the same as that of the first color. As a result, in the portion where all four colors are overlapped, the height of the ink dot is about 4/5 of the diameter, and transfer onto the recording medium 5 can be performed without any problem.

In order to examine the effect of the thermal conductive resistance layer 9 having conductivity, the residual charge of the first color dot was examined.
The potential of the surface potential of about 100 V when there is no conductivity is the heat conductive resistance layer 9 having conductivity of the second specific example.
Was about 10V.

Further, the state of the ink dots formed on the intermediate transfer body 3 was examined by comparing it with the case of a polyimide layer (volume resistivity of 10 ¹² Ωm) having a thickness of 500 μm which does not show conductivity. As a result, in the case of a non-conductive polyimide layer, the adhering positions of the dots of the second and subsequent colors and the amount of ink were not stable, and there were some that deviated from just above the dots of the previous color. In the example, due to the effect of conductivity,
It was possible to form dots of four-color overlapping on the same position, the height of the four-color overlapping dots was kept low, and the effect of the thermal conductive resistance layer was sufficient.

FIG. 11 is an enlarged view of the surface portion of the intermediate transfer member 3 of the third specific example in one embodiment of the ink jet recording apparatus of the present invention. The configuration of the third specific example is shown in FIG.
It is almost the same as the first specific example shown in FIG. In the third specific example, as the intermediate transfer member 3, a heat conductive resistance layer 4 made of polyimide is provided on the surface of an aluminum drum, and a mesh-shaped metal conductive layer 6 is further laminated on the surface. Using. The mesh-shaped conductive layer 6 may be formed as a thick film on a resin substrate, or may be formed by winding a metal wire into a resin by heat, or by uniformly photolithographically etching a metal layer. Can be manufactured by a method.

When an image was recorded using the intermediate transfer member 3 provided with such a mesh-shaped conductive layer 6 under the same conditions as in the first specific example, ink dots adhering to the intermediate transfer member 3 were found. The ink dots were not immediately cooled, but spread along the surface of the intermediate transfer body 3, and ink dots having a height of about 1/8 of the diameter of the ink dots were formed. This is because the conductive layer 6 having a high thermal conductivity λ has a smaller area in contact with the ink dots than in the first specific example. The mesh spacing at this time is 20 μm, and the ratio of the conductive layer 6 to the entire surface of the intermediate transfer member 3 is about 25% in terms of area ratio.

When the residual charge of the dots of the first color was examined, it was almost 0 V in the conductive layer 6 of the third specific example, and the dots of the four colors overlapped neatly, and the outer shape of the dots also had the first color. It became almost the same as the one. As a result, the height of the portion where all four colors are overlapped is ½ of the diameter, and transfer onto the recording medium 16 can be performed without any problem.

FIG. 12 is an explanatory view showing an example of the shape of the conductive layer. In the third specific example, the mesh-shaped conductive layer 6 is provided on the surface of the heat conduction resistance layer 4, but the shape of the conductive layer 6 is not limited to the mesh shape, and a part of the conductive layer 6 may be formed. As long as at least a part of the heat conduction resistance layer 4 is exposed, the above effect can be obtained. Therefore, the shape of the conductive layer 6 is 1 as shown in FIG.
A spiral shape by lines, a large number of linear electrodes as shown in FIG. 12 (B) are arranged in parallel, a ladder shape, or a ridge shape, and a large number of short lines as shown in FIG. 12 (C) intersect. Various shapes such as a curved shape can be used.

FIG. 13 is a graph showing the results of measuring the ink dot height in the first to third specific examples.
In the first specific example, the heat transfer resistance layer 4 made of PET and the thin conductive layer 6 were provided on the surface of the metal roll as the intermediate transfer member 3. The PET thermal conductive resistance layer 4 made it possible to reduce the height of dots as compared with the case of using the conventional intermediate transfer member composed of only metal rolls.
However, in the first specific example, since the conductive layer 6 is arranged on the outermost surface, heat conduction occurs due to this conductive layer 6. In the second specific example, the heat conductive resistance layer 9 having conductivity.
It was possible to prevent heat conduction in the conductive layer 6, delay the cooling of the ink, and make the height of the dots lower than that of the first specific example. Also, in the third specific example, by disposing the mesh-shaped conductive layer 6, the rate at which the heat of the ink escapes through the conductive layer 6 is reduced, and the cooling of the ink is delayed, so that the first specific example. The height of the dots could be made lower than in the example.

FIG. 14 is a schematic constitutional view showing a fourth concrete example of an embodiment of the ink jet recording apparatus of the present invention.
FIG. 15 is a configuration diagram of an example of a recording head using a piezoelectric element. In the figure, the same parts as in FIG. 41 to 44 are recording heads, 51 is a head body, 52 is a head heater, 53 and 59 are electrodes,
54 is a piezoelectric element, 55 is a pressure chamber, 56 is a reservoir, 57
Is a reservoir opening, and 58 is a nozzle. The fourth embodiment shows an example in which a piezoelectric element is used as a recording head and ink is ejected. The recording heads 41 to 44 are black, yellow, magenta, and
Record cyan.

The head heater 52 can be composed of, for example, a thick film resistor, and is arranged on the outer surface of the head main body 51. Then, a head heater drive circuit (not shown) is energized during the standby of the printer and during the printing operation to heat the powder ink 31 in the reservoir 56 to a temperature equal to or higher than its melting point to form the molten ink 32. The powder ink 31 is replenished from the reservoir opening 57 and melted in the reservoir 56 during recording to maintain a molten state. Examples of the ink include SI manufactured by Data products
480 or the like can be used.

On the other hand, the reservoir opening 5 of the head main body 51
A pressure chamber 55 is provided on the opposite side of 7 from each pixel by a partition wall (not shown), and a nozzle 58 is formed on the bottom surface of the pressure chamber 55. A liquid-repellent layer (not shown) is formed on the surface of the pressure chamber 55 facing the intermediate transfer member 15 to prevent the molten ink 20a from flowing out of the recording head due to power and surface tension. The liquid-repellent layer can be formed of, for example, a fluororesin thin film, and the critical surface energy obtained by measuring the contact angle in this case was 0.015 N / m.

On the opposite side of the nozzle 56 on the inner surface of the pressure chamber 55, the piezoelectric element 54 is in contact with the melted ink 20a via the electrode 53. In addition, a voltage according to image data from a signal source (not shown) is applied to the piezoelectric element 54 by the electrodes 59 and 53 on the back surface. The piezoelectric element 54, to which a voltage is applied, is displaced or deformed in the thickness direction, imparts a pressure wave to the molten ink 32 inside the pressure chamber 55, and pushes the molten ink 32 from the nozzle 56 to the outside of the head to eject the ink. Let it fly. The ink ejected from the nozzles adheres to the surface of the heat conduction resistance layer 4 provided on the surface of the intermediate transfer body 3 to form dots.

In this example, when the recording head was heated to 115 ° C. by the head heater 52, the powder ink 31 was melted in the recording head. Further, when a voltage was applied to the piezoelectric element 54 in accordance with the image data, intermittent ink droplets were generated from the nozzle 56, and the ink droplets flew onto the intermediate transfer body 3 and adhered to the surface thereof.

The intermediate transfer member 3 used in this example is a laminate of a heat conductive resistance layer 4 made of polycarbonate and having a thickness of 2 mm on an aluminum substrate, and its thermal conductivity is about 0.23 W / ( m · K). The ink dots reaching the surface of the heat conduction resistance layer 4 transfer heat to the surface of the heat conduction resistance layer 4, and the temperature gradually decreases. The surface temperature of the heat-conducting resistance layer 4 is 20 ° C., which is the same as room temperature, and the ink attached to the surface thereof is gradually cooled and sufficiently spreads on the surface of the heat-conducting resistance layer 4 and then undergoes a phase change to become a solid ink.

As shown in FIG. 4, the height of the ink dot formed by this fourth example is about 1/4 of the height of the ink dot diameter of about 80 μm, It was possible to form an ink dot having a height of about 1/3 of that of a dot formed directly.

In the above description, the drum-shaped intermediate transfer member 3 is shown, but the present invention is not limited to this.
For example, it can be applied to a configuration using the belt-shaped intermediate transfer member 3.

[0070]

As is apparent from the above description, according to the ink jet recording apparatus of the present invention, since the thermal conductive resistance layer is provided on the surface portion of the intermediate transfer member, the ink dots adhered to the surface of the intermediate transfer member. It is possible to reduce the amount of heat taken per unit time in the thickness direction of the intermediate transfer member, and it becomes possible for the ink dots to spread along the surface of the intermediate transfer member. Therefore, an ink dot having a sufficiently low dot height can be formed. As a result, if the dot shape after transfer from the intermediate transfer member to the recording medium is uneven, which has occurred in the past,
It is possible to prevent deterioration of the image due to it and improve the image quality. This is also the case with an inkjet recording apparatus that uses a method that uses electrostatic attraction, and ink dots with a sufficiently low dot height can be formed, and image quality can be improved. Further, by forming the conductive layer on the heat conductive resistance layer, it is possible to achieve positional deviation of the dots of the second and subsequent colors and to stabilize the ink amount when color overlapping is performed. Furthermore, since no means for heating the intermediate transfer member is used, the problem of increasing the volume and weight of the intermediate transfer member can be solved, and the power consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an inkjet recording apparatus of the present invention.

FIG. 2 is an explanatory diagram showing an example of the shape of an ink dot immediately before contact with an intermediate transfer member.

FIG. 3 is an explanatory diagram of the spread of ink dots attached on an intermediate transfer member.

FIG. 4 is a graph showing the relationship between the thickness of the heat conduction resistance layer and the height of ink dots for each material.

FIG. 5 is an explanatory diagram of the relationship between the material of the heat conduction resistance layer and the height of the ink dot.

FIG. 6 is a schematic configuration diagram showing a first specific example in one embodiment of the inkjet recording apparatus of the present invention.

FIG. 7 is a configuration diagram showing an example of a recording head.

FIG. 8 is an explanatory diagram of an example of a printing state of the recording head.

FIG. 9 is an explanatory diagram of an example of transfer fixing from an intermediate transfer member to a recording medium.

FIG. 10 is a schematic configuration diagram showing a second specific example of the embodiment of the inkjet recording apparatus of the present invention.

FIG. 11 is an enlarged view of a surface portion of an intermediate transfer member of a third specific example in one embodiment of the inkjet recording apparatus of the present invention.

FIG. 12 is an explanatory diagram showing an example of the shape of a conductive layer.

FIG. 13 is a graph showing measurement results of ink dot heights in the first to third specific examples.

FIG. 14 is a schematic configuration diagram showing a fourth specific example in an embodiment of the ink jet recording apparatus of the present invention.

FIG. 15 is a configuration diagram of an example of a recording head using a piezoelectric element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thermal melting ink, 2 ... Recording head, 3 ... Intermediate transfer body, 4 ... Thermal conductive resistance layer, 5 ... Recording medium, 6 ... Conductive layer, 7
... back roll, 8 ... cleaner, 9 ... conductive thermal conductive resistance layer, 11-14 ... recording head, 21 ... ink chamber,
22 ... Head heater, 23 ... Flexible substrate, 24 ...
Orifice, 25 ... Control electrode, 26 ... Pixel drive board,
27 ... Steel roll, 28 ... Coating, 31 ... Powder ink, 3
2 ... Molten ink, 33 ... Ink string, 34, 35 ... Ink dots, 41-44 ... Recording head, 51 ... Head body, 52 ... Head heater, 53, 59 ... Electrode, 54 ... Piezoelectric element, 55 ... Pressure chamber , 56 ... Reservoir, 57 ... Reservoir opening, 58 ... Nozzle.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B41M 5/00 A B41J 3/04 103 Z 103 G (72) Inventor Tetsuro Kodera Hongo, Ebina, Kanagawa Prefecture 2274 Fuji Xerox Co., Ltd. (72) Inventor Shigenori Ando 2274 Hongo Ebina, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72) Inventor Koji Adachi 2274 Hongo Ebina City, Kanagawa Fuji Xerox Co., Ltd. 72) Inventor Keizo Abe 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Kazuo Maruyama 2274, Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. A recording head, which holds a heat-meltable ink, and an intermediate transfer member, which is arranged to face the recording head,
The heat-meltable ink is heated and melted, and the heat-meltable ink melted in accordance with image information is caused to fly and adhere to the intermediate transfer body, and the ink adhered to the intermediate transfer body is transferred to a recording medium and recorded. In the ink jet recording apparatus, the thermal conductivity λ is 11.6 on the surface of the intermediate transfer member.
An ink jet recording apparatus comprising a heat conductive resistance layer having a thickness smaller than W / (m · K) and a thickness of 10 μm or more. 2. A recording head, which holds a heat-melting ink having conductivity in a heat-melting state, and an intermediate transfer member, which is arranged so as to face the recording head, wherein the heat-melting ink is melted by heating, An electric field is formed between the recording head and the intermediate transfer member, and the thermally fusible ink melted by electrostatic force is caused to fly and adhere to the intermediate transfer member according to image information, and adheres to the intermediate transfer member. In an inkjet recording apparatus for transferring the heat-meltable ink onto a recording medium for recording, the surface of the intermediate transfer member has a thermal conductivity λ of 11.
An ink jet recording apparatus comprising a thermal conductive resistance layer having a thickness of less than 6 W / (m · K) and a thickness of 10 μm or more, and a conductive layer having a thickness of 10 μm or less.