JPH11227177A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high quality image at a high speed using an intermediate transfer body made of a material having a high ink transfer ratio, high mechanical strength, high solution resistance and high chemical resistance. SOLUTION: The image forming apparatus 1 comprises an endless tape-like intermediate transfer body 40 entrained about an intermediate transfer body feed roller 45 and a transfer heat roller 50. An ink jet 20 is disposed in the vicinity of the roller 45 while the facing intermediate transfer body 40. A platen roller 70 is disposed in the vicinity of the roller 50 such that the roller 70 can come into contact with the intermediate transfer body 40 and a recording medium, i.e., a recording sheet 60, along with the transfer heat roller 50. Surface layer of the intermediate transfer body 40 is formed of fluororesin, a base material layer is formed of polyimide and the contact angle between ink and the surface layer of the intermediate transfer body is set larger than 30 deg. at the time of transferring ink to the recording sheet 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus capable of forming an image at a high speed by using an intermediate transfer member having good releasability of ink. .

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus that directly forms an ink image on a recording medium such as printing paper by an image forming means having an ink head has been generally used.

However, a recording medium on which an image is recorded is
In addition to high quality paper, various papers and OHP sheets having different ink receptivity, such as OHP sheets, are used. Therefore, even if an image is formed by supplying ink in the same manner, if the ink receptivity of the recording medium is different, the formed image is different, and an image of uniform quality can be formed on different recording media. Did not.

Accordingly, a method has been devised in which an image is formed by an ink head on an intermediate transfer member and the ink image formed on the intermediate transfer member is transferred to a recording medium.
In this method, for example, a resin or metal thin film such as a polyimide film formed uniformly is formed in an endless tape or drum shape, and circulated between an ink head and an image transfer unit. If an ink image is formed on this film, an image is always formed on an intermediate transfer member having a uniform ink receptivity, so that an image of uniform quality can always be obtained on the intermediate transfer member. it can. If this uniform quality image is circulated to the image transfer means and transferred to a desired recording medium, a uniform image can be always formed on recording media having different ink receptivities.

The ink image formed on the intermediate transfer member is transferred to a recording medium, and if 100% is removed, the portion of the intermediate transfer member on which the ink image is formed is circulated again to the ink head. Moved to form the next ink image at the same location on the intermediate transfer member, but due to the relationship between the ink and the intermediate transfer member, if the release rate is poor, ink image residue may remain on the intermediate transfer member. . In this case, there is a problem that the transfer rate to the recording medium is reduced and the quality of the image is reduced. Further, if it is used, the next image formation will be hindered. Further, the use of a separate cleaning means for removing these residues increases production costs and complicates the apparatus.

On the other hand, comparing the speed of formation of an ink image on an intermediate transfer member by the ink head and the speed of transfer to a recording medium, if the latter is slower, the image formation by the ink head could be processed faster. However, if the speed is adjusted to the speed, the transfer to the recording medium cannot be completed in time, and the final image formed on the recording medium disappears or fades. Therefore, the image forming speed of the image forming apparatus is limited by the speed of transferring the image to the recording medium.
An intermediate transfer member having high releasability of the ink is desirable so that the ink is quickly transferred from the intermediate transfer member to the recording medium.

Therefore, as described in Japanese Patent Application Laid-Open No. Hei 5-338368, there has been proposed a device in which silicone rubber is used for an intermediate transfer member to enhance the releasability of ink. According to the present invention, the thickness is 1 mm or less and the surface roughness is 5 mm.
A specific silicone rubber having a contact angle cosine of 0.4 μm or less and a density of 0.95 to 1.15 g / cm ³ , to which additives such as silicone oil are added. And used as an intermediate transfer member. As a result of using an intermediate transfer member using such a silicone rubber, it is possible to obtain high ink releasability from the viewpoint of the ink releasability alone.

[0008]

However, although silicone rubber can improve the releasability of the ink, it has a low mechanical strength due to its properties, and the intermediate transfer body has a problem of repeated image formation due to its properties. Since the transfer is performed and it is necessary to circulate between the image forming unit and the transfer unit,
Extremely high durability such as constant tension is required, and silicone rubber has a problem that durability is insufficient in terms of durability.

Further, since the intermediate transfer member is always exposed to ink, extremely high solvent resistance and chemical resistance are required, but silicone rubber has low solvent resistance and chemical resistance, and the There is also a problem that solvents and components are restricted.

In addition, the silicone rubber has a problem that it is easily deformed and an image formed by deformation of the intermediate transfer member is also deformed.

In order to solve the above problems, the present invention comprises a material having a high ink release rate of an intermediate transfer member, high mechanical strength, high solvent resistance and high chemical resistance. It is an object of the present invention to provide an image forming apparatus that can form a high-quality image at a high speed using an intermediate transfer member.

[0012]

In order to achieve the above object, an image forming apparatus according to claim 1 has an intermediate transfer having a substrate layer and a surface layer laminated on the substrate layer and carrying an ink image. Forming an ink image on the intermediate transfer member, and a transfer unit for transferring the ink image formed on the intermediate transfer member to a recording medium to form a final image on the recording medium. In the image forming apparatus, the surface layer of the intermediate transfer body is covered with a fluororesin,
A contact angle between the ink at the time of transfer to the recording medium and a surface layer of the intermediate transfer body is larger than 30 degrees.

In the image forming apparatus having this configuration, the contact angle between the intermediate transfer body and the ink at the time of transfer to the recording medium becomes 30 degrees or more. The formed ink image easily separates from the intermediate transfer body and is transferred to a recording medium, thereby forming a clear final image.

Further, since no residue of the ink image remains on the intermediate transfer member, it does not hinder the formation of the next ink image.
An ink image can be continuously formed on the intermediate transfer member.

Therefore, there is no need for a separate means for cleaning the intermediate transfer member.

Since the surface of the intermediate transfer member is made of a fluororesin having high mechanical strength, the intermediate transfer member has high durability, and further has high solvent resistance and high chemical resistance. Therefore, the range of selection of usable inks is widened.

The image forming apparatus according to a second aspect of the present invention provides
In addition to the configuration of the image forming apparatus according to claim 1, the base layer of the intermediate transfer body is made of polyimide.

In the image forming apparatus having this configuration, the intermediate transfer member has high mechanical strength and high heat resistance in combination with the fluorine resin coating used for the surface layer.

Further, the image forming apparatus according to the third aspect of the present invention,
In addition to the configuration of the image forming apparatus according to claim 1 or 2, the fluorine-based resin is a polytetrafluoroethylene, a perfluoroalkoxy copolymer, or a fluorinated ethylene propylene.

According to this configuration, among the fluororesins, the composition is particularly stable, and has high heat resistance, high mechanical strength, high solvent resistance, and high chemical resistance. can do.

Further, an image forming apparatus according to a fourth aspect is characterized in that, in addition to the configuration of the image forming apparatus according to any one of the first to third aspects, the contact angle is larger than 43 degrees.

According to this configuration, since the contact angle is large,
The ink releasability is extremely improved, and the ink image on the intermediate transfer body can be quickly transferred to a recording medium, so that high-speed image transfer can be performed.

According to a fifth aspect of the present invention, in addition to the configuration of the image forming apparatus according to any one of the first to fourth aspects, the ink is a heat-meltable ink, and the ink image forming means Is provided with an ink jet head, and the transfer means is provided with a heat roller.

According to this configuration, even in a printer having an ink jet head, the ink of the intermediate transfer member has good releasability, a clear image can be formed quickly, and particularly, a heat-meltable ink is used. Also, the final image can be transferred at a high speed from the intermediate transfer member to the recording medium.

According to a sixth aspect of the present invention, in addition to the configuration of the image forming apparatus according to any one of the first to fourth aspects, the ink is a heat-meltable ink, and The means comprises a thermal head, and the transfer means comprises a heat roller.

According to this configuration, even in an image forming apparatus using a heat-meltable ink, a high-quality image can be formed at high speed by using an intermediate transfer member having good ink releasability. it can.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings, with reference to one embodiment. First, the outline of the image forming apparatus according to the present embodiment will be described with reference to FIG.

In the image forming apparatus 1 according to the present embodiment, an intermediate transfer member formed in an endless tape shape is disposed around an intermediate transfer member feed roller 45 and a transfer heat roller 50. . The ink jet head 20 is provided near the intermediate transfer body feed roller 45 toward the intermediate transfer body 40. In the vicinity of the transfer heat roller 50, an intermediate transfer member 4 is provided.
A platen roller 70 is disposed so as to be able to press the recording paper 60 as a recording medium with the transfer heat roller 50 under pressure.

The so-called hot-melt type ink jet head 20 using the hot-melt ink 10 selectively jets the hot-melt ink 10 toward the intermediate transfer body 40 to transfer the hot-melt ink 10 to the intermediate transfer. A desired ink image 30 is formed on the intermediate transfer member 40 by being attached to the member 40.

The ink image 30 formed on the intermediate transfer member 40 by the ink jet head 20 is temporarily
It is held on zero. Next, the ink image 30 formed on the intermediate transfer body 40 is transferred between the recording paper 60 as a recording medium and the transfer heat roller 50 as a transfer unit in order to transfer the ink image 30 to the recording paper 60 as a recording medium. In cooperation with the platen roller 70 disposed on the back surface of the recording paper 60, the intermediate transfer body 40 is pressed against the recording paper while the ink image 30 is being heated, and the ink image 30 is transferred to the recording paper 60. Final image on recording paper 60
It is formed on top.

Next, the structure and operation of each part of the image forming apparatus 1 will be described in detail.

First, as the hot-melt ink 10 used in the present embodiment, a hot-melt ink having the following components was used.

The hot-melt ink 10 is a paraffin wax (paraffin wax standard product 155, as a normal temperature solid wax as a vehicle) as described in Japanese Patent Application Laid-Open No. 8-67840 already proposed by the present applicant.
Ethylene vinyl acetate copolymer (Evaflex 210, manufactured by Mitsui Polychemicals) as a resin
Erucic acid amide (Diamid L-200, manufactured by Nippon Kasei Co., Ltd.) as an unsaturated fatty acid amide, N-stearylstearic acid amide (Nikka Amide S, manufactured by Nippon Kasei Co., Ltd.) as a saturated fatty acid amide, and as a dye Oil-soluble dye C.I. I. Solvent black 3
(Oil Black HBB, manufactured by Orient).

The ink formulation is shown below.

Ink formulation Paraffin wax standard 155 70% by weight Evaflex 210 10% by weight Diamid L-200 8% by weight Nikka amide S 10% by weight Oil Black HBB 2% by weight The above heat-fusible ink is as follows. It can be manufactured by a simple procedure. First, the standard paraffin wax 15
5, Epaflex 210, Diamid L-200,
Nikka amide S is treated at 70 ° C. to 250 ° C., preferably 1
Heat and melt at a temperature of about 00 ° C to 200 ° C.
Mix HACK HBB. This is dispersed by a dissolver at 200 to 10000 RPM, preferably 500 to 50 RPM.
Stir and mix at 00 RPM. The prepared ink composition is filtered using a 2 μm mesh filter with a hot filtration device manufactured by Toyo Roshi Kaisha to obtain a final hot-melt ink. In addition, the melting point of this hot-melt ink is about 8
0 ° C.

The ink jet head 20 extends in a direction perpendicular to the plane of FIG. 1 so as to have a length substantially equal to the width of the recording paper 60. Further, the intermediate transfer body 40 is also formed to have substantially the same length as the recording paper 60. Therefore, the inkjet head 20 is fixedly provided in the image forming apparatus 1 and configured as a so-called page printer capable of forming an image corresponding to one line of the page width of the recording paper 60 without moving the inkjet head 20 at the same time. Have been. Of course, the inkjet head 20 is formed smaller than the width of the recording paper 60,
It is needless to say that a so-called serial printer can be configured so as to be movable in the direction perpendicular to the paper surface of FIG.

FIG. 9 shows a cross section of the ink jet head of this embodiment. A frame 25 made of aluminum has a vibrator 22 having a unimorph structure made of a piezoelectric material and a thin metal layer. Further, a nozzle forming member 24 made of a nickel plate having a thickness of 100 μm is laminated and fixed between the two via a spacer 23 also made of a nickel plate. The vibrator 22 is arranged so that the nozzle forming member 24 and the thin metal layer face each other. The nozzle forming member 24 has a diameter of 50μ.
It has a plurality of nozzles 26 with a minute opening of m. An ink heating heater 27 is provided on the bottom surface of the frame. The ink 10 is mainly made of wax or the like as described above,
This is obtained by dissolving a dye or a pigment. In the present embodiment, the ink 10 in the head is heated by the heater 27 in order to maintain a temperature of 125 ° C. having an appropriate viscosity. The heater 27 is fed back by a temperature sensor (not shown) to keep the ink 10 at a constant temperature.

Next, the operation will be described. The ink 10 is supplied to the head in a solid state. The ink 10 is heated and liquefied by the heater 27 to a predetermined temperature equal to or higher than the melting point, and is supplied to the periphery of the vibrator 22 by capillary force. In the present embodiment, the vibrator 22 and the nozzle forming member 24 maintained at a small size of 20 μm , And is held here.
At the time of ejection, a voltage is applied to the piezoelectric material of a desired one of the plurality of vibrators 22 to cause the vibrator 22 having a unimorph structure to warp. The tip of the cantilevered vibrator 22 having a length of 2 mm is displaced by 15 μm when a voltage of 150 V is applied. Next, when this voltage is released, the vibrator 22 is displaced toward the nozzle forming member 24 by an elastic restoring force, and the ink in the liquid state interposed between the free end of the vibrator 22 and the nozzle forming member 24. The ink 10 is ejected from the nozzle 26 by the pressure generated at the nozzle 10.

The ejected ink droplets of the ink 10 adhere to the intermediate transfer member 40 in a substantially hemispherically raised state, and are rapidly cooled and solidified.

The ink jet head 20 arranged toward the intermediate transfer member 40 ejects the hot melt ink 10 melted by applying a voltage to the ink jet head 20 selectively by a controller (not shown) based on image information. Then, the melted hot-melt ink 10 adheres to a predetermined place, and a desired ink image 30 is formed on the intermediate transfer body 40. The formed ink image 30 is cooled, and when its temperature falls below the freezing point of the hot-melt ink, the hot-melt ink 10 constituting the ink image 30 solidifies and is fixed on the intermediate transfer body 40 once. .

In the embodiment of the present invention, an image forming apparatus using a single color ink will be described as an example as shown in FIG. 1, but a plurality of ink jet heads 20Y, as shown in FIG. 20M, 20C, 20K
, Respectively, yellow, magenta, cyan,
It is needless to say that color printing can be performed using black ink.

Further, as shown in FIG. 3, an ink ribbon 11 carrying the heat-fusible ink 10 and an ink ribbon reel 12 for supplying and recovering the same are selectively heated and melted by a thermal head 21. Intermediate transfer member 40
Alternatively, an ink image 30 may be formed. Of course, even in this case, four thermal heads 21 are provided,
It goes without saying that color printing may be possible.

The intermediate transfer body feed roller 45 is a recording paper 60
A metal cylinder having a length substantially equal to the width of the paper and covered with rubber on its surface is rotatably supported by a roller shaft 46 so that its longitudinal direction is orthogonal to the paper surface in FIG. Are located in The intermediate transfer body feed roller 45 is provided with a driving force by a drive motor (not shown) and a transmission mechanism (not shown), and its rotation is controlled by a controller (not shown).

The transfer heat roller 50 is formed in a cylindrical shape which is rotatably supported by a roller shaft 51 having a similar length and being parallel to the roller shaft 46. The transfer heat roller 50 is also provided with a driving force so as to synchronize with the intermediate transfer body feed roller 45. And this 2
An intermediate transfer body 40 formed in an endless loop tape shape is wound around a book roller so as to be able to circulate.

As shown in FIG. 4, the intermediate transfer member 40 has a two-layer structure including an inner base layer 42 and an outer surface layer 41.

The inner base material layer 42 has a thickness of 25 (μm).
(Hereinafter abbreviated as PI), and is formed so as to have substantially the same width as the recording paper 60 in a direction perpendicular to the paper surface of FIG.

Here, polyimide is a resin having a structure in which aromatic rings are connected by an imide bond, and has extremely high heat resistance among resins, and can be used continuously at 250 ° C. to 300 ° C. Since the tensile strength is high, the dimensional stability is excellent, and the abrasion resistance is high, it is extremely exposed to high temperatures as in the case of the intermediate transfer member 40 of the present embodiment, and even under severe conditions where continuous use is performed while always applying tension. It is a stable material that shows strong durability.

The outer surface layer 41 is a coating layer made of fluorinated ethylene propylene. Specifically, a polyimide base material layer is coated with Kapton Teflon coat (120HR616.RTM.) Of Dupont, USA, and has a thickness of about 2.
5 (μm). According to the coating of the present embodiment, when the contact angle with the ink when the surface was cleaned with ethanol at a temperature of 85 ° C. using the above-described ink was measured, as shown in FIG. As a result,
The result was a maximum of 56.2 degrees, a minimum of 50.1 degrees, and an average of 53.3 degrees (standard deviation 1.51).

The film composed of these two layers is formed into a tape shape having a width substantially equal to that of the recording paper 60 to form an endless loop.
The intermediate transfer body 40 is wound around both the intermediate transfer body feed roller 45 and the transfer heat roller 50 and is freely circulated.
Is configured.

In this embodiment, Dupont of the United States
kapton teflon coat (120HR6
16), but it is well known that other Teflon coatings of the company and other fluorine-based resins also have high ink repellency. Even if coating is performed using these fluorine-based resins, It can be easily imagined that the ink repellency similar to that of the present embodiment is exhibited.

Here, "fluorine resin" is a general term for synthetic resins obtained by polymerization of olefins containing fluorine. Polytetrafluoroethylene [CF ₂ CF ₂ ] n (PTFE) mainly obtained by emulsion polymerization from tetrafluoroethylene (TFE) has extremely high durability against chemicals, has excellent electric properties, and has a high temperature of 325 ° C. It is also stable. It does not exhibit thermoplasticity, and is formed by a heat molding baking method or an extrusion molding method. In addition, the surface has a small coefficient of friction and is difficult to adhere. Trade names such as Teflon (registered trademark of DuPont), Fluon (registered trademark of ICI), gaskets, rods, tubes, insulating materials,
Although used as a coating material, it is not used in applications such as the present invention.

Other fluorine-based resins include various polymers and copolymers mainly improved for facilitating workability, for example, perfluoroalkoxy consisting of tetrafluoroethylene-perfluoroperfluoroalkylvinyl ether copolymer. Copolymer (PFA), fluorinated ethylene propylene (FEP) composed of tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), polychloroethylene Trifluoroethylene-ethylene copolymer (ECT
FE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and the like, and among them, those suitable for the purpose of the present invention can be selected. For example, polychlorotrifluoroethylene [CF ₂ CFCl] obtained by polymerization of chlorotrifluoroethylene
n (PCTFE), which has a relatively low melting point, may not be suitable as an intermediate transfer member of an image forming apparatus using a hot-melt ink depending on the use conditions. [CF ₂ C
It is desirable to use a material having a high melting point such as F ₂ ] n (PTFE). In addition, polyvinylidene fluoride (PVD)
Some of them exhibit extremely high mechanical strength and abrasion resistance as shown in F), and it is possible to produce an intermediate transfer member having high durability by utilizing such properties.

Next, the contact angle of the intermediate transfer member will be described. Here, the contact angle refers to the angle between the liquid and the liquid at the contact point when the liquid comes into contact with the object. FIG. 5 schematically shows that the ink is carried on the intermediate transfer member at different contact angles. FIG. 5 shows that the contact angle θ is 10 °, FIG. 6 shows that the contact angle θ is 30 °, and FIG. The case of 43 ° is shown.
As can be seen from the figure, a liquid having a small contact angle has a higher affinity for the liquid with respect to the object, that is, it requires a larger force to separate the liquid than a liquid having a small contact angle.

Here, experimental results are shown for the case of coating with the fluorine-based resin used in the present embodiment, the case of coating with another fluorine-based resin, and the case of no further coating.

Various polyimide (PI) films were coated under the following conditions, and the above-mentioned hot-melt inks were heated to 85 ° C., respectively.
Using a FACE automatic contact angle meter CA-Z type (manufactured by Kyowa Interface Science Co., Ltd.), PTFE-coated film 120HR616 200F919 Uncoated 4 types of film were measured at 15 points on each material and the average value was obtained. Is shown in FIG.

In the case where the ink was directly carried on the substrate without Kapton Teflon coating, that is, polyimide (PI), the contact angle on the surface was 10 ° or less, and the value could not be measured with the experimental equipment. That is, it is considered that the ink used in the experiment has a very high affinity for the polyimide, and therefore, it is difficult to transfer the uncoated polyimide surface to another recording medium or the like as it is.

On the other hand, it was found that the Teflon coating clearly increased the ink repellency.

The details of the composition of each coating material are not clear because no detailed additives have been disclosed. However, the main composition is tetrafluoroethylene-hexafluoropropylene, which is a fluororesin. Since it is published that it is a polymer (FEP),
There is no doubt that the high ink repellency in any of these experiments is derived from the tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Therefore, as is clear from the results of these experiments, it was proved that coating with a fluororesin can significantly enhance the ink repellency of the surface.

Here, even when the intermediate transfer member 40 coated with Kapton Teflon Coat PI (200F919) and having a contact angle of 43 ° is used instead of Kapton Teflon Coat PI (120R616) of the present embodiment, the transfer is performed. A test was performed, and a good transfer result with a transfer rate of 100% was shown. Therefore, it was proved that the effect of the present invention can be achieved if the contact angle is 43 °.

Next, the structure of the image forming apparatus 1 of the present embodiment for transferring the ink image 30 carried on the intermediate transfer body 40 formed as described above to the recording paper 60 as a recording medium will be described. .

As described above, the intermediate transfer body feed roller 45
In addition, the intermediate transfer body feed roller is rotated by a drive motor (not shown) when the ink image 30 formed of the cooled and solidified hot-melt ink carried on the intermediate transfer body 40 wound around the transfer heat roller 50 is rotated. , And moves below the transfer heat roller 50 in FIG. In the present embodiment, the moving speed of the intermediate transfer body 40 is set at about 1 ppm for the processing speed of the image forming apparatus on JIS standard A4 paper, that is, about 5 mm / sec on the surface of the intermediate transfer body 40. Is the moving speed. A platen roller 70 is disposed below the transfer heat roller 50 in FIG. 1 so as to face the transfer heat roller 50, and the platen roller 70
The intermediate transfer body 40 between the heat roller 50 for transfer and the platen roller 70 and the recording paper inserted therein are urged toward the heat roller 50 for transfer by being freely rotatably supported by the roller shaft 71. 60 is pressed. The pressing force at this time is about 4.4 kg. The transfer heat roller 50 is heated by a heating means (not shown), for example, a halogen lamp or a ceramic heater inserted into the cylinder, and the transfer heat roller 50 is formed of aluminum, so that the transfer heat roller 50 is heated by a heating means. The generated heat is conducted to the surface of the transfer heat roller 50, the temperature of the surface of the cylindrical surface of the transfer heat roller 50 rises, and thereafter, the surface temperature is maintained by a sensor or a controller (not shown) so that the surface temperature becomes about 85 ° C. . The temperature may be changed by setting.

Here, from the right side in FIG.
0 and the recording paper 60 inserted between the platen roller 70
Is transported to the left in FIG. 1 with the movement of the intermediate transfer body 40, and the ink image 30 formed on the intermediate transfer body 40
Is brought into close contact with and pressed against the recording paper 60. At this time, the intermediate transfer member 40 is heated to 85 ° C. by the transfer heat roller 50, and the heat-fusible ink forming the ink image 30 is also heated. Therefore, the heat-fusible ink constituting the ink image 30 melts beyond the melting point. Although the viscosity of the melted hot-melt ink 10 decreases as the temperature rises, there is a difference between the ink repellency of the intermediate transfer body 40 and the ink repellency of the recording paper 60, and the recording paper 6 except for special cases.
0 is smaller in ink repellency, that is, higher in affinity, so that when the intermediate transfer body 40 further moves to the left and the close contact between the intermediate transfer body 40 and the recording paper 60 separates, the thermal fusibility increases. The ink adheres to the recording paper 60 to form the intermediate transfer member 40.
And the transfer to the recording paper 60 is completed.

The ink image composed of the heat-meltable ink transferred to the recording paper 60 is cooled immediately after the transfer is completed, and becomes below the freezing point on the recording paper, and the heat-meltable ink solidifies and is fixed on the recording paper. You.

On the other hand, since the transfer rate of the intermediate transfer body 40 in which the ink image 30 has been transferred to the recording paper 60 is 100% as described above, the ink image 30 completely disappears from the surface thereof. Then, it is circulated and moved by the intermediate transfer body conveying roller 45 to form the next ink image 30.

Although the recording paper 60 is a paper medium as an example of the recording medium, it is needless to say that the recording paper 60 is not limited to an OHP sheet, various sheets, and a sheet-like member depending on the purpose of the image forming apparatus 1. Things.

Next, in the image forming apparatus 1 according to the present embodiment, the transfer rate was measured by changing the temperature of the transfer heat roller 50, that is, the temperature of the hot-melt ink. FIG.
In the case of an image forming apparatus using the intermediate transfer body 40 of the present embodiment coated with Teflon and the intermediate transfer body 40 not provided with Teflon prepared for comparison, the transfer rate is changed for each temperature. This is a summarized table. As shown in this table, when there is a Teflon coating as in the present embodiment, the transfer rate is 100% at 82 ° C., but when there is no Teflon coating, the transfer rate is 94.4 even at 95 ° C. Only%.

Considering that the melting point of the heat-fusible ink is about 80 ° C., the average transfer angle of the Teflon-coated intermediate transfer member 40 is about 53.
It was 3 °, and it was proved that this contact angle resulted in an extremely high release rate. On the other hand, those without the Teflon coating had a contact angle of less than 10 °, but still showed a transfer rate of 74.4% at 85 ° C. FIG. 12 shows a plot of this result. In FIG. 12, curve A shows the transfer rate of the intermediate transfer member 40 having a contact angle of 53.3 °, and curve B shows the case where the contact angle is less than 10 ° and is not Teflon coated. Here, assuming that the melting point of the hot-melt ink is 80 ° C., a safety factor is anticipated and the temperature of the heat roller for transfer is set to 85 ° C., and the transfer rate at 85 ° C. as shown by the curve C is If the curve indicates a transfer rate of 100%, transfer can be sufficiently performed. From this graph, a strong positive correlation can be found between the contact angle and the transfer rate.

Therefore, from the above facts, if the corresponding contact angle is obtained from the curve C, the relationship of the curve C can be obtained at a contact angle of about 30 °.

FIG. 8 shows the relationship between the contact angle at 85 ° C. and the transfer rate. As can be seen from this graph, if the contact angle is about 30 °, a sufficient release rate of the ink can be ensured. This is because the ink having a relatively low release rate used in the present embodiment is used. Therefore, since a sufficient release rate can be ensured, a sufficient release rate can be ensured even when another image forming ink is used.

As is clear from the description of the configuration and operation of the present embodiment as described above, the image forming apparatus of the present embodiment has the following effects.

That is, since the surface layer 41 of the intermediate transfer member 40 is coated with Teflon, the release rate of the ink used for image formation is high, and the transfer of the ink image 30 to the recording paper 60 can be performed at high speed. Not only, a high quality image can be formed without any residue on the intermediate transfer body 40 after the transfer,
Further, there is no need to provide a special cleaning mechanism.

In addition, since the base layer 42 of the intermediate transfer member 40 is made of polyimide and the surface layer 41 is made of FEP,
All materials have extremely high mechanical strength, and even if they can be circulated and moved while being stretched and wound as in the case of the intermediate transfer body 40, they are not easily broken or stretched and are hardly damaged. This has the effect of having durability.

Further, since these materials have excellent chemical resistance, they can be used irrespective of the type of ink for forming an image, and since they are remarkably excellent in solvent resistance and chemical resistance, they can be used for a long time. The intermediate transfer member 40 can be used for a long time.

In addition, any of the materials has extremely high heat resistance as a resin, and has an effect that it is not easily deformed by thermoplasticity even when used for thermal transfer or the like, and is hardly deteriorated.

Although the present invention has been described with reference to one embodiment, the present invention is not limited to this embodiment, and those skilled in the art can appropriately change the present invention without departing from the scope of the claims. Can be implemented.

[0076]

According to the present invention, there is provided an image forming apparatus, comprising: a base layer; an intermediate transfer member having a surface layer laminated on the base layer and carrying an ink image; An image forming apparatus for forming a final image on the recording medium, comprising: an ink image forming unit that forms an ink image on the intermediate transfer body; and a transfer unit that transfers the ink image formed on the intermediate transfer body to a recording medium. In the above, the surface layer of the intermediate transfer body is covered with a fluorine-based resin, and a contact angle between the ink at the time of transfer to the recording medium and the surface layer of the intermediate transfer body is larger than 30 degrees. Since the contact angle between the intermediate transfer body and the ink at the time of transfer to the recording medium is 30 degrees, the release rate of the ink is increased, and the ink image formed on the intermediate transfer body can be easily intermediated. Detach from transfer body and transfer to recording medium It is an effect that can form a sharp final image.

Further, since no residue of the ink image remains on the intermediate transfer member, it does not hinder the formation of the next ink image.
There is also an effect that an ink image can be continuously formed on the intermediate transfer member.

Accordingly, there is an effect that means for separately cleaning the intermediate transfer member is not required.

Since the surface of the intermediate transfer member is made of a fluorine resin having high mechanical strength, the intermediate transfer member has high durability, and further has high solvent resistance and high chemical resistance. Therefore, there is an effect that the range of selection of usable ink is widened.

The image forming apparatus according to claim 2 is
In addition to the effect of the image forming apparatus according to claim 1, the base layer of the intermediate transfer body is made of polyimide, so that the strength of the intermediate transfer body is less than that of the fluororesin used for the surface layer. In combination with the coating, there is an effect of having high mechanical strength and high heat resistance.

The image forming apparatus according to claim 3 is
In addition to the effects of the image forming apparatus according to claim 1 or 2, the fluorine-based resin is a polytetrafluoroethylene, a perfluoroalkoxy copolymer, or a fluorinated ethylene propylene. Among resins, the composition is particularly stable, and has high heat resistance, high mechanical strength, high solvent resistance, and high chemical resistance, and thus has an effect that a desirable intermediate transfer member can be obtained.

Further, the image forming apparatus according to the fourth aspect is characterized in that, in addition to the effect of the image forming apparatus according to any one of the first to third aspects, the contact angle is larger than 43 degrees. Because of the large contact angle, the releasability is extremely improved, and the ink image on the intermediate transfer body can be quickly transferred to the recording medium, so that high-speed image transfer can be achieved.

In the image forming apparatus according to the fifth aspect, in addition to the effects of the image forming apparatus according to any one of the first to fourth aspects, the ink is a heat-meltable ink, and Is provided with an inkjet head, and the transfer means is provided with a heat roller,
Even with a printer equipped with an inkjet head, the release properties of the intermediate transfer body are good, and a clear image can be formed quickly.Especially, even when using a heat-meltable ink, high-speed transfer from the intermediate transfer body to the recording medium is possible. There is an effect that the final image can be transferred.

In the image forming apparatus according to the sixth aspect, in addition to the effects of the image forming apparatus according to any one of the first to fourth aspects, the ink is a heat-meltable ink, and The means includes a thermal head, and the transfer means includes a heat roller. Therefore, even in an image forming apparatus using a heat-meltable ink, an intermediate transfer member having good ink release properties can be provided. There is an effect that a high-quality image can be formed at high speed by using.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an outline of an image forming apparatus according to an embodiment.

FIG. 2 is a schematic diagram illustrating an outline of a first modification of the image forming apparatus of the present embodiment.

FIG. 3 is a schematic diagram illustrating an outline of a second modification of the image forming apparatus of the present embodiment.

FIG. 4 is a schematic diagram showing an intermediate transfer member of the embodiment.

FIG. 5 is a view showing the hot-melt ink in a molten state with a contact angle of 10 ° carried on the intermediate transfer member 40.

FIG. 6 is a view showing a hot-melt ink in a molten state with a contact angle of 30 ° carried on an intermediate transfer member 40.

FIG. 7 is a view showing a hot-melt ink in a molten state with a contact angle of 43 ° carried on an intermediate transfer member 40;

FIG. 8 is a graph showing a relationship between a contact angle and a transfer rate when the transfer heat roller 50 is heated to 85 ° C.

FIG. 9 is a cross-sectional view of the inkjet head.

FIG. 10 is a table showing a difference in contact angle due to a difference in coating of an intermediate transfer member.

FIG. 11 is a table showing the relationship between the transfer rate for each temperature depending on the presence or absence of a Teflon coat.

FIG. 12 is a graph showing the relationship between the transfer rate for each temperature depending on the presence or absence of a Teflon coat.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 10 heat-meltable ink 11 ink ribbon 12 ink ribbon reel 20 inkjet head 21 thermal head 30 ink image 40 intermediate transfer member 41 surface layer 42 base material layer 45 intermediate transfer member feed roller 46 roller shaft 50 transfer heat roller 51 roller shaft 60 recording paper (recording medium) 70 platen roll

Claims (6)

[Claims] 1. An intermediate transfer body having a base layer, a surface layer laminated on the base layer and carrying an ink image, an ink image forming means for forming an ink image on the intermediate transfer body, and the intermediate transfer body A transfer unit for transferring the ink image formed on the recording medium to form a final image on the recording medium, wherein the surface layer of the intermediate transfer body is covered with a fluorine-based resin. An image forming apparatus, wherein a contact angle between ink at the time of transfer to the recording medium and a surface layer of the intermediate transfer body is larger than 30 degrees. 2. The image forming apparatus according to claim 1, wherein the base layer of the intermediate transfer body is made of polyimide. 3. The image forming apparatus according to claim 1, wherein the fluororesin is a polytetrafluoroethylene, a perfluoroalkoxy copolymer, or a fluorinated ethylene propylene. Forming equipment. 4. The image forming apparatus according to claim 1, wherein the contact angle is greater than 43 degrees. 5. The image forming apparatus according to claim 1, wherein the ink is a heat-meltable ink, the ink image forming unit includes an inkjet head, and the transfer unit includes An image forming apparatus comprising: a heat roller. 6. The image forming apparatus according to claim 1, wherein the ink is a heat-meltable ink, the ink image forming unit includes a thermal head, and the transfer unit includes An image forming apparatus comprising: a heat roller.