Image formation device

Abstract

To provide an image formation device that maintains surface nature of an intermediate transfer body even if used over time and suppresses occurrence of image failure due to poor cleaning in transfer type ink jet printing.SOLUTION: An image formation device, which injects an ink to an intermediate transfer body 50, and thereafter, transfers the same to a recording medium and obtains an image, comprises a cleaning part 70 which cleans the ink remaining in the intermediate transfer body 50 without being transferred to the recording medium. The cleaning part 70 has a first cleaning member 71 which cleans a surface of the intermediate transfer body 50, and a second cleaning member 73 which cleans a surface of the first cleaning member 71. A surface adhesion force of the first cleaning member 70 to the ink printed onto the intermediate transfer body 50 after being dried is greater than a surface adhesion force of the intermediate transfer body 50 to the ink.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] As an image forming apparatus, a transfer-type inkjet printing apparatus is known in which ink is ejected onto an intermediate transfer body and then transferred to a recording medium to form an image, and a method for cleaning untransferred ink from the intermediate transfer body has been disclosed. For example, Patent Document 1 discloses a configuration in which a cleaning liquid capable of aggregating ink is applied to an intermediate transfer body, and the aggregated ink on the surface of the transfer body is collected. However, the use of a cleaning solution leads to problems such as increased complexity of the device, reduced maintainability, and increased costs. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention provides an image forming apparatus in transfer inkjet printing that maintains the surface properties of an intermediate transfer member even when used over time, and suppresses the occurrence of image defects due to the elimination of cleaning. [Means for solving the problem]

[0004] In order to solve the above-mentioned problems, the present invention provides: An image forming apparatus in which ink is ejected onto an intermediate transfer body and then transferred onto a recording medium to form an image, a cleaning unit that cleans ink that has not been transferred to the recording medium and remains on the intermediate transfer body; The cleaning unit includes: a first cleaning member that cleans the surface of the intermediate transfer body; a second cleaning member that cleans the surface of the first cleaning member, The first cleaning member has a surface adhesive force to the ink printed on the intermediate transfer body after drying that is greater than a surface adhesive force of the intermediate transfer body to the ink. [Effects of the Invention]

[0005] According to the present invention, it is possible to provide an image forming apparatus in transfer inkjet printing that maintains the surface properties of an intermediate transfer member even after long-term use and suppresses the occurrence of image defects due to insufficient cleaning. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a diagram illustrating an example of the configuration of an inkjet printing apparatus as an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 3A and 3B are diagrams illustrating an example of the configuration of a cleaning unit according to an embodiment of the present invention. [Figure 3] 1A and 1B are diagrams illustrating an example of adhesive strength measurement, where FIG. 1A is a schematic diagram illustrating an example of a measuring device, and FIG. 1B is a diagram illustrating an example of an adhesive strength measurement method. [Figure 4] 3A and 3B are explanatory diagrams illustrating an example of the configuration of a first cleaning member. [Figure 5] 10 is a flowchart illustrating control of the timing of cleaning the first cleaning member. [Figure 6] 10A and 10B are diagrams illustrating an example of a state of the inkjet printing device in a coating mode in which ink is coated on the first cleaning member. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, components such as members and components having the same function or shape are designated by the same reference numerals as far as they can be distinguished, and descriptions thereof will be omitted once they have been described.

[0008] The present invention is characterized in that, in the cleaning process of the intermediate transfer body for removing residual ink that has not been transferred to a recording medium and remains on the intermediate transfer body, the residual ink adheres to materials that are more likely to adhere due to its viscosity, and therefore a material to which ink adheres more easily than the intermediate transfer body is used as the cleaning member. Hereinafter, an embodiment of the present invention will be described.

[0009] Fig. 1 is a diagram illustrating an example of the configuration of an inkjet printing device as an example of an image forming apparatus according to an embodiment of the present invention. Fig. 1 shows a schematic diagram of an example of the configuration of a transfer type (intermediate transfer method) inkjet printing device in which ink is ejected onto an intermediate transfer body in response to a recording signal, and then transferred onto a recording medium to obtain an image. The inkjet printing device 100 includes a printing unit 10, a transfer unit 30, an intermediate transfer body (also referred to as an "intermediate transfer member" or "intermediate transfer belt") 50, a cleaning unit 70, and a heating unit 90. The intermediate transfer body 50 is stretched over a plurality of rollers (rollers 81, 83, etc.).

[0010] The printing unit 10 has an inkjet head, and prints a print image on the surface of the intermediate transfer body 50 with ink ejected from the inkjet head. The heating unit 90 heats the intermediate transfer body 50 and the ink on the intermediate transfer body, thereby removing the solvent component of the ink and making the ink viscous. The roller 83 is a heating roller and heats the intermediate transfer body 50. The transfer unit 30 transfers a print image onto the surface of a recording medium such as paper while applying heat and pressure to the recording medium (also called a "recording body") using a roller nip formed by two rollers 31 and 33. The cleaning unit 70 cleans the ink that has not been transferred to the recording medium due to the unevenness of the paper surface or the characteristics of the recording medium. The ink cleaned by the cleaning unit 70 is collected so that it can be printed again on the surface of the intermediate transfer body 50.

[0011] Next, the cleaning unit 70 will be described in detail. 2 is a diagram illustrating an example of the configuration of a cleaning unit according to an embodiment of the present invention. Residual ink that has not been transferred to the intermediate transfer body 50 in the transfer unit 30 enters (moves to) the cleaning unit .

[0012] The cleaning unit 70 has a first cleaning member (also referred to as a “first cleaning roller”) 71 and a second cleaning member (also referred to as a “second cleaning roller”) 73. The cleaning unit 70 may further have a leveling member 75. After transferring ink from the intermediate transfer body 50 to a recording medium, the first cleaning member 71 cleans the surface of the intermediate transfer body 50. The first cleaning member 71 transports the intermediate transfer body 50 together with a roller 77. The first cleaning member 71 also forms a nip with the roller 77 and comes into contact with the intermediate transfer body 50 to clean it. The second cleaning member 73 cleans the surface of the first cleaning member.

[0013] Here, the relationship between the surface adhesive force of the intermediate transfer body 50 and the first cleaning member 71 with respect to the dried ink will be described. The relationship between the ink adhesion force of the intermediate transfer body 50 and the first cleaning member 71 is set so that the first cleaning member 71 has a greater adhesion force to the ink than the intermediate transfer body 50 (intermediate transfer body 50<first cleaning member 71). In this way, a good cleaning function can be obtained. Furthermore, as a surface characteristic of the cleaning members, it is preferable that the adhesion force to ink increases in the order of intermediate transfer body 50, first cleaning member 71, and second cleaning member 73 (intermediate transfer body 50<first cleaning member 71<second cleaning member 73). However, the tackiness of the first cleaning member 71 must be set lower than that of the second cleaning member 73, and the first cleaning member 71 may not be able to fully exert its cleaning power from the intermediate transfer body 50. In particular, when the intermediate transfer body 50 is driven at a high linear speed to improve printer productivity, it is necessary to increase the size of the device to ensure sufficient cleaning nip time.

[0014] For this reason, the image forming apparatus has a cleaning mode in which the first cleaning member 71 holds the cleaned ink during printing, and the second cleaning member 73 cleans the first cleaning member 71 at a predetermined timing. In this way, the ink collected by the first cleaning member 71 (cleaned ink) is held on the first cleaning member 71 during image formation, and the ink is not transferred again to the intermediate transfer body 50 due to the relationship of surface adhesive force to the ink described above (intermediate transfer body 50<first cleaning member 71).

[0015] If the first cleaning member 71 fails to clean properly, the imperfectly cleaned portion may be transferred to a recording medium such as paper, resulting in an image defect. Therefore, from the perspective of reliability, it is desirable for the first cleaning member 71 to have sufficient cleaning capabilities. Furthermore, in the cleaning process of the second cleaning member 73, even if the ink on the first cleaning member 71 cannot be cleaned in one go, as long as it is not transferred again to the intermediate transfer body 50, cleaning does not necessarily have to be performed in one process. For example, a cleaning mode may be provided that thoroughly cleans the first cleaning member 71 at an adjustment timing between jobs, such as after a predetermined number of prints, or at a time when printing is not being performed, such as at the end of printing (job end). This allows the first cleaning member 71 to be refreshed between jobs, at the end of a job, or when the power is turned on for adjustment, thereby continuously maintaining the cleaning function of the first cleaning member 71.

[0016] The adhesive strength of ink to each component can be measured using a tack tester such as the one shown in Figure 3. The measuring device used was the Rhesca TAC1000 (https: / / www.rhesca.co.jp / lineup / tac / tac1000.html). FIG. 3 is a diagram illustrating an example of adhesive strength measurement, where (A) is a schematic diagram illustrating an example of a measuring device, and (B) is a diagram illustrating an example of an adhesive strength measurement method. The measuring device has a stage 103 on which a dried ink layer 101 is applied, and a probe 105 with an evaluation member 107 attached to its tip. The evaluation member 107 attached to the probe 105 is attached to the ink layer, and the probe 105 is pulled upward to measure the retention time T and evaluation value V.

[0017] It is also preferable that the first cleaning member 71 is coated with ink in advance, and is heated and rotated so as to come into contact with the intermediate transfer body. FIG. 4 is an explanatory diagram showing an example of the configuration of the first cleaning member. The first cleaning member 71 has a core metal 711 and a base layer 713. In addition, the first cleaning member 71 may have an ink layer 715 applied to the surface of the base layer 713. The core metal 711 is a metal roller made of SUS, aluminum, or the like. The base layer 713 is formed by coating the surface of the core metal 711 with a base layer resin. The base layer material (base layer resin) can be, for example, a thermoplastic resin such as polyimide resin or polyether ether ketone (PEEK). These surface layer materials have high adhesive strength with the ink resin component at high temperatures, and can retain both the pre-applied ink layer 715 and the collected ink on the first cleaning member 71.

[0018] The ink layer 715 is a layer coated with at least one of the inks (ink resins) used in image formation as an upper layer of the base layer 713. When multiple inks are used in image formation, the ink layer 715 is coated with at least one of the multiple inks, and when only one ink is used, the ink layer 715 is coated with that ink. When ink resin is in a melted and softened state, ink particles adhere to each other and bond together.

[0019] The first cleaning member 71 collects residual ink remaining on the surface of the intermediate transfer member 50 by pressing it against the intermediate transfer member 50 while being heated and rotated. Specifically, the roller surface of the first cleaning member 71 is heated to make the ink viscous, and the first cleaning member 71 is then rotated and brought into contact with the intermediate transfer member 50. In this way, residual ink is transferred from the surface of the intermediate transfer member 50 to the first cleaning member 71, ensuring reliable cleaning. Furthermore, because the residual ink is cleaned using ink that has been thickened by heating, even at high linear speeds, highly reliable cleaning performance can be achieved without increasing the size of the device.

[0020] Next, the leveling member 75 will be described. The leveling member 75 is a regulating member that contacts the first cleaning member 71 and levels the ink layer 715. The leveling member 75 may be, for example, in the form of a roller or blade. Providing the leveling member 75 has the effect of eliminating unevenness of the first cleaning member 71 due to image conditions (such as a large amount of transfer residue on only a specific side). The leveling member 75 can be, for example, a roller whose surface is coated with a fluororesin or the like that has good releasability, and by contacting the first cleaning member 71 with pressure, the layer thickness on the surface of the ink layer 715 is made uniform. Although FIG. 2 shows an example of a configuration in which the leveling member 75 is provided, the cleaning unit 70 may be configured without the leveling member 75.

[0021] Next, an example of the operation of cleaning the first cleaning member 71 will be described. As ink is collected, ink continues to accumulate on the first cleaning member 71. This poses a risk of the collected ink falling off or being transferred back to the intermediate transfer body 50. For this reason, it is desirable to clean the first cleaning member 71, for example, after every predetermined number of prints. FIG. 5 is a flowchart for explaining the control of the timing for cleaning the first cleaning member 71. A first threshold value P and a second threshold value Q (P < Q, P and Q are positive integers) are set for the continuous sheet count, and the image forming apparatus may determine the timing to shift to a cleaning mode for cleaning the first cleaning member 71 using the threshold values P and Q.

[0022] It is determined whether the continuous print sheet count is P sheets or less (S11). If it exceeds P sheets (NO in S11), the image forming apparatus shifts to the cleaning mode, cleans the first cleaning member 71, and resets the count of the continuous print sheet count to zero (S12). If the continuous print sheet count is P sheets or less (YES in S11), it is determined whether the print job has ended (S13). If the print job has not ended (NO in S13), printing continues. If the print job has ended (YES in S13), it is determined whether the continuous print sheet count is Q sheets or less (S14). If it exceeds Q sheets (NO in S14), the image forming apparatus shifts to the cleaning mode, cleans the first cleaning member 71, resets the count of the continuous print sheet count to zero (S15), and ends the printing. If the continuous print sheet count is Q sheets or less (YES in S14), the printing ends.

[0023] The determination of the timing shown in FIG. 5 may be performed, for example, by control means provided in the image forming apparatus. By providing the cleaning mode as described above, it becomes possible to set to clean the first cleaning member 71 during or after the job end, which is good from the viewpoint of suppressing downtime.

[0024] When the ink layer 715 of the first cleaning member 71 is cleaned by the cleaning mode, the image forming apparatus may cover the ink layer again with the first cleaning. Referring to FIG. 6, an operation example of the image forming apparatus (inkjet printing apparatus) at the time of ink coating will be described. The difference between the print mode in which printing is performed and the ink coating mode (also called the "coating mode") in which cleaning ink is coated (applied) onto the first cleaning member 71 is that the transfer roller (roller 33) of the transfer unit 30 is separated from the roller 31 and does not transport the recording medium. In this state, the print unit 10 prints ink onto the intermediate transfer body 50 and inputs it directly into the cleaning unit 70. The ink collected from the intermediate transfer body 50 is again held by the first cleaning member 71 and forms a new ink layer 715 on the surface of the base layer 713 of the first cleaning member 71. By doing so, the roller of the first cleaning member 71 is coated with ink in advance, and high cleaning performance can be achieved from the start of printing.

[0025] The intermediate transfer body 50 used in the present invention is required to have the property of being able to print ink well. From the viewpoint of the cleaning process, the lower the adhesive strength between the ink and the intermediate transfer body 50, the better the cleaning can be performed. However, if the adhesive strength is too low, the ink on the intermediate transfer body may become water-repellent during printing, which may result in poor printing. From this perspective, it is desirable that the surface energy value (dyne level) of the intermediate transfer body 50 is 40 mN / m or more. In other words, by satisfying this characteristic and the adhesive strength characteristics for dried ink, it is possible to provide a highly reliable image forming apparatus that exhibits high image quality, good cleaning properties, and is free from image defects due to improper cleaning.

[0026] The surface energy value can be measured using a pen-type reagent (for example, Daiko Seisakusho's wettability check pen, https: / / www.daico.co.jp / products / products.php?id=56). The above-mentioned surface energy values ​​are the substrate conditions for allowing ink to be printed satisfactorily on the intermediate transfer body 50. If the surface tension is high, i.e., if the water repellency is high, the ink will be repelled on the intermediate transfer body 50, and a good printed image will not be obtained. By satisfying this characteristic and the adhesive strength characteristics for ink after drying, it is possible to provide a highly reliable image forming apparatus that produces high image quality and is free of image defects due to improper cleaning.

[0027] For example, aspects of the present invention are as follows. <1> An image forming apparatus in which ink is ejected onto an intermediate transfer body and then transferred onto a recording medium to form an image, a cleaning unit that cleans ink that has not been transferred to the recording medium and remains on the intermediate transfer body; The cleaning unit includes: a first cleaning member that cleans the surface of the intermediate transfer body; a second cleaning member that cleans the surface of the first cleaning member, In the image forming apparatus, the first cleaning member has a surface adhesive force to the ink printed on the intermediate transfer body after drying that is greater than a surface adhesive force of the intermediate transfer body to the ink. <2> the above <1> The image forming apparatus according to claim 1, The image forming apparatus is characterized in that the first cleaning member has an ink layer coated with at least one of the inks used in image formation, and recovers residual ink remaining on the surface of the intermediate transfer body by being heated and rotated while being pressed against the intermediate transfer body. <3> the above <1> or <2> The image forming apparatus according to claim 1, the first cleaning member cleans the surface of the intermediate transfer body while retaining the cleaned ink during a printing operation; The image forming apparatus is characterized in that the second cleaning member cleans the first cleaning member at a predetermined timing. <4> the above <2> The image forming apparatus according to claim 1, The image forming apparatus further comprises a leveling member that levels the ink layer on the first cleaning member. <5> the above <1> from <4> 1. An image forming apparatus according to claim 1, The second cleaning member cleans the first cleaning member at the end of a job or at intervals of a predetermined number of printed sheets. The image forming apparatus is characterized in that the cleaning member is cleaned. <6> the above <1> from <5> 1. An image forming apparatus according to claim 1, The image forming apparatus has a coating mode in which the first cleaning member is coated with the ink. <7> the above <1> from <6> 1. An image forming apparatus according to claim 1, The image forming apparatus is characterized in that the surface layer material of the intermediate transfer member has a surface energy value of 40 mN / m or more under the temperature conditions during transfer.

[0028] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0029] 100 Inkjet printing device (image forming device) 10 Printing section 30 Transfer unit 50 Intermediate transfer body 70 Cleaning Department 71 First cleaning member 73 Second cleaning member 75 Leveling material 90 Heating section 711 Core 713 Base layer 715 Ink Layer [Prior art documents] [Patent documents]

[0030] [Patent Document 1] JP 2011-93198 A

Claims

1. An image forming apparatus in which ink is ejected onto an intermediate transfer body and then transferred onto a recording medium to form an image, a cleaning unit that cleans ink that has not been transferred to the recording medium and remains on the intermediate transfer body; The cleaning unit includes: a first cleaning member that cleans the surface of the intermediate transfer body; a second cleaning member that cleans the surface of the first cleaning member, an image forming apparatus, wherein the first cleaning member has a surface adhesive force to ink printed on the intermediate transfer body after drying that is greater than a surface adhesive force of the intermediate transfer body to the ink;

2. 2. The image forming apparatus according to claim 1, The first cleaning member has an ink layer coated with at least one of the inks used in image formation, and is pressed against the intermediate transfer body while being heated and rotated, thereby recovering residual ink remaining on the surface of the intermediate transfer body. An image forming apparatus characterized by:

3. 3. The image forming apparatus according to claim 1, the first cleaning member cleans the surface of the intermediate transfer body while retaining the cleaned ink during a printing operation; The second cleaning member cleans the first cleaning member at a predetermined timing. An image forming apparatus characterized by:

4. 3. The image forming apparatus according to claim 2, a leveling member for leveling the ink layer on the first cleaning member; An image forming apparatus characterized by:

5. 3. The image forming apparatus according to claim 1, The second cleaning member cleans the first cleaning member at the end of a job or at intervals of a predetermined number of printed sheets. An image forming apparatus characterized by:

6. 3. The image forming apparatus according to claim 1, a coating mode for coating the first cleaning member with the ink; An image forming apparatus characterized by:

7. 3. The image forming apparatus according to claim 1, The surface layer material of the intermediate transfer member has a surface energy value of 40 mN / m or more under the temperature conditions during transfer. An image forming apparatus characterized by:

Images