JP2010260204A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ease shocks at the time when an intermediate transfer body dashes at a transfer roller in an inkjet recording system that uses the intermediate transfer body. <P>SOLUTION: The thickness of an advance direction end of the intermediate transfer body is reduced continuously with respect to the advance direction, or the rubber hardness of the advance direction end is lowered than the rubber hardness of a center part. A force applied when the intermediate transfer body contacts the transfer roller is reduced by using the intermediate transfer body, thereby easing the shock. Hence vibration etc. at the time of dashing can be reduced, and variation of a transfer pressure can be suppressed, so that a good transfer ink image can be obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus, and more particularly, to an intermediate transfer type inkjet recording apparatus that transfers an image formed on an intermediate transfer body to a printing medium.

  In recent years, there has been a growing demand for recording high-quality images regardless of the type of printing medium in a wide range of fields by taking advantage of the ink jet recording method. However, when using a printing medium with poor ink permeability using an ink jet recording method, feathering in which ink oozes on the ridge, the ink that has landed first is attracted to the ink droplets that landed later. Phenomenon such as beading and bleeding that ink droplets recorded adjacent to each other are mixed. In addition, cockling or the like, which is a rippling phenomenon of the printing medium that occurs when water-based ink permeates the printing medium, occurs.

  In order to overcome the above problem, a transfer type recording method has been proposed. In this recording method, first, an ink image is formed by applying ink onto an intermediate transfer member by an inkjet recording method. Then, the ink image on the intermediate transfer body is transferred from the intermediate transfer body onto the printing medium. Therefore, in order to suppress the phenomenon such as feathering, beading, and bleeding, it is not necessary to quickly permeate and fix the moisture in the ink on the printing material, and the types of printing materials to be used can be expanded. Also, before transferring the ink image formed on the intermediate transfer body to the printing medium, the amount of liquid penetrating the printing medium side by removing most of the liquid components of the ink forming the ink image Can be reduced. Therefore, cockling is less likely to occur, and the texture of the printing medium is not impaired.

  In a transfer type recording method, a transfer method in which an intermediate transfer body and a printing medium are simultaneously pressed between rollers is widely used. In this transfer step, when the intermediate transfer body and the printing medium are passed between the pressurized rollers, an impact is generated by the collision of the intermediate transfer body and the roller. Due to the impact, the roller and the intermediate transfer member are caused to vibrate, the transfer pressure fluctuates, and the transferred ink image is disturbed.

  As a method for solving this problem, in Patent Document 1, a gap fixing unit that defines a gap between rollers and a pressing unit that generates a predetermined pressing force between the rollers are provided, and transfer is performed by the pressing unit. There has been proposed a method of applying pressure by specifying a force exceeding the pressing force. Patent Document 2 proposes a method of mitigating the impact at the time of entering a roller by configuring the roller with two types of rubbers having different hardnesses.

JP 2004-333632 A JP 2006-317627 A

  However, the impact mitigation method at the time of rushing into the conventional roller described above has the following problems.

  As in Patent Document 1, in the method of controlling the pressure between the rollers every time the printing medium enters, when the recording speed is increased, the rollers are arranged corresponding to the printing medium that is fed at high speed. It is necessary to change the pressure. Therefore, the pressure control between the rollers must be speeded up, and there is a problem that the control device for that purpose becomes complicated.

  Further, as in Patent Document 2, when the rubber hardness of the roller is lowered to reduce the impact at the time of entry, the pressure between the rollers is lowered accordingly, and the pressure necessary for transferring the image is increased. I can't get it. When the pressure applied between the rollers is increased in order to obtain the necessary pressure, the nip width increases, so that a large torque is required to rotate the rollers. Therefore, in order to rotate a roller, a larger motor is needed and there exists a problem that power consumption will also become large.

  In view of the above problems, the present invention provides an ink jet recording apparatus capable of mitigating an impact when an intermediate transfer member enters a pressure roller with a simple configuration without performing control between rollers or changing roller hardness. The purpose is to provide.

  As a result of intensive studies, the present inventors have found that the following configuration has excellent performance as the ink jet recording apparatus with respect to the above problems, and have achieved the present invention.

  An inkjet recording apparatus of the present invention includes an intermediate transfer member that temporarily carries an image made of ink, a drawing unit that forms an image by applying ink onto the intermediate transfer member using an inkjet device, and the image And a transfer unit that transfers the image from the intermediate transfer body to the print body by pressure-bonding the print body with a roller to the intermediate transfer body. The end portion has a portion in which the thickness continuously decreases from the central portion toward the approach direction.

In the ink jet recording apparatus of the present invention, the length of the portion where the thickness of the intermediate transfer member is reduced is defined by the following equation (Equation 1) from the roller diameter r and the thickness t of the central portion of the intermediate transfer member. longer than unit length l ₀ which is characterized by.

  Further, the ink jet recording apparatus of the present invention includes an intermediate transfer member that temporarily carries an image made of ink, a drawing unit that forms an image by applying ink on the intermediate transfer member using an ink jet device, A transfer unit that presses the printing medium onto the image with a roller and transfers the image onto the printing medium from the intermediate transfer body, wherein the intermediate transfer body has a substantially flat plate shape, and the roller A hardness of the end portion in the entering direction is lower than that of the central portion of the intermediate transfer member.

  The reason why the present invention has such excellent properties is not clear, but the present inventors speculate as follows. That is, the impact generated when the intermediate transfer body and the printing medium are passed between the pressurized rollers is a collision between the intermediate transfer body and the roller, more specifically, a collision between the end of the intermediate transfer body in the roller entrance direction and the roller. Caused by.

  At this time, the force generated when the end of the intermediate transfer member in the roller entry direction collides with the roller surface will be considered.

  When a linear force is applied to the cylindrical roller surface, the largest force is generated when the force is applied on the plane of the rotation axis.

  Therefore, on the contrary, the generated force becomes smaller as the place on the roller surface to which the force is applied is separated from the plane of the rotation axis.

  The smallest is when the force vector is tangent to the roller, in other words, when the force "scratches" the roller surface.

  However, as can be easily understood, in such a form, no force (repulsive force) from the roller in the normal direction is generated.

  Speaking of the intermediate transfer member and the roller, the closer the portion where the end of the intermediate transfer member in the roller entry direction is first in contact with the roller surface is closer to the nip portion of the roller, the smaller the force generated when colliding. However, along with this, the force in the normal direction from the roller, that is, the transfer pressure is reduced.

  Therefore, as a result of intensive studies, the present inventors have made it possible to reduce the force generated at the time of collision as much as possible and to minimize the decrease in transfer pressure. It has been found that it is extremely effective to have a portion that continuously decreases from the central portion toward the approach direction, and the present invention has been conceived.

In particular, when the roller diameter is r and the thickness of the central portion of the intermediate transfer member is t, the length of the portion having the above-described configuration and the continuously decreasing thickness is defined by the following formula: It has been found that when the length is longer than l _{o, a} better effect is exhibited.

l _o = (rt−t ² ) / √ (2rt−t ² ) (Equation 1)
Further, the present inventors can reduce the force generated at the time of collision as much as possible by setting the hardness of the end of the intermediate transfer member in the roller entry direction to be lower than the central portion of the intermediate transfer member, and the transfer pressure. As a result, the present invention has been found.

  According to the present invention, since the image formed on the intermediate transfer body is transferred to the printing medium, the impact when the intermediate transfer body enters the pressure roller can be reduced. Therefore, it is possible to realize an ink jet recording apparatus capable of obtaining a transfer image without ink density and distortion.

1 is a schematic cross-sectional view of a recording apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view of an intermediate transfer member of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a state in which the intermediate transfer member of the present invention enters a transfer roller. FIG. 10 is a schematic cross-sectional view of a conventional intermediate transfer member. FIG. 10 is a schematic cross-sectional view showing a state in which a conventional intermediate transfer member enters a transfer roller. FIG. 3 is a schematic cross-sectional view illustrating a state in which the intermediate transfer member of the present invention enters a transfer roller. 1 is a schematic cross-sectional view of an intermediate transfer member of the present invention. 1 is a schematic cross-sectional view of an intermediate transfer member of the present invention. 1 is a schematic cross-sectional view of an intermediate transfer member of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a state in which the intermediate transfer member of the present invention enters a transfer roller. 3 is a schematic cross-sectional view of a transfer portion of the recording apparatus of the present invention. FIG. It is a flowchart for demonstrating the recording process by the recording device of this invention. FIG. 2A is a schematic plan view of an intermediate transfer member of Example 1. (B) is a X arrow view of (a). FIG. 4A is a schematic plan view of an intermediate transfer member of Example 2. (B) is a Y arrow view of (a).

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1. 1 is a schematic cross-sectional view showing a schematic configuration of a recording apparatus according to the present embodiment.

  In FIG. 1, reference numeral 1 denotes a conveyance belt for conveying the intermediate transfer member 2, and the intermediate transfer member 2 is attached to the surface. This conveyance belt 1 is stretched between three belt conveyance rollers 12, 13, and 14, and any one of these conveyance rollers is rotationally driven by a belt driving device (not shown), so that the direction of arrow A It is conveyed to. In this example, the transport roller 13 is a belt drive roller that is rotationally driven. The transport roller 14 is also used as a pressure roller for transfer, and has a heater inside the roller to give a stable temperature during transfer.

  At the peripheral position of the transfer belt 1, the processing liquid application unit 3, the drawing unit 4, the ink image processing unit 5, and the transfer unit 6 are sequentially arranged from the upstream side to the downstream side in the transport direction (arrow A direction) of the transfer belt 1. And a cleaning unit 7 are arranged.

The recording apparatus is provided with a paper feeding / conveying unit 8. The paper feeding / conveying unit 8 conveys the printing medium 10 from a printing medium storage unit (not shown) to the transfer unit 6 by rotating a paper feeding / conveying roller (not shown). The ink image formed on the intermediate transfer body 2 is transferred to the printing medium 10 in the transfer unit 6. In the recording apparatus of this example, the endless belt is adopted for the conveyance structure of the intermediate transfer member, but a drum system may be used.
2. 2. Details of Each Part 2.1 Intermediate Transfer Member The intermediate transfer member has a property (release property) that easily peels off an ink image on the surface thereof. Silicone rubber is one of the optimum materials for forming an intermediate transfer member because it has low surface energy and high peelability. However, the material of the intermediate transfer member is not limited to these, as long as it has preferable releasability and elastic characteristics and has an excellent transfer rate when transferring an ink image to a printing medium. Good. Further, the layer configuration may be changed as appropriate, for example, the intermediate transfer member has a configuration of two or more layers. As another example of the material forming the intermediate transfer member, an organic-inorganic hybrid material synthesized by fluororubber or a sol-gel method can be suitably used.

  FIG. 2 is a schematic sectional view of the intermediate transfer member of the present invention, and FIG. 4 is a schematic sectional view of a conventional example. FIG. 3 is a schematic sectional view showing a transfer unit when the intermediate transfer member of the present invention enters the transfer roller, and FIG. 5 is a schematic sectional view of the transfer unit in the case of a conventional intermediate transfer member. 2, 3, 4, 5, 6, 7, 8, 9, and 10, arrow B indicates the traveling direction of the conveyance belt, and arrow C indicates the rotation direction of the transfer roller.

  As shown in FIG. 2, the intermediate transfer member of the present invention is continuously thinned toward the end of the conveying belt (direction of arrow B) in order to reduce the impact when the transfer roller enters. By providing such an impact mitigating part and moving the point where the intermediate transfer member first contacts the transfer roller in the direction of the conveying belt compared to the conventional case, the force applied in the traveling direction of the conveying belt is reduced, The force applied to the roller and the intermediate transfer member can be reduced.

  Further, regarding the force applied to the transfer roller in the direction perpendicular to the conveyance belt, when the intermediate transfer member of the present invention is used, it takes more time to move the transfer roller upward by the thickness of the intermediate transfer member than in the conventional example. . That is, the movement distance per unit time of the transfer roller is shorter in the present invention than in the conventional example. Accordingly, it is possible to reduce the force applied in the direction perpendicular to the conveyor belt.

  In FIG. 3, the surface of the intermediate transfer member having the largest surface area is bonded and fixed to the conveyance belt. However, the present invention is not limited to such a configuration, and the opposite surface of the adhesive surface of FIG. 3 may be bonded and fixed to the conveyor belt as shown in FIG. In such a configuration, when an ink image is formed on the intermediate transfer member, the distance between the ink head and the intermediate transfer member can be kept constant up to the end, so that a good ink image can be obtained even at the impact mitigation portion. I can do it. Therefore, it is possible to use the impact relaxation portion without wasting it. In FIG. 6, when the intermediate transfer member comes into contact with the transfer roller, since the intermediate transfer member is an elastic body, the impact relaxation portion is bent in the direction of the transport belt, thereby absorbing the impact.

  Further, in order to prevent the impact relaxation portion of the intermediate transfer member in FIG. 6 from being bent in the opposite direction to the conveying belt, the impact relaxation portion may be formed in a shape in which both surfaces are inclined as shown in FIG. Furthermore, the impact relaxation portion does not have to be thin in proportion to the distance, and may have a shape having a curve as shown in FIG. 8 or FIG.

FIG. 10 is a schematic cross-sectional view showing the transfer unit when the intermediate transfer member of the present invention enters the transfer roller. The length of the impact relaxation portion is l, the thickness of the intermediate transfer member is t, the radius of the transfer roller is r, and the point where the intermediate transfer member and the transfer roller first contact is D. FIG. 11 is a schematic cross-sectional view showing the positional relationship between the transfer roller and the conveyance belt in the transfer unit. The position where the distance from the conveyor belt on the circumference when the outer periphery of the transfer roller is a circle is E, s is the tangent drawn at the point E, F is the intersection of the tangent s and the conveyor belt, and the conveyor belt is from the point E the perpendicular intersection with the conveyor belt drawn to G, the distance between the point F and the point G and l _0.

In order to alleviate the impact when the transfer roller enters, the position of the point D needs to be closer to the conveyance belt direction, that is, the nip portion side than the thickness t of the intermediate transfer member. For this purpose, it is necessary to be longer than the length l of the length l _0. When l ₀ is calculated using the radius r and the thickness t, Equation 1 is obtained.

  Further, it is possible to make an impact relaxation portion by lowering the hardness of the tip of the intermediate transfer member. The force generated when the object comes into contact with the object becomes smaller as the hardness of the object is lower, because the generated force is absorbed. However, if the hardness of the entire intermediate transfer member is lowered, deformation at the time of transfer increases, and the transferred image is distorted. Therefore, in the present invention, the hardness of the intermediate transfer member in the vicinity of the point where the intermediate transfer member and the transfer roller first come into contact with each other is lowered, and the other portions are set to the conventional hardness. By adopting such a configuration, it is possible to realize an intermediate transfer body that can alleviate the impact at the time of entering the transfer roller and obtain a transfer image without distortion.

  The conveyance belt 1 that conveys the intermediate transfer member 2 is made of polyurethane, and is provided with an adhesive layer on which the intermediate transfer member 2 is fixed.

  The material used as the conveyor belt 1 is not particularly limited to polyurethane. In addition to rigidity and dimensional accuracy that can withstand pressurization during transfer, any material that satisfies the characteristics required for reducing the inertia of conveyance and improving control responsiveness may be used.

2.2 Treatment liquid application unit 3
In the present invention, it is possible to provide the treatment liquid application unit 3 that can obtain the effect of reducing the fluidity of the ink landed on the intermediate transfer member by using the treatment liquid in order to suppress the occurrence of beading and bleeding. .

  The treatment liquid application unit 3 is disposed on the upstream side in the conveyance direction of the conveyance belt 1 with respect to the drawing unit 4 described later. The application roller 30 applies the treatment liquid 31 to the intermediate transfer body 2 by rotating while being in contact with the transport belt 1.

  If the intermediate transfer member of the present invention is employed, the force applied to the intermediate transfer member and the application roller can be reduced even when the intermediate transfer member 2 passes through the application roller 30. Therefore, it is possible to reduce the vibration caused by the collision between the intermediate transfer member and the application roller, and to uniformly apply the treatment liquid onto the intermediate transfer member. Further, deterioration of the intermediate transfer member due to impact can also be suppressed.

  Here, the processing liquid 31 will be described. The treatment liquid is a liquid for reducing the fluidity of the colored ink or aggregating the color material in the ink. The components include an image fixing component, water, a water-soluble organic solvent, and an auxiliary agent for uniform application and ejection stability. In this example, the processing liquid 31 is applied onto the intermediate transfer body 2, but the processing liquid discharged from the recording head is transferred to the intermediate transfer body using a recording head (liquid discharge head) such as an ink discharge head. 2 can also be applied.

  The image fixing component is a material for reducing the fluidity of the colored ink or aggregating the coloring material in the ink. Specifically, it is a material that plays a role of reducing the fluidity of the ink on the intermediate transfer body 2 by contact with the ink and holding the ink landed on the intermediate transfer body as much as possible at the landing position. If the fluidity of the ink landed on the intermediate transfer body 2 is not lowered, the ink flows on the intermediate transfer body, which may cause beading or bleeding. Therefore, by reacting with the ink using the processing liquid containing the image fixing component, the fluidity of the ink in contact with the ink is lowered, and the ink is landed on the intermediate transfer member and the ink is held at the landing position. Thereby, even if ink droplets contact each other on the intermediate transfer member, occurrence of beading and bleeding can be suppressed.

  As the image fixing component, a material capable of aggregating the ink by contact with the ink is preferable. For example, a metal salt is preferable. The most suitable metal salt includes a polyvalent metal salt. The processing liquid may contain a water-soluble organic solvent together with the metal salt such as the above-described image fixing component such as a polyvalent metal salt. Although there is no restriction | limiting in particular about content in the process liquid of these water-soluble organic solvents, It is 5-60 mass% of the total mass of a process liquid, Preferably it is the range of 5-40 mass%.

  When the application roller 30 is used as in this example, a coating aid may be included in the processing liquid 31 for the purpose of uniform application to the intermediate transfer body 2. As this coating aid, it is preferable to use a surfactant. The addition amount of the surfactant is preferably about 0.05 to 10% by mass, and more preferably about 0.1 to 5% by mass with respect to the treatment liquid. In addition to these, additives such as a viscosity adjusting agent, a pH adjusting agent, a preservative, and an antioxidant may be appropriately added to the treatment liquid as necessary.

2.3 Drawing unit 4
The drawing unit 4 forms an ink image on the intermediate transfer body 2 by applying ink containing at least a colorant in accordance with an image signal sent from the control unit. At this time, if the processing liquid 31 described above is applied onto the intermediate transfer member, the processing liquid 31 and the aggregating component of the ink undergo an aggregating reaction, whereby an image free of beading or bleeding is formed.

  The drawing unit 4 is disposed on the downstream side of the treatment liquid application unit 3 in the transport direction of the transport belt 1 and includes an ink discharge head 40. The ink discharge head 40 has a plurality of nozzles that can discharge ink. As the discharge energy generating means for discharging ink from the nozzle, an electrothermal converter (heater), a piezo element, or the like can be used. When the electrothermal converter is used, the ink can be foamed by the heat generation, and the ink can be ejected from the nozzles using the foaming energy.

  The ink discharge heads are arranged at regular intervals in the transport direction of the transport belt 1. Each ink discharge head can form a color image by discharging ink supplied from an ink tank (not shown) corresponding to the ink discharge head. In this example, the ink ejection head ejects black (K), cyan (C), magenta (M), and yellow (Y) ink, respectively. However, the number of ink ejection heads constituting the ink application unit 4, the order of the ink colors ejected to the image forming area on the intermediate transfer body 2, and the hue of the ink used are limited to the examples described above. It is not a thing.

  The ink image formed on the intermediate transfer body 2 should be a mirror image of the image to be finally formed on the substrate 10 in consideration of reversal during the transfer. Naturally, the image signal supplied to the ink ejection head 40 must be an image signal corresponding to a mirror image. Therefore, in the control system, mirror inversion processing (inversion data is obtained) for the image signal sent from the image supply device (that is, the image signal corresponding to the image finally recorded on the printing medium 10). Process). As a result, an image signal corresponding to the mirror image is acquired and supplied to the ink ejection head.

  The ink used in the drawing unit 4 is not particularly limited, and any general ink-jet ink can be used. In particular, pigment inks can be suitably used because they are less likely to bleed onto a printing material and have excellent water resistance and light resistance compared to dye inks. Hereinafter, the water-based pigment ink that can be suitably used in the present embodiment will be described.

  The pigment in the pigment ink is used in a mass ratio of 1 to 20 mass%, preferably 2 to 12 mass%, based on the total mass of the pigment ink. Specifically, the following pigments can be used.

  Examples of black pigments include carbon black.

  Examples of yellow pigments include C.I. I. Pigment Yellow 1, C.I. I. Pigment Yellow 2, C.I. I. Pigment Yellow 3 is exemplified.

  Examples of magenta pigments include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca).

  Examples of cyan pigments include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15: 3.

  Of course, the present embodiment is not limited to the above pigments. In addition to those listed above, any of self-dispersing pigments, resin-dispersed pigments, microencapsulated pigments and the like can be used.

  As a dispersant for use in the production of an aqueous pigment ink, for example, a dispersant for dispersing the pigments listed above in an aqueous medium, any water-soluble resin may be used. In particular, the weight average molecular weight is preferably in the range of 1,000 to 30,000, more preferably in the range of 3,000 to 15,000. The resin used as the dispersant is soluble in an aqueous solution in which a base is dissolved, and is an alkali-soluble resin. The water-soluble resin used as the pigment dispersant is preferably contained in the range of 0.1 to 5% by mass with respect to the total mass of the pigment ink.

  In particular, in the case of a pigment ink containing a pigment as described above, the entire pigment ink is preferably adjusted to be neutral or alkaline. By adjusting in this way, the solubility of the water-soluble resin used as a pigment dispersant can be improved, and a pigment ink having further excellent long-term storage stability can be obtained. In this case, however, the pH range is preferably 7 to 10 so as not to cause corrosion of various members used in the ink jet recording apparatus. A pigment ink is constituted by dispersing or dissolving a colorant such as a pigment as described above and a water-soluble resin as a dispersant in an aqueous liquid medium.

  A suitable water-soluble solvent in the pigment ink is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

  The content of the water-soluble organic solvent in the pigment ink is generally 3 to 50% by mass, more preferably 3 to 40% by mass, based on the total mass of the pigment ink. The water content used is in the range of 10 to 90 mass%, preferably 30 to 80 mass% of the total mass of the pigment ink.

  In addition to the above-described components, surfactants, antifoaming agents, preservatives, and the like can be appropriately added in order to obtain pigment inks having desired physical property values as necessary. In particular, it is strongly desirable to add an appropriate amount of a surfactant that functions as a penetration enhancer in order to quickly permeate the image fixing component and the liquid component of the pigment ink into the printing medium. An example of the addition amount is 0.05 to 10% by mass, preferably 0.5 to 5% by mass.

  When an alkali-soluble resin as described above is used as the dispersant, it is necessary to add a base in order to dissolve the resin.

  In the drawing unit 4, the above-described pigment ink is ejected from the nozzles of the ink ejection head 40 onto the intermediate transfer body 2 in accordance with an image signal sent from the control unit. When the treatment liquid is applied in advance, the ink rapidly aggregates due to the reaction between the treatment liquid 31 applied on the intermediate transfer body 2 and the pigment ink applied by the ink discharge head 40. An ink aggregated image is formed as the ink image on the body 2. Therefore, a good ink aggregated image without beading or bleeding can be formed on the intermediate transfer member 2.

  In the above, a pigment ink using a pigment as a colorant has been exemplified. However, the present embodiment is not limited to this, and for example, a mixed ink obtained by adding a dye to a pigment may be used. Further, if the image fixing component has a metal salt, a water-soluble resin or a crosslinking agent for enhancing the internal cohesive force of the ink aggregated image may be added to the ink and / or the image fixing component.

2.4 Ink image processing unit 5
In the present invention, the ink image processing unit 5 can be provided in order to optimize the solvent component of the ink image when transferring the ink image from the intermediate transfer body 2 to the printing medium 10 and obtain a good transfer image.

  The ink image processing unit 5 includes a hot air blowing drying furnace 50 and is configured to send warm air into the hot air blowing furnace by a hot air blower (not shown). The ink image processing unit 5 removes the solvent component containing water from the ink image formed on the intermediate transfer body 2 by the drawing unit 4 so as to optimize the transfer condition to the printing medium 10. Process the ink image. The temperature of the warm air is 20 to 100 ° C, preferably 25 ° C to 80 ° C.

  The ink image processing unit 5 adjusts the amount of air blown from the hot air dryer or the temperature of the air in consideration of the permeability and wettability of the ink aggregate image (ink image) with respect to the printing medium 10. Is. In this way, by adjusting the amount of heat applied to the ink image, the transfer characteristic of the ink image to the printing medium 10 is appropriately controlled.

  In addition, although the ink image processing unit 5 of the present embodiment promotes drying of the ink image using the hot air blowing drying furnace 50, the temperature can be adjusted like an infrared heater, and the ink image processing unit 5 Those capable of controlling the transfer characteristics can also be used. Also, as long as the solvent containing water in the ink can be controlled and removed, a known means for absorbing the solvent containing water or a means using a squeegee blade roller for squeezing the solvent containing water is also used. Is possible.

2.5 Transfer unit 6 and paper feeding / conveying section 8
In FIG. 1, the transfer unit 6 includes a conveyance roller 14 for driving a belt and a counter roller 9. The printing medium 10 is transported along with the rotation of the paper feed transport roller of the paper feed transport unit 8. The transfer unit 6 causes the ink image on the intermediate transfer body 2 to be transferred to the surface of the printing body 10 by pressing the printing body 10 against the intermediate transfer body 2 by the counter roller 9.

  The counter roller 9 is disposed so as to allow the printing medium 10 to pass through the nip portion between the counter belt 9 and the conveyor belt 1, and can be formed by a rubber roller, a metal roller, or the like. By adding a pressing control device (not shown) to the transfer unit 6, it is possible to control the pressing of the counter roller 9 against the transport belt 1 and the release thereof.

  The counter roller 9 can be driven and rotated by the conveyor belt 1 via the printing medium 10 in a pressed state against the conveyor belt 1. The counter roller 9 may be rotationally controlled by independent transfer roller driving means (not shown) in addition to such driven rotation. The counter roller 9 generates an ink image on the intermediate transfer body according to the pressing time of the printing medium 10 against the conveyor belt 1 and the transfer time corresponding to the width of the nip portion (nip width) between the counter roller 9 and the conveyor belt 1. Transfer to the substrate 10. The function of the counter roller 9 is to transfer the ink image on the intermediate transfer body to the printing medium 10 in this way.

  If the intermediate transfer member of the present invention is employed, the force applied by the collision between the intermediate transfer member and the counter roller when the intermediate transfer member 2 passes through the counter roller 9 can be reduced. Accordingly, it is possible to reduce the vibration caused by the collision between the intermediate transfer member and the counter roller, and to transfer an ink image without ink density or the like to the printing material. Further, deterioration of the intermediate transfer member due to impact can also be suppressed.

2.6 Cleaning unit 7
In the present embodiment, a cleaning unit 7 can be installed to remove dust and the like on the intermediate transfer member 2.

  The cleaning unit 7 includes a cleaning liquid holding member 70, a cleaning roller 71, and a cleaning liquid supply roller 72. The cleaning liquid holding member 70 stores and holds the cleaning liquid 73. The cleaning roller 71 rotates while being in contact with the transport belt 1, thereby applying a cleaning liquid 73 onto the intermediate transfer body 2 and removing dust and the like on the intermediate transfer body 2. The cleaning liquid supply roller 72 is positioned between the cleaning liquid 73 and the cleaning roller 71 and supplies the cleaning liquid 73 in the cleaning liquid holding member 70 to the cleaning roller 71.

  The cleaning roller 71 may be driven and rotated by the conveyor belt 1 or may be driven and controlled by a driving unit (not shown). The cleaning liquid supply roller 72 may be driven and rotated by the cleaning roller 71, or may be driven and controlled by a driving unit (not shown). In any case, when the cleaning liquid supply roller 72 and the cleaning roller 71 are rotated, the cleaning liquid 74 is applied onto the intermediate transfer body 2 through these rollers, and the intermediate transfer body 2 can be cleaned. .

  The cleaning unit 7 may be any unit that can appropriately clean the surface of the intermediate transfer member 2, and the configuration thereof is not limited to that illustrated. Further, the type of the cleaning liquid 73 is not particularly limited, and for example, an aqueous solution containing a surfactant, a water-soluble organic solvent, or the like used in the treatment liquid 31 can be preferably used.

  Similarly to the transfer unit 6, by adding a pressure control device (not shown) that can control the pressing of the cleaning roller 71 against the transport belt 1, the pressing of the cleaning roller 71 against the transport belt 1 and the release thereof. Control becomes possible.

  If the intermediate transfer member of the present invention is employed, the force applied to the intermediate transfer member and the cleaning roller can be reduced even when the intermediate transfer member 2 passes through the cleaning roller 71. Therefore, it is possible to reduce the vibration caused by the collision between the intermediate transfer member and the cleaning roller, and apply the cleaning liquid uniformly onto the intermediate transfer member. Further, deterioration of the intermediate transfer member due to impact can also be suppressed.

In the present invention, the printing medium 10 is not limited to the continuous printing medium having the roll paper shape as described above, and may be in the form of a single sheet. Further, the printing medium 10 is not limited to paper, and may be a resin film such as PET. In the case of a printing medium such as roll-shaped paper, it is necessary to cut the leading edge and the trailing edge of the printing medium. For this purpose, an existing cutting apparatus may be provided in the apparatus, or the print medium 10 may be cut by a separate cutting machine.
3. Procedure of Recording Operation Next, a series of recording operations of the recording apparatus will be described based on the flowchart of FIG.

  When the recording apparatus is turned on and the start of recording is instructed, a start process is first executed (step S1). In the starting process, the driving of the conveyor belt 1 is started, and the heaters provided for the hot air dryer 50 and the conveyor roller 14 are turned on. Thereby, each part can be set and adjusted to a predetermined temperature.

  In this starting process, the position of each part in the transport system of the printing medium 10 can be set as necessary. Further, when it is desirable to clean the surface of the transport belt 1 prior to an image forming operation described later, the cleaning roller 71 is pressed against the transport belt 1 to apply the cleaning liquid 73 and clean the intermediate transfer body 2. May be performed.

  When an image signal is received from an image supply device such as a computer, based on the image signal, print data for controlling the discharge operation by the ink discharge head 40 is generated and developed into a memory area (step S2). . For example, as an image signal, a binary image signal corresponding to each ink color (K, C, M, and Y) used in this example and corresponding to whether or not ink is ejected from a nozzle is sent from the image supply device. When the image signal is received, mirror inversion processing is performed on the image signal. The data subjected to the mirror inversion process is developed in the memory area for each color ink ejection head as recording data for regulating the ink ejection operation. When a multi-valued image signal of three or more values is sent from the image supply device, the CPU converts the image signal into a binary image signal by executing a predetermined binarization processing program. To do. Then, the converted image signal is subjected to mirror inversion processing and developed.

  More specifically, when a color image having a resolution of 1200 dpi is recorded, first, an image processing unit (not shown) in the recording apparatus converts a multi-valued image signal sent from the image supply apparatus to 2 by an error diffusion method. It binarizes and generates binary recording data of K, C, M and Y.

  In step S <b> 3, a treatment liquid 31 is applied by the application roller 30 to the intermediate transfer member 2 that is being transported. When the treatment liquid 31 is applied, the aggregated ink formed by the treatment liquid 31 and the pigment ink is easily separated from the solid component and the liquid component due to the aggregation. On the other hand, an ink image drawn on the intermediate transfer body 2 without using the treatment liquid 31 adheres strongly to the intermediate transfer body 2 when water is exhausted, and thus is difficult to transfer. For this reason, it is not easy to clean the area where only the pigment ink is applied on the intermediate transfer member. Therefore, the area of the application amount area of the treatment liquid 31 on the intermediate transfer body 2 is preferably larger than the area of the ink application area.

  Thereafter, ink is ejected from the ink ejection head 40 by driving the ink ejection head 40 based on the recording data (ink ejection data). Thus, an ink image (mirror inverted image of the recorded image) is formed on the intermediate transfer body 2 by the ink discharged from the ink discharge head 40 and the processing liquid 31 previously applied by the processing liquid application unit 3. Is done. That is, the ink reacts with the image fixing component of the treatment liquid 31 on the intermediate transfer body 2 to form an ink image in which the color materials are aggregated on the intermediate transfer body 2.

  After that, the ink image is subjected to evaporation and drying of a solvent containing moisture in the ink processing unit 5, and the optimum conditions for subsequent transfer are obtained.

  On the other hand, the printing medium 10 is conveyed so as to be aligned with the position of the ink image on the intermediate transfer body 2 formed in this way (step S4). That is, when the intermediate transfer body 2 reaches the transfer position (nip portion), the printing medium 10 is transported by the transport roller. The arrival of the tip of the intermediate transfer body 2 at the nip portion between the conveyance belt and the transfer roller 25 is detected by a sensor (not shown). When the detection is made, the counter roller 9 is driven in contact with the transport belt 1, and the counter roller 9 is pressed against the drive roller 14 via the printing medium 10 and the transport belt 1. Accordingly, a predetermined transfer pressure is applied by the pressure control device for each roller in the transfer unit 6, and the ink image on the intermediate transfer body is transferred onto the printing medium 10.

  In the step of transferring the ink image on the intermediate transfer body onto the printing medium, the intermediate transfer body is reduced by reducing the thickness of the portion that enters the transfer roller of the intermediate transfer body as in the intermediate transfer body of the present invention. Can reduce the impact caused by the force applied when the roller contacts the transfer roller. In the conventional intermediate transfer member having a uniform thickness, as shown in FIG. 5, the point of contact with the transfer roller is closer to the center point of the transfer roller than the intermediate transfer member of the present invention. The force in the traveling direction of the conveying belt generated when the intermediate transfer member and the transfer roller are in contact increases as the contact point approaches the center point of the transfer roller. Therefore, in the conventional example, the impact at the time of entering the transfer roller is increased and vibrations are generated, so that a good transfer image cannot be obtained.

  When the intermediate transfer body 2 and the transfer roller are in contact, the transfer roller is pushed up to the intermediate transfer body. At this time, if the time required for the lower end of the transfer roller to move to the position of the thickness t is increased, the force applied to the unit time in the vertical direction with respect to the transport belt is reduced. That is, if the point where the transfer roller and the intermediate transfer member first contact each other is a point where the distance from the conveyance belt is shorter than the thickness t of the central portion of the intermediate transfer member, it is compared with the case where contact is made at point E in FIG. Thus, the force applied to the unit time in the direction perpendicular to the conveyor belt can be reduced.

In order to bring the intermediate transfer member and the transfer roller into contact with each other at a point closer to the transport belt than the thickness t, the length l of the portion where the thickness of the transfer member is continuously reduced is lowered from the point E in FIG. and G perpendicular and point of intersection of the conveying belt, tangential s circle at point E is longer needs than the length l ₀ of the point F intersects the surface of the conveyor belt. The length l of the portion where the thickness of the transfer member is continuously reduced by the set longer than the length l _0, it is possible to reduce the force applied to the transfer roller, rush intermediate transfer member to the transfer roller The shock when you do is eased.

  As described above, when recording on the printing medium 10 is completed by a series of operations including application of the treatment liquid 31, formation of an ink image, conveyance of the printing medium, and transfer, an end process is performed (step S5). ). Specifically, a process of separating the counter roller 9 from the transport belt 1 is performed. Further, it is possible to perform a process of cleaning the surface of the intermediate transfer body 2 while applying the cleaning liquid 73 by bringing the cleaning roller 71 into contact with the transport belt 1. Further, when recording is continued on the subsequent printing medium 10, the above series of operations can be repeated according to the image signal. On the other hand, when the recording operation is finished and the power is turned off, the driving of each heater and the rotation driving of the conveyor belt 1 are turned off.

  Examples of the present invention will be described below.

  In this embodiment, an embodiment of an intermediate transfer member having a continuously thin thickness toward the end portion in the traveling direction of the conveyance belt will be described.

  As an intermediate transfer member, a material in which a 0.2 mm PET film surface was coated with a silicone rubber (KE12 manufactured by Shin-Etsu Chemical Co., Ltd.) having a rubber hardness of 40 ° with a thickness of 0.3 mm was prepared. This was cut into a size of 2 cm wide and 4 cm long. Next, the silicone rubber is formed so that the thickness of the cut material is continuously reduced from the position moved 5 mm toward the center from the 2 cm wide surface toward the 2 cm wide surface, and the end thickness is 0.2 μm. The face was cut. 13A and 13B are schematic plan views of the material pieces thus produced.

  Next, surface modification was performed on the surface of the intermediate transfer body using a parallel plate type plasma processing apparatus (Sekisui Chemical Co., Ltd .: APT-203) under the following conditions.

(Surface modification conditions)
Gas used; flow rate: air; 1000 cc / min
N ₂ ; 6000 cc / min
Input voltage: 230V
Frequency: 10kHz
Processing speed: 200mm / min
This intermediate transfer member was affixed to a conveyor belt impregnated with a urethane resin as an intermediate transfer member support, with silicone rubber as the upper surface, and fixed.

  In this embodiment, after applying a reaction liquid having the following composition on the intermediate transfer member, the reaction liquid is applied by an ink discharge head 40 (nozzle arrangement density 1200 dpi, discharge amount 4.8 pl, drive frequency 12 kHz). A mirror-inverted image was formed on the intermediate transfer member. Here, inks having the following prescription (four color inks each containing a color pigment as a coloring material) were used.

(Reaction solution composition)
CaCl ₂ · 2H ₂ O: 10%
Surfactant (Acetylenol EH manufactured by Kawaken Fine Chemicals): 1%
("Acetylenol" is a registered trademark)
Diethylene glycol: 30%
Pure water: 59%
(Ink formulation)
Each of the following pigments: 3 parts Black: Carbon black (Mitsubishi Chemical: MCF88)
Cyan: Pigment Blue 15
Magenta: Pigment Red 7
Yellow: Pigment Yellow 74
Styrene-acrylic acid-ethyl acrylate copolymer: 1 part
(Acid value 240, weight average molecular weight 5000)
Glycerin: 10 parts Ethylene glycol: 5 parts Surfactant: 1 part
(Kawaken Fine Chemicals: Acetylenol EH)
Ion-exchanged water: 80 parts At this time, beading and bleeding did not occur when the ink image was formed on the intermediate transfer member. Further, the ink landing diameter by this ink jet recording apparatus was about 40 μm.

  The water in the ink image on the intermediate transfer member is evaporated by blowing air from the hot air blowing dryer 50 to reduce the fluidity, and then the substrate (Nippon Paper Aurora Coat 40.5) is applied to the counter roller 9. The image was transferred by contact.

  As a result, it was confirmed that a high-quality image was recorded on the substrate. Further, almost no residual ink was observed on the surface of the intermediate transfer member after transfer. Even when the above operation was repeated and recording was continuously performed, no ink remained on the surface of the intermediate transfer member, and images could be continuously recorded.

  The material obtained by applying silicone rubber to the surface of the 0.2 mm PET film produced in Example 1 was cut again into a size of 2 cm in width and 4 cm in length. And unlike Example 1, the surface on the PET film side is cut so that the thickness of the end portion becomes 0.1 mm toward the surface with a width of 2 cm from the position moved from the surface with a width of 2 cm toward the center. did. 14A and 14B are schematic plan views of the material pieces thus produced.

  In the same manner as described in Example 1, the surface modification of the silicone rubber surface was performed. Next, the PET film was peeled off. The surface of the intermediate transfer member, which had been peeled off the PET film, was affixed and fixed to a conveyance belt impregnated with a nonwoven fabric of urethane resin as an intermediate transfer member support. Thereafter, an image was obtained on the substrate by the same procedure as in Example 1.

  As a result, as in Example 1, it was confirmed that a high-quality image was recorded on the printing medium in this example. Further, almost no residual ink was observed on the surface of the intermediate transfer member after transfer. Even when the recording operation was repeated and the recording was continuously performed, the ink could not be left on the surface of the intermediate transfer member, and images could be continuously recorded.

  In this embodiment, an embodiment of an intermediate transfer body having a low hardness at the end in the traveling direction of the conveying belt will be described.

  First, a 0.2 mm PET film was cut into a size of 2 cm in width and 4 cm in length. The surface was coated with a silicone rubber having a hardness of 40A (KE12 manufactured by Shin-Etsu Chemical Co., Ltd.) with a width of 2 cm, a length of 3.5 cm, and a thickness of 0.3 mm from the end of the PET film. Next, a silicone rubber (KE12 manufactured by Shin-Etsu Chemical Co., Ltd.) having a hardness of 20A was applied to a PET surface having a width of 2 cm and a length of 0.5 cm remaining uncoated to a thickness of 0.3 mm. In this way, an intermediate transfer member was obtained.

  Next, the surface modification of the silicone rubber surface was performed in the same manner as described in Example 1. The intermediate transfer member produced in this way is made of a conveyance belt impregnated with a urethane resin as an intermediate transfer member support in a non-woven fabric so that the PET film side is the adhesive surface, and the traveling direction side of the conveyance belt is 20 A silicone rubber. Pasted and fixed. Thereafter, an image was obtained on the substrate by the same procedure as in Example 1.

  As a result, it was confirmed that a high-quality image was recorded on the printing medium as in Example 1 and Example 2. Almost no residual ink was found on the surface of the intermediate transfer member after transfer. Even when the recording operation was repeated and the recording was continuously performed, the ink could not be left on the surface of the intermediate transfer member, and images could be continuously recorded.

[Comparative example]
First, as in Example 1, a material was prepared by coating a 0.2 mm PET film surface with a silicone rubber (KE12 manufactured by Shin-Etsu Chemical Co., Ltd.) having a rubber hardness of 40 A in a thickness of 0.3 mm. In this comparative example, unlike Example 1 and Example 2, this material was not cut. Then, the surface modification of the silicone rubber surface was performed in the same manner as described in Example 1. The thus prepared intermediate transfer member was fixed by adhering the PET film side as an adhesive surface to a conveyance belt in which a nonwoven fabric impregnated with a urethane resin as an intermediate transfer member support was fixed. Thereafter, an image was obtained on the substrate by the same procedure as in Example 1.

  When the obtained image was observed, it was confirmed that the ink density of the image on the printing medium was shaded. Further, residual ink was observed on the surface of the intermediate transfer member after transfer. In particular, a relatively large amount of residual ink could be observed on the traveling direction side of the conveying belt, that is, the side that entered the transfer roller. When the recording operation was repeated and recording was continuously performed, it was confirmed that ink remained on the surface of the intermediate transfer member every time and the residual ink amount increased.

  When the intermediate transfer member enters the transfer roller, a force is applied to the intermediate transfer member and the transfer roller, and both cause vibrations and the like. It is considered that the pressure applied from the transfer roller to the intermediate transfer body and the printing medium is not constant under the influence, and the density of the ink is generated in the transferred image.

DESCRIPTION OF SYMBOLS 1 Conveyor belt 2 Intermediate transfer body 3 Reaction liquid provision part 30 Application | coating roller 31 Processing liquid 32 Processing liquid supply roller 4 Drawing unit 40 Ink discharge head 5 Ink image processing part 50 Hot air ventilation drying furnace 6 Transfer unit 7 Cleaning part 70 Cleaning liquid Holding member 71 Cleaning roller 72 Cleaning liquid supply roller 73 Cleaning liquid 8 Paper feeding / conveying section 9 Counter roller 10 Printed body 12 Conveying roller 13 Conveying roller 14 Conveying roller A Conveying belt traveling direction B Intermediate transfer member traveling direction C Transfer roller rotating direction D Point of contact between the intermediate transfer member and the transfer roller E Point of length t from the surface of the transfer belt on the outer circumference of the transfer roller F Intersection of the tangent line s at point E and the surface of the transfer belt G Vertical line drawn from the point E to the transfer belt and transfer Intersection with belt surface r Distance tangent l ₀ point F and the point G in the length s point E of a thickness l cushioning portion of radius t intermediate transfer member of the transfer roller

Claims (3)

An intermediate transfer member that temporarily carries an image made of ink;
A drawing unit that forms an image on the intermediate transfer member by applying ink using an inkjet device;
A transfer unit for pressing the printing medium to the image with a roller and transferring the image from the intermediate transfer body to the printing body;
In an inkjet recording apparatus having
An ink jet recording apparatus, wherein the intermediate transfer member has a flat plate shape, and has a portion where the thickness continuously decreases from the central portion toward the entering direction at an end portion in the roller entering direction. Claims wherein the length of the portion where the thickness of the intermediate transfer body is reduced, and wherein the longer than unit length l ₀ which is defined by the following equation from the thickness t of the center portion of the roller diameter r and the intermediate transfer member Item 10. The ink jet recording apparatus according to Item 1.
l ₀ = (rt−t ² ) / √ (2rt−t ² ) An intermediate transfer member that temporarily carries an image made of ink;
A drawing unit that forms an image on the intermediate transfer member by applying ink using an inkjet device;
A transfer unit for pressing the printing medium to the image with a roller and transferring the image from the intermediate transfer body to the printing body;
In an inkjet recording apparatus having
An ink jet recording apparatus, wherein the intermediate transfer member has a flat plate shape, and the hardness of the end portion in the roller entrance direction is lower than the central portion of the intermediate transfer member.