JP2020069760A - Ink jet recording device and ink jet recording method - Google Patents

Abstract

To provide an ink jet recording device and an ink jet recording method capable of further certainly transferring ink to a recording medium.SOLUTION: An ink jet recording device includes an ink discharging portion that discharges ink in which viscosity is increased by being applied a predetermined energy; a transferring portion that records an image on a recording medium by transferring the ink discharged from the ink discharging portion and impacted on an impact surface of an intermediate transfer body; an energy generating portion that generates energy to be applied to the ink before impacting on the impact surface and being transferred to the recording medium; and a control portion that controls the action of the energy generating portion so as to make the amount of energy to be applied to a unit area on the impact surface with respect to an ink laminated area of the impact surface smaller than the amount of energy to be applied to a unit area on the impact surface with respect to an ink in an area other than the ink lamination area of the impact surface.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an inkjet recording device and an inkjet recording method.

  Conventionally, an ink jet that ejects ink ejected from a nozzle of a recording head onto a predetermined landing surface of an intermediate transfer body to form a primary image, transfers the primary image onto a recording medium, and records the image on the recording medium. There is a recording device. In such an ink jet recording apparatus, by appropriately increasing the viscosity of the ink that has landed on the landing surface (for example, by irradiating the ultraviolet curable ink with ultraviolet rays to temporarily cure it), the transfer to the recording medium is performed. There is a technique for facilitating the separation of the ink from the landing surface at the time (for example, Patent Document 1).

JP, 2014-8656, A

  However, a plurality of inks ejected onto the intermediate transfer body at different timings may be stacked on the landing surface without coalescing. In such a region where the ink is laminated, the contact area between the ink and the recording medium during transfer is likely to be smaller than in a region where the ink is united to form a single layer. When the contact area between the ink and the recording medium is small, it becomes difficult to obtain the adhesive force of the ink to the recording medium at the time of transfer, and the recording medium does not have sufficient force to separate the ink from the intermediate transfer member, resulting in defective transfer of the ink. There is a problem that it becomes easier.

  An object of the present invention is to provide an inkjet recording device and an inkjet recording method that can transfer ink to a recording medium more reliably.

In order to achieve the above object, the invention of an ink jet recording apparatus according to claim 1 is
An ink ejecting unit that ejects ink whose viscosity is increased by application of predetermined energy,
The ink ejected from the ink ejecting unit has an intermediate transfer body on which a primary image is formed by landing on a predetermined landing surface, and the ink on the landing surface is transferred to a recording medium to form an image on the recording medium. A transfer part to record,
An energy generating unit that generates the energy applied to the ink before landing on the landing surface and being transferred to the recording medium;
A control unit for controlling the operation of the energy generation unit,
Equipped with
The control unit is configured such that an amount of energy applied to a unit area on the landing surface with respect to ink in an ink stacking area including a portion where the ink is stacked on the landing surface is The operation of the energy generating unit is controlled so that the amount of energy applied to the ink in the area excluding the ink stacking area is smaller than the amount of energy applied per unit area on the landing surface.

The invention described in claim 2 is the ink jet recording apparatus according to claim 1,
The predetermined energy is ultraviolet rays.

According to a third aspect of the invention, in the inkjet recording apparatus according to the second aspect,
The control unit controls the intensity of the ultraviolet rays applied to the ink in the ink stacking area of the landing surface to be lower than the intensity of the ultraviolet rays applied to the ink in the area of the landing surface excluding the ink stacking area. Thus, it is characterized in that the energy generating unit irradiates ultraviolet rays.

According to a fourth aspect of the invention, in the ink jet recording apparatus according to the second aspect,
The controller controls the energy so that the irradiation time of the ultraviolet rays to the ink in the ink stacking area of the landing surface is shorter than the irradiation time of the ultraviolet rays to the ink in the area of the landing surface excluding the ink stacking area. It is characterized in that the generation unit irradiates ultraviolet rays.

According to a fifth aspect of the invention, in the inkjet recording apparatus according to the second aspect,
The control unit is configured such that the peak wavelength of the intensity of the ultraviolet rays with which the ink in the ink stacking area of the landing surface is irradiated is the intensity of the ultraviolet light with which the ink in the landing surface excluding the ink stacking area is irradiated. It is characterized in that the energy generating unit irradiates ultraviolet rays so as to have a wavelength longer than the peak wavelength.

According to a sixth aspect of the invention, in the inkjet recording apparatus according to any one of the second to fifth aspects,
The intermediate transfer member is an annular member made of a material that transmits ultraviolet rays,
The energy generation unit is characterized in that ultraviolet rays are incident on the ink on the outer peripheral surface of the intermediate transfer body, which is the landing surface, from the inner peripheral surface side of the intermediate transfer body.

The invention described in claim 7 is the ink jet recording apparatus according to claim 1,
The predetermined energy is thermal energy,
The energy generating unit is characterized by generating the thermal energy applied directly or indirectly to the ink on the landing surface.

The invention described in claim 8 is the ink jet recording apparatus according to claim 7,
The energy generating unit heats the intermediate transfer member to apply thermal energy to the ink on the landing surface via the intermediate transfer member,
The control unit causes the energy generating unit to heat the intermediate transfer member so that the temperature of the ink stacking area of the landing surface becomes lower than the temperature of the area of the landing surface excluding the ink stacking area. It is characterized by

According to a ninth aspect of the invention, in the inkjet recording apparatus according to any one of the first to eighth aspects,
The ink ejecting unit has a plurality of recording heads ejecting inks of different colors, and ejects the inks from the plurality of recording heads in a manner that inks of different colors can be stacked on the landing surface. I am trying.

According to a tenth aspect of the invention, in the ink jet recording apparatus according to any one of the first to ninth aspects,
The ink ejecting unit has a first recording head that ejects a predetermined color of ink and a second recording head that ejects transparent ink, and the transparent ink is ejected from the second recording head onto the landing surface. After ejecting another ink, the first recording head ejects the ink of the predetermined color to stack the transparent ink and the ink of the predetermined color.

In order to achieve the above object, the invention of an ink jet recording apparatus according to claim 11 is
An ink jet recording apparatus in which an ink in which a dispersion material is dispersed in a dispersion medium is landed on a predetermined landing surface of an intermediate transfer body to form a primary image, the primary image is transferred to a recording medium, and the image is recorded on the recording medium. And
An aggregating agent imparting an aggregating agent that agglomerates the dispersion material in the ink to increase the viscosity of the ink by contacting the ink, and an aggregating agent imparting portion that imparts to the landing surface of the intermediate transfer member.
An ink ejecting section for ejecting the ink onto the landing surface provided with the aggregating agent,
A transfer unit having the intermediate transfer member, for transferring the ink on the landing surface to a recording medium to record an image on the recording medium;
A control unit for controlling the operation of the aggregating agent application unit,
Equipped with
The control unit determines the amount of the aggregating agent applied per unit area in the ink stacking region including a portion of the landing surface where ink is to be stacked, excluding the ink stacking region of the landing surface. It is characterized in that the aggregating agent is applied by the aggregating agent applying part so that the amount is smaller than the amount of the aggregating agent applied per unit area in the region.

In order to achieve the above object, the invention of an inkjet recording method according to claim 12 is
An ink jet recording apparatus including an ink ejecting unit that ejects ink whose viscosity increases by applying a predetermined energy, and an intermediate transfer member on which the ink ejected from the ink ejecting unit lands on a predetermined landing surface. An inkjet recording method,
A primary image forming step of ejecting ink by the ink ejecting section to land on the landing surface of the intermediate transfer member and form a primary image on the landing surface;
An energy applying step of applying the energy to the ink that has landed on the landing surface to increase the viscosity of the ink,
A transfer step of transferring the ink on the landing surface to which energy is applied in the energy applying step onto a recording medium to record an image on the recording medium;
Including,
In the energy applying step, the amount of energy applied per unit area on the landing surface to the ink in the ink stacking region including a portion of the landing surface where the ink is stacked is Energy is applied to the ink in the area excluding the ink laminated area so as to be smaller than the amount of energy applied per unit area on the landing surface.

In order to achieve the above object, the invention of an ink jet recording method according to claim 13 is
An ink jet recording method using an ink jet recording apparatus, comprising: an ink ejecting unit that ejects an ink in which a dispersion material is dispersed in a dispersion medium; and an intermediate transfer member on which the ink ejected from the ink ejecting unit lands on a predetermined landing surface. There
An aggregating agent applying step of applying an aggregating agent that agglomerates the dispersion material in the ink to increase the viscosity of the ink by contacting the ink to the landing surface of the intermediate transfer member,
A primary image forming step of forming a primary image on the landing surface by ejecting the ink onto the landing surface to which the aggregating agent is applied to land the ink by the ink ejecting unit,
A transfer step of transferring the ink on the landing surface to a recording medium to record an image on the recording medium,
Including,
In the aggregating agent applying step, the amount of the aggregating agent applied per unit area in the ink stacking region including a portion of the landing surface where the ink is to be stacked in the primary image forming step is the landing surface. Among the above, the aggregating agent is applied so that the amount of the aggregating agent is less than the amount of the aggregating agent applied per unit area in the region excluding the ink layered region.

  According to the present invention, there is an effect that the ink can be more reliably transferred to the recording medium.

It is a figure which shows schematic structure of an inkjet recording device. It is a schematic diagram which shows the structure of a head unit. It is a figure which shows the structure of a 1st ultraviolet irradiation part. FIG. 3 is a block diagram showing a functional configuration of an inkjet recording device. It is a figure explaining the temporary hardening operation of an inkjet recording device. It is a figure which shows the hardening degree of the ink with respect to the amount of ultraviolet irradiation. FIG. 6 is a diagram illustrating the necessity of making the irradiation intensity of ultraviolet rays different between a single-layer ink forming region and an ink stacking region. It is a figure explaining the irradiation operation of the ultraviolet rays in temporary hardening. 6 is a flowchart showing a control procedure of image recording processing. It is a figure which shows the structure of the 1st ultraviolet irradiation part which concerns on the modification 2. It is a figure which shows schematic structure of the inkjet recording device which concerns on 2nd Embodiment. FIG. 7 is a diagram illustrating an ink stacking mode and a temporary curing operation in the second embodiment. It is a figure which shows schematic structure of the inkjet recording device which concerns on 3rd Embodiment. It is a figure which shows the structure of a heater. It is a figure which shows schematic structure of the inkjet recording device which concerns on 4th Embodiment. It is a figure explaining the lamination mode of ink and a temporary hardening operation in a 4th embodiment.

  Hereinafter, embodiments of an inkjet recording apparatus and an inkjet recording method of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of the inkjet recording apparatus 1.
The inkjet recording device 1 includes an ink ejection unit 2, a transfer unit 3, a first ultraviolet irradiation unit 51 (energy generation unit), a second ultraviolet irradiation unit 52, a control unit 4 (see FIG. 4), and the like. I have it. The inkjet recording apparatus 1 ejects ink from the ink ejecting unit 2 onto the belt-shaped intermediate transfer member 10 of the transfer unit 3 to form a primary image on the outer peripheral surface (ink landing surface, image forming surface) of the intermediate transfer member 10. And the ink forming the primary image is transferred to the recording medium M to record an image on the recording medium M. As the recording medium M, various media such as paper, resin plate, metal, cloth and rubber can be used. Examples of the paper include plain paper, paperboard, coated paper, resin-coated paper, synthetic paper and the like.

  The ink ejecting unit 2 ejects ink from the nozzles onto the outer peripheral surface of the intermediate transfer member 10 based on image data to form a primary image on the outer peripheral surface. The ink ejecting section 2 has four head units 21Y, 21M, and 21C, which respectively correspond to four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K). 21K (hereinafter, any one of them is also referred to as a head unit 21). The plurality of head units 21 are arranged such that their respective ink ejection surfaces face the outer peripheral surface of the intermediate transfer body 10 at appropriate intervals. The number of head units 21 may be three or less or five or more.

  FIG. 2 is a schematic diagram showing the configuration of the head unit 21, and is a plan view of the head unit 21 as seen from the side facing the outer peripheral surface of the intermediate transfer member 10. The head unit 21 includes a plate-shaped support portion 21a and a plurality of (here, eight) recording heads 211 fixed to the support portion 21a in a state of being fitted in through holes provided in the support portion 21a. The recording head 211 is fixed to the support portion 21a in a state where the ink ejection surface 212 provided with the opening of the nozzle 213 is exposed from the through hole of the support portion 21a toward the outer peripheral surface side.

  In the recording head 211, the plurality of nozzles 213 are equidistantly arranged in a direction intersecting the direction of the circular movement of the intermediate transfer member 10 (hereinafter also referred to as the circular movement direction) (in the present embodiment, the width direction orthogonal to the circular movement direction). Are arranged in each. In this embodiment, each recording head 211 has four rows of nozzles 213 (nozzle rows) that are one-dimensionally arranged at equal intervals in the width direction. These four nozzle rows are arranged such that the positions in the width direction are shifted from each other so that the positions in the width direction of the nozzles 213 do not overlap. The number of nozzle rows included in the recording head 211 is not limited to four and may be three or less or five or more.

  The eight recording heads 211 in the head unit 21 are arranged in a zigzag pattern so that the arrangement range of the nozzles 213 in the width direction is continuous. The widthwise arrangement range of the nozzles 213 included in the head unit 21 covers the widthwise width of the area on the outer peripheral surface of the intermediate transfer body 10 where the primary image can be formed. The head unit 21 is used with its position fixed at the time of forming the primary image, and ejects ink from the nozzle 213 to each position at a predetermined interval in the orbital movement direction according to the orbital movement of the intermediate transfer member 10. , Forming a primary image by a single pass method. The ink ejection mechanism for ejecting ink from each nozzle 213 may be a piezo type that uses a piezoelectric element, or may be a thermal type that heats and ejects the ink.

  As the ink ejected from the nozzles of the head unit 21, the ink whose viscosity increases when energy is applied by a predetermined method is used. In the present embodiment, as such an ink, an ultraviolet curable ink whose viscosity increases due to the progress of a curing reaction upon irradiation with ultraviolet rays is used. When the ultraviolet curable ink is used, the transferability of the ink can be enhanced by appropriately irradiating the ink landed on the outer peripheral surface of the intermediate transfer member 10 with ultraviolet rays to increase the viscosity of the ink to a certain degree. .. A method of irradiating ultraviolet rays for this purpose will be described in detail later.

The ink used in this embodiment is a phase change ink that changes its phase between a gel state and a sol state depending on the temperature. From the nozzle 213 of the head unit 21, ink that has become a sol due to heating is ejected, and the ink that has landed on the outer peripheral surface of the intermediate transfer member 10 quickly becomes a gel when cooled. The viscosity of the gelled ink is adjusted by irradiation with ultraviolet rays.
The ink used in this embodiment contains a photopolymerizable compound (monomer), a photopolymerization initiator, a gelling agent, and a colorant. Among them, the photopolymerizable compound is a compound that undergoes a polymerization reaction to be polymerized by being irradiated with ultraviolet rays. This polymerization increases the viscosity of the ink and cures it. The photopolymerization initiator is a compound for initiating the above polymerization reaction. The gelling agent dissolves in the ink when the ink is heated to a temperature higher than the sol formation temperature to make the ink a sol, and when the ink is cooled to a temperature lower than the gelation temperature, forms a crosslinked structure or forms a fibrous aggregate. It is a compound having the property of gelling the ink by forming it. In addition, the colorant includes a pigment or dye having a color related to the ink.

  The transfer unit 3 in FIG. 1 moves and contacts the intermediate transfer body 10 and the recording medium M supplied from a sheet feeding unit (not shown) to transfer the primary image formed on the intermediate transfer body 10 to the recording medium M. Let The transfer unit 3 includes an intermediate transfer body 10, a drive roller 31, a driven roller 32, a pressure roller 33, a transport roller 34, and the like.

  The intermediate transfer body 10 is an endless belt body (annular member) having an outer peripheral surface (landing surface) on which the ink ejected from the ink ejection unit 2 lands. A primary image is formed on the outer peripheral surface of the intermediate transfer member 10 by the deposited ink, and the primary image is transferred to the recording medium M. The intermediate transfer body 10 is wound around a driving roller 31, a driven roller 32, and a pressure roller 33, and moves in an orbital manner so that the outer peripheral surface orbits a predetermined orbiting path according to the rotating operation of the driving roller 31. At least a portion of the intermediate transfer member 10 facing the ink ejection portion 2 is supported by a support member (not shown) having a flat surface to form a horizontal surface.

  In addition, the intermediate transfer member 10 is composed of a member made of a material that transmits ultraviolet rays. Therefore, as will be described later, by irradiating the inner peripheral surface of the intermediate transfer member 10 with ultraviolet light from the first ultraviolet irradiation unit 51, the ink on the outer peripheral surface is irradiated with ultraviolet light through the intermediate transfer member 10. It can be made to (incident). As a constituent member of the intermediate transfer member 10, a material that transmits ultraviolet rays and has durability against ultraviolet rays, for example, PET (polyethylene terephthalate), polyimide, polyolefin, ETFE (ethylene-tetrafluoroethylene copolymer) or the like is used. You can

  The viscosity of the ink on the outer peripheral surface of the intermediate transfer body 10 is increased to some extent by being irradiated with ultraviolet rays from the first ultraviolet ray irradiation section 51. Hereinafter, this step of increasing the viscosity of the ink before transfer on the intermediate transfer body 10 is also referred to as “temporary curing”.

  The drive roller 31 rotates about a rotation axis by driving a motor (not shown). The driven roller 32 is arranged at a predetermined distance from the drive roller 31, and rotates around the rotation axis of the drive roller 31 parallel to the rotation axis of the intermediate transfer body 10.

  The intermediate transfer member 10 is stretched around the pressure roller 33. The pressure roller 33 may be movably provided so as to be able to absorb the bending of the intermediate transfer body 10.

The transport roller 34 transports the recording medium M in the roller rotation direction by rotating the recording medium M supplied from a sheet feeding unit (not shown) while holding the recording medium M on the outer peripheral surface. The transport roller 34 is arranged so as to form a nip portion N with the pressure roller 33. The intermediate transfer body 10 and the recording medium M are sandwiched and pressed by the nip portion N. As a result, the ink (primary image) on the outer peripheral surface of the intermediate transfer body 10 is transferred to the recording medium M, and the image is recorded on the recording medium M.
Note that instead of the mode in which the recording medium M is held and conveyed on the outer peripheral surface of the conveying roller 34, the recording medium M is (in the horizontal direction from the right direction in FIG. 1) in the nip portion N between the pressure roller 33 and the conveying roller 34. It is also possible to adopt a mode in which the plug is directly inserted.

  Further, a cleaning unit for cleaning the outer peripheral surface 10 a of the intermediate transfer body 10 may be provided between the nip portion N and the drive roller 31 in the orbital movement direction of the intermediate transfer body 10. As the cleaning member used in the cleaning unit, cloth, non-woven fabric, blade member or the like may be used. In addition, the cleaning liquid may be applied to the outer peripheral surface 10a or the cleaning member to remove ink, dirt and the like.

  The first ultraviolet irradiation unit 51 is provided between the driven roller 32 and the pressure roller 33 at a position facing the inner peripheral surface of the intermediate transfer member 10. That is, the first ultraviolet irradiation unit 51 is arranged so as to face the portion of the intermediate transfer member 10 immediately before entering the nip portion N. The first ultraviolet irradiation unit 51 irradiates the inner peripheral surface of the intermediate transfer body 10 with ultraviolet light to cause the ultraviolet rays to be incident on the ink on the outer peripheral surface through the intermediate transfer body 10.

FIG. 3 is a diagram showing a configuration of the first ultraviolet irradiation unit 51, and is a plan view of the first ultraviolet irradiation unit 51 seen from the outer peripheral surface side of the intermediate transfer member 10 through the intermediate transfer member 10. ..
The first ultraviolet irradiation unit 51 includes a plurality of ultraviolet light sources 511 that are one-dimensionally arranged in the width direction of the intermediate transfer member 10. The plurality of ultraviolet light sources 511 are arranged at positions and intervals that can irradiate the entire intermediate transfer member 10 with ultraviolet light in the width direction. Each ultraviolet light source 511 emits ultraviolet light independently of each other under the control of the control unit 4. Further, each ultraviolet light source 511 can irradiate ultraviolet light with a plurality of different intensities. The intensity of the ultraviolet light emitted from each ultraviolet light source 511 is controlled by the control unit 4.

The second ultraviolet irradiation unit 52 shown in FIG. 1 is provided at a position facing the outer peripheral surface of the transport roller 34 on the downstream side of the nip portion N in the transport direction of the recording medium M by the transport roller 34. Under the control of the control unit 4, the second ultraviolet irradiation unit 52 irradiates the surface of the recording medium M on the transport roller 34 with ultraviolet light of a predetermined intensity in the width direction over the entire recording medium M. The ink transferred to the recording medium M is completely cured by the ultraviolet irradiation from the second ultraviolet irradiation unit 52, and is fixed and fixed on the surface of the recording medium M by the anchor effect. Hereinafter, the step of curing the ink by the second ultraviolet irradiation section 52 is also referred to as “main curing”.
The recording medium M that has passed through the second ultraviolet irradiation unit 52 is removed from the outer peripheral surface of the transport roller 34 and is transported to a predetermined paper discharge unit (not shown).

FIG. 4 is a block diagram showing the functional configuration of the inkjet recording apparatus 1.
The inkjet recording apparatus 1 includes a control unit 4, a head unit 21 having a head driving unit 214 and a recording head 211, a first ultraviolet irradiation unit 51, a second ultraviolet irradiation unit 52, and a roller driving unit 53. An operation display unit 54, a communication unit 55, a bus 56 and the like are provided.

  The control unit 4 integrally controls the overall operation of the inkjet recording device 1. The control unit 4 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), a storage unit 44, and the like.

  The CPU 41 reads out various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various arithmetic processes. Further, the CPU 41 centrally controls the overall operation of the inkjet recording apparatus 1.

  The RAM 42 provides the CPU 41 with a working memory space and stores temporary data. The RAM 42 may include a non-volatile memory.

  The ROM 43 stores various control programs executed by the CPU 41, setting data, and the like. A rewritable non-volatile memory such as a flash memory may be used instead of the ROM 43.

  The storage unit 44 stores image data to be recorded, job data including operation settings related to the recording operation of the image data, which are input from an external device via the communication unit 55. As the storage unit 44, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may be used together.

  The head driving unit 214 outputs image data and control signals to the recording head 211 at appropriate timings according to the circular movement of the intermediate transfer member 10 based on the control signals supplied from the control unit 4, thereby causing the recording head 211 to print. Ink is ejected from the nozzle 213 of 211.

  The roller drive unit 53 outputs a drive signal that causes a motor that rotates the drive roller 31 to rotate at a set speed, based on a control signal supplied from the control unit 4, thereby causing the intermediate transfer body 10 to rotate. Circulates at a predetermined speed.

  The operation display unit 54 includes a display device such as a liquid crystal display or an organic EL display, operation keys, and an input device such as a touch panel that is arranged so as to be overlapped with the screen of the display device. The operation display unit 54 displays various kinds of information on the display device, converts the user's input operation on the input device into an operation signal, and outputs the operation signal to the control unit 4.

  The communication unit 55 communicates with an external device to exchange information. The communication unit 55 performs communication control corresponding to various communication standards related to wired or wireless communication by LAN. The received data includes the job data described above. The transmitted data includes status information relating to the progress of the image recording operation according to the job data.

  The bus 56 is a signal path for transmitting and receiving signals between the control unit 4 and each unit.

  Next, the temporary curing operation of the inkjet recording device 1 for performing the above-described temporary curing of the ink will be described.

FIG. 5 is a diagram illustrating a temporary curing operation of the inkjet recording device 1.
FIG. 5 is a schematic cross-sectional view of the intermediate transfer body 10 after the ink has landed, and the first ultraviolet irradiation unit 51 facing the intermediate transfer body 10. As shown in FIG. 5, the ink ejected from the ink ejection unit 2 lands and spreads on the outer peripheral surface 10 a of the intermediate transfer member 10. The ink on the outer peripheral surface 10a is irradiated with ultraviolet rays from the ultraviolet light source 511 of the first ultraviolet irradiation unit 51 through the intermediate transfer body 10 to temporarily cure the ink.

Thus, by irradiating the ink with ultraviolet rays from the side of the ink surface that is in contact with the outer peripheral surface 10a (hereinafter, simply referred to as the outer peripheral surface 10a side), the curing reaction of the surface of the ink on the outer peripheral surface 10a side is performed. Progresses and the viscosity increases. As a result, the ink can be easily separated from the outer peripheral surface 10a, and the deterioration of the image quality due to the crushing of the ink during transfer can be suppressed.
Further, since the ultraviolet rays incident from the outer peripheral surface 10a side of the ink are partially absorbed before reaching the side (recording medium M side) opposite to the outer peripheral surface 10a side of the ink, the surface of the ink on the recording medium M side. Is relatively hard to cure and remains low in viscosity. By keeping the viscosity of the ink on the recording medium M side low in this way, the adhesive force (adhesive force) of the ink to the recording medium M is maintained in a state where it is easy to obtain (a state in which it adheres easily), so that the recording medium is easily Ink can be transferred to M.
As described above, the temporary curing makes the outer peripheral surface 10a side of the ink hard and the recording medium M side relatively soft, so that the adhesive force of the ink to the intermediate transfer body 10 is weakened and the adhesive force to the recording medium M is secured. Therefore, the recording medium M can easily obtain a sufficient force to separate the ink from the intermediate transfer body 10, and the ease of transferring the ink can be improved.

  In the inkjet recording apparatus 1, as shown on the right side of FIG. 5, a plurality of inks are laminated in a partial area on the outer peripheral surface 10a depending on the number of types of inks used for recording an image and the ejection timing of the inks. It will be in the state of being. Hereinafter, the stacking of the ink will be described.

In the inkjet recording apparatus 1, by causing inks of different colors among YMCK to land within a predetermined vicinity range on the outer peripheral surface 10a, various colors are mixed due to a color mixing effect when the colors are macroscopically viewed. The colors are represented. Here, since the timings at which the plurality of head units 21 having different colors of ink face the specific positions on the outer peripheral surface 10a are different from each other, the timings at which the inks of the respective colors are ejected and land at the specific positions are also different from each other. different. For this reason, in the inks of a plurality of colors that have landed in the vicinity range, the second color of ink has landed at a timing when a predetermined time has elapsed after the inks of the first landed colors have coalesced and wet and spread. It spreads in a range where it partially overlaps the landed ink.
At this time, as shown on the right side of FIG. 5, the ink that has landed first (here, the yellow ink InY) and the ink that has landed at a position that overlaps the ink (here, the magenta ink InM) are The inks are laminated with an interface between them without being united (not mixed with each other).

In the following, the ink of the lowermost layer in the portion where the inks are laminated is also referred to as the primary color ink and the second layer of ink superimposed on the primary color ink is also referred to as the secondary color ink.
Further, in the outer peripheral surface 10a, a region where the inks of the same color are united to form a single layer is referred to as an ink non-laminated region R1, and a region including a portion where the ink is laminated is referred to as an ink laminated region R2. That is, the ink non-laminated region R1 corresponds to a region of the outer peripheral surface 10a excluding the ink laminated region R2. The left side of FIG. 5 shows the ink non-stacking region R1, and the right side shows the ink stacking region R2.
In the ink stacking region R2 of FIG. 5, an example in which the ink InM that is the secondary color ink is stacked within the formation range of the ink InY that is the primary color ink is shown. The present invention is not limited to this, and the secondary color ink may spread over the range from the primary color ink formation range to the outside of the formation range.

In the ink stacking region R2, a plurality of inks of different colors are stacked without coalescing. This is because the primary color ink gels and thickens after the primary color ink has landed. This is because the secondary color ink having a lower viscosity than the viscous primary color ink lands. More specifically, when the viscosity of the primary color ink is increased, a gelling agent, which is a wax component contained in the ink, is deposited on the surface of the primary color ink to cause liquid repellency to the secondary color ink on the surface of the primary color ink. Sex increases. As a result, the primary color ink and the secondary color ink are prevented from coalescing with each other, an interface is formed between the inks, and the inks are stacked.
In the present embodiment, since the primary color ink gels and thickens in a time shorter than the time difference between the ink ejection from the adjacent head units 21 to the same position on the outer peripheral surface 10a, the inks of different colors are ejected to the same position. In that case, an interface is created between the inks and the inks are stacked regardless of the color combination.

  The wax component is deposited on the surface of the primary color ink to increase the liquid repellency with respect to the secondary color ink, so that the primary color is better than the liquid repellency with respect to the primary color ink on the outer peripheral surface 10a of the intermediate transfer member 10. The liquid repellency of the ink surface with respect to the secondary color ink is greater (the contact angle is greater). As a result, even when the same amount of the primary color ink and the secondary color ink land on the same position, the primary color ink gets wet on the outer peripheral surface 10a as shown on the right side of FIG. The area where the secondary color ink wets and spreads on the surface of the primary color ink is smaller than the area where it spreads.

  Therefore, the area of the secondary color ink in the laminated ink tends to be small. Therefore, the area in which the ink (secondary color ink) contacts the recording medium M in the ink laminated area R2 is greater than the area in which the ink (primary color ink) contacts the recording medium M in the ink non-laminated area R1. Also tends to be small. Further, the ease of transferring the ink to the recording medium M tends to decrease as the contact area of the ink decreases. This is because when the contact area between the ink and the recording medium M is small, the adhesive force of the ink to the recording medium M at the time of transfer becomes difficult to obtain, and the recording medium M lacks the force for separating the ink from the intermediate transfer body 10. This is because it is easy. Therefore, the smaller the contact area with the recording medium M, the lower the transfer rate to the recording medium M is likely to be. Therefore, if the ink is uniformly temporarily cured and thickened in the ink non-lamination region R1 and the ink lamination region R2, the contact area between the ink and the recording medium M is relatively small in the ink lamination region R2. It becomes difficult to transfer the ink, and defective transfer of the ink easily occurs.

Therefore, in the ink jet recording apparatus 1 of the present embodiment, the amount of ultraviolet rays irradiated per unit area on the outer peripheral surface 10a for the ink in the ink laminated area R2 is equal to the outer peripheral surface for the ink in the ink non-laminated area R1. Ultraviolet rays are emitted from the first ultraviolet ray irradiation unit 51 so as to be smaller than the amount of ultraviolet rays emitted per unit area on 10a.
That is, as shown in FIG. 5, the ink of the ink non-laminated region R1 is irradiated with the ultraviolet light of the intensity I1 from the first ultraviolet irradiation unit 51, while the ink of the ink laminated region R2 is irradiated. , 1st ultraviolet irradiation part 51 irradiates the ultraviolet of intensity I2 (<I1).
This makes it possible to make the degree of curing (viscosity) of the surface of the secondary color ink in the ink layered region R2 sufficiently smaller than the degree of curing of the surface of the primary color ink in the ink non-layered region R1. In the example of FIG. 5, the degree of curing of the outer peripheral surface 10a side surface of the primary color ink in the ink non-laminated region R1 is 60, whereas the outer peripheral surface 10a side surface of the ink laminated region R2 in the secondary color ink is cured. The degree is reduced to 30. As described above, the degree of curing of the surface of the secondary color ink is suppressed and the surface of the secondary color ink is softer than the surface of the primary color ink. As a result, when the ink is transferred to the recording medium M, the recording medium of the secondary color ink in the ink stack region R2 is recorded. The adhesive force with respect to M is increased (that is, it is easy to adhere), and the occurrence of the above-mentioned defective transfer of ink can be suppressed.

Even when the irradiation intensity of ultraviolet rays is relatively weakened in the ink stacking region R2 in this way, the ink non-stacking region R1 and the ink stacking region R2 have substantially the same degree of curing on the outer peripheral surface 10a side surface of the ink. can do. In the example of FIG. 5, the degree of curing of the surface of the outer peripheral surface 10a of the ink is 100 in both the ink non-laminated region R1 and the ink laminated region R2. This is because, as shown in FIG. 6, the rate of increase in the curing degree of the ink is saturated as the cumulative ultraviolet ray irradiation amount to the ink is increased.
Therefore, even if the irradiation intensity of the ultraviolet rays is weakened in the ink layered region R2, the ease of peeling the ink from the intermediate transfer member 10 can be ensured in both the ink non-layered region R1 and the ink layered region R2.

FIG. 7 is a diagram for explaining the necessity of making the irradiation intensity of ultraviolet rays different between the ink non-laminated region R1 and the ink laminated region R2.
In FIG. 7, the curing degree of the ink at each distance from the outer peripheral surface 10a of the intermediate transfer member 10 when the ink is irradiated with ultraviolet rays having intensities I0 to I3 (I0>I1>I2> I3) for a predetermined time. It is a representation. The origin P0 on the horizontal axis corresponds to the position of the outer peripheral surface 10a of the intermediate transfer member 10, P1 corresponds to the surface position of the primary color ink in the ink non-stacked region R1, and P2 is 2 in the ink stacked region R2. It corresponds to the surface position of the next color ink.
Further, the vertical arrows at the positions P0 to P2 represent the range of the appropriate ink curing degree at the positions. That is, by setting the degree of curing of the ink surface within the range of the arrow at the surface position P1 of the primary color ink and the surface position P2 of the secondary color ink, the outer surface 10a including the single-layer ink and the laminated ink is The adhesive force of the ink to the recording medium M is obtained so that the entire primary image of the ink can be appropriately transferred to the recording medium M.

Focusing on the straight line corresponding to the ultraviolet intensity I1 in FIG. 7, it can be seen that by irradiating the ultraviolet ray having the intensity I1, an appropriate degree of ink curing can be obtained at the surface position P1 of the primary color ink.
Further, focusing on the straight line corresponding to the ultraviolet intensity I2, it can be seen that by irradiating the ultraviolet ray having the intensity I2, an appropriate degree of ink curing can be obtained at the surface position P2 of the secondary color ink.
From this, in order to properly transfer the ink in both the ink non-lamination region R1 and the ink lamination region R2, it is necessary to make the irradiation intensity of ultraviolet rays different between the ink non-lamination region R1 and the ink lamination region R2. I understand. In other words, when the ink non-laminated region R1 and the ink laminated region R2 are irradiated with ultraviolet light with a uniform intensity I1 or with uniform intensity I2, the surface position P1 of the primary color ink An appropriate degree of curing cannot be obtained at any one of the surface positions P2 of the secondary color ink and the secondary color ink, and transfer failure may occur.

Next, a specific ultraviolet irradiation operation by the first ultraviolet irradiation unit 51 during temporary curing will be described.
FIG. 8A to FIG. 8C are diagrams explaining the irradiation operation of ultraviolet rays in the temporary curing. These figures show a portion of the intermediate transfer body 10 conveyed in the orbiting movement direction, which faces the first ultraviolet irradiation section 51, and the intermediate transfer body 10 from the outer peripheral surface 10a side. The 1st ultraviolet irradiation part 51 when seeing through 10 is also shown.

FIGS. 8A to 8C show an image forming region R in which one primary image is formed and distributions of the ink non-laminating region R1 and the ink laminating region R2 in the image forming region R. There is. Here, in the image forming area R, the front end portion (about 1/3 from the end portion on the downstream side in the orbiting movement direction) is the ink non-laminated region R1, and the rear end portion (from the end portion on the upstream side in the orbiting movement direction). About 1/3) is the ink laminating area R2, and the remaining 1/3 in the middle is an example in which the ink non-laminating area R1 and the ink laminating area R2 are mixed.
Which part of the image forming area R becomes the ink stacking area R2 can be specified based on, for example, the image data of the image to be recorded. Specifically, in the image to be printed, a region within a predetermined distance range from a portion of the YMCK in which a color represented by a mixture of a plurality of different colors is arranged can be specified as the ink stacking region R2. ..

  FIG. 8A is a diagram showing a state in which the front end of the image forming area R is approaching the ultraviolet irradiation area of the first ultraviolet irradiation section 51. In this state, all the ultraviolet light sources 511 of the first ultraviolet irradiation unit 51 face the ink non-laminated region R1, and therefore, all the ultraviolet light sources 511 emit the ultraviolet light having the intensity I1.

  FIG. 8B is a diagram showing a state in which the central portion of the image forming area R approaches the ultraviolet irradiation area of the first ultraviolet irradiation section 51. In this state, some of the ultraviolet light sources 511 of the first ultraviolet irradiation unit 51 face the ink non-laminated region R1 and the remaining ultraviolet light sources 511b face the ink laminated region R2. Therefore, the ultraviolet light source 511a emits the ultraviolet light of the intensity I1 and the ultraviolet light source 511b emits the ultraviolet light of the intensity I2.

  FIG. 8C is a diagram showing a state in which the vicinity of the rear end of the image forming area R is approaching the ultraviolet irradiation area by the first ultraviolet irradiation unit 51. In this state, since each of the ultraviolet light sources 511 of the first ultraviolet irradiation unit 51 faces the ink stacking region R2, all the ultraviolet light sources 511 emit the ultraviolet light of the intensity I2.

  As a result of such an ultraviolet irradiation operation, the ink non-laminated region R1 of the image forming region R is irradiated with ultraviolet light of intensity I1 and the ink laminated region R2 is irradiated with ultraviolet light of intensity I2. As described above, the temporary curing is performed in a state where the degree of curing of the ink surface of the ink laminated region R2 is relatively suppressed.

  Next, a control procedure by the control unit 4 of the image recording process executed by the inkjet recording apparatus 1 will be described.

FIG. 9 is a flowchart showing the control procedure of the image recording process.
When the image recording process is started, the control unit 4 identifies the image data of the image to be recorded (step S101).

  The control unit 4 supplies the image data and the control signal specified in step S101 to the head driving unit 214, and outputs the driving signal from the head driving unit 214 to the recording head 211 at an appropriate timing according to the circular movement of the intermediate transfer member 10. Output to the outer peripheral surface 10a of the intermediate transfer body 10 from the nozzles 213 of the head unit 21 (recording head 211) to land and form a primary image on the outer peripheral surface 10a (step S102: primary image formation). Process).

  The control unit 4 identifies the ink stacking region R2 in the image forming region R based on the image data identified in step S101 (step S103). As a result, the ink non-lamination region R1 which is a region of the image forming region R excluding the ink lamination region R2 is also specified.

  The control unit 4 irradiates ultraviolet rays from each ultraviolet light source 511 of the first ultraviolet irradiation unit 51 at an appropriate timing in the circular movement of the intermediate transfer member 10 to temporarily cure the ink on the intermediate transfer member 10 (step S104). : Energy application step). That is, the control unit 4 irradiates the ink non-stacking region R1 with the ultraviolet light having the intensity I1 and the ink stacking region R2 with the intensity I2 based on the identification result of the ink non-stacking region R1 and the ink stacking region R2 in step S103. The drive timing of each ultraviolet light source 511 of the first ultraviolet irradiation unit 51 and the ultraviolet irradiation intensity are controlled so that the ultraviolet rays are irradiated, and the ink on the intermediate transfer member 10 is temporarily cured.

  The controller 4 supplies the recording medium M onto the transport roller 34 so that the image forming area R of the intermediate transfer body 10 and the recording medium M on the transport roller 34 simultaneously enter the nip portion N, and the intermediate transfer body By driving 10 and the conveyance roller 34, the primary image on the intermediate transfer member 10 is transferred to the recording medium M at the nip portion N (step S105: transfer step).

The control unit 4 controls the second ultraviolet irradiation unit 52 so that the recording medium M on the transport roller 34 passes through a region facing the second ultraviolet irradiation unit 52 while the second ultraviolet irradiation unit 52 is emitting the ultraviolet light. The ink on the recording medium M is fully cured by driving the ultraviolet irradiation unit 52 and the transport roller 34 (step S106).
When the process of step S106 ends, the control unit 4 ends the image recording process.

As described above, the inkjet recording apparatus 1 according to the present embodiment ejects from the ink ejection unit 2 that ejects ink whose viscosity increases by being irradiated with ultraviolet rays as a predetermined energy, and the ink ejection unit 2. The ink has an intermediate transfer member 10 on which the primary image is formed by landing the ink on the outer peripheral surface 10a (predetermined landing surface). The ink on the outer peripheral surface 10a is transferred to the recording medium M to form an image on the recording medium M. The transfer section 3 for recording, the first ultraviolet ray irradiation section 51 as an energy generating section for generating ultraviolet rays which are radiated to the ink before landing on the outer peripheral surface 10a and transferred to the recording medium M, and the control section 4. And the amount of ultraviolet rays irradiated per unit area on the outer peripheral surface 10a with respect to the ink in the ink lamination region R2 including the portion of the outer peripheral surface 10a on which the ink is laminated. The first ultraviolet irradiation unit 51 irradiates the outer peripheral surface 10a with ultraviolet rays so that the amount of ultraviolet rays applied per unit area on the outer peripheral surface 10a is smaller than that of the ink in the area excluding the ink stacking area R2. Let
According to such a configuration, before the transfer of the ink to the recording medium M, the viscosity (curing degree) of the surface of the ink laminated on the recording medium M side in the ink laminating region R2 of the outer peripheral surface 10a is set to the non-ink level. It can be made sufficiently smaller than the viscosity of the surface of the single layer ink on the recording medium M side in the laminated region R1. In the ink stacking region R2, since the contact area between the ink and the recording medium M becomes small due to the stacking of the ink, the transferability tends to be low. However, as described above, the viscosity of the ink on the recording medium M side surface is small. By setting the (soft) state, the adhesive force of the ink to the recording medium M is increased, and a sufficient force for the recording medium M to separate the ink from the intermediate transfer body 10 is obtained, so that desired transferability is secured. be able to. As a result, the ink can be more reliably transferred to the recording medium M in the entire ink non-laminating area R1 and the ink laminating area R2, so that the ink transfer rate is partially reduced in the ink laminating area R2 and the image quality is improved. It is possible to effectively suppress the occurrence of defects.

  Further, by using ultraviolet rays as the predetermined energy, the viscosity of the ink can be adjusted to a desired state by a simple method of irradiating the ultraviolet rays.

  Further, the control unit 4 irradiates the ink in the ink non-laminated region R1 of the outer peripheral surface 10a except for the ink laminated region R2 with the intensity of the ultraviolet rays with which the ink in the ink laminated region R2 of the outer peripheral surface 10a is irradiated. Ultraviolet rays are emitted from the first ultraviolet ray irradiation section 51 so as to be smaller than the intensity of ultraviolet rays. According to this, the viscosity of the ink can be adjusted to a desired state by a simple method of changing the intensity of the ultraviolet rays to be irradiated.

  The intermediate transfer body 10 is a ring-shaped member made of a material that allows ultraviolet rays to pass therethrough. The first ultraviolet irradiation section 51 includes an outer peripheral surface 10a that forms an ink landing surface from the inner peripheral surface 10b side of the intermediate transfer body 10. Ultraviolet rays are incident on the ink above. As a result, the surface of the ink on the outer peripheral surface 10a side undergoes a curing reaction to increase the viscosity, so that the ink can be easily separated from the outer peripheral surface 10a, and the ink is crushed during transfer. Image quality deterioration can be suppressed. On the other hand, the ultraviolet rays that have entered from the outer peripheral surface 10a side of the ink are partially absorbed by the time they reach the side (recording medium M side) opposite to the outer peripheral surface 10a side of the ink. The surface is hardened and the viscosity is kept low. By keeping the viscosity of the ink on the recording medium M side low as described above, the adhesive force of the ink to the recording medium M is easily maintained, and thus the ink can be easily transferred to the recording medium M. Become.

  The ink ejecting unit 2 has a plurality of recording heads 211 that eject inks of different colors, and ejects the inks from the plurality of recording heads 211 in a manner that inks of different colors can be stacked on the outer peripheral surface 10a. .. According to such a configuration, various colors can be expressed by the color mixing effect when the portion where the inks of different colors are stacked is macroscopically viewed.

  In the inkjet recording method of the present embodiment, the ink is ejected by the ink ejecting unit 2 to land on the outer peripheral surface 10a of the intermediate transfer member 10, and a primary image is formed on the outer peripheral surface 10a. An energy applying step of irradiating the ink landed on 10a with ultraviolet rays to increase the viscosity of the ink, and the ink on the outer peripheral surface 10a irradiated with ultraviolet rays in the energy applying step is transferred to the recording medium M and then the recording medium. And a step of recording an image on M. In the energy applying step, the ink in the ink stacking region R2 including the part of the outer peripheral surface 10a where the ink is stacked is irradiated per unit area on the outer peripheral surface 10a. The amount of the generated ultraviolet rays per unit area on the outer peripheral surface 10a with respect to the ink in the ink non-laminated region R1 of the outer peripheral surface 10a. Isa is irradiated with ultraviolet light so as to be smaller than the amount of ultraviolet radiation. According to such a method, the ink can be more reliably transferred to the recording medium M even when the ink is laminated on the intermediate transfer body 10.

(Modification 1)
Next, a modified example 1 of the first embodiment will be described.
In this modification, the viscosity of the ink is adjusted to a desired state by changing the irradiation time of the ultraviolet rays from the first ultraviolet irradiation section 51 between the ink non-laminated region R1 and the ink laminated region R2.
Specifically, the ultraviolet irradiation intensity of all the ultraviolet light sources 511 is made constant, and the moving speed of the intermediate transfer member 10 is made sufficiently slow. Then, the ratio of the irradiation time of the ultraviolet light to the length of the period during which the ink at each position on the intermediate transfer member 10 moves within the ultraviolet irradiation range of the first ultraviolet irradiation unit 51 is the ink non-lamination. The emission period of each ultraviolet light source 511 is adjusted under the control of the control unit 4 so that the ink stacking region R2 is smaller than the region R1. Also by such a method, the amount of ultraviolet rays irradiated to the ink in the ink laminated region R2 per unit area is smaller than the amount of ultraviolet rays irradiated to the ink in the ink non-laminated region R1 per unit area. can do.

  As described above, in the control unit 4 of the present modification, the irradiation time of the ultraviolet rays to the ink in the ink stacking region R2 of the outer peripheral surface 10a is shorter than the irradiation time of the ultraviolet light to the ink in the ink non-stacking region R1 of the outer peripheral surface 10a. The first ultraviolet irradiation section 51 irradiates ultraviolet rays so that According to this, the viscosity of the ink can be adjusted to a desired state by a simple method of changing the irradiation time of ultraviolet rays.

(Modification 2)
Next, a modified example 2 of the first embodiment will be described.
In this modified example, the viscosity of the ink is adjusted to a desired state by changing the wavelength band of the ultraviolet rays irradiated from the first ultraviolet ray irradiation unit 51 between the ink non-laminated area R1 and the ink laminated area R2.

FIG. 10 is a diagram showing the configuration of the first ultraviolet irradiation unit 51 according to the second modification.
As shown in FIG. 10A, the first ultraviolet light irradiation unit 51 of the present modified example includes a first light source group G1 including a plurality of first ultraviolet light sources 5111 arranged one-dimensionally in the width direction, A second light source group G2 including a plurality of second ultraviolet light sources 5112 arranged one-dimensionally in the width direction. Each of the plurality of first ultraviolet light sources 5111 is arranged at the same position in the width direction as one of the plurality of second ultraviolet light sources 5112.

  The first ultraviolet light source 5111 and the second ultraviolet light source 5112 are different from each other in the wavelength range of ultraviolet rays to be applied. That is, the first ultraviolet light source 5111 emits light with the emission spectrum S1 shown in FIG. 10B, and the second ultraviolet light source 5112 emits light with the emission spectrum S2 shown in FIG. 10B. Here, the emission spectrum S1 corresponds to a wavelength band shifted to the short wavelength side with respect to the emission spectrum S2, and the peak wavelength λ1 of the emission spectrum S1 is shorter than the peak wavelength λ2 of the emission spectrum S2. .. That is, the peak wavelength λ1 of the intensity of the ultraviolet light emitted from the first ultraviolet light source 5111 is shorter than the peak wavelength λ2 of the intensity of the ultraviolet light emitted from the second ultraviolet light source 5112. Therefore, when light is emitted with the same power, the energy applied to the ink from the first ultraviolet light source 5111 is larger than the energy applied to the ink from the second ultraviolet light source 5112.

  In this modification, in the temporary curing, the ink in the ink non-laminated region R1 is irradiated with ultraviolet rays from the first ultraviolet light source 5111, and the ink in the ink laminated region R2 is irradiated with ultraviolet light from the second ultraviolet light source 5112. Is irradiated. Also by such a method, the amount (energy amount) of ultraviolet rays irradiated per unit area to the ink in the ink laminated area R2 is equal to the ultraviolet ray irradiated per unit area to the ink in the ink non-laminated area R1. Can be smaller than the amount.

  As described above, the control unit 4 of the present modified example irradiates the ink in the ink non-laminated region R1 of the outer peripheral surface 10a with the peak wavelength of the intensity of the ultraviolet rays with which the ink in the ink laminated region R2 of the outer peripheral surface 10a is irradiated. The first ultraviolet irradiator 51 irradiates the ultraviolet light so that it becomes longer than the peak wavelength of the intensity of the ultraviolet light. According to this, the viscosity of the ink can be adjusted to a desired state by a simple method of changing the wavelength band of the ultraviolet rays to be irradiated.

(Second embodiment)
Next, a second embodiment will be described.
The second embodiment is different from the first embodiment in that a transparent ink that serves as an overcoat for covering the color inks on the recording medium M is further used. Below, it demonstrates centering around difference with 1st Embodiment.

FIG. 11 is a diagram showing a schematic configuration of the inkjet recording apparatus 1 according to the second embodiment.
The ink ejection unit 2 of the present embodiment includes four head units 21 that eject YMCK color ink and a head unit 21OC that ejects the transparent ink InOC serving as an overcoat. The components of the transparent ink InOC are the same as the components of the color ink except that they do not contain a coloring agent such as a pigment or a dye.
The head unit 21OC is arranged on the upstream side of the other four head units 21 in the revolving direction of the intermediate transfer member 10. The recording heads 211 provided on the four head units 21 for ejecting YMCK color ink constitute a “first recording head”, and the recording heads 211 provided on the head unit 21OC constitute a “second recording head”. Constitute.

FIG. 12 is a diagram illustrating an ink stacking mode and a temporary curing operation in the second embodiment.
When an image is recorded by the inkjet recording apparatus 1 of the present embodiment, as shown in FIG. 12, first, the transparent ink InOC is formed on the entire surface of the image forming area R of the outer peripheral surface 10a by the most upstream head unit 21OC. When ejected, a layer of transparent ink InOC having a uniform thickness is formed. Subsequently, the color ink is ejected from the other head unit 21 at a timing after the gelling agent which is a wax component is deposited on the surface of the transparent ink InOC, so that a single layer or two layers are formed on the transparent ink InOC. The layers of the above color inks are laminated. Therefore, in the present embodiment, the portion of the outer peripheral surface 10a where only the single layer of transparent ink InOC is provided constitutes the ink non-lamination region R1, and at least one layer of color ink is superposed on the transparent ink InOC. The area including the part that forms the ink stack area R2.
Then, the color ink and the transparent ink InOC are transferred to the recording medium M after the ink is provisionally cured by the ultraviolet irradiation from the first ultraviolet irradiation unit 51. As a result, on the recording medium M, the surface of the color ink is covered with the overcoat made of the transparent ink InOC.

  In the temporary curing of the present embodiment, as shown in FIG. 12, the ink non-laminated region R1 in which only the single layer transparent ink InOC is provided is irradiated with the ultraviolet light having the intensity I0, and the transparent ink InOC and one color The ink layered region R2a in which two layers of ink including color inks are provided is irradiated with ultraviolet light of intensity I1 (<I0), and three layers of ink including transparent ink InOC and two color inks are provided. Ultraviolet rays having an intensity I2 (<I1) are applied to the formed ink laminated region R2b. As a result, the smaller the contact area of the ink with the recording medium M, the lower the degree of curing (viscosity) of the surface of the ink on the recording medium M is suppressed, and the higher the adhesive force of the ink with respect to the recording medium M. As a result, the decrease in transferability is covered, and uniform and desired transferability is secured in the entire image forming region R.

  As described above, the ink ejection unit 2 of the present embodiment has the recording head 211 that ejects the ink of the predetermined color and the recording head 211 that ejects the transparent ink InOC, and the transparent ink InOC is formed on the outer peripheral surface 10a. After the ejection, the ink of the predetermined color is ejected to stack the transparent ink InOC and the ink of the predetermined color. With such a configuration, the transparent ink InOC is transferred onto the recording medium M together with the color inks, so that the overcoat made of the transparent ink InOC can be formed on the recording medium M. Further, the laminated ink containing the transparent ink InOC can be more reliably transferred to the recording medium M.

(Third Embodiment)
Next, a third embodiment will be described.
The third embodiment is different from the first embodiment in that an aqueous ink in which a coloring material such as pigment particles is dispersed in water as a dispersion medium is used. Below, it demonstrates centering around difference with 1st Embodiment.

The water-based ink used in this embodiment is obtained by dispersing particles of a predetermined color such as pigment particles in water as a dispersion medium. A water-soluble organic solvent may be further added to the water-based ink for the purpose of improving ejection properties and adjusting physical properties of the ink.
After landing on the outer peripheral surface 10a, the solvent of the water-based ink evaporates and dries, or the pigment agglomerates on the surface of the ink to increase the viscosity and become highly liquid repellent to other inks. Therefore, similar to the ultraviolet curable ink of the above-described embodiment, when ink is ejected from different head units 21 to the same position, an interface is formed between the inks and the inks are stacked. Also in the water-based ink, the thickened primary color ink has higher liquid repellency with respect to the secondary color ink, so that the area of the secondary color ink on the primary color ink becomes smaller as with the ultraviolet curable ink. Cheap.

The water-based ink increases the viscosity by removing the water in the dispersion medium by applying heat energy. Therefore, in the present embodiment, provisional curing is performed by applying thermal energy to the ink on the intermediate transfer body 10 (that is, by heating the ink). In addition, a heater is provided inside the pressure roller 33, and the ink is heated when the ink is transferred to the recording medium M at the nip portion N between the pressure roller 33 and the transport roller 34. Fixing (main curing) is performed.
In the temporary curing, the intermediate transfer member 10 is heated to selectively heat the outer peripheral surface 10a side surface of the ink to increase the viscosity, so that the outer peripheral surface 10a side of the ink becomes hard as in the first embodiment. The ease of transfer of ink can be improved by making the recording medium M side relatively soft.

FIG. 13 is a diagram showing a schematic configuration of the inkjet recording device 1 according to the third embodiment.
In the inkjet recording apparatus 1 of the present embodiment, the first ultraviolet irradiation unit 51 and the second ultraviolet irradiation unit 52 are not provided, and instead of these, an intermediate portion between the driven roller 32 and the pressure roller 33 is provided. A heater 61 (energy generating portion) is provided at a position facing the inner peripheral surface 10b of the transfer body 10. That is, the heater 61 is arranged so as to face the portion of the intermediate transfer member 10 immediately before entering the nip portion N. The heater 61 generates heat energy as a predetermined energy to heat the intermediate transfer body 10, thereby applying heat energy to the ink on the outer peripheral surface 10 a via the intermediate transfer body 10. Although the specific configuration of the heater 61 is not particularly limited, for example, a halogen heater, a carbon heater, a silicon rubber heater or the like can be used.

FIG. 14 is a diagram showing the configuration of the heater 61, and is a plan view of the heater 61 as seen through the intermediate transfer body 10 from the outer peripheral surface side of the intermediate transfer body 10.
The heater 61 includes a plurality of sub-heaters 611 that are one-dimensionally arranged in the width direction of the intermediate transfer body 10. The plurality of sub-heaters 611 are arranged at positions and intervals that can heat the entire intermediate transfer member 10 in the width direction. The sub-heaters 611 generate heat independently of each other under the control of the controller 4 and apply thermal energy to the intermediate transfer body 10. In addition, each sub-heater 611 can heat the intermediate transfer member 10 at a plurality of different temperatures. The heating temperature of each sub-heater 611 is controlled by the controller 4.

  Further, the controller 4 causes the heater 61 to heat the intermediate transfer member 10 so that the temperature of the ink laminating area R2 of the outer peripheral surface 10a becomes lower than the temperature of the ink non-laminating area R1 of the outer peripheral surface 10a. That is, the control unit 4 controls the heating timing and the heating temperature of each sub-heater 611 so that the temperature T2 of the ink laminating area R2 on the outer peripheral surface of the intermediate transfer body 10 becomes lower than the temperature T1 of the ink non-laminating area R1. To control. As a result, the degree of curing (viscosity) of the surface of the secondary color ink in the ink layered region R2 can be made sufficiently smaller than the degree of curing of the surface of the primary color ink in the ink non-layered region R1. As described above, the degree of curing of the surface of the secondary color ink is suppressed and the surface of the secondary color ink is softer than the surface of the primary color ink. As a result, when the ink is transferred to the recording medium M, the recording medium of the secondary color ink in the ink stack region R2 is recorded. The adhesive force to M is easily obtained, and the occurrence of the above-described ink transfer failure can be suppressed.

Even when the water-based ink is used, the transparent ink for forming the overcoat may be further used as in the second embodiment.
Although the heater 61 has been described as an example of indirectly heating the ink via the intermediate transfer body 10, the heater 61 may directly heat the ink on the intermediate transfer body 10. In this case, in addition to the mode in which the ink is heated by the radiant heat from the heater, the drying of the ink may be promoted by applying hot air to the ink.

(Fourth Embodiment)
Next, a fourth embodiment will be described.
The fourth embodiment is different from the third embodiment in the method of increasing the viscosity of the water-based ink. Below, it demonstrates centering around difference with 3rd Embodiment.

FIG. 15 is a diagram showing a schematic configuration of the inkjet recording device 1 according to the fourth embodiment.
In addition to the four head units 21 that eject the YMCK color ink, the ink ejecting unit 2 of the present embodiment ejects (applies) a predetermined coagulant to the outer peripheral surface 10a of the intermediate transfer member 10F. (Aggregating agent application part). The aggregating agent ejected from the head unit 21F is a liquid that increases the viscosity of the ink by aggregating the dispersed material such as pigment particles in the ink by coming into contact with the ink. The head unit 21F is arranged on the upstream side of the other four head units 21 in the revolving direction of the intermediate transfer member 10.

As the aggregating agent, when the pigment dispersed in the ink is an anionic material, an acid or a cationic compound is used.
The acid causes the pH of the ink to fluctuate, thereby aggregating the anionic dispersion material in the ink and increasing the viscosity of the ink. As the acid-based coagulant, malonic acid, malic acid, citric acid, phosphoric acid, succinic acid or the like can be used.
The cationic compound causes the anionic dispersion material in the ink to aggregate by salting out to increase the viscosity of the ink. As the aggregating agent for the cationic compound, a polyvalent metal salt, calcium chloride, magnesium nitrate, aluminum chloride or the like can be used.

FIG. 16 is a diagram for explaining an ink stacking mode and a temporary curing operation in the fourth embodiment.
When an image is recorded by the inkjet recording apparatus 1 of the present embodiment, first, the coagulant is ejected and applied from the head unit 21F to the outer peripheral surface 10a of the intermediate transfer member 10, and then the YMCK color ink is ejected. It As a result, the ink thickens on the intermediate transfer member 10 due to the action of the aggregating agent, and the ink is temporarily cured.

Specifically, as shown in FIG. 16, the head unit 21F first ejects the coagulant F onto the entire outer peripheral surface 10a of the image forming region R to form a layer of the coagulant F (coagulant applying step). .. At this time, under the control of the control unit 4, the application amount of the aggregating agent F per unit area in the ink lamination region R2 is smaller than the application amount of the aggregating agent F per unit area in the ink non-laminating region R1. The discharge amount (applying amount) of the coagulant F from the nozzle is adjusted. Therefore, in FIG. 16, the thickness of the coagulant F in the ink laminated area R2 is drawn smaller than the thickness of the coagulant F in the ink non-laminated area R1.
After that, the color ink is ejected from the other head unit 21, whereby a single layer or two or more layers of color ink are laminated on the aggregating agent F to form a primary image (primary image forming step). .. When the ink lands on the aggregating agent F in this manner, the aggregating agent F and the color ink come into contact with each other, and the action of the aggregating agent F causes the disperse material such as the pigment in the ink to aggregate to increase the viscosity of the ink. ..

Here, the greater the amount of the aggregating agent applied per unit area on the outer peripheral surface 10a, the greater the effect of increasing the viscosity of the ink. Since the amount of the aggregating agent F in the ink stacking region R2 is smaller than that in the ink non-stacking region R1, the increase in viscosity of the ink is less likely to proceed than in the ink non-stacking region R1. As a result, the degree of curing (viscosity) of the surface of the secondary color ink in the ink layered region R2 can be made sufficiently smaller than the degree of curing of the surface of the primary color ink in the ink non-layered region R1. As a result, the smaller the contact area of the ink with the recording medium M, the lower the degree of curing (viscosity) of the surface of the ink on the recording medium M is suppressed, and the higher the adhesive force of the ink with respect to the recording medium M. Therefore, the contact area is smaller. As a result, the decrease in transferability is covered, and uniform and desired transferability is secured in the entire image forming region R.
Then, after thickening (temporary curing) is performed by the action of the aggregating agent F, the ink is transferred to the recording medium M (transfer step), and an image is recorded on the recording medium M.

The method of applying the coagulant F to the outer peripheral surface 10a is not limited to the method of discharging from the head unit 21F, and may be applied by, for example, a roll coating method or screen printing.
Further, also in the present embodiment, as in the third embodiment, a heater 61 for heating the ink on the intermediate transfer member 10 to increase the viscosity may be further provided.

As described above, in the inkjet recording apparatus 1 of the present embodiment, the ink in which the dispersion material is dispersed in the dispersion medium is landed on the outer peripheral surface 10a of the intermediate transfer body 10 to form a primary image, and the primary image is recorded on the recording medium. An inkjet recording apparatus 1 for transferring an image to a recording medium M to record an image on the recording medium M, wherein an aggregating agent F that agglomerates particles in the ink by contacting the ink to increase viscosity of the ink The head unit 21F applied to the outer peripheral surface 10a of the transfer body 10, the ink ejecting section 2 that ejects ink to the outer peripheral surface 10a provided with the aggregating agent F, and the intermediate transfer body 10 have the ink on the outer peripheral surface 10a. A transfer part 3 for transferring the image onto the recording medium M to record an image on the recording medium M, and a control part 4. The control part 4 is an aggregating agent applied per unit area in the ink laminating region R2. Amount, a flocculant F is applied by the head unit 21F so as to be smaller than the amount of flocculant F which is applied per unit area in the ink non-laminated region R1 of.
In the inkjet recording method of the present embodiment, the aggregating agent applying step of applying the aggregating agent F to the outer peripheral surface 10a of the intermediate transfer member 10 and the ink ejecting section 2 to apply the ink to the outer peripheral surface 10a to which the aggregating agent F is applied. A primary image forming step of discharging and landing to form a primary image on the outer peripheral surface 10a, a transfer step of transferring the ink on the outer peripheral surface 10a to the recording medium M and recording an image on the recording medium M, In the coagulant applying step, the amount of the coagulant F applied per unit area in the ink laminating region R2 of the outer peripheral surface 10a is smaller than the amount of the coagulant F applied per unit area in the ink non-laminating region R1. The coagulant F is added so that
With such a configuration and method as well, before the transfer of the ink to the recording medium M, the viscosity (curing degree) of the surface of the ink laminated on the recording medium M on the recording medium M side in the ink non-laminated area R1 is measured. It can be made sufficiently smaller than the viscosity of the surface of the recording medium M of the single-layer ink. As a result, it is possible to secure desired transferability with respect to the ink in the ink stack region R2. As a result, it is possible to effectively suppress the occurrence of defective image quality due to a partial decrease in the ink transfer rate in the ink laminated region R2.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.
For example, in the above-described embodiment, the example in which the color inks are stacked in two layers at the maximum is described, but the invention is not limited to this, and the inks may be ejected in a mode in which the color inks can be stacked in three layers or more. In this case, the transferability of the ink in each part of the image forming region R is improved by decreasing the amount of energy applied per unit area or decreasing the amount of the aggregating agent in a region having a larger number of layers. It can be approached uniformly.
Further, color inks of the same color may be laminated.

  Further, instead of the phase change ink, ink that maintains the liquid state after ejection may be used.

  The method of identifying the ink layer area R2 is not limited to the method based on the image data of the recorded image. For example, the height of ink at each position on the outer peripheral surface 10a may be detected, and the ink stacking region R2 may be specified based on the detection result.

  Further, the intermediate transfer body 10 is not limited to an endless belt, and various members having a landing surface on which ink lands can be used. For example, as the intermediate transfer member 10, a cylindrical member having a fixed shape may be used.

Further, in the case where the ultraviolet curable ink is used, the example in which the first ultraviolet irradiation unit 51 is provided at the position facing the inner peripheral surface 10b of the intermediate transfer body 10 has been described. The installation position is not limited to this. That is, the first ultraviolet irradiation unit 51 is provided at another arbitrary position (for example, outside the intermediate transfer body 10), and the ultraviolet light emitted from the first ultraviolet irradiation unit 51 is guided by a light guide or a mirror. Then, ultraviolet rays may be incident on the ink on the outer peripheral surface 10a from the inner peripheral surface 10b side of the intermediate transfer body 10 through the intermediate transfer body 10.
Further, the ink on the outer peripheral surface 10a may be directly irradiated with ultraviolet rays (that is, from the side in contact with the recording medium M).

  Further, even when the ultraviolet curable ink is used, a heating member such as a halogen heater may be provided inside at least part of the drive roller 31, the driven roller 32, the pressure roller 33 and the transport roller 34. As a result, the intermediate transfer body 10 that is moving in a circular manner can be heated, and the viscosity of the ink on the intermediate transfer body 10 can be adjusted more appropriately.

  Further, in each of the above-described embodiments, the single-pass type inkjet recording apparatus 1 has been described as an example, but the present invention may be applied to an inkjet recording apparatus that records an image while scanning the recording head 211.

  Although some embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and the equivalent scope thereof. ..

1 Inkjet recording device 2 Ink ejection unit 3 Transfer unit 4 Control unit 41 CPU
42 RAM
43 ROM
44 storage unit 10 intermediate transfer body 10a outer peripheral surface 10b inner peripheral surface 21 head unit 211 recording head 212 ink ejection surface 213 nozzle 214 head drive unit 31 drive roller 32 driven roller 33 pressure roller 34 transport roller 51 first ultraviolet irradiation unit 511 UV light source 52 Second UV irradiation unit 53 Roller drive unit 54 Operation display unit 55 Communication unit 56 Bus 61 Heater 611 Sub heater F Coagulant M Recording medium N Nip portion R Image forming area R1 Ink non-laminated area R2, R2a, R2b ink layer area

Claims (13)

An ink ejecting unit that ejects ink whose viscosity is increased by application of predetermined energy,
The ink ejected from the ink ejecting unit has an intermediate transfer body on which a primary image is formed by landing on a predetermined landing surface, and the ink on the landing surface is transferred to a recording medium to form an image on the recording medium. A transfer part to record,
An energy generating unit that generates the energy applied to the ink before landing on the landing surface and being transferred to the recording medium;
A control unit for controlling the operation of the energy generation unit,
Equipped with
The control unit is configured such that an amount of energy applied to a unit area on the landing surface with respect to ink in an ink stacking area including a portion where the ink is stacked on the landing surface is An ink jet recording apparatus, wherein the operation of the energy generation unit is controlled so that the amount of energy applied to a unit area on the landing surface is smaller than that of the ink in the area excluding the ink stacking area.   The inkjet recording apparatus according to claim 1, wherein the predetermined energy is ultraviolet light.   The control unit controls the intensity of the ultraviolet rays applied to the ink in the ink stacking area of the landing surface to be lower than the intensity of the ultraviolet rays applied to the ink in the area of the landing surface excluding the ink stacking area. The inkjet recording apparatus according to claim 2, wherein the energy generating unit irradiates ultraviolet rays.   The controller controls the energy so that the irradiation time of the ultraviolet rays to the ink in the ink stacking area of the landing surface is shorter than the irradiation time of the ultraviolet rays to the ink in the area of the landing surface excluding the ink stacking area. The inkjet recording apparatus according to claim 2, wherein the generation unit emits ultraviolet rays.   The control unit is configured such that the peak wavelength of the intensity of the ultraviolet rays with which the ink in the ink stacking area of the landing surface is irradiated is the intensity of the ultraviolet light with which the ink in the landing surface excluding the ink stacking area is irradiated. 3. The ink jet recording apparatus according to claim 2, wherein the energy generation unit irradiates the ultraviolet rays so that the wavelength becomes longer than the peak wavelength. The intermediate transfer member is an annular member made of a material that transmits ultraviolet rays,
6. The energy generating unit causes ultraviolet rays to be incident on the ink on the outer peripheral surface of the intermediate transfer body, which is the landing surface, from the inner peripheral surface side of the intermediate transfer body. The inkjet recording device according to any one of claims. The predetermined energy is thermal energy,
The ink jet recording apparatus according to claim 1, wherein the energy generating unit generates the thermal energy applied directly or indirectly to the ink on the landing surface. The energy generating unit heats the intermediate transfer member to apply thermal energy to the ink on the landing surface via the intermediate transfer member,
The control unit causes the energy generating unit to heat the intermediate transfer member so that the temperature of the ink stacking area of the landing surface becomes lower than the temperature of the area of the landing surface excluding the ink stacking area. The inkjet recording apparatus according to claim 7, wherein the inkjet recording apparatus is an inkjet recording apparatus.   The ink ejecting unit has a plurality of recording heads ejecting inks of different colors, and ejects the inks from the plurality of recording heads in a manner that inks of different colors can be stacked on the landing surface. The inkjet recording apparatus according to any one of claims 1 to 8.   The ink ejecting unit has a first recording head that ejects a predetermined color of ink and a second recording head that ejects transparent ink, and the transparent ink is ejected from the second recording head onto the landing surface. 10. The transparent ink and the ink of the predetermined color are laminated by ejecting the ink of the predetermined color from the first recording head after ejecting various inks. The inkjet recording apparatus according to any one of 1. An ink jet recording apparatus in which an ink in which a dispersion material is dispersed in a dispersion medium is landed on a predetermined landing surface of an intermediate transfer body to form a primary image, the primary image is transferred to a recording medium, and the image is recorded on the recording medium. And
An aggregating agent imparting an aggregating agent that agglomerates the dispersion material in the ink to increase the viscosity of the ink by contacting the ink, and an aggregating agent imparting portion that imparts to the landing surface of the intermediate transfer member.
An ink ejecting section for ejecting the ink onto the landing surface provided with the aggregating agent,
A transfer unit having the intermediate transfer member, for transferring the ink on the landing surface to a recording medium to record an image on the recording medium;
A control unit for controlling the operation of the aggregating agent application unit,
Equipped with
The control unit determines the amount of the aggregating agent applied per unit area in the ink stacking region including a portion of the landing surface where ink is to be stacked, excluding the ink stacking region of the landing surface. An ink jet recording apparatus, characterized in that the aggregating agent is applied by the aggregating agent applying part so that the amount of the aggregating agent applied per unit area in the region is smaller. An ink jet recording apparatus including an ink ejecting unit that ejects ink whose viscosity increases by applying a predetermined energy, and an intermediate transfer member on which the ink ejected from the ink ejecting unit lands on a predetermined landing surface. An inkjet recording method,
A primary image forming step of ejecting ink by the ink ejecting section to land on the landing surface of the intermediate transfer member and form a primary image on the landing surface;
An energy applying step of applying the energy to the ink that has landed on the landing surface to increase the viscosity of the ink,
A transfer step of transferring the ink on the landing surface to which energy is applied in the energy applying step onto a recording medium to record an image on the recording medium;
Including,
In the energy applying step, the amount of energy applied per unit area on the landing surface to the ink in the ink stacking region including a portion of the landing surface where the ink is stacked is An ink jet recording method, characterized in that energy is applied to ink in an area excluding the ink laminated area so as to be smaller than an amount of energy applied per unit area on the landing surface. An ink jet recording method using an ink jet recording apparatus, comprising: an ink ejecting unit that ejects an ink in which a dispersion material is dispersed in a dispersion medium; and an intermediate transfer member on which the ink ejected from the ink ejecting unit lands on a predetermined landing surface. There
An aggregating agent applying step of applying an aggregating agent that agglomerates the dispersion material in the ink to increase the viscosity of the ink by contacting the ink to the landing surface of the intermediate transfer member,
A primary image forming step of forming a primary image on the landing surface by ejecting the ink onto the landing surface to which the aggregating agent is applied to land the ink by the ink ejecting unit,
A transfer step of transferring the ink on the landing surface to a recording medium to record an image on the recording medium,
Including,
In the aggregating agent applying step, the amount of the aggregating agent applied per unit area in the ink stacking region including a portion of the landing surface where the ink is to be stacked in the primary image forming step is the landing surface. An ink jet recording method, wherein the aggregating agent is applied so that the amount of the aggregating agent is less than the amount of the aggregating agent applied per unit area in the area excluding the ink layered area.

Images