JP7176357B2 - Inkjet recording apparatus and inkjet recording method - Google Patents

Description

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

Conventionally, ink ejected from nozzles of a recording head lands on a predetermined landing surface of an intermediate transfer body to form a primary image, and the primary image is transferred to a recording medium to record an image on the recording medium. There is a recording device. In such an inkjet recording apparatus, by appropriately increasing the viscosity of the ink that has landed on the landing surface (for example, by irradiating UV light to the UV curable ink to temporarily cure it), transfer to the recording medium There is a technique for making it easy to separate the ink from the landing surface at the time of the ink landing (for example, Patent Document 1).

JP 2014-8656 A

However, there are cases where a plurality of inks ejected onto the intermediate transfer body at different timings are stacked without being combined on the landing surface. In the area where the inks are laminated in this way, the contact area between the ink and the recording medium during transfer tends to be smaller than in the area where the inks are united to form a single layer. If the contact area between the ink and the recording medium is small, it becomes difficult for the ink to adhere to the recording medium during transfer, and the recording medium does not have enough force to separate the ink from the intermediate transfer body, resulting in defective ink transfer. There is a problem of making it easier.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet recording apparatus and an inkjet recording method capable of more reliably transferring ink to a recording medium.

In order to achieve the above object, the invention of the ink jet recording apparatus according to claim 1,
an ink ejection unit that ejects ink whose viscosity increases when a predetermined amount of energy is applied;
An intermediate transfer member on which ink ejected from the ink ejection unit lands on a predetermined landing surface to form a primary image is provided, and the ink on the landing surface is transferred to a recording medium to form an image on the recording medium. a transfer unit for recording;
an energy generating unit that generates the energy that is applied to the ink before it lands on the landing surface and is transferred to the recording medium;
a control unit that controls the operation of the energy generation unit;
with
the intermediate transfer member is an annular member made of a material through which the energy is transmitted;
The energy generating section causes the energy to enter the ink on the outer peripheral surface of the intermediate transfer body forming the landing surface from the inner peripheral surface side of the intermediate transfer body,
The controller determines that the amount of energy applied per unit area on the impact surface to ink in an ink-stacked region including a portion of the impact surface where ink is stacked is the By controlling the operation of the energy generating section so that the amount of energy applied per unit area on the landing surface to the ink in the area excluding the ink stacking area is smaller than the amount of the ink in the ink stacking area, the ink in the ink stacking area is lower than the curing degree of the ink in the area excluding the ink lamination area
It is characterized by

The invention according to claim 2 is the inkjet recording apparatus according to claim 1,
The predetermined energy is ultraviolet rays.

The invention according to claim 3 is the inkjet recording apparatus according to claim 2,
The controller controls the intensity of the ultraviolet rays irradiated to the ink in the ink layered region on the impact surface to be smaller than the intensity of the ultraviolet rays irradiated to the ink in the region of the impact surface excluding the ink layered region. It is characterized in that the energy generating section irradiates ultraviolet rays as described above.

The invention according to claim 4 is the inkjet recording apparatus according to claim 2,
The control unit controls the energy so that the UV irradiation time for the ink in the ink lamination region of the impact surface is shorter than the UV irradiation time for the ink in the region of the impact surface excluding the ink lamination region. It is characterized by irradiating ultraviolet rays by the generating part.

The invention according to claim 5 is the inkjet recording apparatus according to claim 2,
The controller controls the peak wavelength of the intensity of the ultraviolet rays irradiated to the ink in the ink stacking region on the impact surface to be the intensity of the ultraviolet light irradiated to the ink in the region of the impact surface excluding the ink stacking region. It is characterized in that the energy generating section irradiates ultraviolet rays so that the wavelength becomes longer than the peak wavelength of .

The invention according to claim 6 is the inkjet recording apparatus according to claim 1,
the predetermined energy is thermal energy;
The energy generating section is characterized by generating the thermal energy that is directly or indirectly applied to the ink on the landing surface.

The invention according to claim 7 is the ink jet recording apparatus according to claim 6 ,
The energy generating unit heats the intermediate transfer body to apply thermal energy to the ink on the landing surface via the intermediate transfer body,
The control unit heats the intermediate transfer member by the energy generating unit so that the temperature of the ink-stacked area of the landing surface becomes lower than the temperature of the area of the landing surface excluding the ink-stacked area. It is characterized by

The invention according to claim 8 is the inkjet recording apparatus according to any one of claims 1 to 7 ,
The ink ejection unit has a plurality of recording heads that eject inks of different colors, and the inks are ejected from the plurality of recording heads in such a manner that inks of different colors can be stacked on the landing surface. and

The invention according to claim 9 is the inkjet recording apparatus according to any one of claims 1 to 8 ,
The ink ejection section has a first recording head that ejects ink of a predetermined color and a second recording head that ejects transparent ink. and then ejecting the ink of the predetermined color from the first recording head to laminate the transparent ink and the ink of the predetermined color.

In order to achieve the above object, the invention of the ink jet recording apparatus according to claim 10 ,
An inkjet recording apparatus that forms a primary image by causing ink, in which a dispersion material is dispersed in a dispersion medium, to land on a predetermined landing surface of an intermediate transfer member, transfers the primary image to a recording medium, and records the image on the recording medium. and
an aggregating agent imparting unit that imparts to the landing surface of the intermediate transfer body an aggregating agent that agglomerates the dispersed material in the ink and increases the viscosity of the ink by coming into contact with the ink;
an ink ejection unit that ejects the ink onto the landing surface to which the aggregating agent is applied;
a transfer unit having the intermediate transfer member and transferring the ink on the landing surface to a recording medium to record an image on the recording medium;
a control unit that controls the operation of the coagulant application unit;
with
The controller determines that the amount of the aggregating agent applied per unit area in an ink-stacked region including a portion of the landing surface where the ink is to be stacked is equal to or greater than the ink-stacked region of the landing surface. By applying the aggregating agent by the aggregating agent application unit so that the amount of the aggregating agent applied per unit area in the region is smaller than the amount of the aggregating agent applied per unit area , the degree of curing of the ink in the ink lamination region is determined by the ink lamination region. Lower than the ink cure in the excluded area
It is characterized by

Further, in order to achieve the above object, the invention of the ink jet recording method according to claim 11 comprises:
By an inkjet recording apparatus comprising an ink ejection section that ejects ink whose viscosity increases when a predetermined energy is applied, and an intermediate transfer member on which the ink ejected from the ink ejection section lands on a predetermined landing surface. An inkjet recording method,
a primary image forming step of ejecting ink from the ink ejecting unit to land on the landing surface of the intermediate transfer body to form a primary image on the landing surface;
an energy application 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 has been applied in the energy applying step to a recording medium to record an image on the recording medium;
including
the intermediate transfer member is an annular member made of a material through which the energy is transmitted;
In the energy applying step, the amount of energy applied per unit area on the landing surface to ink in an ink-stacked region including a portion of the landing surface where the ink is stacked is the The landing surface is formed from the inner peripheral surface side of the intermediate transfer body so that the amount of energy applied per unit area on the landing surface to the ink in the area excluding the ink stacking area is smaller than the amount. By applying energy to the ink on the outer peripheral surface of the intermediate transfer member, the curing degree of the ink in the ink-stacked region is made lower than the curing degree of the ink in the region other than the ink-stacked region.
It is characterized by

Further, in order to achieve the above object, the invention of the ink jet recording method according to claim 12 ,
An ink jet recording method using an ink jet recording apparatus comprising an ink ejection section for ejecting 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 ejection section lands on a predetermined landing surface. There is
an aggregating agent application step of applying an aggregating agent to the landing surface of the intermediate transfer body, which aggregates the dispersed material in the ink by contact with the ink to increase the viscosity of the ink;
a primary image forming step of ejecting the ink from the ink ejection unit onto the landing surface to which the aggregating agent has been applied to form a primary image on the landing surface;
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 an ink laminating region including a portion of the landing surface where the ink is to be laminated in the primary image forming step is equal to the landing surface. By applying the aggregating agent so that the amount of the aggregating agent applied per unit area is smaller than the amount of the aggregating agent applied per unit area in the region excluding the ink lamination region, the degree of curing of the ink in the ink lamination region is determined by the ink Make it lower than the curing degree of the ink in the area excluding the laminated area
It is characterized by

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. 3 is a schematic diagram showing the configuration of a head unit; FIG. It is a figure which shows the structure of a 1st ultraviolet irradiation part. 1 is a block diagram showing the functional configuration of an inkjet recording apparatus; FIG. It is a figure explaining temporary hardening operation|movement of an inkjet recording device. FIG. 4 is a diagram showing the degree of curing of ink with respect to the amount of UV irradiation; FIG. 5 is a diagram for explaining the necessity of differentiating the irradiation intensity of ultraviolet rays between a single-layer ink formation region and an ink lamination region. It is a figure explaining irradiation operation|movement of the ultraviolet-ray in temporary hardening. 4 is a flowchart showing a control procedure of image recording processing; FIG. 10 is a diagram showing a configuration of a first ultraviolet irradiation unit according to modification 2; It is a figure which shows schematic structure of the inkjet recording device which concerns on 2nd Embodiment. FIG. 11 is a diagram for explaining the ink layering mode and temporary curing operation in the second embodiment. FIG. 11 is a diagram showing a schematic configuration of an inkjet recording apparatus according to a third 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|stacking aspect and temporary hardening operation|movement of the ink in 4th Embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an inkjet recording apparatus and an inkjet recording method according to the present invention will be described below with reference to the drawings.

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

The ink ejection unit 2 ejects ink from 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 ejection unit 2 includes four head units 21Y, 21M, 21C, 21Y, 21M, 21C, 21C, 21C, 21Y, 21C, 21C, 21Y, 21C, 21C, 21Y, 21M, 21C, 21C, 21Y, 21M, 21C, 21Y, 21C, 21C, 21Y, 21C, and 21C, respectively. 21K (any one of these will also be referred to as head unit 21 hereinafter). The plurality of head units 21 are arranged so that their ink ejection surfaces face the outer peripheral surface of the intermediate transfer member 10 at appropriate intervals. Note that 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 viewed from the side facing the outer peripheral surface of the intermediate transfer member 10. FIG. The head unit 21 has 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 in which the ink ejection surface 212 provided with the openings of the nozzles 213 is exposed from the through holes of the support portion 21a toward the outer peripheral surface side.

In the recording head 211, a plurality of nozzles 213 are equally spaced in a direction (in this embodiment, a width direction perpendicular to the direction of circular movement) intersecting the direction of circular movement of the intermediate transfer member 10 (hereinafter also referred to as the direction of circular movement). are arranged in each. In this embodiment, each print head 211 has four rows (nozzle rows) of nozzles 213 that are one-dimensionally arranged at equal intervals in the width direction. These four nozzle rows are arranged such that the widthwise positions of the nozzles 213 do not overlap with each other. Note that the number of nozzle rows that the print head 211 has is not limited to four, and may be three or less or five or more.

The eight print heads 211 in the head unit 21 are arranged in a houndstooth pattern so that the arrangement range of the nozzles 213 in the width direction is continuous. The arrangement range in the width direction of the nozzles 213 included in the head unit 21 covers the width in the width direction of the area on the outer peripheral surface of the intermediate transfer member 10 where the primary image can be formed. The head unit 21 is used at a fixed position during the formation of the primary image, and ejects ink from the nozzles 213 to each position at predetermined intervals in the direction of rotation in accordance with the rotation of the intermediate transfer member 10 . , to form the primary image in a single pass manner. The ink ejection mechanism for ejecting ink from each nozzle 213 may be of a piezo type using a piezoelectric element or of a thermal type that heats and ejects ink.

As the ink ejected from the nozzles of the head unit 21, one whose viscosity increases when energy is applied by a predetermined method is used. In this embodiment, an ultraviolet curable ink is used as such an ink, in which a curing reaction progresses when irradiated with ultraviolet rays and the viscosity increases. When UV curable ink is used, the ink that has landed on the outer peripheral surface of the intermediate transfer body 10 is appropriately irradiated with UV rays to increase the viscosity of the ink to some extent in a predetermined manner, thereby increasing the ease of transfer of the ink. . A method of irradiating ultraviolet rays for this purpose will be described in detail later.

In addition, the ink used in the present embodiment is a phase change ink that changes phase between a gel state and a sol state depending on the temperature. Heated sol-like ink is ejected from the nozzles 213 of the head unit 21 , and the ink that lands on the outer peripheral surface of the intermediate transfer body 10 is quickly cooled and gel-like. Viscosity adjustment is performed on the gelled ink by irradiating ultraviolet rays.
The ink used in this embodiment contains a photopolymerizable compound (monomer), a photopolymerization initiator, a gelling agent and a colorant. Among these, the photopolymerizable compound is a compound that undergoes a polymerization reaction and polymerizes when irradiated with ultraviolet rays. This polymerization causes the ink to thicken and harden. A photopolymerization initiator is a compound for initiating the polymerization reaction. The gelling agent dissolves in the ink to form a sol when the ink is heated to a temperature higher than the sol-forming temperature, and forms a cross-linked structure or a fibrous aggregate when the ink is cooled to a temperature lower than the gelling temperature. It is a compound that has the property of gelling the ink by forming it. Also, the colorant includes a pigment or dye of the color associated with the ink.

The transfer unit 3 shown in FIG. 1 moves and contacts an intermediate transfer member 10 and a recording medium M supplied from a paper feeding unit (not shown) to transfer the primary image formed on the intermediate transfer member 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 member 10 is an endless belt member (annular member) having an outer peripheral surface (landing surface) on which 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 ink that has landed, and the primary image is transferred to the recording medium M. As shown in FIG. The intermediate transfer member 10 is wound around a drive roller 31, a driven roller 32, and a pressure roller 33, and the outer peripheral surface of the intermediate transfer member 10 circulates along a predetermined circulating path as the drive roller 31 rotates. At least a portion of the intermediate transfer member 10 facing the ink ejection section 2 is supported by a support member (not shown) having a flat surface to form a horizontal surface.

Further, the intermediate transfer member 10 is made of a material that transmits ultraviolet rays. Therefore, as will be described later, ultraviolet rays are emitted from the first ultraviolet irradiation unit 51 to the inner peripheral surface of the intermediate transfer body 10, so that the ink on the outer peripheral surface is irradiated with the ultraviolet rays through the intermediate transfer body 10. (Injection) is possible. As a constituent member of the intermediate transfer member 10, a material that transmits ultraviolet rays and has durability against ultraviolet rays, such as PET (polyethylene terephthalate), polyimide, polyolefin, ETFE (ethylene-tetrafluoroethylene copolymer), etc., is used. can be done.

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

The drive roller 31 rotates about its rotation axis by being driven by a motor (not shown). The driven roller 32 is spaced apart from the drive roller 31 by a predetermined distance, and rotates about a rotation axis parallel to the rotation axis of the drive roller 31 as the intermediate transfer body 10 is rotated.

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

The transport roller 34 rotates while holding the recording medium M supplied from a paper feeding unit (not shown) on its outer peripheral surface, thereby transporting the recording medium M in the roller rotation direction. The transport roller 34 is arranged to form a nip portion N with the pressure roller 33 . The intermediate transfer member 10 and the recording medium M are nipped in the nip portion N and pressed. As a result, the ink (primary image) on the outer peripheral surface of the intermediate transfer member 10 is transferred to the recording medium M, and an image is recorded on the recording medium M. FIG.
Note that instead of the mode in which the recording medium M is held and transported by the outer peripheral surface of the transport roller 34, the recording medium M is placed in the nip portion N between the pressure roller 33 and the transport roller 34 (horizontally from the right direction in FIG. 1). 2) may be directly inserted.

Further, a cleaning portion for cleaning the outer peripheral surface 10a of the intermediate transfer body 10 may be provided between the nip portion N and the drive roller 31 in the circular movement direction of the intermediate transfer body 10 . A cloth, a nonwoven fabric, a blade member, or the like can be used as a cleaning member used in the cleaning section. Further, a configuration may be employed in which a cleaning liquid for removing ink, dirt, etc. is applied to the outer peripheral surface 10a or a member for cleaning.

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

FIG. 3 is a diagram showing the configuration of the first ultraviolet irradiation section 51, and is a plan view of the first ultraviolet irradiation section 51 seen through the intermediate transfer body 10 from the outer peripheral surface side of the intermediate transfer body 10. FIG. .
The first ultraviolet irradiation section 51 includes a plurality of ultraviolet light sources 511 arranged one-dimensionally in the width direction of the intermediate transfer member 10 . The plurality of ultraviolet light sources 511 are arranged at positions and intervals so as to irradiate the entire intermediate transfer member 10 with ultraviolet light in the width direction. Each ultraviolet light source 511 irradiates ultraviolet rays independently of each other under the control of the control unit 4 . Moreover, each ultraviolet light source 511 can irradiate ultraviolet rays with a plurality of different intensities. The intensity of the ultraviolet rays emitted from each ultraviolet light source 511 is controlled by the controller 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 rays of a predetermined intensity over the entire width of the recording medium M. The ink transferred to the recording medium M is completely cured by the ultraviolet irradiation from the second ultraviolet irradiation section 52, and fixed to 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 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. As shown in FIG.
The inkjet recording apparatus 1 includes a control section 4, a head driving section 214 and a head unit 21 having a recording head 211, a first ultraviolet irradiation section 51, a second ultraviolet irradiation section 52, a roller driving section 53, It includes an operation display unit 54, a communication unit 55, a bus 56, and the like.

The control unit 4 performs overall control of the overall operation of the inkjet recording apparatus 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 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 processing. Further, the CPU 41 centrally controls the overall operation of the inkjet recording apparatus 1 .

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

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

The storage unit 44 stores job data including image data to be recorded and 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 timing according to the circular movement of the intermediate transfer member 10 based on the control signal supplied from the control unit 4. Ink is ejected from nozzles 213 of 211 .

Based on a control signal supplied from the control unit 4 , the roller drive unit 53 outputs a drive signal to the motor that rotates the drive roller 31 to perform a rotation operation at a set speed. is rotated at a predetermined speed.

The operation display unit 54 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as operation keys and a touch panel that is superimposed on the screen of the display device. The operation display unit 54 displays various types of information on the display device, converts the user's input operation to 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 transmit and receive 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 and the like regarding the progress of the image recording operation according to the job data.

A 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 apparatus 1 for temporarily curing the ink described above will be described.

5A and 5B are diagrams for explaining the temporary curing operation of the inkjet recording apparatus 1. FIG.
FIG. 5 is a schematic cross-sectional view of the intermediate transfer body 10 after ink has landed and the first ultraviolet irradiation section 51 facing the intermediate transfer body 10 . As shown in FIG. 5, the ink ejected by the ink ejection unit 2 lands on the outer peripheral surface 10a of the intermediate transfer member 10 and spreads wet. The ink on the outer peripheral surface 10a is irradiated with ultraviolet rays from the ultraviolet light source 511 of the first ultraviolet irradiation section 51 through the intermediate transfer member 10, and the ink is temporarily cured.

In this way, 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 surface of the ink on the outer peripheral surface 10a side undergoes a curing reaction. progresses and the viscosity increases. As a result, the ink can be easily peeled off from the outer peripheral surface 10a, and deterioration in image quality due to crushing of the ink during transfer can be suppressed.
In addition, since the ultraviolet rays incident from the outer peripheral surface 10a side of the ink are partially absorbed before reaching the side opposite to the outer peripheral surface 10a side of the ink (the recording medium M side), the surface of the ink on the recording medium M side is relatively difficult to cure and remains low in viscosity. By keeping the viscosity of the ink on the side of the recording medium M low in this way, the ink is maintained in a state in which it is easy to obtain adhesive strength (adherence) to the recording medium M (a state in which it is easy to adhere), so that the ink can be easily applied to the recording medium. Ink can be transferred to M.
In this way, the temporary curing makes the ink hard on the outer peripheral surface 10a side and relatively soft on the recording medium M side. Therefore, the recording medium M can easily obtain a sufficient force to separate the ink from the intermediate transfer body 10, and the transferability of the ink can be improved.

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

In the inkjet recording apparatus 1, by causing a plurality of different colors of ink among YMCK to land within a predetermined vicinity range on the outer peripheral surface 10a, various colors are produced by a color mixing effect when the plurality of colors are macroscopically viewed. color is represented. Here, the timings at which the plurality of head units 21 with different ink colors face specific positions on the outer peripheral surface 10a differ from each other. different. For this reason, among the inks of a plurality of colors that land in the vicinity range, after the ink of the color that landed first coalesces and spreads, the ink of the second color lands at the timing when a predetermined time has passed, and the ink of the first color lands. Wet and spread in a range that partially overlaps with the landed ink.
At this time, as shown on the right side of FIG. 5, the first ink (here, yellow ink InY) and the ink (here, magenta ink InM) that landed at a position overlapping the ink are They are laminated with an interface between the inks without coalescing (without mixing with each other).

In the following description, the lowermost layer of ink in the area where the inks are stacked 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, of the outer peripheral surface 10a, a region where ink of the same color is combined to form a single layer is referred to as an ink non-laminated region R1, and a region including a portion where ink is laminated is referred to as an ink laminated region R2. That is, the ink non-laminated area R1 corresponds to the area of the outer peripheral surface 10a excluding the ink laminated area R2. The left side in FIG. 5 indicates the non-laminated ink region R1, and the right side indicates the laminated ink region R2.
In the ink lamination region R2 of FIG. 5, an example is shown in which the ink InM, which is the secondary color ink, is laminated within the formation range of the ink InY, which is the primary color ink. Not limited to this, the secondary color ink may wet and spread from within the formation range of the primary color ink to outside the formation range.

In the ink stacking region R2, the plurality of inks of different colors are stacked without coalescing because after the primary color ink lands, the primary color ink gels and thickens. This is because the secondary color ink, which has a lower viscosity than the viscous primary color ink, lands. More specifically, when the primary color ink increases in viscosity, a gelling agent, which is a wax component contained in the ink, precipitates on the surface of the primary color ink, making the surface of the primary color ink repellent to the secondary color ink. sexuality increases. As a result, coalescence of the primary color ink and the secondary color ink is prevented, an interface is generated between the inks, and the inks are laminated.
In this embodiment, since the primary color ink gels and thickens in a time period shorter than the time difference between inks ejected from the adjacent head units 21 to the same position on the outer peripheral surface 10a, different color inks are ejected to the same position. In this case, regardless of the color combination, an interface occurs between the inks and the inks are layered.

Since the wax component is deposited on the surface of the primary color ink to increase the liquid repellency to the secondary color ink, the liquid repellency of the outer peripheral surface 10a of the intermediate transfer member 10 to the primary color ink is lower than that of the primary color ink. The liquid repellency of the ink surface to the secondary color ink is increased (the contact angle is increased). As a result, even if the same amount of primary color ink and secondary color ink land on the same position, the primary color ink is wetted on the outer peripheral surface 10a as shown on the right side of FIG. The area over which the secondary color ink spreads on the surface of the primary color ink is smaller than the spreading area.

Therefore, the area of the secondary color ink in the laminated ink tends to be small. Therefore, the area where the ink (secondary color ink) contacts the recording medium M in the ink laminated region R2 is larger than the area where the ink (primary color ink) contacts the recording medium M in the ink non-laminated region R1. also tend to be smaller. In addition, the transferability of the ink to the recording medium M tends to decrease as the contact area of the ink decreases. This is because if the contact area between the ink and the recording medium M is small, it becomes difficult for the ink to adhere to the recording medium M during transfer, and the recording medium M does not have enough force to separate the ink from the intermediate transfer body 10 . because it is easy. Therefore, the smaller the contact area with the recording medium M, the more likely the transfer rate to the recording medium M is reduced. Therefore, even if the ink is uniformly pre-cured and thickened in the non-laminated ink region R1 and the laminated ink region R2, the contact area between the ink and the recording medium M is relatively small in the laminated ink region R2. It becomes difficult to transfer ink, and ink transfer failure tends to occur.

Therefore, in the inkjet recording apparatus 1 of the present embodiment, the amount of ultraviolet rays irradiated per unit area on the outer peripheral surface 10a to the ink in the ink lamination region R2 is greater than that of the ink in the ink non-lamination region R1. Ultraviolet rays are irradiated from the first ultraviolet irradiation section 51 so that the amount of ultraviolet rays irradiated per unit area on 10a is smaller than that.
That is, as shown in FIG. 5, the ink in the non-laminated ink region R1 is irradiated with ultraviolet light having an intensity I1 from the first ultraviolet irradiation unit 51, while the ink in the laminated ink region R2 is irradiated with ultraviolet light having an intensity of I1. , the first ultraviolet irradiation unit 51 emits ultraviolet rays having an intensity of I2 (<I1).
This makes it possible to make the degree of cure (viscosity) of the surface of the secondary color ink in the ink lamination region R2 sufficiently smaller than the degree of cure of the surface of the primary color ink in the ink non-lamination region R1. In the example of FIG. 5, the hardening degree of the surface on the outer peripheral surface 10a side of the primary color ink in the ink non-laminating region R1 is 60, whereas the hardening degree of the surface on the outer peripheral surface 10a side of the secondary color ink in the ink laminating region R2 is 60. Reduced to 30 degrees. As a result of suppressing the hardening degree of the surface of the secondary color ink and making it softer than the surface of the primary color ink, when the ink is transferred to the recording medium M, the recording medium of the secondary color ink in the ink stacking region R2. The adhesive force to M increases (that is, adhesion becomes easier), and the occurrence of the ink transfer failure described above can be suppressed.

It should be noted that even if the irradiation intensity of the ultraviolet rays in the ink lamination region R2 is relatively weak in this way, the hardening degree of the surface of the ink on the outer peripheral surface 10a side is almost the same between the ink non-lamination region R1 and the ink lamination region R2. can do. In the example of FIG. 5, the degree of cure of the ink on the surface on the side of the outer peripheral surface 10a is 100 in both the non-laminated ink region R1 and the laminated ink region R2. This is because, as shown in FIG. 6, the rate of increase in the degree of curing of the ink saturates as the cumulative amount of UV irradiation to the ink increases.
Therefore, even if the irradiation intensity of the ultraviolet rays is reduced in the ink laminated region R2, it is possible to ensure the ease of removing the ink from the intermediate transfer body 10 in both the ink non-laminated region R1 and the ink laminated region R2.

FIG. 7 is a diagram for explaining the necessity of differentiating the irradiation intensity of ultraviolet rays between the non-laminated ink region R1 and the laminated ink region R2.
FIG. 7 shows 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 light having an intensity of I0 to I3 (I0>I1>I2>I3) for a predetermined time. It is represented. The origin P0 of the horizontal axis corresponds to the position of the outer peripheral surface 10a of the intermediate transfer body 10, P1 corresponds to the surface position of the primary color ink in the ink non-laminated region R1, and P2 corresponds to the second color ink in the ink laminated region R2. It corresponds to the surface position of the next color ink.
Also, the vertical arrows at the respective positions P0 to P2 represent the range of appropriate ink curing degree at the position. That is, by keeping the degree of curing of the ink surface within the range of the arrows at the surface position P1 of the primary color ink and the surface position P2 of the secondary color ink, the outer peripheral surface 10a including the single layer ink and the laminated ink Adhesion of the ink to the recording medium M is obtained such that the entire primary image can be properly 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 an appropriate ink curing degree can be obtained at the surface position P1 of the primary color ink by irradiating the ultraviolet rays of the intensity I1.
Focusing on the straight line corresponding to the intensity of the ultraviolet rays I2, it can be seen that an appropriate curing degree of the ink can be obtained at the surface position P2 of the secondary color ink by irradiating the ultraviolet rays of the intensity I2.
For this reason, in order to properly transfer the inks in both the non-ink-laminated region R1 and the ink-laminated region R2, it is necessary to make the UV irradiation intensity different between the ink-non-laminated region R1 and the ink-laminated region R2. I know it will be. In other words, when the non-laminated ink region R1 and the laminated ink region R2 are irradiated with ultraviolet light at a uniform intensity I1 or at a uniform intensity I2, the surface position P1 of the primary color ink is changed. and the surface position P2 of the secondary color ink, an appropriate degree of curing cannot be obtained, and transfer failure may occur.

Next, a specific ultraviolet irradiation operation by the first ultraviolet irradiation unit 51 in temporary curing will be described.
FIGS. 8(a) to 8(c) are diagrams for explaining the operation of irradiating ultraviolet rays in temporary curing. These figures show a portion of the intermediate transfer body 10 being conveyed in the direction of rotation, which faces the first ultraviolet irradiation section 51. Also shown is the first ultraviolet irradiation section 51 when viewed through the lens 10 .

8(a) to 8(c) show an image forming area R in which one primary image is formed, and the distribution of the non-laminated ink area R1 and the laminated ink area R2 in the image forming area R. there is Here, the leading end portion (approximately 1/3 from the end portion on the downstream side in the rotational movement direction) of the image forming region R is the ink non-laminating region R1, and the rear end portion (from the end portion on the upstream side in the rotational movement direction). Approximately 1/3) is the ink-stacked region R2, and the remaining 1/3 in the middle is used as an example in which the ink non-stacked region R1 and the ink-stacked region R2 are mixed.
Which part of the image forming area R is to be the ink lamination area R2 can be specified based on image data relating to the image to be recorded, for example. Specifically, in the image to be recorded, an area within a predetermined distance range from a portion where a color represented by a mixture of a plurality of different colors of YMCK is arranged can be specified as the ink layered area R2. .

FIG. 8A is a diagram showing a state in which the leading edge of the image forming area R reaches the area irradiated with ultraviolet rays by the first ultraviolet irradiation section 51. FIG. In this state, since all the ultraviolet light sources 511 of the first ultraviolet irradiation section 51 face the non-ink layer region R1, all the ultraviolet light sources 511 irradiate the ultraviolet rays with the intensity I1.

FIG. 8(b) is a diagram showing a state in which the central portion of the image forming area R is approaching the ultraviolet irradiation area by the first ultraviolet irradiation section 51. As shown in FIG. In this state, some of the ultraviolet light sources 511a of the plurality of 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 ultraviolet light with an intensity of I1, and the ultraviolet light source 511b emits ultraviolet light with an intensity of 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 area irradiated with ultraviolet rays by the first ultraviolet irradiation section 51 . In this state, since all the ultraviolet light sources 511 of the first ultraviolet irradiation section 51 face the ink layered region R2, ultraviolet light having an intensity of I2 is emitted from all the ultraviolet light sources 511. FIG.

By such an ultraviolet irradiation operation, the non-laminated ink region R1 of the image forming region R is irradiated with ultraviolet rays of intensity I1, and the laminated ink region R2 is irradiated with ultraviolet rays of intensity I2. Temporary curing is performed in a state in which the degree of curing of the ink surface of the ink lamination region R2 is relatively suppressed so that the ink is cured.

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

FIG. 9 is a flowchart showing a control procedure for image recording processing.
When the image recording process is started, the control unit 4 identifies image data related to an 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 a 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. , ink is ejected from the nozzles 213 of the head unit 21 (recording head 211) onto the outer peripheral surface 10a of the intermediate transfer member 10, and the primary image is formed on the outer peripheral surface 10a (step S102: primary image formation process).

Based on the image data specified in step S101, the control unit 4 specifies the ink stacking area R2 in the image forming area R (step S103). As a result, the non-laminated ink area R1, which is the area of the image forming area R excluding the laminated ink area R2, is also specified.

The control unit 4 irradiates ultraviolet light from each ultraviolet light source 511 of the first ultraviolet irradiation unit 51 at an appropriate timing during 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, based on the results of identifying the non-laminated ink region R1 and the laminated ink region R2 in step S103, the control unit 4 irradiates the non-laminated ink region R1 with ultraviolet light having an intensity of I1, and irradiates the non-laminated ink region R2 with ultraviolet light having an intensity of I2. The ink on the intermediate transfer member 10 is preliminarily cured by controlling the driving timing and the intensity of the ultraviolet irradiation of each ultraviolet light source 511 of the first ultraviolet irradiation unit 51 so that ultraviolet rays are irradiated.

The control unit 4 supplies the recording medium M onto the transport roller 34 so that the image forming area R of the intermediate transfer member 10 and the recording medium M on the transport roller 34 enter the nip portion N at the same time. 10 and the transport 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 the area facing the second ultraviolet irradiation unit 52 while the second ultraviolet irradiation unit 52 is irradiating ultraviolet rays. By driving the ultraviolet irradiation unit 52 and the transport roller 34, the ink on the recording medium M is fully cured (step S106).
When the process of step S106 ends, the control section 4 ends the image recording process.

As described above, the ink jet recording apparatus 1 according to the present embodiment includes the ink ejection section 2 that ejects ink whose viscosity increases when irradiated with ultraviolet light as a predetermined energy, and the ink that is ejected from the ink ejection section 2. It has an intermediate transfer member 10 on which ink lands on an outer peripheral surface 10a (predetermined landing surface) to form a primary image. A transfer unit 3 for recording, a first ultraviolet irradiation unit 51 as an energy generation unit for generating ultraviolet rays that irradiate ink that has landed on the outer peripheral surface 10a and is applied to the ink before being transferred to the recording medium M, and a control unit 4. The control unit 4 determines that the amount of ultraviolet rays irradiated per unit area on the outer peripheral surface 10a to the ink in the ink stacking region R2 including the portion where the ink is stacked on the outer peripheral surface 10a is The first ultraviolet irradiation unit 51 irradiates the ink in the area of the outer peripheral surface 10a excluding the ink stacking area R2 with ultraviolet rays so that the amount of ultraviolet rays applied per unit area on the outer peripheral surface 10a becomes smaller than the amount of ultraviolet rays. .
According to such a configuration, before the ink is transferred to the recording medium M, the viscosity (curing degree) of the ink laminated in the ink lamination region R2 of the outer peripheral surface 10a on the side of the recording medium M is adjusted to the non-ink level. The viscosity of the single-layer ink in the lamination region R1 can be made sufficiently lower than that of the recording medium M side surface. In the ink lamination region R2, the contact area between the ink and the recording medium M is reduced by laminating the ink, so that the ease of transfer tends to be low. The (soft) state increases the adhesion of the ink to the recording medium M, and the recording medium M obtains sufficient force to separate the ink from the intermediate transfer body 10, thereby ensuring the desired ease of transfer. be able to. As a result, the ink can be more reliably transferred to the recording medium M in the entirety of the non-laminated ink region R1 and the laminated ink region R2, so that the transfer rate of the ink is partially reduced in the laminated ink region R2 and the image quality is improved. It is possible to effectively suppress the occurrence of defects.

Moreover, by using ultraviolet rays as the predetermined energy, it is possible to adjust the viscosity of the ink to a desired state by a simple method of irradiating ultraviolet rays.

In addition, the control unit 4 causes the intensity of the ultraviolet rays irradiated to the ink in the ink-stacked region R2 of the outer peripheral surface 10a to be applied to the ink in the ink-non-stacked region R1 of the outer peripheral surface 10a excluding the ink-stacked region R2. The first ultraviolet irradiation unit 51 irradiates ultraviolet rays so that the intensity of the ultraviolet rays becomes lower than that of the 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 irradiated ultraviolet rays.

The intermediate transfer body 10 is an annular member made of a material that transmits ultraviolet rays. Ultraviolet rays are made incident on the upper ink. As a result, the curing reaction of the surface of the ink on the side of the outer peripheral surface 10a proceeds and the viscosity increases, so that the ink can be easily peeled off from the outer peripheral surface 10a. It is possible to suppress deterioration of image quality. On the other hand, the ultraviolet rays incident from the outer peripheral surface 10a side of the ink are partially absorbed before reaching the side opposite to the outer peripheral surface 10a side of the ink (the recording medium M side). The surface is hard to harden and remains low viscosity. By keeping the viscosity of the ink on the side of the recording medium M low in this manner, the adhesive strength of the ink to the recording medium M is maintained in a state in which it is easy to obtain, so that the ink can be easily transferred to the recording medium M. Become.

The ink ejection section 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 such 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 represented by the color mixing effect when the portion where the inks of different colors are laminated is macroscopically viewed.

Further, the ink jet recording method of the present embodiment includes a primary image forming step of ejecting ink from the ink ejecting section 2 to land on the outer peripheral surface 10a of the intermediate transfer member 10 to form a primary image on the outer peripheral surface 10a. An energy application step of irradiating the ink that has 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 application step is transferred to the recording medium M and transferred to the recording medium. In the energy application step, the ink in the ink lamination region R2 including the portion of the outer peripheral surface 10a where the ink is laminated is irradiated per unit area on the outer peripheral surface 10a. The amount of ultraviolet rays applied to the ink in the non-laminated ink region R1 of the outer peripheral surface 10a is smaller than the amount of ultraviolet rays applied per unit area on the outer peripheral surface 10a. According to such a method, it is possible to more reliably transfer the ink to the recording medium M even when the ink is laminated on the intermediate transfer member 10 .

(Modification 1)
Next, Modification 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 unit 51 in the non-laminated ink region R1 and the laminated ink 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 body 10 is sufficiently slowed down. In addition, the ratio of the length of the ultraviolet irradiation time 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 by the first ultraviolet irradiation unit 51 is the ink non-stacking time. The light emission period of each ultraviolet light source 511 is adjusted under the control of the control unit 4 so that the light emission period of each of the ultraviolet light sources 511 is smaller in the ink lamination area R2 than in the area R1. Also by such a method, the amount of ultraviolet rays irradiated per unit area to the ink in the ink lamination region R2 is made smaller than the amount of ultraviolet rays irradiated per unit area to the ink in the ink non-lamination region R1. can do.

As described above, the control unit 4 of this modification makes the UV irradiation time for the ink in the ink laminated region R2 of the outer peripheral surface 10a shorter than the UV irradiation time for the ink in the ink non-laminated region R1 of the outer peripheral surface 10a. Ultraviolet rays are emitted from the first ultraviolet irradiation part 51 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 the ultraviolet rays.

(Modification 2)
Next, Modification 2 of the first embodiment will be described.
In this modification, the viscosity of the ink is adjusted to a desired state by changing the wavelength band of the ultraviolet rays emitted from the first ultraviolet irradiation section 51 in the non-laminated ink region R1 and the laminated ink region R2.

FIG. 10 is a diagram showing the configuration of the first ultraviolet irradiation section 51 according to Modification 2. As shown in FIG.
As shown in FIG. 10( a ), the first ultraviolet irradiation unit 51 of this modification includes a first light source group G1 composed of a plurality of first ultraviolet light sources 5111 arranged one-dimensionally in the width direction, and a second light source group G2 composed of a plurality of second ultraviolet light sources 5112 one-dimensionally arranged 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 the irradiated ultraviolet light. That is, the first ultraviolet light source 5111 emits light with the emission spectrum S1 shown in FIG. 10(b), and the second ultraviolet light source 5112 emits light with the emission spectrum S2 shown in FIG. 10(b). Here, the emission spectrum S1 corresponds to the 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 ultraviolet rays emitted from the first ultraviolet light source 5111 is shorter than the peak wavelength λ2 of the intensity of ultraviolet rays emitted from the second ultraviolet light source 5112 . Therefore, the energy imparted to the ink from the first ultraviolet light source 5111 is greater than the energy imparted to the ink from the second ultraviolet light source 5112 when light is emitted with the same power.

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

In this way, the control unit 4 of the present modification causes the peak wavelength of the intensity of the ultraviolet rays irradiated to the ink in the ink-stacked region R2 of the outer peripheral surface 10a to irradiate the ink in the ink-non-stacked region R1 of the outer peripheral surface 10a. The first ultraviolet irradiation unit 51 irradiates ultraviolet rays so that the wavelength is longer than the peak wavelength of the intensity of the ultraviolet rays emitted. 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 irradiated ultraviolet rays.

(Second embodiment)
Next, a second embodiment will be described.
The second embodiment differs from the first embodiment in that transparent ink, which serves as an overcoat that covers the color ink on the recording medium M, is further used. Differences from the first embodiment will be mainly described below.

FIG. 11 is a diagram showing a schematic configuration of an inkjet recording apparatus 1 according to the second embodiment.
The ink ejection section 2 of this embodiment includes four head units 21 that eject color inks of YMCK, and a head unit 21OC that ejects transparent ink InOC as an overcoat. The components of the clear ink InOC are the same as those of the color inks except that they do not contain colorants such as pigments or dyes.
The head unit 21OC is arranged upstream of the other four head units 21 with respect to the circular movement direction of the intermediate transfer member 10 . The recording heads 211 provided in the four head units 21 for ejecting YMCK color ink constitute a "first recording head", and the recording head 211 provided in the head unit 21OC constitutes a "second recording head". Configure.

12A and 12B are diagrams for explaining the ink layering mode and 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, the most upstream head unit 21OC first applies transparent ink InOC to the entire image forming region R of the outer peripheral surface 10a. It is ejected to form a layer of transparent ink InOC of uniform thickness. Subsequently, at the timing after the gelling agent, which is a wax component, is deposited on the surface of the transparent ink InOC, color ink is ejected from another head unit 21 to form a single layer or two layers on the transparent ink InOC. The above color ink layers are laminated. Therefore, in the present embodiment, the portion of the outer peripheral surface 10a where only the single layer of the transparent ink InOC is provided constitutes the ink non-lamination region R1, and at least one layer of color ink is superimposed on the transparent ink InOC. The area including the portion where the ink is stacked constitutes the ink layered area R2.
Then, the color ink and the transparent ink InOC are transferred to the recording medium M after the ink is temporarily cured by the ultraviolet irradiation from the first ultraviolet irradiation unit 51 . As a result, the surface of the color ink on the recording medium M is covered with an overcoat made of the transparent ink InOC.

In the temporary curing of the present embodiment, as shown in FIG. 12, the non-laminated ink region R1 in which only a single layer of the transparent ink InOC is provided is irradiated with ultraviolet light having an intensity of I0. In the ink lamination region R2a in which two layers of color ink are provided, ultraviolet light having an intensity of I1 (<I0) is irradiated, and three layers of ink including a transparent ink InOC and two color inks are provided. The ink layered region R2b is irradiated with ultraviolet light having an intensity of I2 (<I1). As a result, the degree of curing (viscosity) of the surface of the ink on the side of the recording medium M is suppressed in a region where the contact area of the ink with respect to the recording medium M is small, and the adhesion of the ink to the recording medium M is increased, so the contact area is small. The deterioration of the transfer easiness due to this is covered, and the uniform and desired transfer easiness is ensured in the entire image forming area R.

As described above, the ink ejection section 2 of the present embodiment has the recording head 211 that ejects the ink of a predetermined color and the recording head 211 that ejects the transparent ink InOC. After ejecting, the ink of a predetermined color is ejected to laminate the transparent ink InOC and the ink of the predetermined color. According to such a configuration, an overcoat made of the transparent ink InOC can be formed on the recording medium M by transferring the transparent ink InOC to the recording medium M together with the color ink. Moreover, the layered ink containing the transparent ink InOC can be transferred to the recording medium M more reliably.

(Third embodiment)
Next, a third embodiment will be described.
The third embodiment differs from the first embodiment in that a water-based ink in which a coloring material such as pigment particles is dispersed in water as a dispersion medium is used. Differences from the first embodiment will be mainly described below.

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 the water-based ink lands on the outer peripheral surface 10a, the solvent evaporates and dries, or the pigment agglomerates on the surface of the ink, thereby increasing its viscosity and making it highly repellent to other inks. Therefore, similarly to the ultraviolet curable ink of the above-described embodiment, when inks are ejected from different head units 21 to the same position, an interface is formed between the inks and the inks are laminated. In water-based inks as well, since the primary color ink with increased viscosity has higher liquid repellency against the secondary color ink, the area of the secondary color ink on the primary color ink becomes smaller as in the case of the ultraviolet curable ink. Cheap.

When thermal energy is applied to water-based ink, the water in the dispersion medium is removed and the viscosity increases. Therefore, in the present embodiment, provisional curing is performed by applying thermal energy to the ink on the intermediate transfer member 10 (that is, by heating the ink). Further, by providing a heater inside the pressure roller 33 and heating the ink when transferring the ink to the recording medium M at the nip portion N between the pressure roller 33 and the conveying roller 34, the ink is transferred to the recording medium M. Fixing (main curing) is performed.
In the temporary curing, the intermediate transfer member 10 is heated to selectively heat the surface of the ink on the side of the outer peripheral surface 10a to increase the viscosity of the ink. , the ease of ink transfer can be enhanced by making the recording medium M side relatively soft.

FIG. 13 is a diagram showing a schematic configuration of an inkjet recording apparatus 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 unit is provided between the driven roller 32 and the pressure roller 33 A heater 61 (energy generator) is provided at a position facing the inner peripheral surface 10b of the transfer member 10 . That is, the heater 61 is arranged so as to face a portion of the intermediate transfer member 10 immediately before entering the nip portion N. As shown in FIG. The heater 61 generates thermal energy as predetermined energy to heat the intermediate transfer body 10 , thereby imparting thermal energy to the ink on the outer peripheral surface 10 a via the intermediate transfer body 10 . A specific configuration of the heater 61 is not particularly limited, but 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 seen through the intermediate transfer body 10 from the outer peripheral surface side of the intermediate transfer body 10. FIG.
The heater 61 includes a plurality of sub-heaters 611 arranged one-dimensionally in the width direction of the intermediate transfer member 10 . A plurality of sub-heaters 611 are arranged at positions and intervals capable of heating the entire intermediate transfer member 10 in the width direction. Each sub-heater 611 generates heat independently of each other under the control of the control unit 4 to apply heat energy to the intermediate transfer member 10 . Also, 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 control unit 4 causes the heater 61 to heat the intermediate transfer member 10 so that the temperature of the ink laminated region R2 of the outer peripheral surface 10a becomes lower than the temperature of the ink non-laminated region R1 of the outer peripheral surface 10a. That is, the control unit 4 controls the heating timing and heating temperature of each sub-heater 611 so that the temperature T2 of the ink laminated region R2 is lower than the temperature T1 of the ink non-laminated region R1 on the outer peripheral surface of the intermediate transfer body . to control. This makes it possible to make the degree of cure (viscosity) of the surface of the secondary color ink in the ink lamination region R2 sufficiently smaller than the degree of cure of the surface of the primary color ink in the ink non-lamination region R1. As a result of suppressing the hardening degree of the surface of the secondary color ink and making it softer than the surface of the primary color ink, when the ink is transferred to the recording medium M, the recording medium of the secondary color ink in the ink stacking region R2. Adhesion to M can be easily obtained, and the occurrence of the ink transfer failure described above can be suppressed.

Note that, even when water-based ink is used, a transparent ink for forming an overcoat may be used as in the second embodiment.
Further, although the heater 61 indirectly heats the ink through the intermediate transfer body 10, the heater 61 may directly heat the ink on the intermediate transfer body 10. FIG. In this case, in addition to heating the ink with radiant heat from a heater, drying of the ink may be accelerated by applying hot air to the ink.

(Fourth embodiment)
Next, a fourth embodiment will be described.
The fourth embodiment differs from the third embodiment in the method of thickening water-based ink. Differences from the third embodiment will be mainly described below.

FIG. 15 is a diagram showing a schematic configuration of an inkjet recording apparatus 1 according to the fourth embodiment.
In addition to the four head units 21 that eject YMCK color inks, the ink ejection section 2 of this embodiment includes a head unit 21F that ejects (applies) a predetermined coagulant onto the outer peripheral surface 10a of the intermediate transfer member 10. (Aggregating agent application unit). The aggregating agent ejected from the head unit 21F is a liquid that increases the viscosity of the ink by aggregating dispersed materials such as pigment particles in the ink by coming into contact with the ink. The head unit 21</b>F is arranged upstream of the other four head units 21 with respect to the circular movement direction of the intermediate transfer member 10 .

As a flocculant, an acid or a cationic compound is used when the pigment dispersed in the ink is an anionic material.
The acid changes the pH of the ink, causing the anionic dispersed material in the ink to aggregate and thicken the ink. Malonic acid, malic acid, citric acid, phosphoric acid, succinic acid and the like can be used as acid-based flocculants.
The cationic compound aggregates the anionic dispersed material in the ink by salting out to thicken the ink. As cationic compound flocculants, polyvalent metal salts, calcium chloride, magnesium nitrate, aluminum chloride and the like can be used.

16A and 16B are diagrams for explaining the layering state of ink and the temporary curing operation in the fourth embodiment.
When an image is recorded by the inkjet recording apparatus 1 of the present embodiment, first, a flocculating agent is ejected from the head unit 21F onto the outer peripheral surface 10a of the intermediate transfer member 10, and then YMCK color inks are ejected. be. As a result, the viscosity of the ink is increased on the intermediate transfer member 10 by the action of the aggregating agent, and the ink is temporarily cured.

Specifically, as shown in FIG. 16, first, the head unit 21F discharges the coagulant F onto the entire image forming region R of the outer peripheral surface 10a to form a layer of the coagulant F (coagulant application step). . At this time, under the control of the control unit 4, the amount of the aggregating agent F applied per unit area in the ink lamination region R2 is less than the amount of the aggregating agent F applied per unit area in the ink non-lamination region R1. The discharge amount (application amount) of the coagulant F from the nozzle is adjusted. Therefore, in FIG. 16, the thickness of the coagulant F in the ink-laminated region R2 is depicted to be smaller than the thickness of the coagulant F in the ink-non-laminated region R1.
After that, by ejecting color ink from another head unit 21, a primary image is formed by laminating a single layer or two or more layers of color ink on the aggregating agent F (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 aggregates dispersed materials such as pigments in the ink, increasing 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. In the ink lamination region R2, since the amount of the aggregating agent F is smaller than that in the ink non-lamination region R1, it is more difficult for the ink to thicken than in the ink non-lamination region R1. This makes it possible to make the degree of cure (viscosity) of the surface of the secondary color ink in the ink lamination region R2 sufficiently smaller than the degree of cure of the surface of the primary color ink in the ink non-lamination region R1. As a result, the degree of curing (viscosity) of the surface of the ink on the side of the recording medium M is kept low in areas where the contact area of the ink with respect to the recording medium M is small, and the adhesion of the ink to the recording medium M is increased, so the contact area is small. The deterioration of the transfer easiness due to this is covered, and the uniform and desired transfer easiness is ensured in the entire image forming area R.
Then, after thickening (temporary curing) 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. FIG.

The method of applying the aggregating agent 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 a roll coating method, screen printing, or the like.
Also in this embodiment, as in the third embodiment, a heater 61 for heating and thickening the ink on the intermediate transfer member 10 may be further provided.

As described above, the inkjet recording apparatus 1 of the present embodiment forms a primary image by causing ink, in which a dispersion material is dispersed in a dispersion medium, to land on the outer peripheral surface 10a of the intermediate transfer member 10, and prints the primary image on the recording medium. An inkjet recording apparatus 1 for recording an image on a recording medium M by transferring an image onto a recording medium M. It has a head unit 21F that applies to the outer peripheral surface 10a of the transfer body 10, an ink ejection section 2 that ejects ink to the outer peripheral surface 10a to which the aggregating agent F is applied, and an intermediate transfer body 10, and ink on the outer peripheral surface 10a. onto the recording medium M to record an image on the recording medium M, and a control unit 4. The control unit 4 controls the coagulant F applied per unit area in the ink lamination region R2 is smaller than the amount of coagulant F applied per unit area in the ink non-laminated region R1.
Further, in the ink jet recording method of the present embodiment, the flocculant application step of applying the flocculant F to the outer peripheral surface 10a of the intermediate transfer body 10, the ink ejecting section 2 applies ink to the outer peripheral surface 10a to which the flocculant F has been applied. A primary image forming step of ejecting 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 application step, the amount of the coagulant F applied per unit area in the ink-laminated 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-laminated region R1. The flocculant F is applied so that the
Even with such a configuration and method, the viscosity (curing degree) of the ink layered in the ink layered region R2 on the surface of the recording medium M is measured in the ink non-layered region R1 before the ink is transferred to the recording medium M. The viscosity of the single-layer ink on the recording medium M side surface can be made sufficiently smaller. Thereby, the desired ease of transfer can be ensured for the ink in the ink lamination region R2. As a result, it is possible to effectively prevent the ink transfer rate from partially decreasing in the ink lamination region R2 and the occurrence of image quality defects.

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 are possible.
For example, in the above-described embodiment, an example in which two layers of color ink are laminated at maximum has been described. In this case, the transfer easiness 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 as the number of layers increases. can be approached evenly.
Also, color inks of the same color may be laminated.

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

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

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

Further, in the case of using the ultraviolet curable ink, the example in which the first ultraviolet irradiation section 51 is provided at a 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 section 51 is provided at another arbitrary position (for example, outside the intermediate transfer member 10), and the ultraviolet rays emitted from the first ultraviolet irradiation section 51 are guided by a light guide or a mirror. Alternatively, ultraviolet rays may be incident on the ink on the outer peripheral surface 10a through the intermediate transfer member 10 from the inner peripheral surface 10b side of the intermediate transfer member 10. FIG.
Alternatively, 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 . As a result, the intermediate transfer body 10 that is circulating 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 printing apparatus 1 has been described as an example, but the present invention may be applied to an inkjet printing apparatus that prints an image while scanning the print head 211 .

Although several 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 equivalent ranges thereof. .

1 inkjet recording device 2 ink discharge unit 3 transfer unit 4 control unit 41 CPU
42 RAMs
43 ROMs
44 Storage unit 10 Intermediate transfer member 10a Outer peripheral surface 10b Inner peripheral surface 21 Head unit 211 Recording head 212 Ink discharge 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 Flocculating agent M Recording medium N Nip portion R Image forming region R1 Ink non-laminated regions R2, R2a, R2b Ink lamination area

Claims (12)

an ink ejection unit that ejects ink whose viscosity increases when a predetermined amount of energy is applied;
An intermediate transfer member on which ink ejected from the ink ejection unit lands on a predetermined landing surface to form a primary image is provided, and the ink on the landing surface is transferred to a recording medium to form an image on the recording medium. a transfer unit for recording;
an energy generating unit that generates the energy that is applied to the ink before it lands on the landing surface and is transferred to the recording medium;
a control unit that controls the operation of the energy generation unit;
with
the intermediate transfer member is an annular member made of a material through which the energy is transmitted;
The energy generating section causes the energy to enter the ink on the outer peripheral surface of the intermediate transfer body forming the landing surface from the inner peripheral surface side of the intermediate transfer body,
The controller determines that the amount of energy applied per unit area on the impact surface to ink in an ink-stacked region including a portion of the impact surface where ink is stacked is the By controlling the operation of the energy generating section so that the amount of energy applied per unit area on the landing surface to the ink in the area excluding the ink stacking area is smaller than the amount of the ink in the ink stacking area, the ink in the ink stacking area is lower than the curing degree of the ink in the area excluding the ink lamination area
An inkjet recording apparatus characterized by: 2. An ink jet recording apparatus according to claim 1, wherein said predetermined energy is ultraviolet rays. The controller controls the intensity of the ultraviolet rays irradiated to the ink in the ink layered region on the impact surface to be smaller than the intensity of the ultraviolet rays irradiated to the ink in the region of the impact surface excluding the ink layered region. 3. An ink jet recording apparatus according to claim 2, wherein said energy generating section irradiates ultraviolet rays in such a manner. The control unit controls the energy so that the UV irradiation time for the ink in the ink lamination region of the impact surface is shorter than the UV irradiation time for the ink in the region of the impact surface excluding the ink lamination region. 3. An ink jet recording apparatus according to claim 2, wherein the ultraviolet rays are emitted from the generating portion. The controller controls the peak wavelength of the intensity of the ultraviolet rays irradiated to the ink in the ink stacking region on the impact surface to be the intensity of the ultraviolet light irradiated to the ink in the region of the impact surface excluding the ink stacking region. 3. An ink jet recording apparatus according to claim 2, wherein said energy generator irradiates ultraviolet rays so as to have a wavelength longer than the peak wavelength of . the predetermined energy is thermal energy;
The inkjet recording apparatus according to claim 1, wherein the energy generating section generates the thermal energy that is directly or indirectly applied to the ink on the landing surface. The energy generating section heats the intermediate transfer body to apply thermal energy to the ink on the landing surface via the intermediate transfer body,
The control unit heats the intermediate transfer member by the energy generating unit so that the temperature of the ink-stacked area of the landing surface becomes lower than the temperature of the area of the landing surface excluding the ink-stacked area. 7. The inkjet recording apparatus according to claim 6 , characterized in that: The ink ejection unit has a plurality of recording heads that eject inks of different colors, and the inks are ejected from the plurality of recording heads in such 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 7 . The ink ejection section has a first recording head that ejects ink of a predetermined color and a second recording head that ejects transparent ink. 8 , wherein the ink of the predetermined color is ejected from the first recording head after the ink of the predetermined color is ejected, and the transparent ink and the ink of the predetermined color are laminated. The inkjet recording apparatus according to any one of . An inkjet recording apparatus that forms a primary image by causing ink, in which a dispersion material is dispersed in a dispersion medium, to land on a predetermined landing surface of an intermediate transfer member, transfers the primary image to a recording medium, and records the image on the recording medium. and
an aggregating agent imparting unit that imparts to the landing surface of the intermediate transfer body an aggregating agent that agglomerates the dispersed material in the ink and increases the viscosity of the ink by coming into contact with the ink;
an ink ejection unit that ejects the ink onto the landing surface to which the aggregating agent is applied;
a transfer unit having the intermediate transfer member and transferring the ink on the landing surface to a recording medium to record an image on the recording medium;
a control unit that controls the operation of the coagulant application unit;
with
The controller determines that the amount of the aggregating agent applied per unit area in an ink-stacked region including a portion of the landing surface where the ink is to be stacked is equal to or greater than the ink-stacked region of the landing surface. By applying the aggregating agent by the aggregating agent application unit so that the amount of the aggregating agent applied per unit area in the region is smaller than the amount of the aggregating agent applied per unit area , the degree of curing of the ink in the ink lamination region is determined by the ink lamination region. Lower than the ink cure in the excluded area
An inkjet recording apparatus characterized by: By an inkjet recording apparatus comprising an ink ejection section that ejects ink whose viscosity increases when a predetermined energy is applied, and an intermediate transfer member on which the ink ejected from the ink ejection section lands on a predetermined landing surface. An inkjet recording method,
a primary image forming step of ejecting ink from the ink ejecting unit to land on the landing surface of the intermediate transfer body to form a primary image on the landing surface;
an energy application 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 has been applied in the energy applying step to a recording medium to record an image on the recording medium;
including
the intermediate transfer member is an annular member made of a material through which the energy is transmitted;
In the energy applying step, the amount of energy applied per unit area on the landing surface to ink in an ink-stacked region including a portion of the landing surface where the ink is stacked is the The landing surface is formed from the inner peripheral surface side of the intermediate transfer body so that the amount of energy applied per unit area on the landing surface to the ink in the area excluding the ink stacking area is smaller than the amount. By applying energy to the ink on the outer peripheral surface of the intermediate transfer member, the curing degree of the ink in the ink-stacked region is made lower than the curing degree of the ink in the region other than the ink-stacked region.
An inkjet recording method characterized by: An ink jet recording method using an ink jet recording apparatus comprising an ink ejection section for ejecting 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 ejection section lands on a predetermined landing surface. There is
an aggregating agent application step of applying an aggregating agent to the landing surface of the intermediate transfer body, which aggregates the dispersed material in the ink by contact with the ink to increase the viscosity of the ink;
a primary image forming step of ejecting the ink from the ink ejection unit onto the landing surface to which the aggregating agent has been applied to form a primary image on the landing surface;
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 an ink laminating region including a portion of the landing surface where the ink is to be laminated in the primary image forming step is equal to the landing surface. By applying the aggregating agent so that the amount of the aggregating agent applied per unit area is smaller than the amount of the aggregating agent applied per unit area in the region excluding the ink lamination region, the degree of curing of the ink in the ink lamination region is determined by the ink Make it lower than the curing degree of the ink in the area excluding the laminated area
An inkjet recording method characterized by:

Images