JP2007230232A - Image forming apparatus and method for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for forming a preferred image in which irregularity in density unevenness is not visually recognized by inhibiting interference between impacts when liquid reaches a target on a medium, and a method for forming an image. <P>SOLUTION: In an inkjet recording device 10 which transfers an image on this intermediate transcript 16 to a recording medium 20, processing liquid 30 having a viscosity of 5 to 300 mPa s at 25°C to adhere to the intermediate transcript 16, ink 32 containing a color material is dropped to a domain to which the processing liquid 30 of the intermediate transcript 16 adhered, after the viscosity of the ink on the intermediate transcript 16 is increased, the image containing dot by the ink 32 formed on the intermediate transcript 16 is transferred to the recording medium 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming technique for forming an image on a recording medium using a liquid such as ink.

  In an ink jet recording apparatus that forms a desired image by ejecting ink onto a medium, high quality of the image is required, and on the other hand, high speed image recording is required. These are in a mutually contradictory relationship, and various ideas have been made to solve both of these conflicting problems. For example, when a recording medium having permeability such as paper is used, ink droplets permeate into the recording medium, resulting in image deterioration such as bleeding and spreading of dots (shape abnormality). A technique is used in which, after an image is once formed on an impermeable intermediate transfer member, this image is transferred to a recording medium, thereby suppressing ink permeation into the recording medium.

  In the invention described in Patent Document 1, UV ink that forms a primary image is thickened by irradiating UV light to the primary image recorded on the intermediate transfer medium using UV ink that is cured when irradiated with UV light. Thus, the primary image can be transferred to a recording medium, and the secondary image can be recorded on the recording medium in a short time.

  In the invention described in Patent Document 2, in an ink jet recording method in which a radiation curable ink is cured on an intermediate transfer medium with radiation, and then the cured ink is transferred by heating, Tg (glass transition temperature) of the cured ink is used. It is configured to transfer at a higher heating temperature.

  In the invention described in Patent Document 3, the intermediate transfer body that temporarily holds the ink ejected from the recording head is provided with light irradiation means for irradiating light that causes the ink to cure, and the amount of light irradiation is reduced. The ink discharge unit discharges ink from the head, the transfer unit transfers the ink to a recording medium, and the cleaning unit removes residual ink from the intermediate transfer member.

In the invention described in Patent Document 4, a high-viscosity ink of 10,000 mPa · s or more coated on a transfer roll with a roll coater or blade is applied, and an image is drawn with a low-viscosity UV-curable color ink for inkjet. It is configured to transfer to a printing roll, and realizes transfer of a curved print medium without impairing image quality.
Japanese Patent Laid-Open No. 10-250052 JP 2005-161603 A JP 2001-179960 A JP 2005-153368 A

  However, if the inks come into contact with each other before fixing on the medium on which the image is formed by the ink ejected from the head, landing interference such as coalescence occurs, and the positional deviation or shape abnormality of the dots formed by the ink Occurs, and the image quality is significantly reduced. In particular, this phenomenon appears remarkably when using a non-penetrable medium in which ink does not penetrate (penetration speed is very slow).

FIG. 16 shows the state of the landing interference described above. As shown in the figure, the heads 12C and 12M
, 12K, and 12Y, the ink 32 ejected onto the intermediate transfer body 16 comes into contact with the ink 32 that has landed first on the intermediate transfer body 16 and is attracted to the previously landed ink 32 to bead (unify). ) Occurs. When such beading occurs, a shift occurs in the dot formation position.

  In the inventions described in Patent Document 1 and Patent Document 2, landing interference occurs when the inks come into contact with each other before UV light irradiation. Also, in the invention described in Patent Document 3, when high-speed printing is performed, If the inks come into contact with each other before the light is emitted to the ink discharge unit by the light irradiation means, landing interference occurs.

  The invention described in Patent Document 4 does not disclose a method for avoiding landing interference of color ink ejected by an inkjet head. If the viscosity of the high-viscosity ink applied first is too high, the low-viscosity color ink cannot enter the film of the high-viscosity ink, and landing interference may occur when the color ink lands. Also, in order to attach a high viscosity ink of 10,000 mPa · s or more to the transfer roller, the only way to apply the ink to the entire surface of the transfer roll using a roll coater or blade is to increase the consumption of the high viscosity ink. End up.

  The present invention has been made in view of such circumstances, and provides an image forming apparatus and an image forming method for preventing a landing interference when a liquid lands on a medium and forming a preferable image in which density unevenness is not visually recognized. For the purpose.

  In order to achieve the above object, an image forming apparatus according to claim 1 is an image forming apparatus for forming an image on an intermediate transfer member and transferring the image on the intermediate transfer member to a recording medium. A liquid adhering means for adhering a first liquid having a viscosity of 15 mPa · s or more and 300 mPa · s or less at 25 ° C. to the intermediate transfer member; and a thickness of 1.6 μm or more of the first liquid on the intermediate transfer member. In such a state, droplet ejection means for ejecting the second liquid containing the color material onto the area of the intermediate transfer body to which the first liquid is adhered, and viscosity increasing means for increasing the viscosity of the second liquid And transfer means for transferring an image including dots of the second liquid formed on the intermediate transfer member to the recording medium.

  According to the present invention, a first liquid having a viscosity of 15 mPa · s to 300 mPa · s at 25 ° C. is deposited on the intermediate transfer member, and the color material is applied in a state where the thickness of the first liquid is 1.6 μm or more. Since the contained second liquid is landed, landing interference does not occur even when the second liquids contact each other on the intermediate transfer member, and a preferable image can be obtained.

  Further, the viscosity of the image including the dots formed by the second liquid is increased on the intermediate transfer member, and the dots (image) formed by the second liquid are assumed on the intermediate transfer member and then transferred to the recording medium. Therefore, image disturbance on the intermediate transfer member and image disturbance during transfer can be prevented.

  The first liquid is a transparent liquid containing no substantial color material. “Containing substantially no color material” includes the case of containing a very small amount of color material of 1% by weight or less.

  The viscosity increasing means includes a cooling means for cooling the second liquid and a hardening energy applying means for applying hardening energy to the second liquid. The second liquid may have a viscosity that does not move from a predetermined position on the intermediate transfer member (for example, a semi-cured state). After the second liquid is cured on the intermediate transfer member by the viscosity increasing means, it may be configured such that the viscosity of the second liquid is lowered to a viscosity suitable for transfer when transferring to the recording medium.

Further, the viscosity increasing means may increase the viscosity on the first liquid intermediate transfer member. Of course, the viscosity at the time of landing of the first liquid may be maintained. In the aspect in which the first liquid maintains the viscosity at the time of landing, the first liquid is removed before the second liquid (image) is transferred to the recording medium (removal means for removing the first liquid is provided. ) Embodiment is preferred.

  In an aspect in which the first liquid is applied to the intermediate transfer member, there is an aspect in which a droplet ejection unit that ejects the first liquid is applied. There is also an aspect in which the first liquid is applied.

  The droplet ejecting means includes a nozzle that ejects liquid (droplet), a liquid chamber that accommodates the liquid that is ejected from the nozzle, and an ejection force generation element that imparts ejection force to the liquid contained in the liquid chamber. There exists an aspect provided with these. The droplet ejection unit for ejecting the first liquid may have the same configuration as the droplet ejection unit for ejecting the second liquid, or may have a different configuration.

  The recording medium includes various media. For example, there are papers such as continuous paper and cut paper, resin sheets, metal sheets, fibers (cloth), and the like.

  A second aspect of the present invention relates to an aspect of the image forming apparatus according to the first aspect, wherein the first liquid has a dynamic surface tension value γ1 at a surface life of 0.1 sec and the surface of the second liquid. The relationship with the dynamic surface tension value γ2 at a lifetime of 0.1 sec satisfies the following expression γ1 <γ2.

In the present invention, the value of the dynamic surface tension is measured by a maximum bubble pressure method. In the maximum bubble pressure method, gas is sent from a capillary with a known radius r submerged in a sample solution at a predetermined speed to form bubbles. The pressure in this process is measured to determine the maximum pressure value. From the maximum pressure value ρ _max , the initial pressure value ρ ₀ , and the capillary radius, the surface tension σ = {(ρ _max −ρ ₀ ) × r} / 2 at a certain surface age is obtained. The surface life corresponds to the time until the bubble pressure becomes maximum. By varying the gas flow rate and measuring the surface tension for various surface lifetimes, the dynamic surface tension can be measured.

  According to the second aspect of the present invention, by appropriately adjusting the relationship between the dynamic surface tension γ1 of the first liquid and the second liquid dynamic surface tension γ2, the second liquid is added to the intermediate transfer member. The landing interference at the time of landing is prevented.

  A third aspect of the present invention relates to an aspect of the image forming apparatus according to the first or second aspect, wherein the droplet ejecting unit applies the second liquid over a length corresponding to the width direction of the intermediate transfer body. It includes a full line type liquid discharge head having a nozzle row in which nozzles to be discharged are arranged.

  According to the third aspect of the present invention, when a full line type liquid discharge head is applied to the droplet ejection means, a short head having a length shorter than the width of the intermediate transfer member is scanned in the width direction in the same direction. High-speed printing (image formation) is possible as compared with a shuttle scan type liquid discharge head that discharges liquid. In addition, it is possible to obtain a preferable image without landing interference and dot spread even when performing high-speed printing.

  According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first, second, or third aspect, wherein the second liquid contains a radiation curable polymerizable compound, and the viscosity increasing means is a radiation. It includes a beam irradiation means.

  Radiation rays include ultraviolet rays and electron beams, and have energy for generating a polymerization reaction of the polymerizable compound. There exists an aspect provided with the radiation irradiation control means which controls on / off of a radiation irradiation means, irradiation amount (irradiation energy), irradiation time, etc.

  The invention according to claim 5 relates to an aspect of the image forming apparatus according to claim 1, 2, or 3, wherein the second liquid contains a radiation curable polymerizable compound, and the intermediate transfer member is It has a hollow cylindrical shape and has radiation irradiation means for irradiating the second liquid deposited on the intermediate transfer body with radiation, and at least the radiation irradiation means irradiates the radiation. The region is formed of a member that transmits radiation.

According to the fifth aspect of the present invention, by irradiating radiation from the inside of the intermediate transfer member, the second
The surface where the liquid (and the first liquid) comes into contact with the intermediate transfer member can be intensively cured. Further, the apparatus can be reduced in size by incorporating the radiation irradiation means in the intermediate transfer member.

  A sixth aspect of the invention relates to an aspect of the image forming apparatus according to any one of the first to fifth aspects, wherein the second liquid contains an ultraviolet curable polymerizable compound, and At least one of the first liquid and the second liquid contains a polymerization initiator, and the viscosity increasing means includes ultraviolet irradiation means.

  According to the sixth aspect of the present invention, the viscosity of the second liquid can be increased efficiently by using a relatively inexpensive ultraviolet irradiation means.

  The polymerization initiator may be contained in the first liquid or in the second liquid. In addition, the aspect contained in the 1st liquid which does not contain an ultraviolet curable polymeric compound is preferable.

  According to a seventh aspect of the present invention, there is provided the image forming apparatus according to any one of the first to sixth aspects, wherein the viscosity increasing means is a second liquid landed on the intermediate transfer member. The viscosity is 5000 mPa or more.

  Particularly, in the aspect in which the viscosity of the second liquid is set to 5000 mPa · s or more using the ultraviolet irradiation means described in claim 6, the increase in the viscosity of the second liquid can be accelerated.

  According to an eighth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to seventh aspects, further comprising a main curing unit that performs main curing of the image transferred to the recording medium. It is characterized by that.

  According to the invention described in claim 8, it is possible to reliably fix the image on the recording medium.

  In the embodiment in which the second liquid described in claim 4 contains a radiation (ultraviolet) curable polymerizable compound, radiation (ultraviolet) irradiation means can be applied to the main curing means.

  A ninth aspect of the present invention relates to an aspect of the image forming apparatus according to any one of the first to eighth aspects, wherein the transfer means converts dots of the second liquid into the second liquid. A heating means for heating to a temperature higher than the glass transition point is included.

  According to the ninth aspect of the present invention, the releasability of the second liquid is improved, and image distortion when transferring an image from the intermediate transfer member to the recording medium can be prevented with a simple configuration.

  A method invention is provided to achieve the above object. That is, the image forming method according to claim 10 is a liquid discharge head that discharges a first liquid onto a medium, and forms an image on an intermediate transfer member, and the image on the intermediate transfer member is recorded on a recording medium. In the image forming apparatus that transfers to the intermediate transfer member, a liquid attaching step of attaching a first liquid having a viscosity of 15 mPa · s to 300 mPa · s at 25 ° C. to the intermediate transfer member; In a state where the liquid has a thickness of 1.6 μm or more, the second liquid containing a coloring material is ejected onto a region of the intermediate transfer body to which the first liquid has adhered; A viscosity increasing step for increasing the viscosity of the liquid; and a transfer step for transferring an image including dots formed by the second liquid formed on the intermediate transfer member to the recording medium.

The invention according to claim 11 relates to an aspect of the image forming method according to claim 10, wherein the viscosity increasing step cures the second liquid, and the transfer step is cured by the viscosity increasing step. And a heating step of heating the second liquid to a temperature not lower than the glass transition temperature of the second liquid.

  According to the eleventh aspect of the present invention, the second liquid is cured to prevent image deterioration on the intermediate transfer member, and the second liquid is softened to a viscosity suitable for transfer at the time of transfer, thereby improving efficiency. Image transfer is realized.

  A twelfth aspect of the invention relates to an aspect of the image forming method according to the tenth aspect of the invention, wherein the viscosity increasing step sets the second liquid to a viscosity suitable for transfer in the transfer step. And

  According to the twelfth aspect of the present invention, it is expected that the entire image formation is speeded up along with the speeding up of the viscosity increasing step.

  According to the present invention, a first liquid having a viscosity of 15 mPa · s to 300 mPa · s at 25 ° C. is deposited on the intermediate transfer member, and the color material is applied in a state where the thickness of the first liquid is 1.6 μm or more. Since the contained second liquid is landed, landing interference does not occur even when the second liquids contact each other on the intermediate transfer member, and a preferable image can be obtained.

  In addition, since the viscosity of the second liquid is increased on the intermediate transfer member and dots (images) formed by the second liquid are assumed on the intermediate transfer member and then transferred to the recording medium, the intermediate transfer is performed. Image disturbance on the body and image disturbance during transfer are prevented.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a processing liquid head 12S corresponding to the processing liquid (S, first liquid) 30, and cyan (C), magenta (M), yellow (Y), A printing unit 12 having a plurality of inkjet heads (hereinafter referred to as heads) 12C, 12M, 12Y, and 12K provided corresponding to each black (K) ink (second liquid) 32; Yes.

  The treatment liquid (first liquid) 30 applied to this example is a transparent (substantially free of coloring material) liquid containing an ultraviolet curable polymerizable compound (monomer, oligomer, or these compounds). The viscosity is 15 to 300 mPa · s at 25 ° C. Note that even if the treatment liquid 30 contains 1% by weight or less of ink color material, it is substantially transparent.

  The ink 32 corresponding to each color contains a color material (pigment) of each color and a polymerization initiator. In addition, the processing liquid 30 and the ink 32 contain a surfactant and other additives, and the dynamic surface tension γ1 of the surface life of the processing liquid 30 is 0.1 seconds. These additives are formulated so as to be smaller than the target surface tension γ2 (that is, satisfying the relationship of γ1 <γ2). Details of the treatment liquid 30 and the ink 32 will be described later.

  Further, the ink jet recording apparatus 10 includes a storage / loading unit 14 for storing the ink 32 supplied to each head 12C, 12M, 12Y, 12K and the processing liquid 30 supplied to the processing liquid head 12S, and the heads 12S, 12C. , 12M, 12Y, and 12K, the intermediate transfer body 16 on which an image is formed by the processing liquid 30 and the ink 32 ejected from the ink, and the ink 32 (or the processing liquid 30) on the intermediate transfer body 16 are irradiated with ultraviolet rays. The image of the intermediate transfer body 16 is transferred to the ultraviolet ray light source 18 (viscosity increasing means) that increases the viscosity of the liquid 32 (or the processing liquid 30) and the recording medium 20 that is conveyed while being supported by the support roller 19 so as to maintain flatness. The transfer unit 22 that transfers while being heated by the heating roller 40 and the cleaning ink that removes residual ink (and residual processing liquid) from the intermediate transfer body 16 after transfer. And parts 24, and a.

  As shown in FIG. 1, an endless belt-like member wound around five rollers 26 is applied to the intermediate transfer member 16, and when each roller 26 rotates clockwise, the intermediate transfer member 16 has the printing unit 12. In the opposite area, the movement moves from left to right in FIG. When a belt-like member is applied to the intermediate transfer member 16, the heads 12S, 12C, 12M, 12Y, and 12K can be arranged horizontally.

  In the region where the intermediate transfer body 16 faces the printing unit 12, the treatment liquid 30 ejected by the head 12S adheres to a predetermined image forming region of the intermediate transfer body 16, and the thickness t becomes 1.6 μm or more. Each color ink droplet 32 is ejected from the heads 12C, 12M, 12Y, 12K.

  The intermediate transfer member 16 is applied with a non-permeable medium through which the processing liquid 30 and the ink droplets 32 do not penetrate. The non-permeable medium may include a medium in which the treatment liquid 30 and the ink droplets 32 penetrate very slowly. Specific examples of the intermediate transfer member 16 include resin and metal.

  FIG. 2 shows a state in which the ink 32 ejected from the heads 12C, 12M, 12Y, and 12K has landed on the intermediate transfer body 16 to which the processing liquid 30 has adhered. As shown in FIG. 2, the presence of the treatment liquid 30 on the intermediate transfer body 16 causes the ink droplets 32 'that have landed on the intermediate transfer body 16 (the treatment liquid film 30 having a predetermined thickness) to exist independently. Then, dots are formed at predetermined positions in the ink droplet 32 'without causing landing interference.

  The treatment liquid 30 adhering to the intermediate transfer member 16 and the ink droplet 32 ′ that has landed on the intermediate transfer member 16 are cured by ultraviolet rays (energy) applied from the ultraviolet light source 18 of FIG. 1 and temporarily fixed to the intermediate transfer member 16. (Assumed)

  It is not necessary to completely cure the treatment liquid 30 and the ink droplet 32 ′ by this ultraviolet irradiation, and it is sufficient that the ink droplet 32 ′ is cured to the extent that it does not move on the intermediate transfer body 16. That is, it is sufficient that the viscosity of the ink droplet 32 ′ is set to 5000 mPa · s or more by the ultraviolet irradiation.

  When the ultraviolet light emitted from the ultraviolet light source 18 is applied to the nozzles 51 of the heads 12C, 12M, 12Y, and 12K that eject ink droplets 32 (liquid containing an ultraviolet curable polymerizable compound), the nozzles Since the ink in the ink 51 is cured, the ultraviolet light source 18 needs to be arranged so that the ultraviolet light does not reach the nozzles 51 of the heads 12C, 12M, 12Y, and 12K.

  In a mode in which the heads 12C, 12M, 12Y, and 12K are disposed close to the ultraviolet light source 18, it is preferable that the heads 12C, 12M, 12Y, and 12K include a light shielding member that blocks the ultraviolet light emitted from the ultraviolet light source 18.

  The processing liquid 30 and the ink droplet 32 ′ temporarily fixed to the intermediate transfer body 16 in this way are heated to a temperature equal to or higher than the glass transition temperature by the heating roller 40 of the transfer unit 22 and are pressed with a predetermined pressure. Thus, the image is transferred from the intermediate transfer body 16 to the recording medium 20.

  In an embodiment in which the ink droplet 32 ′ is not completely cured on the intermediate transfer body 16, the ultraviolet ray irradiation amount (irradiation) is performed so that the ink droplet 32 ′ is increased to a viscosity suitable for transfer by the transfer unit 22 by ultraviolet irradiation. Time). In such an embodiment in which the ink droplet 32 'is not completely cured, heating in the transfer unit 22 is unnecessary, and the curing time of the ink droplet 32' by ultraviolet irradiation and the shortening of the softening time of the ink droplet 32 'at the time of transfer are shortened. (Omitted) becomes possible, and the efficiency of the entire image recording is expected. That is, at the time of transfer, the viscosity of the ink droplet 32 'may be set to 5000 mPa · s or more.

  Specific examples of the recording medium 20 include various media such as papers such as continuous paper and cut paper, resin films such as OHP sheets, metal sheets, cloth, and wood.

  When the image formed on the intermediate transfer body 16 is transferred to the recording medium 20 in this way, the image forming area of the intermediate transfer body 16 moves to the cleaning unit 24, and the processing liquid 30 and the residual liquid 30 remaining in the image forming area The ink droplet 32 is removed. The cleaning unit 24 illustrated in FIG. 1 includes a blade 42 that removes the residual processing liquid and residual ink while contacting the intermediate transfer member 16, and a recovery unit 44 that recovers the residual residual processing liquid and residual ink. .

  Examples of the mode for removing the residual treatment liquid and residual ink from the intermediate transfer member 16 include a method of niping a brush roll, a water absorption roll, etc., an air blow method of blowing clean air, or a combination thereof. . In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  The storage / loading unit 14 includes a processing liquid tank 14S that stores a processing liquid corresponding to the head 12S, and tanks 14C, 14M, 14Y, and 14K that store inks of colors corresponding to the heads 12C, 12M, 12Y, and 12K. And each tank communicates with the heads 12S, 12C, 12M, 12Y, and 12K through a required flow path.

  The storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying that when the amount of processing liquid and ink is low, and a mechanism for preventing erroneous loading between colors. Have.

  Although not shown in FIG. 1, there is an aspect in which the paper supply unit that supplies the recording medium 20 includes a magazine for rolled paper (continuous paper). A plurality of magazines having different paper widths, paper quality, etc. may be provided. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Thus, it is preferable to automatically determine the type of recording medium (media type) to be used and perform ink ejection control so as to realize appropriate ink ejection according to the media type.

  Further, the recording medium 20 delivered from the paper supply unit described above retains curl due to having been loaded in the magazine. In order to remove the curl, a decurling unit is provided, and heat is applied to the recording medium with a heating drum in a direction opposite to the curl direction of the magazine in the decurling unit. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

In the case of an apparatus configuration using roll paper, a cutter (first cutter) is provided, and the roll paper is cut into a desired size by the cutter. The cutter has an aspect composed of a fixed blade having a length equal to or greater than the conveyance path width of the recording medium 20 and a round blade that moves along the fixed blade, and the fixed blade is provided on the back side of the print, A round blade is arranged on the printing surface side across the conveyance path. In addition, when using cut paper, a cutter is unnecessary.

  Each head 12S, 12C, 12M, 12Y, and 12K of the printing unit 12 has a length corresponding to the maximum width of the intermediate transfer member 16 (image forming area), and the nozzle surface is processed over the entire width of the image forming area. This is a full-line head in which a plurality of nozzles for discharging liquid and ink are arranged (see FIG. 3).

  The heads 12S, 12C, 12M, 12Y, and 12K are disposed from the upstream side along the feed direction of the intermediate transfer body 16, from the processing liquid (S), cyan (C), magenta (M), yellow (Y), and black (K). The heads 12S, 12C, 12M, 12Y, and 12K are fixedly installed so as to extend in the conveyance direction of the intermediate transfer body 16.

  A color image can be formed on the intermediate transfer member 16 by discharging the processing liquid and different color inks from the heads 12S, 12C, 12M, 12Y, and 12K while conveying the intermediate transfer member 16, respectively.

  As described above, according to the configuration in which the full-line heads 12C, 12M, 12Y, and 12K having nozzle rows covering the entire width of the intermediate transfer body 16 are provided for each color, the intermediate transfer is performed in the transport direction (sub-scanning direction). An image can be recorded on the entire surface of the intermediate transfer member 16 by performing the operation of relatively moving the body 16 and the printing unit 12 once (that is, by one sub-scan). Thereby, it is possible to perform high-speed printing as compared with a shuttle type head in which the head reciprocates in a direction orthogonal to the transport direction, and productivity can be improved.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, a configuration in which an ink jet head that discharges light ink such as light cyan and light magenta can be added, and a plurality of processing liquid heads 12S corresponding to a plurality of processing liquids (for example, different physical properties such as viscosity) can be provided. It is possible to provide an aspect. Also, the arrangement order of the color heads is not particularly limited.

  The printed matter generated in this way (the recording medium 20 on which a desired image is formed) is discharged from a paper discharge unit (not shown). It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a sorting means (not shown) for switching the paper discharge path in order to select the printed matter of the main image and the printed matter of the test print and send them to the respective discharge portions. When the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter). The cutter is provided immediately before the paper discharge unit, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter is the same as that of the first cutter described above, and is composed of a fixed blade and a round blade. The paper output unit for the target prints is provided with a sorter for collecting prints according to print orders.

[Head structure]
Next, the structure of the head will be described. Since the structures of the heads 12S, 12C, 12M, 12Y, and 12K for each color are common, the heads are represented by the reference numeral 50 in the following.

  4 (a) is a plan perspective view showing an example of the structure of the head 50, and FIG. 4 (b) is an enlarged view of a part thereof. 4C is a plan perspective view showing another example of the structure of the head 50, and FIG. 5 is a sectional view showing the three-dimensional configuration of the ink chamber unit (5-5 in FIGS. 4A and 4B). In order to increase the dot pitch formed on the intermediate transfer body 16 (recording medium 20), it is necessary to increase the nozzle pitch in the head 50. As shown in FIGS. 4A and 4B, the head 50 includes a plurality of ink chamber units 53 including nozzles 51 serving as ink droplet ejection holes and pressure chambers 52 corresponding to the nozzles 51. It has a structure that is arranged in a staggered matrix (two-dimensionally), so that the substantial nozzle interval (projection) projected so as to be aligned along the head longitudinal direction (direction perpendicular to the paper feed direction) Nozzle pitch) is increased.

  The form in which one or more nozzle rows are formed over a length corresponding to the entire width of the intermediate transfer member 16 in a direction substantially orthogonal to the conveyance direction of the intermediate transfer member 16 is not limited to this example. For example, instead of the configuration of FIG. 4 (a), short head blocks 50 ′ in which a plurality of nozzles 51 are two-dimensionally arranged are arranged in a staggered manner and connected as shown in FIG. 4 (c). A line head having a nozzle row having a length corresponding to the entire width of the intermediate transfer member 16 (the entire width of the image forming area) may be configured.

  The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape, and the nozzle 51 and the supply port 54 are provided at both corners on the diagonal line. Each pressure chamber 52 communicates with a common flow channel 55 through a supply port 54. The common flow channel 55 communicates with a tank (not shown in FIG. 5, described as reference numeral 60 in FIG. 6) as a supply source of the processing liquid and ink, and the processing liquid and ink supplied from the tank are the same as those in FIG. It is distributed and supplied to each pressure chamber 52 via the flow path 55.

  An actuator 58 having an individual electrode 57 is joined to a diaphragm 56 that constitutes the top surface of the pressure chamber 52 and also serves as a common electrode, and the actuator 58 is deformed by applying a drive voltage to the individual electrode 57. Thus, ink is ejected from the nozzle 51. When ink is ejected, new ink is supplied from the common channel 55 to the pressure chamber 52 through the supply port 54.

  As shown in FIG. 4B, the ink chamber units 53 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of this example is realized.

  That is, with a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to be aligned in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 51 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction.

  In implementing the present invention, the nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied.

  In this example, the head 12S corresponding to the processing liquid and the heads 12C, 12M, 12Y, and 12K corresponding to the respective color inks are configured in the same manner. However, the processing liquid head 12S includes the heads 12C, 12M, and 12Y. , 12K, the nozzle density can be reduced.

  That is, the dots formed by the treatment liquid 30 and the dots formed by the ink 32 do not necessarily correspond one-to-one, and the treatment liquid 30 exists in a region including the landing position of the ink 32 and its periphery. It only has to be. In addition, a plurality of dots of ink may land on one dot of the treatment liquid 30. In the aspect in which the nozzle density of the processing liquid head 12S is configured to be lower than that of the heads 12C, 12M, 12Y, and 12K, the time required for attaching the processing liquid 30 to the intermediate transfer body 16 is expected to be shortened, and the processing liquid head The ease of manufacturing 12S is improved.

[Configuration of ink supply system]
FIG. 6 is a schematic diagram illustrating the configuration of the treatment liquid and the ink supply system in the inkjet recording apparatus 10. Since the treatment liquid supply system and the ink supply system have the same configuration, FIG. 6 shows the ink supply system, and the ink supply system will be described here.

  A tank 60 shown in FIG. 6 is a base tank that supplies ink to the head 50 and is installed in the storage / loading unit 14 described with reference to FIG. The form of the tank 60 includes a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the ink remaining amount is low. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

  As shown in FIG. 6, a filter 62 is provided in the flow path between the tank 60 and the head 50 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm). Although not shown in FIG. 6, a configuration in which a sub tank is provided in the vicinity of the head 50 or integrally with the head 50 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 10 is provided with a cap 64 as a means for preventing the nozzle 51 from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 66 as a nozzle surface cleaning means. The maintenance unit including the cap 64 and the cleaning blade 66 can be moved relative to the head 50 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the head 50 as necessary.

  The cap 64 is displaced up and down relatively with respect to the head 50 by an elevator mechanism (not shown). The cap 64 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the head 50, thereby covering the nozzle surface with the cap 64.

  The cleaning blade 66 is made of an elastic member such as rubber, and can slide on the ink discharge surface (nozzle plate surface) of the head 50 by a blade moving mechanism (not shown). When ink droplets or foreign substances adhere to the nozzle plate, the nozzle plate surface is wiped by sliding the cleaning blade 66 on the nozzle plate to clean the nozzle plate surface.

  During printing or standby, when a specific nozzle is used less frequently and the ink viscosity in the vicinity of the nozzle increases, preliminary discharge is performed toward the cap 64 to discharge the deteriorated ink.

  When air bubbles are mixed in the ink in the head 50 (in the pressure chamber 52), the cap 64 is applied to the head 50, and the ink in the pressure chamber 52 (ink in which the air bubbles are mixed) is removed by suction with the suction pump 67. Then, the sucked and removed ink is sent to the collection tank 68. In this suction operation, the deteriorated ink having increased viscosity (solidified) or the deteriorated ink mixed with bubbles is sucked out when the initial ink is loaded into the head 50 or when the ink is used after being stopped for a long time.

If the head 50 is not ejected for a certain period of time, the ink solvent near the nozzles evaporates and the viscosity of the ink near the nozzles increases. Will not discharge. Therefore, before this state is reached (within the viscosity range in which ink can be discharged by the operation of the actuator 58), the actuator 58 is operated toward the ink receiver to discharge ink in the vicinity of the nozzle whose viscosity has increased. “Preliminary discharge” is performed. In order to prevent foreign matter from entering the nozzle 51 by the wiper rubbing operation after the dirt on the nozzle plate surface is cleaned by a wiper such as a cleaning blade 66 provided as a nozzle surface cleaning means. Preliminary discharge is performed. Note that the preliminary discharge may be referred to as “empty discharge”, “purge”, “spitting”, or the like.

  In addition, if bubbles are mixed into the nozzle 51 or the pressure chamber 52 or if the viscosity increase of the ink in the nozzle 51 exceeds a certain level, ink cannot be ejected by the preliminary ejection, and the suction operation described below is performed.

  That is, when bubbles are mixed in the ink in the nozzle 51 or the pressure chamber 52, or when the ink viscosity in the nozzle 51 rises to a certain level or more, the ink can be ejected from the nozzle 51 even if the actuator 58 is operated. Disappear. In such a case, a suction means for sucking ink in the pressure chamber 52 with a pump or the like is brought into contact with the nozzle surface of the head 50 to suck ink mixed with bubbles or thickened ink.

  However, since the above suction operation is performed on the entire ink in the pressure chamber 52, the ink consumption is large. Therefore, when the increase in viscosity is small, it is preferable to perform preliminary discharge as much as possible.

[Explanation of control system]
FIG. 7 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, a light source driver 58, and the like.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74.

  The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 72 controls each part such as the communication interface 70, the image memory 74, the motor driver 76, the heater driver 78, etc., performs communication control with the host computer 86, read / write control of the image memory 74, etc. A control signal for controlling the motor 88 and the heater 89 of the transport system is generated.

  The image memory 74 stores programs executed by the CPU of the system controller 72 and various data necessary for control. Note that the image memory 74 may be a non-rewritable storage means, or may be a rewritable storage means such as an EEPROM. The image memory 74 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heater 89 in accordance with an instruction from the system controller 72. Examples of the heater 89 include a heater built in the heating roller 40 of the transfer unit 22 shown in FIG. 1 and a heater for adjusting the temperature in the head 50.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print It is a control unit that supplies data (dot data) to the head driver 84. Necessary signal processing is performed in the print control unit 80, and the ejection amount and ejection timing of the ink droplets of the head 50 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  The head driver 84 drives the processing liquid and the actuators 58 of the respective color heads 12S, 12C, 12M, 12Y, and 12K based on the print data supplied from the print control unit 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  Since dots formed by the treatment liquid do not require resolution compared to dots formed by the respective color inks, a mode in which the dot data of the treatment liquid is different from the dot data of the respective color inks is also possible. That is, image data to be printed is input from the outside via the communication interface 70 and stored in the image memory 74. At this stage, RGB image data is stored in the image memory 74.

  The image data stored in the image memory 74 is sent to the print controller 80 via the system controller 72, and is converted into dot data for each ink color by the print controller 80. That is, the print control unit 80 performs processing for converting the input RGB image data into dot data of four colors of KCMY. The dot data generated by the print controller 80 is stored in the image buffer memory 82.

  The head driver 84 generates a drive control signal for the head 50 based on the dot data stored in the image buffer memory 82. By applying the drive control signal generated by the head driver 84 to the head 50, ink is ejected from the head 50. An image is formed on the intermediate transfer member 16 by controlling ink ejection from the head 50 in synchronization with the conveyance speed of the intermediate transfer member 16.

  Various control programs are stored in the program storage unit 90, and the control programs are read and executed in accordance with instructions from the system controller 72. The program storage unit 90 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media. The program storage unit 90 may also be used as a recording means (not shown) for operating parameters.

  The print controller 80 controls the ultraviolet light source (UV light source) 18 via the light source driver 85. That is, on the basis of a control signal sent from the print control unit 80 to the light source driver 85, the light source driver 85 controls on / off of the ultraviolet light source 18, irradiation amount, irradiation time, etc. in connection with the conveyance control of the intermediate transfer body 16. Execute.

[Description of treatment liquid and ink]
Next, physical properties of the treatment liquid and ink applied to the present invention will be described in detail. The results of an evaluation experiment on the presence / absence of landing interference and the degree of landing interference due to the difference in physical properties of the processing liquid and ink based on the granularity of the solid image are shown below.

  In this evaluation experiment, IJET1000 (manufactured by Microjet Co., Ltd.) is used as the processing liquid and ink ejection device, and Personal IAS (ISO / IEC 13660 compliant, manufactured by qea) is used as the solid image granularity evaluation device. )It was used. Silicone rubber is used for the ejection medium (corresponding to the intermediate transfer body 16), and after the treatment liquid and ink are landed on the ejection medium in this order, the treatment liquid and the ink are fixed (cured) to the ejection medium by ultraviolet irradiation. ) To create a sample.

<Preparation of treatment solution>
The following compounds were mixed with stirring at room temperature, filtered through a 5 μm membrane filter, and eight kinds of liquids from the following 101 liquids to 108 liquids were prepared as treatment liquids.

101st liquid
HDDA: polymerizable monomer 85.0% by weight
DPCA60: Polymerizable monomer 9.5.
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 0.5% by weight
102nd liquid
HDDA: polymerizable monomer 20.0% by weight
BPE-10: Polymerizable monomer 74.0% by weight
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 1.0 wt%
103rd liquid
HDDA: polymerizable monomer 40.0% by weight
BPE-10: polymerizable monomer 54.0% by weight
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 1.0 wt%
104th liquid
HDDA: Polymerizable monomer 45.0% by weight
BPE-10: Polymerizable monomer 49.0% by weight
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 1.0 wt%
105th liquid
HDDA: polymerizable monomer 85.0% by weight
DPCA60: 9.5% by weight of polymerizable monomer
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 0.5% by weight
106th liquid
HDDA: polymerizable monomer 85.5% by weight
DPCA60: 9.5% by weight of polymerizable monomer
Irg1870: Polymerization initiator 5.0 wt%
107th liquid
HDDA: polymerizable monomer 85.3 wt%
DPCA60: 9.5% by weight of polymerizable monomer
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 0.2% by weight
108th liquid
HDDA: polymerizable monomer 84.0% by weight
DPCA60: polymerizable monomer 9.0% by weight
Irg1870: Polymerization initiator 5.0 wt%
F781F: Surfactant 2.0% by weight
Moreover, three types of liquids from the following 201 liquids to 203 liquids were prepared as inks.

No. 201 Polymerizable monomer: DPCA60 (Nippon Kayaku) 2.6 wt%
Coloring material: Phthalocyanine 5.0% by weight
Dispersant: sol32000 0.25 wt%
Polymerization initiator: Irg1870 6.0 wt%
Megafuck F781F 0.5 wt%
Monomer: 1,6 hexanediol diacrylate (manufactured by HDDA Daicel UCP) Remaining part 202 Polymerizable monomer: DPCA60 (Nippon Kayaku) 2.6% by weight
Coloring material: Phthalocyanine 5.0% by weight
Dispersant: sol32000 0.25 wt%
Polymerization initiator: Irg1870 6.0 wt%
Mega Fuck F781F 1.0 wt%
Monomer: 1,6 hexanediol diacrylate (manufactured by HDDA Daicel UCP) Remaining part 203 Polymerizable monomer: DPCA60 (Nippon Kayaku) 2.6% by weight
Coloring material: Phthalocyanine 5.0% by weight
Dispersant: sol32000 0.25 wt%
Polymerization initiator: Irg1870 6.0 wt%
Mega Fuck F781F 0.75 wt%
Monomer: 1,6 hexanediol diacrylate (manufactured by HDDA Daicel UCP) balance Note that the criterion for this evaluation experiment is that the granularity is 1.0 or more as xx, and this is highly visible in uneven density due to landing interference Indicates the state to be performed. Further, the granularity is 0.6 or more and less than 1.0, and this is a state where density unevenness is visually recognized, and the granularity is 0.4 or more and less than 0.6 is represented by Δ, which is slightly The state where density unevenness is visually recognized is shown.

  That is, when the determination display is displayed as xx, x, or Δ, density unevenness due to landing interference is visually recognized in the recorded image. On the other hand, a granularity of 0.3 or more and less than 0.4 is represented by ◯, and a granularity of 0.3 or less is represented by ◎. These states indicate that a preferable recorded image in which density unevenness is not visually recognized can be obtained.

  In FIG. 8, the evaluation result by the difference in the thickness t (refer FIG. 2) of a process liquid is shown. In the evaluation experiment showing the results in FIG. 10, the appropriate amount of ink droplets forming one dot (ink ejected by one ejection operation) was set to 70 pl. Moreover, the 101st liquid mentioned above was used as a process liquid, and the 201st liquid and 202 were used as an ink.

  As shown in FIG. 8, when the thickness t of the treatment liquid (the 101st liquid) on the ejection medium is in the range of 0 μm (none) to 1.5 μm, both the 201st liquid and the 202nd liquid are judged as xx, x, or Δ. In the image formed on the ejection medium, density unevenness is visible.

  On the other hand, when the thickness t of the processing liquid on the ejection medium is 1.6 μm, 2 μm, 5 μm, and 10 μm, both the 201st liquid and the 202nd are judged as “◎” or “O”, and the thickness t of the processing liquid on the ejection medium is 1. If it is 6 μm or more, landing interference of ink droplets does not occur, and a preferable image in which image deterioration such as density unevenness is not visually recognized can be obtained. That is, the preferable thickness t of the treatment liquid is 1.6 μm or more.

  Note that the thickness t of the processing liquid tends to depend on the amount of ink droplets (if the amount of ink droplets is large, the thickness of the processing liquid (the amount of processing liquid) is preferably large). In the range of several pl to several tens of pl, a good image can be obtained by setting the thickness t of the treatment liquid to 1.6 μm or more.

  The thickness t of the treatment liquid with particularly good results is 10 μm for both the 201st liquid and the 202nd liquid. Therefore, the thickness t of the treatment liquid is more preferably 10 μm or more.

  In this evaluation experiment, the 101st liquid was used as an example of the processing liquid, but the same result can be obtained even if the other processing liquids (the 102nd liquid to the 108th liquid) described above are used.

  FIG. 9 shows an evaluation result based on a difference in viscosity of the treatment liquid at 25 ° C. In the evaluation experiment showing the evaluation results in FIG. 9, the treatment liquid was deposited on the ejection medium so as to have a thickness of 10 μm, and ink was landed thereon. The 101st liquid to the 105th liquid were used for the treatment liquid, and the 201st liquid and the 202th liquid were used for the ink.

  When the 103rd liquid having a viscosity at 25 ° C. of 482 mPa · s and the 104th liquid having a viscosity of 310 mPa · s are used as the treatment liquid, the determination is X or Δ when either the 201st liquid or the 202nd liquid is used as the ink. In addition, density unevenness is visually recognized in the recorded image.

  On the other hand, when the 101st, 104th, and 105th liquids having a viscosity at 25 ° C. of 287 mPa · s, 48 mPa · s, and 15 mPa · s, respectively, were used, when either the 201st liquid or the 202nd liquid was used. Is also judged as ◎ or ○. Therefore, when a treatment liquid having a viscosity of 15.3 mPa · s to 287 mPa · s is used, a preferable image in which density unevenness is not visually recognized can be obtained.

  That is, a preferable viscosity range of the treatment liquid is 15 mPa · s or more and 300 mPa · s or less. The viscosity of the treatment liquid that obtained particularly good results is 15.3 mPa · s, and it is more preferable that the treatment liquid has a low viscosity within the preferred range of the treatment liquid viscosity. It is estimated that the same result can be obtained even if No. 203 is used as the ink.

  FIG. 10 shows the evaluation results when the relative relationship between the dynamic surface tension γ1 of the surface life of the treatment liquid of 0.1 seconds and the dynamic surface tension γ2 of the ink is changed. The dynamic surface tension value was measured using a bubble pressure surface tension meter BP2 manufactured by KRUSS. The value of the dynamic surface tension is measured by, for example, the maximum bubble pressure method. Details of the maximum bubble pressure method can be found on the KRUSS website (URL: http://www.kruss.info/techniques/bubble_pressure_e.html). In the evaluation experiment showing the results in FIG. 10, the 101st liquid and the 106th liquid to the 108th liquid were used as the treatment liquid, and the 201st liquid to the 203rd liquid were used as the ink.

In any combination of treatment liquid and ink, when the relationship between the dynamic surface tension γ1 of the treatment liquid and the dynamic surface tension γ2 of the ink satisfies γ1 <γ2, the determination is ◎, and density unevenness is visually recognized. It is possible to obtain a preferable image that is not.

  The combinations of the treatment liquid and the ink that obtained particularly good results are the combination of the 101st liquid and the 201st to 203rd liquids, the combination of the 107th liquid and the 201st liquid, the 108th liquid and the 201st liquid to the 201st liquid. It is a combination of 203 liquids. That is, in addition to the thickness condition of the treatment liquid 30 described with reference to FIG. 8 and the viscosity condition of the treatment liquid 30 described with reference to FIG. 9, the dynamic surface tension γ1 of the treatment liquid 30 described with reference to FIG. When the dynamic surface tension γ2 satisfies the relationship γ1 <γ2, landing interference of the ink 32 can be more effectively prevented.

  More preferably, the difference between the surface tension γ1 of the treatment liquid and the surface tension γ2 of the ink is large. In this evaluation experiment, silicone rubber was used as the ejection medium, but similar results can be obtained when glass or stainless steel is used.

  FIG. 11 shows the results of an evaluation experiment on the viscosity of the ink on the intermediate transfer member. In the evaluation experiment showing the results of FIG. 11, the ink deposited on the intermediate transfer member was irradiated with ultraviolet rays under predetermined conditions to create different states of ink viscosity, and the ink was transferred from the intermediate transfer member to the PET film. The ink transfer rate was calculated by weight measurement. The viscosity value of the ink droplet is a value obtained by collecting the ink that has been irradiated with ultraviolet rays under the same conditions and measuring the viscosity.

  In the experimental results shown in FIG. 11, the transfer rate is less than 90% xx, the transfer rate is 90% to less than 95%, the transfer rate is 95% to less than 99%, and the transfer rate is 99% to less than 99.9%. A, and a transfer rate of 99.9% or more was expressed as ◎.

  As shown in FIG. 11, when the viscosity of the ink is 3020 mPa · s or less, the transfer rate is less than 95%, and the image transferred to the PET film is visually degraded. On the other hand, when the viscosity of the ink is 5000 mPa · s (4870 mPa · s) or more, the ink transfer rate is 95% or more, and the image transferred to the PET film is not visually deteriorated.

  That is, it is preferable that the viscosity of the liquid (transferred liquid) that forms an image on the intermediate transfer body 16 when the image is transferred from the intermediate transfer body 16 to the recording medium 20 is 5000 mPa · s or more.

  In the ink jet recording apparatus 10 configured as described above, the processing liquid 30 having a viscosity of 15 mPa · s to 300 mPa · s at 25 ° C. is attached to a predetermined image forming region on the intermediate transfer member 16, and the thickness of the processing liquid 30 is increased. Since the ink 32 is ejected onto the image forming area in a state where t is 1.6 μm or more, a preferable image free from landing interference and beading is formed in the image forming area of the intermediate transfer body 16. .

  Furthermore, since the image is temporarily fixed on the intermediate transfer member 16 and then transferred to the recording medium 20, a good image free from bleeding and image distortion can be obtained.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 12 is a schematic overall configuration diagram of an inkjet recording apparatus 300 according to the second embodiment. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st Embodiment mentioned above, or is the same, and the description is abbreviate | omitted.

  As shown in FIG. 12, the intermediate transfer member 302 has a hollow cylindrical shape. In an aspect in which such a drum-shaped member is applied to the intermediate transfer member 302, an effect is obtained that the slow distance (the distance between the nozzle forming surface of the heads 12S, 12C, 12M, 12Y, and 12K and the intermediate transfer member 16) is stabilized. be able to.

  In addition, in the embodiment shown in FIG. 12, an ultraviolet light source 304 for fixing the image transferred to the recording medium 20 to the recording medium 20 is provided. The ultraviolet light source 304 can be of the same standard as the ultraviolet light source 18 that temporarily fixes the ink deposited on the intermediate transfer member 302 to the intermediate transfer member 302. However, when the image is fixed on the recording medium 20. Since the energy to be applied requires a larger amount of energy than the energy to temporarily fix the image on the intermediate transfer member 302, the ultraviolet light source 304 may be applied with an energy application capability greater than that of the ultraviolet light source 18. preferable.

  In the embodiment shown in FIG. 12, a flow path 306 communicating with the recovery unit 44 that recovers the residual processing liquid and residual ink removed from the intermediate transfer member 302, and a recycling processing unit 308 that performs a recycling process on the residual processing liquid and residual ink. And. Thus, by recycling the residual treatment liquid and the residual ink, it becomes possible to reuse the expensive ultraviolet curable polymerizable compound, which contributes to the reduction of the running cost of the inkjet recording apparatus 300.

  Note that the embodiment shown in FIG. 1 is also preferably provided with an ultraviolet light source 304 that fully cures the image transferred to the recording medium 20 in FIG. 12 and a recycling processing unit 308 that recycles the remaining processing liquid and remaining ink.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 13 is a schematic overall configuration diagram of an inkjet recording apparatus 400 according to the third embodiment. In addition, the same code | symbol is attached | subjected to the part which is the same as that of 1st, 2nd embodiment mentioned above, or similar, and the description is abbreviate | omitted.

  As shown in FIG. 13, the ink jet recording apparatus 400 includes a coating roller 402 as means for applying the treatment liquid 30 to the intermediate transfer body 16. According to the aspect in which the processing liquid 30 is applied using the application roller 402, the configuration of the means for applying the processing liquid to the intermediate transfer body 16 as compared with the aspect in which the processing liquid 30 is ejected by the processing liquid head 12S shown in FIG. Can be simplified, and a treatment liquid having a higher viscosity than that of the embodiment using the head 12S can be handled. The viscosity range of the treatment liquid suitable for treatment liquid application by the application roller 402 is 5 mPa · s to 300 mPa · s. In the embodiment using the head 12S, the preferred viscosity range of the treatment liquid is 5 mPa · s to 30 mPa · s. .

  In the embodiment using the application roller 402, the thickness of the treatment liquid 30 formed on the intermediate transfer body 16 is made uniform by appropriately adjusting the clearance and pressure between the intermediate transfer body 16 and the application roller 402. Can do. On the other hand, in the embodiment using the processing liquid head 12S shown in FIG. 1, the processing liquid 30 can be attached only to a necessary portion (a range where the ink 32 is ejected or a range slightly wider than the ink 32 is ejected). The consumption of processing liquid can be saved.

  FIG. 13 shows an aspect in which a cooling fan 404 is provided as means for temporarily fixing the processing liquid 30 and the ink 32 landed on the intermediate transfer body 16 to the intermediate transfer body 16 (increasing the viscosity of the processing liquid 30 and the ink 32). Show. The processing liquid 30 and the ink 32 that have landed on the intermediate transfer member 16 are cooled by a cooling fan 404 so that the viscosity thereof increases. The treatment liquid 30 does not necessarily have to increase the viscosity, and it is sufficient to temporarily fix the ink 32 to the intermediate transfer body 16 by increasing the viscosity of at least the ink 32.

  In the embodiment in which the cooling fan 404 is used as a means for temporarily fixing the ink 32 that has landed on the intermediate transfer member 16, the treatment liquid 30 does not need to contain an ultraviolet curable polymerizable compound, and the treatment liquid 30 in this case is a surfactant. And other additives. The ink 32 does not need to contain a polymerization initiator, and the ink 32 contains a pigment and other additives.

  In the embodiment shown in FIG. 13, the cooling means is exemplified as the means for temporarily fixing the ink landed on the intermediate transfer body 16, but the ink 32 (or the processing liquid 30 is obtained by electron beam irradiation or a chemical reaction between the processing liquid 30 and the ink 32. ) May be increased. The composition of the treatment liquid 30 and the ink 32 is appropriately determined according to the temporary fixing means (viscosity increasing means).

  The treatment liquid 30 may be temporarily fixed to the intermediate transfer body 16 or may not be temporarily fixed. In an embodiment in which the treatment liquid 30 is not temporarily fixed to the intermediate transfer member 16, it is preferable that the treatment liquid 30 be removed before transfer to the recording medium 20. As a means for removing the treatment liquid 30 on the intermediate transfer body 16, there is an aspect in which contact removal is performed using an absorption roller (absorbing member) including a nonwoven fabric or the like. When removing the treatment liquid, it is preferable that the pressure (absorbing force) of the absorbing roll can be adjusted so as not to remove the ink.

  In addition, the drum-shaped intermediate transfer body 302 of FIG. 12 may be applied to the embodiment shown in FIG. 13, or a recycle processing unit 308 for recycling the residual processing liquid and residual ink may be provided.

[Application example]
Next, application examples of the first to third embodiments described above will be described. In the ink jet recording apparatus 500 shown in FIG. 14, the heads 12 </ b> S, 12 </ b> C, 12 </ b> M, 12 </ b> Y, and 12 </ b> K are scanned in the same direction while scanning a short head that is less than the width of the intermediate transfer body 16 in the width direction. A shuttle scan type head that performs printing is applied.

  Such a short head is easier to manufacture than a full-line head corresponding to the full width of the intermediate transfer member 16 as shown in FIG. 3, and contributes to a reduction in manufacturing cost.

  Further, the inkjet recording apparatus 300 ′ shown in FIG. 15 has a hollow cylindrical shape and includes an intermediate transfer body 302 ′ having an ultraviolet light source 18 therein, and the ultraviolet light source is disposed in the outer direction of the intermediate transfer body 302 ′. It can be irradiated with ultraviolet rays.

  Further, the intermediate transfer member 302 ′ is made of a transparent member (or semi-transparent member) that can transmit ultraviolet rays, and is internally contained in the treatment liquid 30 and ink 32 ejected from the heads 12S, 12C, 12M, 12Y, and 12K. To have a structure capable of irradiating ultraviolet rays. A light shielding member 316 that blocks ultraviolet rays is provided inside the intermediate transfer member 302 ′ corresponding to the droplet ejection area 304 where the treatment liquid 30 and the ink 32 are ejected from the heads 12 S, 12 C, 12 M, 12 Y, and 12 K. . That is, the intermediate transfer member 302 ′ has a light shielding structure in which ultraviolet rays are not irradiated to the nozzle portions of the heads 12 S, 12 C, 12 M, 12 Y, and 12 K.

  The entire intermediate transfer body 16 does not need to be formed of a transparent member, and at least the ultraviolet irradiation region 318 irradiated with ultraviolet rays from the ultraviolet light source 18 may be formed of a transparent member (ultraviolet transmitting member). In a mode in which a transparent member is used for a part of the intermediate transfer member 302 ′, the light shielding member 316 in FIG. 15 can be omitted. Examples of the member that can transmit ultraviolet rays include glass and transparent resin.

  In the above embodiment, an ink jet recording apparatus that forms an image on the recording medium 20 by ejecting ink from nozzles provided in the print head has been described. However, the scope of application of the present invention is not limited to this, and other than ink such as resist. The present invention can be widely applied to an image forming apparatus that forms an image (three-dimensional shape) with a liquid, a liquid ejecting apparatus such as a dispenser that ejects a chemical solution, water, or the like from a nozzle (ejection hole).

1 is an overall configuration diagram of an inkjet recording apparatus according to the present invention. The figure explaining the state of the process liquid and ink droplet which adhered to the intermediate transfer body FIG. 1 is a plan view of a main part around a printing unit of the ink jet recording apparatus shown in FIG. Plane perspective view showing structural example of print head 4 (a) and 4 (b) are cross-sectional views along line 5-5 Schematic diagram showing the configuration of the supply system of the ink jet recording apparatus shown in FIG. 1 is a principal block diagram showing the system configuration of the ink jet recording apparatus shown in FIG. The figure explaining the degree of landing interference by the difference in the thickness of processing liquid Diagram explaining the degree of landing interference due to differences in the viscosity of the treatment liquid The figure explaining the degree of landing interference by the difference in the dynamic surface tension of processing liquid and ink Diagram explaining the relationship between ink viscosity and transfer rate Overall configuration diagram of an inkjet recording apparatus according to a second embodiment of the present invention Overall configuration diagram of an inkjet recording apparatus according to a third embodiment of the present invention 1 is an overall configuration diagram of an ink jet recording apparatus according to an application example of the present invention. 14 is a schematic configuration diagram of an ink jet recording apparatus according to another application example shown in FIG. The figure explaining the landing interference of the inkjet recording device which concerns on a prior art

Explanation of symbols

  10, 300, 300 ', 400, 500 ... inkjet recording apparatus, 12S, 12C, 12M, 12Y, 12K, 12SB, 50 ... head, 16, 302, 302' ... intermediate transfer member, 18, 304 ... ultraviolet light source, 20 ... Recording medium, 22 ... Transfer section, 24 ... Cleaning section, 30, 30 '... Processing liquid, 32 ... Ink, 402 ... Applying roller, 404 ... Cooling fan

Claims (12)

In an image forming apparatus for forming an image on an intermediate transfer member and transferring the image on the intermediate transfer member to a recording medium,
A liquid adhering means for adhering a first liquid having a viscosity of 15 mPa · s or more and 300 mPa · s or less at 25 ° C. to the intermediate transfer member;
In a state where the thickness of the first liquid is 1.6 μm or more on the intermediate transfer body, the second liquid containing a coloring material is deposited on the area of the intermediate transfer body to which the first liquid has adhered. A droplet ejection means,
Viscosity increasing means for increasing the viscosity of the second liquid;
Transfer means for transferring an image including dots formed by the second liquid formed on the intermediate transfer member to the recording medium;
An image forming apparatus comprising: A dynamic surface tension value gamma ₁ of the first surface age 0.1sec liquid, the dynamic surface tension value gamma ₂ in the second surface age 0.1sec liquid, is related by the following equation gamma ₁ <Γ ₂
The image forming apparatus according to claim 1, wherein:   The droplet ejection means includes a full line type liquid ejection head having a nozzle row in which nozzles for ejecting the second liquid are arranged over a length corresponding to the width direction of the intermediate transfer member. Item 3. The image forming apparatus according to Item 1 or 2. The second liquid contains a radiation curable polymerizable compound,
The image forming apparatus according to claim 1, wherein the viscosity increasing unit includes a radiation irradiation unit. The second liquid contains a radiation curable polymerizable compound,
The intermediate transfer body has a hollow cylindrical shape, and has radiation irradiation means for irradiating the second liquid deposited on the intermediate transfer body with radiation, and at least the radiation irradiation means. 4. The image forming apparatus according to claim 1, wherein the region irradiated with radiation is constituted by a member that transmits radiation. The second liquid contains an ultraviolet curable polymerizable compound, and at least one of the first liquid and the second liquid contains a polymerization initiator,
The image forming apparatus according to claim 1, wherein the viscosity increasing unit includes an ultraviolet irradiation unit.   The image forming apparatus according to claim 1, wherein the viscosity increasing unit sets the viscosity of the second liquid landed on the intermediate transfer member to 5000 mPa or more.   The image forming apparatus according to claim 1, further comprising a main curing unit that performs main curing on the image transferred to the recording medium.   9. The transfer unit according to claim 1, wherein the transfer unit includes a heating unit that heats the dots formed by the second liquid to a temperature equal to or higher than a glass transition point of the second liquid. Image forming apparatus. In an image forming apparatus for forming an image on an intermediate transfer member and transferring the image on the intermediate transfer member to a recording medium,
A liquid adhering step of adhering a first liquid having a viscosity of 15 mPa · s to 300 mPa · s at 25 ° C. to the intermediate transfer member;
In a state where the thickness of the first liquid is 1.6 μm or more on the intermediate transfer body, the second liquid containing a coloring material is deposited on the area of the intermediate transfer body to which the first liquid has adhered. A droplet ejection process,
A viscosity increasing step for increasing the viscosity of the second liquid;
A transfer step of transferring an image including dots formed by the second liquid formed on the intermediate transfer member to the recording medium;
An image forming method comprising: In the viscosity increasing step, the second liquid is cured,
The image forming method according to claim 10, wherein the transfer step includes a heating step of heating the second liquid cured in the viscosity increasing step to a temperature equal to or higher than a glass transition temperature of the second liquid. .   The image forming method according to claim 10, wherein the viscosity increasing step sets the second liquid to 5000 mPa · s or more.

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