Patent Grant
10384474
The present invention relates to an inkjet recording apparatus and an inkjet recording method.
Inkjet recording methods include an image forming system in which a liquid composition containing a coloring material (ink) is used to form an image on an intermediate transfer medium and the image is transferred onto a recording medium such as paper. In such a conventional system, a challenge is to achieve high transferability. U.S. Patent Application Publication No. 2008/0006176 discloses a system of heating a transfer medium to a temperature not lower than the minimum film-forming temperature (MFT) of a polymer emulsion in an ink.
Such a system of heating a medium to which an ink is ejected from an ink ejection head to form an image (hereinafter called an ejection target medium) as the system of heating a transfer medium disclosed in U.S. Patent Application Publication No. 2008/0006176 may cause condensation on the ink ejection head. If condensation is caused on a nozzle of an ink ejection head, an ink meniscus near the nozzle may be broken, and the ink may leak onto an ejection target medium.
In order to solve the problem, the present invention is intended to provide an inkjet recording apparatus that has a structure using an ink ejection head to form an image on a heated ejection target medium and suppresses condensation on the ink ejection head and to provide an inkjet recording method.
An aspect of the present invention provides an inkjet recording apparatus including
an ejection head configured to eject an ink to form an image,
a transfer medium configured to temporarily hold the image formed by the ejection head,
a head heater configured to heat the ejection head to a target temperature T1,
a transfer medium heater configured to heat the transfer medium,
a transfer unit configured to transfer the image, temporarily held on the transfer medium, onto a recording medium, and
a control unit configured to perform such adjustment as to satisfy a relationship of T1>T2, where T1 is the target temperature of the ejection head and T2 is a heated temperature of the transfer medium at an image forming position by the ejection head.
In the inkjet recording apparatus,
the ejection head is movable between the image forming position and an escape position displaced from the image forming position, and
the control unit is configured to perform such control as to start heating of the ejection head at the escape position and, after heating adjustment of the temperature of the ejection head to the target temperature T1, to move the ejection head to the image forming position.
Another aspect of the present invention provides an inkjet recording apparatus including
an ejection head configured to eject an ink to form an image,
a transfer medium configured to temporarily hold the image formed by the ejection head,
a head heater configured to heat the ejection head to a target temperature T1,
a transfer medium heater configured to heat the transfer medium,
a transfer unit configured to transfer the image, temporarily held on the transfer medium, onto a recording medium, and
a control unit configured to perform such adjustment as to satisfy a relationship of T1>T2, where T1 is the target temperature of the ejection head and T2 is a heated temperature of the transfer medium at an image forming position by the ejection head.
In the inkjet recording apparatus,
after heating adjustment of the ejection head to the target temperature T1, the control unit starts heating adjustment of the transfer medium at the image forming position.
Still another aspect of the present invention provides an inkjet recording apparatus including
an ejection head configured to eject an ink to form an image,
a transfer medium configured to temporarily hold the image formed by the ejection head,
a head heater configured to heat the ejection head to a target temperature T1,
a transfer medium heater configured to heat the transfer medium,
a transfer unit configured to transfer the image, temporarily held on the transfer medium, onto a recording medium, and
a control unit configured to perform such adjustment as to satisfy a relationship of T1>T2, where T1 is the target temperature of the ejection head and T2 is a heated temperature of the transfer medium at an image forming position by the ejection head.
In the inkjet recording apparatus,
the control unit allows the head heater to heat the ejection head at the image forming position and the transfer medium heater to heat the transfer medium and controls the head heater and the transfer medium heater in such a way that a temperature of the transfer medium is lower than a temperature of the ejection head before the ejection head reaches the target temperature T1.
Still another aspect of the present invention provides an inkjet recording apparatus including
an ejection head configured to eject an ink to form an image,
a support unit facing the ejection head at an image forming position and configured to support a recording medium on which an image is formed,
a head heater configured to heat the ejection head to a target temperature T1,
a support unit heater configured to heat the support unit, and
a control unit configured to perform such adjustment as to satisfy a relationship of T1>T2, where T1 is the target temperature of the ejection head and T2 is a heated temperature of the recording medium on the support unit at the image forming position by the ejection head.
In the inkjet recording apparatus,
the control unit is configured to perform such adjustment that, at startup of the apparatus, a temperature of the ejection head at the image forming position is maintained to be higher than a temperature of the support unit at the image forming position.
Still another aspect of the present invention provides an inkjet recording method using an inkjet recording apparatus that includes
an ejection head configured to eject an ink to form an image,
a transfer medium configured to temporarily hold the image formed by the ejection head,
a head heater configured to heat the ejection head,
a transfer medium heater configured to heat the transfer medium, and
a transfer unit configured to transfer the image, temporarily held on the transfer medium, onto a recording medium.
The inkjet recording method includes a head heating step of adjusting the ejection head by heating to a target temperature T1, and a transfer medium heating step of adjusting the transfer medium by heating, at an image forming position by the ejection head, to a heated temperature T2.
In the method, the temperature T1 and the temperature T2 satisfy a relationship of T1>T2.
In the head heating step, the heating of the ejection head is started at an escape position displaced from the image forming position and, after heating adjustment of the ejection head to the target temperature T1, the ejection head moves to the image forming position, and
in the transfer medium heating step, before or after the movement of the ejection head to the image forming position, a temperature of the transfer medium at the image forming position is adjusted by heating to the temperature T2.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.
In the system of heating an ejection target medium, condensation may be observed on an ink ejection head when the temperature of an ejection target medium (a transfer medium or a recording medium) under ink ejection is higher than the temperature of the ink ejection head. In the present invention, it has been found that the condensation can be prevented when the temperature of the ink ejection head at the time of image formation (called T1) is higher than the temperature of the ejection target medium under ink ejection (called T2). It has been also found that the condensation may be insufficiently prevented depending on temperature increase processes at the time of apparatus startup when heating of a transfer medium or a support member on a recording medium and heating of a head are started. Various studies on both the temperature increase processes demonstrate that it is important to perform such control that the temperature of the ejection head located at an image forming position at the time of apparatus startup is higher than the temperature of the transfer medium or the support member on a recording medium at the image forming position.
In other words, an inkjet recording apparatus pertaining to an embodiment of the present invention includes an ejection head configured to eject an ink to form an image, an ejection target medium on which an image is formed by the ejection head (a transfer medium or a recording medium), a head heater configured to heat the ejection head to a target temperature T1, and a heater configured to heat the ejection target medium. The inkjet recording apparatus is characterized by including a control unit configured to perform such adjustment as to satisfy the relationship of T1>T2 at the time of formation of the image where T1 is the temperature of the ejection head and T2 is the heated temperature of the ejection target medium at a position where an image is formed by the ejection head (image forming position).
An inkjet recording apparatus pertaining to an embodiment of the present invention will now be described with reference to drawings.
The inkjet recording apparatus of the embodiment includes the following two types. One is an inkjet recording apparatus in which an ink is ejected onto a transfer medium as an ejection target medium to form an ink image, then a liquid is absorbed from the ink image by a liquid absorbing member (liquid removing member), and the ink image is transferred to a recording medium. The other is an inkjet recording apparatus in which an ink image is formed on a recording medium such as paper and fabric as an ejection target medium and a liquid is absorbed from the ink image on the recording medium by a liquid absorbing member. In the present invention, the former inkjet recording apparatus is called a transfer type inkjet recording apparatus, and the latter inkjet recording apparatus is called a direct drawing type inkjet recording apparatus, for convenience hereinafter. The transfer medium in the transfer type inkjet recording apparatus is also called a medium for temporarily holding an ink image.
First, the transfer type inkjet recording apparatus will be described.
(Transfer Type Inkjet Recording Apparatus)
The transfer type inkjet recording apparatus 3100 of the present invention, as shown in
The transfer medium 3101 rotates around a rotating shaft 3102a of the support member 3102 as the center in the arrow direction A in
The movement of the liquid removing device 3105 synchronizes with the rotation of the transfer medium 3101. The ink image formed on the transfer medium 3101 undergoes the state of contact with the moving liquid absorbing member 3105a. During the contact state, the liquid absorbing member 3105a removes the liquid component from the ink image on the transfer medium. In the contact state, the liquid absorbing member 3105a is particularly preferably pressed against the transfer medium 3101 at a certain pressing force for helping the liquid absorbing member 3105a to function effectively.
The removal of the liquid component can be expressed from a different point of view as concentrating the ink constituting the image formed on the transfer medium. Concentrating the ink means that the proportion of the solid component contained in the ink, such as a coloring material and a polymer, increases relative to the liquid component contained in the ink owing to reduction in the liquid component.
The ink image after liquid component removal has a higher ink concentration than the ink image before liquid removal and is moved by the transfer medium 3101 to a transfer section 3111 at which the ink image comes into contact with a recording medium 3108 conveyed by recording medium conveying devices 3107. When a pressing member 3106 presses against the transfer medium 3101 while the ink image after liquid removal is in contact with the recording medium 3108, the ink image is transferred onto the recording medium 3108. The ink image transferred onto the recording medium 3108 is a reverse image of the ink image after liquid removal.
In the present embodiment, the reaction liquid is applied onto the transfer medium, and then inks are applied to form an image. Hence, in a non-imaging area where no image is formed by inks, the reaction liquid is not reacted with inks but is left. In the apparatus, the liquid absorbing member 3105a comes into contact with not only an image but also an unreacted reaction liquid and removes the liquid component in the reaction liquid together.
Although the above description expresses that the liquid component is removed from the image, the expression is not limited to removal of the liquid component only from the image but means that the liquid component is removed at least from the image on the transfer medium.
The liquid component may be any liquid component that does not have a certain shape but has flowability and a substantially constant volume.
The liquid component is exemplified by water and an organic solvent contained in an ink or a reaction liquid.
Members constituting the transfer type inkjet recording apparatus in the embodiment will next be described.
<Transfer Medium>
The transfer medium 3101 includes a surface layer having an image formation surface. As the material of the surface layer, various materials such as polymers and ceramics can be appropriately used, and a material having a high compressive elastic modulus is preferred from the viewpoint of durability and the like. Specific examples include acrylic polymers, acrylic silicone polymers, fluorine-containing polymers and condensates prepared by condensation of a hydrolyzable organic silicon compound. In order to improve the wettability of a reaction liquid, transferability and the like, a surface treatment may be performed. Examples of the surface treatment include flame treatment, corona treatment, plasma treatment, polishing treatment, roughening treatment, active energy ray-irradiation treatment, ozone treatment, surfactant treatment and silane coupling treatment. These treatments may be performed in combination. The surface layer may have any surface shape.
The transfer medium preferably includes a compressible layer having such a function as to absorb pressure fluctuations. A provided compressible layer absorbs deformation to disperse local pressure fluctuations, and satisfactory transferability can be maintained even during high speed printing. Examples of the member for the compressible layer include acrylonitrile-butadiene rubber, acrylic rubber, chloroprene rubber, urethane rubber and silicone rubber. It is preferred that at the time of molding of such a rubber material, predetermined amounts of a vulcanizing agent, a vulcanization accelerator and the like be added, and a foaming agent, hollow microparticles or a filler such as sodium chloride be further added as needed to form a porous material. In such a porous compressible layer, bubble portions are compressed with volume changes against various pressure fluctuations, thus deformation except in a compression direction is small, and more stable transferability and durability can be achieved. The porous rubber material includes a material having a continuous pore structure in which pores are connected to each other and a material having a closed pore structure in which pores are independent of each other. In the present invention, either of the structures may be used, or the structures may be used in combination.
The transfer medium preferably further includes an elastic layer between the surface layer and the compressible layer. As the member for the elastic layer, various materials such as polymers and ceramics can be appropriately used. From the viewpoint of processing characteristics and the like, various elastomer materials and rubber materials are preferably used. Specific examples include silicone rubber, fluorosilicone rubber, phenylsilicone rubber, fluororubber, chloroprene rubber, urethane rubber, nitrile rubber, ethylene-propylene rubber, natural rubber, styrene rubber, isoprene rubber, butadiene rubber, ethylene/propylene/butadiene copolymers and nitrile-butadiene rubber. Specifically, silicone rubber, fluorosilicone rubber and phenylsilicone rubber, which have a small compress set, are preferred from the viewpoint of dimensional stability and durability. These materials have a small temperature change in elastic modulus, and thus are preferred from the viewpoint of transferability.
Between the layers included in the transfer medium (the surface layer, the elastic layer, the compressible layer), various adhesives or double-sided adhesive tapes may be interposed in order to fix/hold the layers. The transfer medium may also include a reinforcing layer having a high compressive elastic modulus in order to suppress lateral elongation when installed in an apparatus or to maintain resilience. A woven fabric may be used as the reinforcing layer. The transfer medium can be prepared by combination of any layers made from the above materials.
The size of the transfer medium can be freely selected depending on the size of an intended print image. The shape of the transfer medium may be any shape and is specifically exemplified by a sheet shape, a roller shape, a belt shape and an endless web shape.
<Support Member>
The transfer medium 3101 is supported on a support member 3102. As the supporting manner of the transfer medium, various adhesives or double-sided adhesive tapes may be used. Alternatively, a transfer medium attached with an installing member made from a metal, ceramics, a polymer or the like may be supported on the support member 3102 by using the installing member.
The support member 3102 is required to have a certain structural strength from the viewpoint of conveyance accuracy and durability. As the material for the support member, metals, ceramics, polymers and the like are preferably used. Specifically, aluminum, iron, stainless steel, acetal polymers, epoxy polymers, polyimide, polyethylene, polyethylene terephthalate, nylon, polyurethane, silica ceramics, and alumina ceramics are particularly preferably used in terms of the rigidity capable of withstanding the pressure at the time of transfer, dimensional accuracy and reduction of the inertia during operation to improve the control responsivity. Combination use of these materials is also preferred.
<Transfer Medium Heating Device>
A transfer medium heating device (transfer medium heater) 3112 is a device for heating an ink image on the transfer medium before transfer. By heating an ink image, a polymer in the ink image is melted to improve the transferability to a recording medium. The heating temperature can be not lower than the minimum film-forming temperature (MFT) of a polymer. The MFT can be determined with an apparatus in accordance with a conventionally known technique including JIS K 6828-2: 2003 and ISO2115: 1996. From the viewpoint of transferability and image toughness, an ink image may be heated at a temperature higher than MFT by 10° C. or more or may be heated at a temperature higher than MFT by 20° C. or more. The transfer medium heating device 3112 may be a known heating device such as various lamps including an infrared lamp and a warm air fan. In terms of heating efficiency, an infrared heater can be used.
The temperature detecting device for the transfer medium 3101 may be any device, and a noncontact detecting device using, for example, luminance, color or infrared intensity or a contact detecting device using, for example, thermoelectromotive force, electric resistance or magnetism can be used. A noncontact detecting device is preferred from the viewpoint of deterioration in durability of the transfer medium 3101.
The location of the temperature detecting device for the transfer medium is not limited to particular sites, and the temperature can be detected in the transfer medium or from the outside.
<Temperature Control Section>
3115 is a control unit for controlling the operations of the ink applying device 3104 and the transfer medium heating device 3112 (heating adjustment, movement, for example) in response to temperature information from the temperature detecting devices 3113, 3114 and a device for detecting the temperature of an ejection head in the ink applying device 3104 (not shown). The control unit 3115 can further control the operations of the reaction liquid applying device, the liquid removing device, the pressing member for transfer, the recording medium conveying device, the transfer medium cleaning member, the transfer medium cooling member and the like.
<Reaction Liquid Applying Device>
The inkjet recording apparatus of the embodiment includes a reaction liquid applying device 3103 for applying a reaction liquid onto the transfer medium 3101. The reaction liquid applying device 3103 in
The reaction liquid applying device 3103 may be any device capable of applying a reaction liquid onto a transfer medium 3101, and conventionally known various devices can be appropriately used. Specific examples include a gravure offset roller, an inkjet head, a die coater and a blade coater. The application of a reaction liquid by the reaction liquid applying device may be performed before the ink application or after the ink application as long as the reaction liquid can be mixed (reacted) with an ink on the transfer medium. Preferably, the reaction liquid is applied before the ink application. The application of a reaction liquid before the ink application enables suppression of bleeding, which is caused by mixing of inks applied adjacent to each other, or beading, which is caused by pulling of a previously applied ink by a subsequently applied ink, at the time of image recording by the inkjet system.
<Reaction Liquid>
The reaction liquid causes aggregation of a component having an anionic group (a polymer, a self-dispersible pigment, for example) in an ink when coming into contact with the ink, and contains a reactant. Examples of the reactant include cationic components such as a polyvalent metal ion and a cationic polymer and organic acids.
Examples of the polyvalent metal ion include divalent metal ions such as Ca2+, Cu2+, Mg2+, Sr2+, Ba2+ and Zn2+; and trivalent metal ions such as Fe3+, Cr3+, Y3+ and Al3+. To allow the reaction liquid to contain a polyvalent metal ion, a polyvalent metal salt (optionally a hydrate) formed by bonding a polyvalent metal ion with an anion can be used. Examples of the anion include inorganic anions such as Cl−, Br−, I−, ClO−, ClO2−, ClO3−, ClO4−, NO2−, NO3−, SO42−, CO32−, HCO3−, PO43−, HPO42− and H2PO4−; and organic anions such as HCOO−, (COO−)2, COOH(COO−), CH3COO−, C2H4(COO−)2, C6H5COO−, C6H4(COO−)2 and CH3SO3−. When a polyvalent metal ion is used as the reactant, the content (% by mass) in terms of polyvalent metal salt in the reaction liquid is preferably 1.00% by mass or more to 10.00% by mass or less relative to the total mass of the reaction liquid.
The reaction liquid containing an organic acid has a buffer capacity in an acidic region (a pH of lower than 7.0, preferably a pH of 2.0 to 5.0), thus makes an anionic group of a component present in an ink into an acid form, and causes the component to aggregate. Examples of the organic acid include monocarboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furan carboxylic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid and coumaric acid, and salts thereof; dicarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid and tartaric acid, and salts and hydrogen salts thereof; tricarboxylic acids, such as citric acid and trimellitic acid, and salts and hydrogen salts thereof, and tetracarboxylic acids such as pyromellitic acid and salts and hydrogen salts thereof.
Examples of the cationic polymer include a polymer having a primary to tertiary amine structure and a polymer having a quaternary ammonium salt structure. Specific examples include polymers having a structure such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine and guanidine. In order to improve the solubility in the reaction liquid, a cationic polymer may be used in combination with an acidic compound, or a cationic polymer may be subjected to quaternarization treatment. When a cationic polymer is used as the reactant, the content (% by mass) of the cationic polymer in the reaction liquid is preferably 1.00% by mass or more to 10.00% by mass or less relative to the total mass of the reaction liquid.
As components other than the reactant in the reaction liquid, those substantially the same as the water, the water-soluble organic solvents and the additional additives exemplified later as usable in the ink can be used.
<Transfer Medium Cleaning Device>
The inkjet recording apparatus of the embodiment includes a transfer medium cleaning device (transfer medium cleaning member) 3109 for cleaning the transfer medium 3101. The transfer medium cleaning device 3109 in
<Transfer Medium Cooling Device>
The inkjet recording apparatus of the embodiment includes a transfer medium cooling device (transfer medium cooling member) 3110 for cooling the transfer medium 3101. The transfer medium cooling device 3110 in
<Ink Applying Device>
The inkjet recording apparatus of the embodiment includes an ink applying device 3104 for applying an ink to the transfer medium 3101. On the transfer medium, a reaction liquid and an ink are mixed, and the reaction liquid and the ink form an ink image. The liquid removing device 3105 then absorbs a liquid component from the ink image.
In the present embodiment, the ink applying device 3104 includes a full-line circulation head (hereinafter also called an ejection head) extending in the Y-direction. On the ejection head, nozzles are arranged in a region covering the width of an image recording area on a usable recording medium with the maximum size. The ejection head has, on the bottom face (the transfer medium 3101 side), an ink ejection surface having nozzle openings, and the ink ejection surface faces the surface of the transfer medium 3101 while a small clearance (about several millimeters) is interposed therebetween.
In the case of the present embodiment, each recording head 3 is a full-line head extending in the Y-direction, and nozzles are arranged in a region covering the width of an image recording area on a usable recording medium with the maximum size. The recording head 3 has, on the bottom face, an ink ejection surface having nozzle openings, and the ink ejection surface faces the surface of the transfer medium 3101 while a small clearance (for example, several millimeters) is interposed therebetween. In the case of the embodiment, the transfer medium 3101 has such a structure as to cyclically move on a circular orbit, and thus a plurality of recording heads 3 are radially arranged.
Each nozzle has an ejection element. The ejection element is, for example, an element that generates a pressure in a nozzle to eject an ink in the nozzle, and an inkjet head technique for a known inkjet printer is applicable. Examples of the ejection element include an element that causes film boiling of an ink by an electrothermal transducer to form bubbles and ejects the ink, an element that ejects an ink by an electromechanical converter and an element that ejects an ink by using static electricity. From the viewpoint of high-density recording at high speed, an ejection element using an electrothermal transducer can be used.
In the case of the present embodiment, nine recording heads 3 are provided. The recording heads 3 eject different types of inks from each other. The different types of inks are, for example, inks different in coloring material, and are inks including a yellow ink, a magenta ink, a cyan ink and a black ink. A single recording head 3 ejects a single type of an ink, but a single recording head 3 may eject a plurality of types of inks. When a plurality of recording heads 3 are provided as above, some of the recording heads may eject an ink containing no coloring material (for example, a clear ink).
A carriage 1100 supports the plurality of recording heads 3. The end of each recording head 3 at the ink ejection surface side is fixed to the carriage 1100. With this structure, the clearance between the ink ejection surface and the surface of the transfer medium 3101 can be more precisely maintained. As shown in
The guide members RL extends over the transfer medium 3101 and the recovery unit 12. The recording heads 3 are displaceable by the guidance of the guide members RL between an ejection position POS1 of the recording heads 3 indicated by solid lines and a recovery position POS3 of the recording heads 3 indicated by broken lines and are moved by a driving mechanism not shown in the drawings.
The ejection position POS1 is an image forming position at which recording heads 3 eject inks to the transfer medium 3101 and is a position at which the ink ejection surfaces of the recording heads 3 face the surface of the transfer medium 3101. The recovery position POS3 is an escape position displaced from the ejection position POS1 and is a position at which the recording heads 3 are located above the recovery unit 12. The recovery unit 12 can perform recovery treatment of the recording heads 3 when the recording heads 3 are located at the recovery position POS3. In the case of the embodiment, the recovery treatment can also be performed while the recording heads 3 are still moving toward the recovery position POS3. A preliminary recovery position POS2 is between the ejection position POS1 and the recovery position POS3, and the recovery unit 12 can perform preliminary recovery treatment of the recording heads 3 at the preliminary recovery position POS2 while the recording heads 3 are moving from the ejection position POS1 toward the recovery position POS3.
The recording device 1000 in the embodiment includes a heater for the ejection heads in order to prevent condensation, and thus heat may increase the viscosity of an ink. However, by using such a head capable of circulating an ink as shown below, the viscosity increase of an ink can be suppressed. The structure of a full-line circulation head will be described.
<Full-Line Circulation Head>
In the first circulation mode, an ink in a main tank 1006 is supplied by a replenishing pump 1005 to the buffer tank 1003 and then is supplied by a second circulation pump 1004 through a liquid connection section 111 to a liquid supply unit 220 of the liquid ejection head 3. Next, the ink is adjusted by a negative pressure control unit 230 connected to the liquid supply unit 220 to have two different negative pressures (high pressure, low pressure), and the divided inks circulate through two flow paths for high pressure and low pressure. The inks in the liquid ejection head 3 circulate in the liquid ejection head by the action of the first circulation pump (for high pressure) 1001 and the first circulation pump (for low pressure) 1002 located downstream of the liquid ejection head 3, then are discharged through liquid connection sections 111 from the liquid ejection head 3, and return to the buffer tank 1003.
The buffer tank 1003 as a sub tank is connected to the main tank 1006, has an air communication hole (not shown) for communication between the inside and the outside of the tank and can discharge bubbles in the ink to the outside. Between the buffer tank 1003 and the main tank 1006, the replenishing pump 1005 is provided. The replenishing pump 1005 sends an ink consumed by ink ejection (discharge) from ejection ports of the liquid ejection head 3, for example, by recording with ink ejection or suction recovery, from the main tank 1006 to the buffer tank 1003.
The two first circulation pumps 1001, 1002 draw a liquid from the liquid connection sections 111 of the liquid ejection head 3 and send the liquid to the buffer tank 1003. The first circulation pump is preferably a displacement pump capable of quantitatively sending a liquid. Specific examples include a tube pump, a gear pump, a diaphragm pump and a syringe pump. The first circulation pump may be a pump having a typical constant flow valve or a relief valve at the pump outlet to achieve a constant flow rate, for example. To drive the liquid ejection head 3, the first circulation pump (for high pressure) 1001 and the first circulation pump (for low pressure) 1002 are activated, and an ink flows at a predetermined flow rate through the common supply flow path 211 and the common collection flow path 212. By allowing an ink to flow in this manner, the temperature of the liquid ejection head 3 at the time of recording is maintained at an optimum temperature. The predetermined flow rate at the time of driving of the liquid ejection head 3 is preferably set to a certain flow rate or more that can maintain such differences in temperature among recording element substrates 10 in the liquid ejection head 3 as not to affect recorded image qualities. If an excessively high flow rate is set, pressure drop in flow paths in the liquid ejection unit 300 increases negative pressure differences among the recording element substrates 10, causing density unevenness on an image. Hence, the flow rate is preferably set in consideration of temperature differences and negative pressure differences among the recording element substrates 10.
The negative pressure control unit 230 is provided on a route between the second circulation pump 1004 and the liquid ejection unit 300. The negative pressure control unit 230 functions to maintain the pressure at the downstream side from the negative pressure control unit 230 (i.e., the liquid ejection unit 300 side) at a preset constant pressure even when the flow rate of an ink in a circulation system fluctuates due to differences in ejection amount per unit area, for example. Two pressure adjustment mechanisms for high pressure (H) and low pressure (L) included in the negative pressure control unit 230 may be any mechanism capable of controlling the pressure at the downstream side from the negative pressure control unit 230 within a certain fluctuation range of an intended set pressure as the center. As an example, a mechanism similar to what is called a “pressure-reducing regulator” can be adopted. In the circulation flow path in the embodiment, the second circulation pump 1004 is used to press the upstream side of the negative pressure control unit 230 through the liquid supply unit 220. With such a structure, the effect of the hydraulic head pressure of the buffer tank 1003 on the liquid ejection head 3 can be suppressed, and thus the layout of the buffer tank 1003 in the recording device 1000 can be more freely designed.
The second circulation pump 1004 may be any pump that has a pump head pressure not lower than a certain value, within the range of an ink circulation flow rate when the liquid ejection head 3 is driven, and a turbo pump or a displacement pump can be used, for example. Specifically, a diaphragm pump is applicable, for example. In place of the second circulation pump 1004, a hydraulic head tank located to give a certain hydraulic head difference with respect to the negative pressure control unit 230 is also applicable, for example.
As shown in
As described above, in the liquid ejection unit 300, such a flow that while a liquid flows in the common supply flow path 211 and the common collection flow path 212, some of the liquid passes through each recording element substrate 10 is generated. Hence, heat generated in each recording element substrate 10 can be exhausted to the outside of the recording element substrate 10 by an ink flowing in the common supply flow path 211 and the common collection flow path 212. With such a structure, when recording is performed with the liquid ejection head 3, an ink flow can be generated also in an ejection port or a pressure chamber not ejecting an ink. This reduces the viscosity of an ink causing viscosity increase in an ejection port, and thus the increase in viscosity of an ink can be suppressed. In addition, an ink causing viscosity increase or foreign substances in an ink can be discharged to the common collection flow path 212. Hence, the liquid ejection head 3 of the embodiment enables high quality image recording at high speed.
<Description of Second Circulation Mode>
In the second circulation mode, as shown in
The negative pressure control unit 230 in the second circulation mode functions to stabilize pressure fluctuations at the upstream side of the negative pressure control unit 230 (i.e., the liquid ejection unit 300 side) within a certain range of a preset pressure as the center even when the flow rate fluctuates due to differences in ejection amount per unit area. In the circulation flow path in the embodiment, the second circulation pump 1004 is used to reduce the pressure at the downstream side of the negative pressure control unit 230 through a liquid supply unit 220. With such a structure, the effect of the hydraulic head pressure of the buffer tank 1003 on the liquid ejection head 3 can be suppressed, and thus the layout of the buffer tank 1003 in the recording device 1000 can be more freely selected. In place of the second circulation pump 1004, a hydraulic head tank located to give a certain hydraulic head difference with respect to the negative pressure control unit 230 is also applicable, for example. In the second circulation mode, the negative pressure control unit 230 includes two pressure adjustment mechanisms H, L that are set at different control pressures from each other as with the above first circulation mode. Of the two negative pressure adjustment mechanisms, the mechanism for setting a high pressure (indicated by H in
With such a second circulation mode, a similar ink flow state to that in the first circulation mode is achieved in the liquid ejection unit 300, but this mode has two different advantages from the case of the first circulation mode. The first is that the negative pressure control unit 230 is located at the downstream side of the liquid ejection head 3 in the second circulation mode, and thus dust or foreign substances generated from the negative pressure control unit 230 are unlikely to flow into the liquid ejection head 3. The second is that in the second circulation mode, the maximum required flow amount supplied from the buffer tank 1003 to the liquid ejection head 3 can be smaller than that in the case of the first circulation mode.
The total flow amount in the common supply flow path 211 and the common collection flow path 212 when an ink circulates during recording standby is regarded as a flow amount A. The value of a flow amount A is defined as the minimum flow amount required to control the temperature difference in a liquid ejection unit 300 within an intended range, for example, for temperature adjustment of a liquid ejection head 3 at the time of recording standby. The ejection flow amount when all the ejection ports of the liquid ejection unit 300 eject an ink (whole ejection) is defined as a flow amount F (ejection amount per ejection port×ejection frequency per unit time×number of ejection ports).
<Description of Liquid Ejection Head Structure>
The structure of a liquid ejection head 3 pertaining to the first embodiment will be described.
The chassis 80 includes a liquid ejection unit support section 81 and an electrical wiring board support section 82, supports the liquid ejection unit 300 and the electrical wiring board 90, and ensures the rigidity of the liquid ejection head 3. The electrical wiring board support section 82 is for supporting the electrical wiring board 90 and is fixed to the liquid ejection unit support section 81 by screwing. The liquid ejection unit support section 81 has the function of correcting a warpage or deformation of the liquid ejection unit 300 to ensure the relative location accuracy of a plurality of recording element substrates 10 and accordingly suppresses streaky lines or unevenness on a recorded product. Hence, the liquid ejection unit support section 81 preferably has a sufficient rigidity, and the material thereof is preferably a metal material such as SUS and aluminum or a ceramic such as alumina. The liquid ejection unit support section 81 has openings 83, 84 into which joint rubbers 100 are inserted. A liquid supplied from a liquid supply unit 220 is introduced through a joint rubber into a third flow path forming member 70 included in the liquid ejection unit 300.
The liquid ejection unit 300 includes a plurality of ejection modules 200 and a flow path forming member 210, and onto the face of the liquid ejection unit 300 facing a recording medium, a cover member 130 is attached. The cover member 130 is, as shown in
Next, the structure of the flow path forming member 210 included in the liquid ejection unit 300 will be described. As shown in
Communication holes 72 of the third flow path forming member 70 (see
The first to third flow path forming members are preferably made from a material having corrosion resistance to a liquid and having a low coefficient of linear expansion. As the material, a composite material (polymer material) containing alumina, a liquid crystal polymer (LCP), polyphenylsulfide (PPS) or polysulfone (PSF) as a base material and containing an inorganic filler including silica microparticles or fibers can be preferably used, for example. As the formation method of the flow path forming member 210, three flow path forming members may be stacked and bonded to each other, or when a polymer composite material is used as the material, a joining method using welding may be used.
In the flow path forming member 210, common supply flow paths 211 (211a, 211b, 211c, 211d) and common collection flow paths 212 (212a, 212b, 212c, 212d) extending in the longitudinal direction of the liquid ejection head 3 are formed for the respective colors. The common supply flow path 211 for each color is connected to a plurality of individual supply flow paths (213a, 213b, 213c, 213d) defined by individual flow path grooves 52 through communication holes 61. The common collection flow path 212 for each color is connected to a plurality of individual collection flow paths (214a, 214b, 214c, 214d) defined by individual flow path grooves 52 through communication holes 61. With such a flow path structure, an ink can be aggregated from a corresponding common supply flow path 211 through the individual supply flow paths 213 to the recording element substrates 10 located at the center of the flow path forming member. An ink can also be collected from the recording element substrates 10 through the individual collection flow paths 214 to the corresponding common collection flow path 212.
The common supply flow path 211 for each color is connected to a negative pressure control unit 230 (for high pressure) for the corresponding color through the liquid supply unit 220, and the common collection flow path 212 is connected to the corresponding negative pressure control unit 230 (for low pressure) through the liquid supply unit 220. The negative pressure control units 230 generate a differential pressure (difference in pressure) between the common supply flow path 211 and the common collection flow path 212. With this structure, in the liquid ejection head in the present embodiment including connected flow paths as shown in
<Description of Ejection Module>
<Description of Structure of Recording Element Substrate>
As shown in
With reference to
In the first circulation mode shown in
<Description of Positional Relation Between Recording Element Substrates>
(Inkjet Recording Apparatus in Second Embodiment)
Next, the structure of an inkjet recording apparatus 2000 and a liquid ejection head 2003 in a second embodiment that differs from the above inkjet recording apparatus in the first embodiment will be described. In the following description, only different portions from the recording apparatus in the first embodiment are mainly described, and the same portions as in the apparatus in the first embodiment are not described.
<Description of Inkjet Recording Apparatus>
A recording apparatus 2000 in the present embodiment differs from the first embodiment in that four single-color liquid ejection heads 2003 corresponding to cyan C, magenta M, yellow Y, and black K inks are arranged in parallel to perform full color recording on a recording medium. Only a single ejection port array can be used for a single color in the first embodiment, whereas 20 ejection port arrays can be used for a single color in the present embodiment. Hence, recording data can be appropriately distributed to a plurality of ejection port arrays for recording, and this enables ultrahigh-speed recording. In addition, even when an ejection port fails to eject an ink, an ejection port in another array located at a position corresponding to the failing ejection port in the conveying direction of a recording medium can complementarily eject the ink, thus improving the reliability. Such an apparatus is preferred for business recording or the like. As with the first embodiment, a supply system, a buffer tank 1003 and a main tank 1006 of the recording apparatus 2000 (see
<Description of Circulation Route>
As with the first embodiment, the liquid circulation route between the recording apparatus 2000 and the liquid ejection head 2003 can be the first or second circulation mode shown in
<Description of Structure of Liquid Ejection Head>
The two negative pressure control units 2230 are configured to control pressures at relatively high and low negative pressures different from each other. When negative pressure control units 2230 for high pressure and for low pressure are installed on the respective ends of the liquid ejection head 2003 as shown in
Next, the flow path forming member 2210 of the liquid ejection unit 2300 will be specifically described. As shown in
<Description of Ejection Module>
<Description of Structure of Recording Element Substrate>
The description in the above embodiments is not intended to limit the scope of the invention. As an example, the present embodiment has described a thermal system that uses heat generation elements for generating bubbles to eject a liquid, but the present invention is also applicable to liquid ejection heads using a piezoelectric system or other various liquid ejection systems.
The present embodiment has described an inkjet recording apparatus (recording device) in which a liquid such as an ink is circulated between a tank and a liquid ejection head, but other modes may be used. In another exemplary mode, an ink is not circulated, but two tanks are provided at an upstream side and a downstream side of a liquid ejection head to allow an ink to flow from one tank to the other tank, thereby allowing the ink to flow in a pressure chamber.
As shown in these figures, the above-mentioned ink circulation generates an ink flow 17 through a pressure chamber 23 with a recording element 15 on a substrate 11 of the liquid ejection head and through flow path 24 before and after the pressure chamber. In other words, a differential pressure generating an ink circulation allows an ink supplied from a liquid supply path (supply flow path) 18 through a supply port 17a provided in the substrate 11 passes through the flow path 24, the pressure chamber 23 and the flow path 24 and flows through a collection port 17b to a liquid collection path (discharge flow path) 19.
While an ink flows as above, the space from the recording element (energy generating element) 15 to an ejection port 13 located above the element is filled with the ink at the time of non-ejection, and an ink meniscus (ink interface 13a) is formed near the end of the ejection port 13 in the ejection direction. In
<Relationship Among P, W and H>
In the liquid ejection head of the present embodiment, the relationship among the height H of the flow path 24, the thickness P of an orifice plate (flow path forming member 12) and the length (diameter) W of the ejection port is defined in the following description.
In
In the present embodiment, in order to suppress the increase in viscosity of an ink due to evaporation of the ink from an ejection port 13 or the like, the following structure is adopted.
In the present embodiment, the height H of the flow path 24, the length P of the ejection port section 13b and the length W of the ejection port section 13b in the ink flow direction satisfy the relationship of Formula (1).
H−0.34×P−0.66×W>1.5 Formula (1)
In the liquid ejection head in the embodiment satisfying the condition, as shown in
In the present embodiment, the neighboring region corresponding to an opening 21a or opening 21b is regarded as a temperature control adjustment area 101 as shown in
When the temperature sensor 103 in an area 101 detects a temperature not lower than a certain threshold T1 temperature, the temperature control heater 102 in the area is stopped, and when the temperature sensor detects a temperature lower than the threshold T1, the corresponding temperature control heater 102 is driven for heating. In this manner, a target temperature T1 can be maintained. With this structure, an ink having a relatively low temperature flows near the openings 21a through which the ink flows into the recording element substrate, and thus the corresponding temperature sensors 103 detect relatively low temperatures. In the resulting temperature control, heating with the corresponding temperature control heaters 102 is performed more frequently or for a longer time. In contrast, an ink near the openings 21b through which the ink flows out has a comparatively high temperature, and thus the corresponding temperature sensors 103 detect relatively high temperatures. In the resulting temperature control, heating with the corresponding temperature control heaters 102 is performed less frequently or for a shorter time or the heating is not performed. As a result, ink temperature fluctuations that can be caused along ejection port arrays by ink circulation can be suppressed. In the present embodiment, the number of openings can be the same as the number of temperature control areas, and the member of temperature sensors or temperature control heaters can be reduced. The temperature control of the liquid ejection head can be performed at the preliminary recovery position POS2 or the recovery position POS3 as escape positions displaced from the image forming position shown in
The present invention is not limited by the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention.
The ink application amount can be expressed by an image density or an ink thickness, for example. In the present embodiment, the mass of each ink dot is multiplied by the number of dots applied, and the result is divided by a printed area to give an average as the ink application amount (g/m2). The maximum ink application amount in an image region means an ink application amount in at least an area of 5 mm2 or more within a region used as information of an ejection target medium (transfer medium) from the viewpoint of removing the liquid component in an ink.
The ink applying device 3104 may include a plurality of inkjet heads in order to apply various color inks onto an ejection target medium. For example, when a yellow ink, a magenta ink, a cyan ink and a black ink are used to form a color image, the ink applying device includes four inkjet heads each ejecting a corresponding ink of the four inks onto an ejection target medium. These inkjet heads are arranged in the X-direction.
The ink applying device may include an inkjet head for ejecting a clear ink that contains no coloring material, or contains a coloring material at an extremely small content, and is substantially transparent. The clear ink can be used to form an ink image together with a reaction liquid and color inks. For example, the clear ink can be used to improve the glossiness of an image. To express a glossy appearance on an image after transfer, appropriate polymer components can be added, and the ejection position of the clear ink can be adjusted. The clear ink is preferably present more closely to the surface layer than the color ink in a final recorded product, and thus the clear ink is applied onto the transfer medium 3101 before the application of color inks in a transfer type recording apparatus. Hence, in the moving direction of the transfer medium facing the ink applying device, the inkjet head for a clear ink can be provided at the upstream side from the inkjet heads for color inks.
Separately from the clear ink for gloss, a clear ink can be used to improve the transferability of an image from the transfer medium 3101 to a recording medium. For example, a large amount of a component exhibiting higher tackiness than that of color inks is added, and a resulting clear ink can be applied onto the color inks and thus can be used as a transferability improving liquid. For example, in the moving direction of the transfer medium facing the recording device 1000, an inkjet head for the clear ink for improving transferability is provided at the downstream side from the inkjet heads for color inks. After application of color inks onto the transfer medium, the clear ink is applied onto the transfer medium with the color inks, and consequently the clear ink is present on the outermost face of an ink image. When the ink image is transferred to a recording medium by the transfer section 3111, the clear ink on the surface of the ink image adheres to the recording medium 3108 at a certain adhesive power, and this facilitates the transfer of the ink image after liquid removal to the recording medium 3108.
<Ink>
Each component of the ink applied to the present embodiment will be described.
(Coloring Material)
As the coloring material contained in the ink applied to the present embodiment, a pigment or a dye can be used. In the ink, the content of the coloring material is preferably 0.5% by mass or more to 15.0% by mass or less and more preferably 1.0% by mass or more to 10.0% by mass or less relative to the total mass of the ink.
The pigment usable as the coloring material is not limited to particular types. Specific examples of the pigment include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, imidazolone pigments, diketopyrrolopyrrole pigments and dioxazine pigments. These pigments can be used singly or in combination of two or more of them as needed. The dispersion manner of the pigment is not limited to particular manners. For example, a polymer-dispersed pigment dispersed with a polymer dispersant or a self-dispersible pigment in which a hydrophilic group such as an anionic group is bonded directly or through an additional atomic group to the particle surface of a pigment can be used. Needless to say, pigments different in dispersion manners can be used in combination.
As the polymer dispersant for dispersing a pigment, a known polymer dispersant used in an aqueous inkjet ink can be used. Specifically, an acrylic, water-soluble polymer dispersant having both a hydrophilic unit and a hydrophobic unit in the molecular chain is preferably used in the embodiment. Examples of the polymer, in terms of structure, include a block copolymer, a random copolymer, a graft copolymer and combinations of them.
The polymer dispersant in the ink may be in a dissolved state in a liquid medium or in a dispersed state as polymer particles in a liquid medium. In the present invention, the water-soluble polymer is a polymer that does not form particles having such a particle diameter as to be determined by dynamic light scattering when the polymer is neutralized with an equivalent amount of an alkali to the acid value thereof.
The hydrophilic unit (unit having a hydrophilic group such as an anionic group) can be formed by polymerizing a monomer having a hydrophilic group, for example. Specific examples of the monomer having a hydrophilic group include acidic monomers having an anionic group, such as (meth)acrylic acid and maleic acid and anionic monomers including anhydrides and salts of these acidic monomers. Examples of the cation included in a salt of an acidic monomer include a lithium ion, a sodium ion, a potassium ion, an ammonium ion and organic ammonium ions.
The hydrophobic unit (unit not having a hydrophilic group such as an anionic group) can be formed by polymerizing a monomer having a hydrophobic group, for example. Specific examples of the monomer having a hydrophobic group include monomers having an aromatic ring, such as styrene, α-methylstyrene and benzyl (meth)acrylate; and monomers having an aliphatic group, such as ethyl (meth)acrylate, methyl (meth)acrylate and butyl (meth)acrylate (i.e., (meth)acrylate monomers).
The polymer dispersant preferably has an acid value of 50 mg KOH/g or more to 550 mg KOH/g or less and more preferably 100 mg KOH/g or more to 250 mg KOH/g or less. The polymer dispersant preferably has a weight average molecular weight of 1,000 or more to 50,000 or less. The mass ratio of the content (% by mass) of the pigment to the content of the polymer dispersant (pigment/polymer dispersant) is preferably 0.3 times or more to 10.0 times or less.
As the self-dispersible pigment, a pigment in which an anionic group such as a carboxylic acid group, a sulfonic acid group and a phosphonic acid group is bonded directly or through an additional atomic group (—R—) to the particle surface of the pigment can be used. The anionic group may be either an acid form or a salt form. An anionic group in a salt form may dissociate partly or completely. Examples of the cation as the counter ion of an anionic group in a salt form include alkali metal cations; ammonium; and organic ammoniums. Specific examples of the additional atomic group (—R—) include linear or branched alkylene groups having 1 to 12 carbon atoms, arylene groups such as a phenylene group and a naphthylene group, an amido group, a sulphonyl group, an amino group, a carbonyl group, an ester group, and an ether group. The additional atomic group may be a combination group of them.
The dye usable as the coloring material is not limited to particular types, but a dye having an anionic group is preferably used. Specific examples of the dye include azo dyes, triphenylmethane dyes, (aza)phthalocyanine dyes, xanthene dyes and anthrapyridone dyes. These dyes can be used singly or in combination of two or more of them as needed.
What is called a self-dispersible pigment that is dispersible due to surface modification of a pigment itself and eliminates the use of the dispersant is also preferably used in the present embodiment.
(Polymer Particles)
The ink applied to the present embodiment can contain polymer particles. The polymer particles do not necessarily contain a coloring material. Polymer particles may have the effect of improving image quality or fixability and thus are preferred.
The material of the polymer particles usable in the present embodiment is not limited to particular materials, and known polymers can be appropriately used. Specific examples include polymer particles made of various materials such as an olefinic polymer, a styrenic polymer, a urethane polymer and an acrylic polymer. The polymer particles preferably have a weight average molecular weight (Mw) of 1,000 or more to 2,000,000 or less. The polymer particles preferably have a volume average particle diameter of 10 nm or more to 1,000 nm or less and more preferably 100 nm or more to 500 nm or less, where the volume-average particle diameter is determined by dynamic light scattering. In the ink, the content (% by mass) of the polymer particles is preferably 1.0% by mass or more to 50.0% by mass or less and more preferably 2.0% by mass or more to 40.0% by mass or less relative to the total mass of the ink.
(Aqueous Medium)
The ink usable in the present embodiment can contain water or an aqueous medium as a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. In an aqueous ink, the content (% by mass) of water is preferably 50.0% by mass or more to 95.0% by mass or less relative to the total mass of the ink. In an aqueous ink, the content (% by mass) of the water-soluble organic solvent is preferably 3.0% by mass or more to 50.0% by mass or less relative to the total mass of the ink. As the water-soluble organic solvent, any solvent usable in inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds and sulfur-containing compounds, can be used, and the ink can contain one or more water-soluble organic solvents.
(Additional Additives)
The ink usable in the present embodiment can contain, in addition to the above components, various additives such as an antifoaming agent, a surfactant, a pH adjuster, a viscosity modifier, an anticorrosive, an antiseptic agent, an antifungal agent, an antioxidant, a reduction inhibitor and a water-soluble polymer, as needed.
<Liquid Removing Device>
A liquid removing device 3105 in the embodiment is a liquid absorbing device including a liquid absorbing member 3105a and a pressing member for liquid absorption 3105b that presses the liquid absorbing member 3105a against an ink image on the transfer medium 3101. The liquid absorbing member 3105a and the pressing member 3105b may have any shape. Such a configuration as shown in
In the present embodiment, the liquid absorbing member 3105a preferably has a belt shape in consideration of the space in the inkjet recording apparatus, for example.
The liquid absorbing device 3105 including such a belt-shaped liquid absorbing member 3105a may also include stretching members for stretching the liquid absorbing member 3105a. In
In the liquid absorbing device 3105, the pressing member 3105b allows the liquid absorbing member 3105a including a porous body to come into contact with and to press against an ink image, and thus the liquid absorbing member 3105a absorbs a liquid component contained in the ink image to reduce the liquid component.
As the method of removing and reducing the liquid component in an ink image, the above system of bringing a liquid absorbing member into contact with an ink image is not used, but other systems including a heating method, a method of blowing air with low humidity and a decompression method can be used. Such a method can be applied to an ink image after liquid removal by the system of bringing a liquid absorbing member into contact with an ink image, thus further reducing the liquid component.
The liquid absorbing device 3105 may further include a liquid amount adjusting means 3105d for optimizing the amounts of a liquid and a treatment liquid absorbed in the liquid absorbing member 3105a, a pretreatment means 3105e for applying a treatment liquid to the liquid absorbing member and a cleaning member 3105f for cleaning the liquid absorbing member. 3105d to 3105f are optional members, and a structure not including any or all of these members is encompassed.
<Liquid Absorbing Member>
In the present embodiment, at least some of the liquid component is absorbed and removed from an ink image before liquid removal by bringing the liquid absorbing member having a porous body into contact, and thus the content of the liquid component in the ink image is reduced. The contact face of the liquid absorbing member with an ink image is regarded as a first face, and the porous body is placed on the first face. Such a liquid absorbing member including a porous body preferably has such a configuration that the liquid absorbing member moves as the ejection target medium moves, then comes into contact with an ink image, and further rotates at a certain cycle to come into contact with another ink image before liquid removal, enabling liquid absorption. Examples of the shape include an endless-belt shape and a drum shape.
(Porous Body)
The porous body of the liquid absorbing member pertaining to the present embodiment preferably has a smaller average pore diameter on the first face than the average pore diameter on a second face that is opposite to the first face. In order to suppress the adhesion of a coloring material in an ink to the porous body, the pore diameter is preferably small, and at least the porous body on the first face that comes into contact with an image preferably has an average pore diameter of 10 μm or less. In the present embodiment, the average pore diameter means an average diameter on the surface of the first face or the second face, and can be determined by a known technique such as a mercury penetration method, a nitrogen adsorption method and SEM image observation.
In order to evenly achieve high breathability, the porous body preferably has a small thickness. The breathability can be expressed as a Gurley value in accordance with JIS P8117, and the Gurley value is preferably 10 seconds or less.
A thin porous body, however, cannot ensure a capacity sufficient to absorb a liquid component in some cases, and thus the porous body can have a multilayer structure. In the liquid absorbing member, only the layer to come into contact with an ink image is required to be a porous body, and a layer not to come into contact with an ink image is not necessarily a porous body.
In this manner, an ink image from which the liquid component is removed to reduce the liquid component is formed on the transfer medium 3101. The ink image after liquid removal is transferred onto a recording medium 3108 by the subsequent transfer section 3111. The device configuration and conditions for transfer will be described.
<Pressing Member for Transfer>
In the present embodiment, the ink image after liquid removal on the transfer medium 3101 is brought into contact with a recording medium 3108 conveyed by recording medium conveying devices 3107, by a pressing member for transfer 3106 and is thereby transferred onto the recording medium 3108. The liquid component contained in the ink image on the transfer medium 3101 is removed, then the image is transferred onto the recording medium 3108, and consequently a recorded image prevented from causing curling, cockling or the like can be produced.
The pressing member 3106 is required to have a certain structural strength from the viewpoint of the conveyance accuracy of a recording medium 3108 and durability. As the material of the pressing member 3106, metals, ceramics, polymers and the like are preferably used. Specifically, aluminum, iron, stainless steel, acetal polymers, epoxy polymers, polyimide, polyethylene, polyethylene terephthalate, nylon, polyurethane, silica ceramics and alumina ceramics are preferably used in terms of the rigidity capable of withstanding the pressure at the time of transfer, dimensional accuracy, and reduction of the inertia during operation to improve the control responsivity. These materials may be used in combination.
The pressing time of the pressing member 3106 against the transfer medium for transferring an ink image after liquid removal on the transfer medium 3101 to a recording medium 3108 is not limited to particular values, but is preferably 5 ms or more to 100 ms or less in order to achieve satisfactory transfer and not to deteriorate the durability of the transfer medium. The pressing time in the embodiment represents the time during the contact of a recording medium 3108 with a transfer medium 3101 and is the value determined by the following procedure: a surface pressure distribution measuring device (“I-SCAN” manufactured by Nitta) is used to perform surface pressure measurement; and the length of a pressed region in the conveying direction is divided by the conveying speed to give the pressing time.
The pressure of the pressing member 3106 against the transfer medium 3101 for transferring an ink image after liquid removal on the transfer medium 3101 to a recording medium 3108 is also not limited to particular values, but is so controlled as to achieve satisfactory transfer and not to deteriorate the durability of the transfer medium. Hence, the pressure is preferably 9.8 N/cm2 (1 kg/cm2) or more to 294.2 N/cm2 (30 kg/cm2) or less. The pressure in the embodiment represents the nip pressure between a recording medium 3108 and a transfer medium 3101, and is a value determined by the following procedure: a surface pressure distribution measuring device is used to perform surface pressure measurement; and the load in a pressed region is divided by the area to give the pressure.
The temperature when the pressing member 3106 presses against the transfer medium 3101 for transferring an ink image after liquid removal on the transfer medium 3101 to a recording medium 3108 is also not limited to particular values, but is preferably not lower than the glass transition point or not lower than the softening point of a polymer component contained in an ink. A preferred embodiment for heating includes a heating means for heating an ink image after liquid removal (a second image) on the transfer medium 3101 and a recording medium 3108. In a preferred embodiment, a transfer medium heating device 3112 is used for heating.
The shape of the pressing member 3106 is not limited to particular shapes, and is exemplified by a roller shape.
<Recording Medium and Recording Medium Conveying Device>
In the present embodiment, the recording medium 3108 is not limited to particular media, and any known recording medium can be used. Examples of the recording medium include long media rolled into a roll and sheet media cut into a certain size. Examples of the material include paper, plastic films, wooden boards, cardboard and metal films.
In
<Control System>
The transfer type inkjet recording apparatus in the present embodiment includes a control system for controlling each device.
In
3401 is a CPU for controlling the whole printer, 3402 is a ROM for storing a control program of the CPU, and 3403 is a RAM for executing a program. 3404 is an application specific integrated circuit (ASIC) including a network controller, a serial IF controller, a controller for generating head data, a motor controller and the like. 3405 is a liquid absorbing member conveyance control section for driving a liquid absorbing member conveying motor 3406 and is controlled by a command from the ASIC via a serial IF. 3407 is a transfer medium drive control section for driving a transfer medium driving motor 3408 and is also controlled by a command from the ASIC via a serial IF. 3409 is a head control section and performs final discharge data generation for the inkjet device 3305 and drive voltage generation, for example. 3410 is a temperature control section and corresponds to the control unit 3115 shown in
(Direct Drawing Type Inkjet Recording Apparatus)
As another embodiment of the present invention, a direct drawing type inkjet recording apparatus is exemplified. In the direct drawing type inkjet recording apparatus, the ejection target medium is a recording medium on which an image is to be formed.
Hence, a reaction liquid applying device 4103 for applying a reaction liquid onto a recording medium 4108, an ink applying device 4104 for applying an ink onto the recording medium 4108 and a liquid absorbing device 4105 including a liquid absorbing member 4105a that comes into contact with an ink image on the recording medium 4108 to absorb a liquid component contained in the ink image have the same structures as those in the transfer type inkjet recording apparatus, and are not described.
In the direct drawing type inkjet recording apparatus of the embodiment, the liquid absorbing device 4105 includes a liquid absorbing member 4105a and a pressing member for liquid absorption 4105b that presses the liquid absorbing member 4105a against an ink image on the recording medium 4108. The liquid absorbing member 4105a and the pressing member 4105b may have any shape, and members having substantially the same shapes as those of the liquid absorbing member and the pressing member usable in the transfer type inkjet recording apparatus can be used. The liquid absorbing device 4105 may further include stretching members for stretching the liquid absorbing member. In
<Recording Medium Conveying Device>
In the direct drawing type inkjet recording apparatus 4100 of the embodiment, a recording medium conveying device 4107 is not limited to particular devices, and a conveying means in a known direct drawing type inkjet recording apparatus can be used. As shown in
<Heating Device>
In the direct drawing type inkjet recording apparatus 4100 of the embodiment, a heating device 4112 is a mechanism of heating an ink image on a recording medium 4108 through the support member 4107a. The heating device 4112 may be a known heating device such as various lamps including an infrared lamp and a warm air fan. In terms of heating efficiency, an infrared heater can be used.
The temperature detecting device for a recording medium 4108 and the support member 4107a may be any device, and a noncontact detecting device using, for example, luminance, color or infrared intensity or a contact detecting device using, for example, thermoelectromotive force, electric resistance or magnetism can be used.
The location of the temperature detecting device for the transfer medium is not limited to particular sites, and the temperature can be detected from an ink applying side of the recording medium 4108 or from the back face of the support member 4107a.
<Temperature Control Section>
4115 is a control unit for controlling the working (heating adjustment) of a heater of an ejection head included in the ink applying device 4104 and the heating device 4112 in response to temperature information from the temperature detecting device 4113 and a means for detecting the temperature of the ejection head in the ink applying device 4104 (not shown). The control unit 4115 can also control the working (transfer, drive) of the reaction liquid applying device, the ink applying device, the liquid absorbing device and the recording medium conveying device.
<Control System>
The direct drawing type inkjet recording apparatus in the embodiment has a control system for controlling each device. A block diagram of the control system for the whole direct drawing type inkjet recording apparatuses 4100, 4200 shown in
<Inkjet Recording Method>
The temperature T1 of the ejection head is a temperature at which liquid components in an ink do not boil, and when an aqueous ink is used, the temperature T1 is lower than 100° C. and preferably 90° C. or lower. Meanwhile, the temperature T2 of the transfer medium strongly depends on the temperature T3 of the transfer medium at the time of transfer and varies with treatments after transfer. When T2 is excessively low, much energy is required for heating to T3. When a reaction liquid is applied, T2 is preferably not lower than the cloud point of a surfactant in the reaction liquid. The cloud point of a surfactant can be determined by heating a 1% by mass aqueous surfactant solution. For example, T2 can be 50° C. or higher. The difference between T1 and T2 is not limited to particular values as long as a vaporizing liquid on the transfer medium does not cause condensation on the ejection surface of the ejection head, and the difference is preferably 5° C. or more, more preferably 10° C. or more, and most preferably 20° C. or more. T2 at the time of apparatus startup may be the same as or different from T2 at the time of continuous printing.
As described above, the transfer type inkjet recording apparatus pertaining to the present embodiment and the inkjet recording method using the recording apparatus are characterized in that, at the time of apparatus startup, the temperature of the ejection head at an image forming position is adjusted by heating to a temperature higher than the temperature of the transfer medium at the image forming position. To achieve this, the following techniques are included.
(1) The temperature of the ejection head is adjusted by heating to the temperature T1, and then the temperature of the transfer medium at the image forming position is adjusted by heating to the temperature T2.
(2) The apparatus further includes a means of moving the ejection head between the image forming position and an escape position displaced from the image forming position, and is so controlled that temperature heating of the ejection head is started at the escape position, then the temperature of the ejection head is adjusted by heating to the temperature T1, and the ejection head is moved to the image forming position.
The present invention will next be described in further detail with reference to examples and comparative examples. The present invention is not intended to be limited to the following examples without departing from the scope of the invention. In the following description in examples, “part” is based on mass unless otherwise noted.
In the example, the transfer type inkjet recording apparatus shown in
The transfer medium 3101 in the example is fixed to the support member 3102 with an adhesive. In the example, a PET sheet having a thickness of 0.5 mm was coated with a silicone rubber (KE12 manufactured by Shin-Etsu Chemical) into a thickness of 0.3 mm, and the resulting sheet was used as the elastic layer of the transfer medium. Glycidoxypropyltriethoxysilane and methyltriethoxysilane were mixed at a molar ratio of 1:1, and the mixture was heated and refluxed. The resulting condensate was mixed with a photocationic polymerization initiator (SP150 manufactured by ADEKA) to give a mixture. The surface of the elastic layer was subjected to atmospheric pressure plasma treatment to have a contact angle with water of 10° or less. The above mixture was applied onto the elastic layer and subjected to UV irradiation (with a high-pressure mercury lamp, an integrated exposure amount of 5,000 mJ/cm2) and to thermal curing (150° C., 2 hours) to form a film, yielding a transfer medium 3101 including the elastic body on which a surface layer having a thickness of 0.5 μm was formed.
In the structure, a double-sided adhesive tape, not shown in the drawings for simple explanation, was used between the transfer medium 3101 and the support member 3102 for holding the transfer medium 3101.
The reaction liquid to be applied by the reaction liquid applying device 3103 had the following formulation, and the application amount was 1 g/m2.
The ink to be applied by the ink applying device 3104 was prepared by the following procedure.
<Preparation of Polymer Particles>
In a four-necked flask with a stirrer, a reflux condenser and a nitrogen inlet tube, 18.0 parts of butyl methacrylate, 2.0 parts of polymerization initiator (2,2′-azobis(2-methylbutyronitrile)) and 2.0 parts of n-hexadecane were placed, then nitrogen gas was introduced into the reaction system, and the mixture was stirred for 0.5 hours. Into the flask, 78.0 parts of 6.0% aqueous solution of an emulsifier (product name: NIKKOL BC15, manufactured by Nikko Chemicals) was added dropwise, and the whole was stirred for 0.5 hours. Next, the mixture was sonicated with a sonicator for 3 hours to be emulsified. Subsequently, the mixture was polymerized under a nitrogen atmosphere at 80° C. for 4 hours. The reaction system was cooled to 25° C., then the component was filtered, and an appropriate amount of pure water was added, giving an aqueous dispersion liquid of polymer particles 1 having a polymer particle 1 content (solid content) of 20.0%.
<Preparation of Aqueous Polymer Solution>
A styrene-ethyl acrylate-acrylic acid copolymer (polymer 1) having an acid value of 150 mg KOH/g and a weight average molecular weight of 8,000 was prepared. Next, 20.0 parts of the polymer 1 was neutralized with potassium hydroxide in an equivalent molar amount to the acid value, and an appropriate amount of pure water was added, giving an aqueous solution of polymer 1 having a polymer content (solid content) of 20.0%.
<Preparation of Pigment Dispersion Liquid>
First, 10.0 parts of a pigment (carbon black), 15.0 part of an aqueous solution of polymer 1 and 75.0 parts of pure water were mixed. The mixture and 200 parts of 0.3-mm zirconia beads were placed in a batch type vertical sand mill (manufactured by Aimex) and dispersed for 5 hours while cooled with water. Next, the mixture was centrifuged to remove coarse particles and was subjected to pressure filtration through a cellulose acetate filter with a pore size of 3.0 μm (manufactured by Advantec), giving a pigment dispersion liquid K having a pigment content of 10.0% and a polymer dispersant (polymer 1) content of 3.0%.
(Preparation of Ink)
The components shown below were mixed and thoroughly stirred, and the resulting mixture was subjected to pressure filtration through a cellulose acetate filter with a pore size of 3.0 μm (manufactured by Advantec), giving an ink. Acetylenol E100 is a surfactant manufactured by Kawaken Fine Chemicals.
As the ink applying unit, an inkjet head including an electrothermal transducer for ejecting an ink on demand was used, and the ink application amount was 20 g/m2. The liquid absorbing member 3105a is so adjusted by the stretching rollers 3105c as to have substantially the same speed as the moving speed of the transfer medium 3101. The recording medium 3108 is conveyed by the recording medium delivery roller 3107a and the recording medium winding roller 3107b so as to have substantially the same speed as the moving speed of the transfer medium 3101. In the example, the conveyance speed was 0.2 m/s, and Aurora Coat paper (manufactured by Nippon Paper Industries, a basis weight of 104 g/m2) was used as the recording medium 3108.
The flow at the time of apparatus startup before the start of image formation in Example 1 will be described with reference to
In the transfer medium heating device 3112, a plurality of radiation heating sources each including a halogen lamp and a reflecting mirror as a pair are arranged in the rotation direction of the transfer medium 3101. The halogen lamps and the reflecting mirrors used were manufactured by Fintech Tokyo. The halogen lamp had a maximum output of 10×103 W/m, and the reflecting mirror was a parabolic mirror made of aluminum and having a mirror polished surface.
At the time of printing, the moving speed of the transfer medium was 0.4 m/s, and the output of the halogen lamp was so adjusted as to give a transfer medium temperature of 120° C. that was detected by the temperature detector 3113.
After the flow shown in
In the step sequence shown in Table 1, the condensation on the ejection head and the temperature change from the start of transfer medium heating to the temperature stabilization of the transfer medium were evaluated as described later.
Example 2 is the same as in Example 1 except that the ejection head was heated at the escape position. The step sequence is shown in Table 1.
The flow in Example 2 at the time of apparatus startup before the start of image formation will be described with reference to
After the temperature T1 of the ejection head reached 80° C., the ejection head was controlled to move to the image forming position as shown in
When the temperature control of the ejection head is performed while the ejection head is displaced from the image forming position as in Example 2, the temperature of the ejection head from the start of temperature control to T1 may be lower than the temperature of the transfer medium under the ejection head as shown in
The same procedure as in Example 1 was performed except that the temperature T2 was 75° C., and the condensation on the ejection head and the temperature change from the start of transfer medium heating to the temperature stabilization of the transfer medium were evaluated.
The same procedure as in Example 1 was performed except that transfer medium heating was started and then a reaction liquid was applied with the reaction liquid applying device 3103 (
The same procedure as in Example 4 was performed except that a reaction liquid was applied with the reaction liquid applying device 3103 (
The same procedure as in Example 1 was performed except that the transfer medium cooling device 3110, the transfer medium cleaning member 3109, the reaction liquid applying device 3103 and the liquid removing device 3105 were in contact with the transfer medium 3101 and each unit was activated (
The same procedure as in Example 1 was performed except that the transfer medium heating and the head heating were simultaneously performed while the ejection head was placed at the image forming position (
The same procedure as in Example 1 was performed (
The same procedure as in Example 2 was performed (
The same procedure as in Example 1 was performed (
The same procedure as in Example 1 was performed (
[Evaluation]
In the examples and comparative examples, the condensation on the ejection head and the transfer medium was evaluated.
The temperature change after the start of transfer medium heating before the transfer medium temperature reached T2 and was stabilized was evaluated.
(Condensation)
A: No condensation was observed.
B: Condensation was partly observed on an ejection head.
C: Condensation was observed on an ejection head. Some ejection ports of an ejection head leaked an ink, and the ink adhered onto a transfer medium. This is supposed to be because a dew condensation on the ejection head came into contact with an ink in an ejection port.
(Temperature Change Before Temperature Stabilization)
The temperature change by transfer medium temperature heating after the temperature of a transfer medium under an ejection head once reached T2 before stabilization of temperature T2 was
A: within ±5° C. or less,
B: more than ±5° C. and not more than ±10° C., or
C: more than ±10° C.
The obtained evaluation results are shown in Table 1.
The inkjet recording apparatus and the inkjet recording method according to the present invention can suppress the condensation on an ink ejection head.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-131278, filed Jul. 4, 2017, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-131278 | Jul 2017 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5875373 | Sato | Feb 1999 | A |
| 6655772 | Danzuka et al. | Dec 2003 | B2 |
| 7697881 | Hayashi | Apr 2010 | B2 |
| 9102137 | Koitabashi et al. | Aug 2015 | B2 |
| 20080006176 | Houjou | Jan 2008 | A1 |
| 20160303847 | Soma et al. | Oct 2016 | A1 |
| 20170217216 | Ohnishi et al. | Aug 2017 | A1 |
| 20170341381 | Aoki et al. | Nov 2017 | A1 |
| 20180154670 | Sano | Jun 2018 | A1 |
| 20180345657 | Inoue et al. | Dec 2018 | A1 |
| 20190009549 | Takada et al. | Jan 2019 | A1 |
| 20190009592 | Okushima et al. | Jan 2019 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20190009577 A1 | Jan 2019 | US |
