JP5181435B2 - Inkjet printer and image forming method - Google Patents

Description

  The present invention relates to an ink jet printer having a novel structure using an ink containing a cationic polymerizable composition and an image forming method.

  In recent years, the inkjet recording method is simple and inexpensive, and has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In general, water-based ink-jet ink containing water as the main solvent is recorded on special paper with ink absorbability, but phase change ink-jet method using solid wax ink at room temperature, ink mainly composed of fast-drying organic solvent Ink jets other than water-based ink jet systems, such as a solvent-based ink jet system that uses a UV light, and an actinic ray curable ink jet system that is crosslinked by irradiation with active energy rays (radiation) such as ultraviolet rays (UV light) after recording, have been put into practical use.

  Among them, the ultraviolet curable ink jet method has been attracting attention in recent years because it has a relatively low odor compared to the solvent ink jet method, can be quickly dried, and can be recorded on a recording medium having no ink absorption ability. An actinic ray curable ink jet technology is disclosed.

  Actinic ray curable ink jet inks that use radically polymerizable compounds represented by (meth) acrylates have been put into practical use, but recently, they have adhesion to recording media, low odor, and polymerization inhibition by oxygen. For reasons such as few, proposals have been made on an actinic ray curable ink jet ink using a cationically polymerizable compound and an ink jet printer using the ink (for example, see Patent Documents 1 and 2).

  On the other hand, in an ink jet printer, a material constituting an ink tank or an ink supply path between the ink tank and the ink jet recording head often uses a metal such as stainless steel or aluminum from the viewpoint of durability and ease of processing. In particular, for the purpose of removing foreign matters in ink and preventing clogging, a filter is installed in the ink supply path, and metal is often used as a member constituting these filters.

When an image is formed using an actinic ray curable inkjet ink containing a cationically polymerizable compound by an inkjet printer composed of a metal material as described above, depending on the usage environment of the inkjet printer and the constituent materials of the ink supply path, the ink It has been found that precipitates are generated inside, and the precipitates clog the ink supply path or reach the nozzle portion to cause ejection failure. In general, actinic ray-curable inkjet deposition may be caused by actinic ray leakage light, and measures have been taken so far, but with regard to the generation of precipitates by electron transfer, There is no description, and there has been no description so far that it can be controlled by the material and configuration of the ink contact member used for the exchange of electrons.
JP 2005-290246 A JP 2004-34543 A

  The present invention has been made in view of the above-described problems, and its object is to suppress the generation of precipitates in the apparatus in an inkjet printer using an actinic ray curable inkjet ink containing a cationically polymerizable compound, and to stabilize it. Another object of the present invention is to provide an ink jet printer and an image forming method capable of performing the recorded image.

  The above object of the present invention is achieved by the following configurations.

1. In an ink jet printer that ejects ink containing a cationic polymerizable composition onto a recording medium, an ink tank that stores the ink and an ink contact member that configures an ink supply path from the ink tank to a nozzle that ejects ink There are a plurality of ink contact members, each of which is made of a different conductive material, and an insulating material is provided between the plurality of ink contact members so that the plurality of ink contact members are in an insulated state. An inkjet printer characterized by the above.
2. In an ink jet printer that ejects ink containing a cationic polymerizable composition onto a recording medium, a filter is provided in an ink tank that stores the ink or an ink supply path from the ink tank to a nozzle that ejects ink, and the filter A filter adjacent portion that is adjacent to and holds the filter, the filter and the filter adjacent portion are made of different conductive materials, and an insulating material is provided between the filter and the filter adjacent portion, and the filter and the filter adjacent portion are provided. An ink jet printer characterized in that a filter adjacent portion is insulated.
3. 3. The ink jet printer as described in 1 or 2 above, wherein the ink containing the cationic polymerizable composition contains a photoacid generator.
4). 4. The ink jet printer according to any one of 1 to 3, wherein a water content of the ink containing the cationic polymerizable composition is 0.5% by mass or more and 3.0% by mass or less.
5. 5. An image forming method comprising: forming an image by ejecting ink containing a cationic polymerizable composition onto a recording medium using the inkjet printer according to any one of 1 to 4 above.

  INDUSTRIAL APPLICABILITY According to the present invention, in an ink jet printer using an actinic ray curable ink jet ink containing a cationically polymerizable compound, an ink jet printer and an image forming method capable of suppressing the generation of precipitates in the apparatus and performing stable image recording Could be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventor of the present invention 1) In an ink jet printer that ejects ink containing a cationic polymerizable composition onto a recording medium, an ink tank for storing the ink and the ink tank Or an ink jet printer characterized in that the ink contact member constituting the ink supply path from the nozzle to the nozzle for ejecting ink does not substantially exchange electrons with the ink, or 2) a cationically polymerizable composition In an ink jet printer that ejects ink containing a liquid onto a recording medium, the ink tank for storing the ink or an ink supply path to the nozzle that ejects ink from the ink tank includes a filter, and the filter and the filter adjacent portion include , Wherein the ink is substantially not exchanged with the ink. That the ink-jet printer, to suppress the occurrence of precipitates in the apparatus, found that the ink jet printer can be realized that it is possible to perform stable image recording, a completed the invention.

  That is, in an ink containing a cationically polymerizable composition, a photoacid generator that is present at the same time usually generates an acid when irradiated with active energy rays, and polymerization of the cationically polymerizable monomer is initiated by the acid. The

However, when the ink containing the cationic polymerizable composition is stagnated for a long period of time in an ink tank or an ink flow path and receives supply of electrons from the ink contact portion, the electrons are not irradiated with active energy rays. As a result of the transfer of acid, acid was generated in the ink, which caused polymerization to start, and it was first found out that an incorrect polymerization composition was generated.

  As a result of intensive investigations on means for preventing the generation of the above-mentioned illegal polymer, it has been found that the ink contact member of the ink jet printer can be solved by configuring it so as not to substantially exchange electrons with ink. Is.

  Hereinafter, details of each component of the present invention will be described.

[Inkjet printer]
The ink jet printer of the present invention mainly includes an ink tank for storing ink containing a cationic polymerizable composition, an ink supply path for feeding ink from the ink tank to a recording head, and supply from the ink supply path. A recording head that emits the ink onto the recording medium, and an actinic ray irradiation light source for curing ink droplets that have landed on the recording medium, and an ink supply path between the ink tank and the recording head includes Filters or intermediate tanks are provided.

  FIG. 1 is a diagram showing an overall configuration of an inkjet printer including a filter and an intermediate tank according to an embodiment of the present invention.

  Reference numeral 1 denotes an ink tank 1 that stores and supplies ink containing a cationic polymerizable composition. In FIG. 1, for example, a yellow ink tank 1Y, a magenta ink tank 1M, a cyan ink tank 1C, and a black ink tank 1K are used. Is shown. J is a joint connecting the ink tank 1 and the ink supply path.

  Reference numeral 2 denotes a recording head having nozzles for ejecting ink droplets onto a recording medium to form an image, and includes a yellow recording head 2Y, a magenta recording head 2M, a cyan recording head 2C, and a black recording head 2K. Reference numeral 3 denotes an active energy ray source that irradiates ink that has landed on the recording medium with ultraviolet rays that are active energy rays.

  Reference numeral 4 denotes a carriage. The carriage 4 integrally mounts the recording head 2 and the energy beam source 3, and is reciprocated as indicated by arrows WX 1 and WX 2 guided by the carriage guide 5 to scan the recording medium P. Then, an image is formed on the recording medium P.

  A filter box 6 includes a yellow filter box 6Y, a magenta filter box 6M, a cyan filter box 6C, and a black filter box 6K. An intermediate tank 7 includes a yellow intermediate tank 7Y, a magenta intermediate tank 7M, a cyan intermediate tank 7C, and a black intermediate tank 7K.

  The recording ink is sent from the ink tank 1 to the intermediate tank 7 and supplied from the intermediate tank 7 to the recording head 2 through the ink supply path 8. The ink supply path 8 is composed of supply paths for yellow ink, magenta ink, cyan ink, and black ink. Each single color ink is independently supplied from the ink tank 1 via the ink supply path 8 and the recording head. 2 is supplied.

  A maintenance unit 10 performs a recovery process of the recording head 2 and includes a suction cap 9 for capping the recording head 2. A waste ink container 12 for storing waste ink receives and stores ink forcedly ejected from the recording head 2 during flushing.

  FIG. 2 is a schematic configuration diagram showing an example of the ink supply path configuration of the ink jet printer of the present invention.

  In FIG. 2a, the ink tank 101 is connected to the ink supply path 102 via the joint J1, and the end of the ink supply path 102 is stored in the carriage 103 via the joint J2. It is connected to the head 104. Ink droplets are ejected onto the recording medium from the nozzles N of the recording head 104 in accordance with the image formation information, and then, the active energy rays are instantaneously irradiated from the active energy ray source L to cure the ink. .

  FIG. 2B shows an example in which an intermediate tank unit 105 with a built-in filter is provided in the middle of the ink supply path 102. The discharge port of the ink tank 101 and the ink supply path 102 are connected by a joint J1, and are connected to the intermediate unit tank 105 through a joint J3. The ink is fed from the joint J3 to the intermediate tank front chamber 106, and then is fed to the intermediate tank 108 by removing a foreign substance or the like by the filter 107. Next, the intermediate tank 108 and the ink supply path 102 are connected via a joint J 4, and an ink supply line that supplies filtered ink stored in the intermediate tank 108 to the recording head 104. Note that reference numeral 109 shown in FIG. 2B denotes a filter adjacent portion adjacent to the filter 107.

  FIG. 2c) shows an example in which a filter box 110 is provided in place of the intermediate tank unit 105 in FIG. A filter 107 is provided in a filter box 110 connected to the ink supply path 102 via the joint J5 on the ink entrance side and via the joint J6 on the ink exit side. An ink supply line that supplies ink to the recording head 104 after removing foreign matter or the like. 2 indicates a filter adjacent portion adjacent to the filter 107.

  In FIG. 2 described above, for convenience, only lines for supplying ink to the magenta recording head are shown. However, as shown in FIG. 1, similar supply lines are provided for the yellow recording head and the cyan recording head. The head and the black recording head are also provided. In addition, FIG. 2 shows only the configuration necessary for the description, and although not shown in FIG. 2, for example, an electromagnetic valve, a branch joint, and a liquid feed pump for controlling the liquid delivery of ink, a record A head control unit and the like are provided.

  The ink jet according to the present invention is, for example, in the ink jet printer or ink ink supply line shown in FIG. 1 or 2. The ink member is a material that does not substantially transfer electrons with ink; or 2) an ink tank that stores ink or a filter in an ink supply path from an ink tank to a nozzle that emits ink; The filter and the filter adjacent portion are formed of a material that does not substantially exchange electrons with ink.

  In the present invention, the ink contact part is an ink tank, an ink supply path, an intermediate tank unit, a filter box, and the like, and a joint group connecting them, and is directly connected to the ink containing the cationic polymerizable composition according to the present invention. In the ink supply line shown in FIG. 2A, for example, the inside of the ink tank 101, the inside of the ink supply path 102, the joints J1 and J2, and the inside 104 of the recording head. 2B), the inside of the ink tank 101, the inside of the ink supply path 102, the joints J1 to J4, the filter 107 and the filter adjacent portion 109 of the intermediate tank unit 105, and the inside 104 of the recording head. is there. Further, in the ink supply line shown in FIG. 2C, the inside of the ink tank 101, the inside of the ink supply path 102, the joints J1, J2, J5, and J6, the filter 107 in the filter box 110, the filter adjacent portion 111, and the recording. This is the inside 104 of the head.

  In the present invention, the members constituting these ink contact portions are materials that do not substantially exchange electrons with ink. The substantial transfer of electrons with the ink in the present invention means that any component constituting the ink is oxidized or reduced. When a material having such characteristics is used for the ink contact portion, for example, In addition, when the ink and the member having the electron transfer contact for a long period of time, a precipitate is generated by the transfer of electrons between the two, and as a result, the precipitate reaches the recording head, thereby clogging the nozzle, This results in a defect of nozzle missing or oblique emission.

  Therefore, in the ink jet printer of the present invention, the ink contact portion is constituted by a member that does not cause substantial transfer of electrons with the ink, and further, at least one selected from the configurations described below, Alternatively, by combining them, it is possible to prevent the generation of precipitates by preventing the occurrence of a potential difference in the ink contact portion and preventing the substantial transfer of electrons with the ink.

  1) All of the ink contact member is made of an insulating material, 2) At least a part of the ink contact member is made of a single conductive material, and 3) The ink contact member is made of a plurality of conductive materials. 4) The material constituting the ink-contacting member is a metal element whose ionization tendency is less than or equal to a hydrogen element. 5) The filter and the filter adjacent part are made of an insulating material. 6) The filter and the filter adjacent part are made of a single conductive material. 7) The filter and the filter adjacent part. A plurality of conductive materials, and a plurality of conductive materials are substantially insulated from each other. 8) The material constituting the filter and the filter adjacent portion has an ionization tendency less than that of a hydrogen element. It is a metal element, also a method such that a material constituting the intermediate tank and the like.

  Hereinafter, the members that do not cause substantial transfer of electrons with the ink will be further described.

The insulating material according to the above 1) and 5) in the present invention is a material having a surface resistivity of 1 × 10 ⁸ Ω □ cm or more, more preferably a surface resistivity of 1 × 10 ¹⁰ Ω □. It is a material of cm or more. The surface resistivity of the insulating material can be measured based on a method based on JIS K6911 using a circular electrode (for example, “HR probe” of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). Further, the insulating material according to the present invention may be composed of a single material having the surface resistivity defined above, or a conductive material, for example, a metal material may be used as a base material. The part which coat | covered with the said insulating material may be covered, and the form which provided insulation may be sufficient.

  Examples of the insulating material according to the present invention include rubber, plastic material, fiber, ceramic and the like, and examples of the ink supply path where flexibility is required include nitrile rubber (NBR), hydrogenation, and the like. Nitrile rubber (HNBR), fluorine rubber (FKM), perfluoro rubber (FFKM), millable silicone rubber, fluorosilicone rubber (FVMQ), ethylene propylene rubber (EPM, EPDM), styrene butadiene rubber (SBR), silicone rubber ( VQM), acrylic rubber (ACM, ANM), butyl rubber (IIR), chlorosulfonated polyethylene rubber (CSM), epichlorohydrin rubber (CO, ECO), chloroprene rubber (CR), and the like can be used.

  In addition, for example, polyolefin, polypropylene, polyethylene, polyester, vinyl chloride, polycarbonate, TFE (tetrafluoroethylene), PFA (perfluoroalkoxy resin; tetrafluoroethylene-pearl) are used for ink tanks, intermediate tanks, filter boxes, joints, and the like. Oriented alkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), FFKM, FEPM, PI (polyimide) and the like can be appropriately selected and used.

  Moreover, as a metal base material which coat | covers the said insulating material, using the alloy using iron, aluminum, copper, nickel, tin, zinc, lead, silver, gold | metal | money, these metals, or another metal is used, for example. it can.

  As the conductive material according to the above items 2), 3) and 6), 7) in the present invention, a metal material to which formation of a structure is generally applied can be used. , Aluminum, copper, nickel, tin, zinc, lead, silver, gold, and alloys of these metals or other metals can be used. Among them, stainless steel and aluminum are particularly easy to handle and cost effective. Desirable in terms. Thus, by forming the ink contact member or the filter and the filter adjacent portion using a single conductive material, it is possible to substantially prevent the exchange of electrons with the ink.

  In addition, when the ink contact member or the filter and the filter adjacent portion are constituted by a plurality of different conductive materials, the plurality of conductive materials are substantially insulated from each other, for example, between different conductive materials. By providing the insulating material to insulate between the two conductive materials, substantial exchange of electrons with the ink can be prevented.

  Inkjet printers that apply conductive materials to the ink contact parts include ink tanks, joints, ink supply path branching parts, ink pumps, intermediate tanks, filters, valves, and other flow paths. In particular, it is important to adopt the above-described configuration in the filter section having a large contact area with ink, the ink tank in which the ink residence time is long, the vicinity of the ink tank, especially the intermediate tank disposed in the vicinity of the recording head. It becomes.

  The nozzle provided in the recording head of the ink jet printer of the present invention is a minute hole having an inner diameter of 100 μm or less, and it is an important requirement for stable emission to reliably remove minute foreign matters in the ink. . Accordingly, the filter applied to the present invention preferably has a configuration capable of removing fine foreign matters as described above. For example, a single-layered wire net made of an alloy such as stainless steel called a screen mesh, stainless steel, or the like Sintered metal filters made by laminating metal meshes made of these alloys, sintered metal filters in which each layer is sintered, sintered metal fiber filters in which the contact points between the fibers are sintered in a metal mesh in which fine fibers of stainless steel are knitted in complex, and metal powders are fired. The sintered metal filter etc. which were tied are mentioned, Among these, it is preferable to use a box-shaped sintered metal fiber filter especially.

  The metal elements whose ionization tendency according to the above 4) and 8) in the present invention is a hydrogen element or lower can include copper, mercury, silver, platinum and gold, and these ionizations can be used as ink contact members. By using a metal element whose tendency is less than or equal to the hydrogen element, it is possible to substantially prevent the exchange of electrons with the ink.

[Ink containing cationically polymerizable compound]
Next, the ink applied to the ink jet printer of the present invention will be described.

  The ink according to the present invention is characterized by containing a cationically polymerizable compound as the radiation curable compound.

  In the present invention, various known cationic polymerizable monomers can be used as the cationic polymerizable compound, and among them, compounds having an oxirane group such as JP-A-6-9714 and JP-A-2001-31892. JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and JP-A-2001-220526 include epoxy compounds, vinyl ether compounds, oxetane compounds, and the like. Can be mentioned.

  Examples of the epoxy compound include the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  Preferred as the aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or its Examples thereof include di- or polyglycidyl ethers of alkylene oxide adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is preferable.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like.

Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable.

In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  In the present invention, from the viewpoint of safety such as AMES and sensitization, the epoxy compound having an oxirane group is particularly preferably at least one of an epoxidized fatty acid ester and an epoxidized fatty acid glyceride.

  The epoxidized fatty acid ester and the epoxidized fatty acid glyceride are not particularly limited as long as an epoxy group is introduced into the fatty acid ester or fatty acid glyceride.

  The epoxidized fatty acid ester is produced by epoxidizing an oleic acid ester, and examples thereof include methyl epoxy stearate, butyl epoxy stearate, octyl epoxy stearate and the like. Similarly, the epoxidized fatty acid glyceride is produced by epoxidizing soybean oil, linseed oil, castor oil and the like, and epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil and the like are used.

  In the present invention, in order to further improve the curability and ejection stability, the photopolymerizable compound is 30 to 95% by mass of a compound having an oxetane ring and 5 to 70% by mass of a compound having an oxirane group. It is preferable to contain 0-40 mass% of vinyl ether compounds.

  As the oxetane compound that can be used in the present invention, any known oxetane compound as described in JP-A Nos. 2001-220526 and 2001-310937 can be used.

  Examples of vinyl ether compounds that can be used in the present invention include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, Di- or trivinyl ether compounds such as cyclohexanedimethanol divinyl ether and trimethylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol Bruno vinyl, n- propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  In the ink containing the cationic polymerizable compound according to the present invention, it is preferable to contain a photoacid generator as a polymerization initiator. As the photoacid generator that can be used in the present invention, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (Organic Materials Research Group, “Organic Material for Imaging”, Bunshin Publishing (1993), see pages 187-192). Examples of compounds suitable for the present invention are listed below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium and phosphonium Can be mentioned.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  The photo acid generator (photo cationic polymerization initiator) is preferably contained in a ratio of 0.2 to 20 parts by mass with respect to 100 parts by mass of the cationic polymerizable monomer. If the content of the photocationic polymerization initiator is less than 0.2 parts by mass, it is difficult to obtain a cured product, and even if the content exceeds 20 parts by mass, a further effect of improving curability cannot be expected. These cationic photopolymerization initiators can be used alone or in combination of two or more.

  The ink according to the present invention preferably contains a color material, and the color material is preferably a pigment.

  As the pigment used in the ink according to the present invention, an organic and surface-treated organic pigment is preferably used, and the content of the dispersant in the ink is preferably 35 to 65% of the pigment mass. . In the ink of the present invention, if the content of the dispersant is less than 35%, the dispersant may not be sufficiently adsorbed on the entire pigment surface, and the dispersion stability may be insufficient. If the content exceeds 65%, the pigment The dispersant that is not adsorbed on the surface may be released into the ink, causing polymerization inhibition and causing a problem. The amine value of the pigment is preferably larger than the acid value, and the difference is more preferably 1 mg / g KOH or more and less than 10 mg / g. If it is less than 1 mg / g KOH, the effect is not obtained, and if it is 10 mg / g or more, it is necessary to perform the basic treatment excessively, which not only increases the cost but also causes polymerization inhibition.

  Examples of the pigment used in the present invention include carbon pigments such as carbon black, carbon refined, and carbon nanotubes, and metal oxide pigments such as iron black, cobalt blue, zinc oxide, titanium oxide, chromium oxide, and iron oxide. Sulfide pigments such as zinc sulfide, phthalocyanine pigments, pigments composed of salts such as metal sulfates, carbonates, silicates and phosphates, and aluminum powders, bronze powders, and zinc powders Inorganic pigments such as metallic powders, nitro pigments, aniline black, nitroso pigments such as naphthol green B, azo pigments such as Bordeaux 10B, Lake Red 4R, and chromoftal red (azo lakes, insoluble azo pigments, condensed azo pigments, Including chelate azo pigments), Peacock Blue Lake and Rhodamine Ray Lake pigments, phthalocyanine pigments such as phthalocyanine blue, polycyclic pigments (perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinofuranone pigments), thioindigo red Organic pigments such as selenium pigments such as Indatron Blue, quinacridone pigments, quinacridine pigments, and isoindolinone pigments can also be used.

  Specific examples of the pigment include C.I. I Pigmen Yellow-1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 180, 185, C.I. I Pigmen Orange-16, 36, 38, C.I. I Pigmen Red-5, 7, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202, C.I. I Pigmen Violet-19, 23, C.I. I Pigmen Blue-1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60, C.I. I Pigmen Green-7, 36, C.I. I Pigmen White-6, 18, 21, C.I. I Pigmen Black-7, and the like.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Further, a dispersing agent can be added when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used. Examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound. However, the photocurable ink of the present invention is preferably solvent-free because it reacts and cures after printing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle diameter of the pigment particles is 0.08 to 0.5 μm, and the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained. In the ink according to the present invention, the color material concentration is preferably 1 to 10% by mass of the whole ink.

  In the ink according to the present invention, various additives other than those described above can be used. For example, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, for the purpose of improving storage stability, any known basic compound can be used, but representative examples include basic organic compounds such as basic alkali metal compounds, basic alkaline earth metal compounds, and amines. Compound etc. are mentioned. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  In addition, in the ink according to the present invention containing cationic polymerizability, the water content is adjusted in the range of 0.5% by mass or more and 3.0% by mass or less in order to improve the storage stability of the ink. Is preferred. When the water content is less than 0.5% by mass, the ink storage stability decreases, and when the water content exceeds 3.0% by mass, the generation of precipitates increases, nozzle clogging and ejection stability decrease.

  In the ink according to the present invention, when used for inkjet image formation, the viscosity at 25 ° C. is preferably 7 to 50 mPa · s.

  In the present invention, various recording media can be used as a recording medium used when forming an image with the ink according to the present invention by the ink jet printer according to the present invention, but the characteristics of the ink according to the present invention are fully exhibited. From the viewpoint of being capable of being recorded, it is preferable that the recording medium has substantially no ink absorbing ability. In addition to ordinary non-coated paper, coated paper, and the like, various non-absorbing plastics and films thereof used for so-called soft packaging Examples of various plastic films include polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, triaceti It includes cellulose (TAC) film or the like. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, polyvinyl alcohol (PVA), rubbers and the like can be used. Moreover, it is applicable also to metals and glass. Among these recording media, the configuration of the present invention is effective particularly when an image is formed on a PET film, OPS film, OPP film, ONy film, or PVC film that can be shrunk by heat. These substrates are not only susceptible to curling and deformation of the film due to ink curing shrinkage and heat generation during the curing reaction, but also the ink film is difficult to follow the substrate shrinkage.

  The surface energies of these various plastic films differ greatly, and depending on the recording medium, the dot diameter after ink landing has been a problem in the past. The ink according to the present invention forms a good high-definition image on a wide range of recording media having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. it can.

  In the present invention, it is more advantageous to use a long (web) recording medium in terms of the cost of the recording medium such as the packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of ink>
(Preparation of cyan ink)
A cyan ink having the following composition was prepared.

  First, the pigment C.I. was dissolved in a solution obtained by stirring and dissolving for 1 hour while heating the whole amount of PB822 (dispersant manufactured by Ajinomoto Fine Techno Co., Ltd.) and 14 parts of oxetane OXT221 on a hot plate at 65 ° C. I. A total amount of Pigment Blue 15: 4 was added, sealed in a glass bottle together with zirconia beads having a diameter of 0.3 mm, and dispersed by a paint shaker for 4 hours, and then the zirconia beads were removed to prepare a dispersion.

  Next, the following remaining additives were added to the prepared dispersion to prepare a cyan ink. The composition of each additive in the final cyan ink is shown below.

Pigment: C.I. I. Pigment Blue 15: 4 4.0 parts Addis Bar PB822 (manufactured by Ajinomoto Fine Techno Co., Ltd., dispersant) 2.0 parts Oxetane OXT221 (Oxetane compound produced by Toa Gosei Co., Ltd.) 71.0 parts Oxetane OXT212 (Oxetane compound produced by Toa Gosei Co., Ltd.) 0 parts Oxetane OXT101 (Oxetane compound manufactured by Toa Gosei Co., Ltd.) 5.0 parts Alicyclic epoxy compound 1 18.0 parts Photopolymerization initiator 1 (molecular weight 466, having 3 aryl groups per molecular weight) 4.0 parts Polymerization Inhibitor (triisopropanolamine) 0.1 part Hydroquinone 0.1 part Water 1.0 part

(Preparation of yellow ink)
In the preparation of the cyan ink, a pigment (CI Pigment Blue 15: 4) was added to C.I. I. A yellow ink was prepared in the same manner except that it was changed to Pigment Yellow 150.

(Preparation of magenta ink)
In the preparation of the cyan ink, a pigment (CI Pigment Blue 15: 4) was added to C.I. I. A magenta ink was prepared in the same manner except that it was changed to Pigment Red 122.

(Preparation of black ink)
In the preparation of the cyan ink, a pigment (CI Pigment Blue 15: 4) was added to C.I. I. A black ink was prepared in the same manner except that it was changed to Pigment Black 7.

<Inkjet printer>
Ink jet printers 1 to 4 having an ink supply line having the configuration shown in FIG. 2A and having the ink tank 101 and the joints J1 and J2 shown in Table 1 were prepared. In addition, as an insulating member of Table 1, the surface of the ink contact portion of the ink tank was covered with a polyethylene resin so as to be in an insulating state. Further, the ink supply path 102 is configured by covering an ink-resistant Teflon (registered trademark) tube, which is an insulating member, with a black polyolefin tube.

<< Evaluation of deposition resistance of inkjet printer >>
Each ink prepared as described above was filled from the ink tank of each inkjet printer to the joint J2. Table 1 shows the results obtained by visually observing the presence or absence of precipitates in the ink tank 101 and the joint J1 after leaving the ink filled in an environment of 23 ° C. for 3 days.

  From the results shown in Table 1, the ink jet printer 1 of the comparative example in which the joint part and the ink tank are made of different metal materials generates precipitates by contacting with the ink containing the cationic polymerizable composition for a long period of time. Was recognized. On the other hand, in the inkjet printers 2 and 3 made of the same type of metal and the inkjet printer 4 made of a different kind of metal but having the ink contact portion covered with an insulating material, electronic transfer with the ink is prevented. It turns out that generation | occurrence | production of the thing is suppressed.

Example 2
<Inkjet printer>
An ink supply line having a configuration provided with the filter box described in c) of FIG. 2 was prepared, and the constituent members of the filter 107 and the filter adjacent portion 111 were prepared in the inkjet printers 5 to 11 having the configurations described in Table 2. . As the insulating member shown in Table 2, oleethylene resin was used, and the entire surface of the ink contact portion adjacent to the filter was covered to obtain an insulating state. Further, the ink supply path 102 is formed by covering an ink-resistant Teflon (registered trademark) tube, which is an insulating member, with a black polyolefin tube, and each joint is made the same as the filter adjacent portion material.

<< Evaluation of deposition resistance and ejection stability of inkjet printer >>
(Evaluation of precipitation resistance)
Each ink prepared as described above was filled from the ink tank of each inkjet printer to the joint J2. After leaving the ink filled in an environment of 23 ° C. for 3 days, the presence or absence of precipitates in the filter box was determined.

(Evaluation of ejection stability)
After each ink was left in the ink supply line for 3 days in an environment of 23 ° C., multi-size dots with 256 nozzles and 2 to 20 pl were transferred to 720 × 720 dpi (dpi represents the number of dots per 2.54 cm) The recording head heated at 50 ° C. was used for continuous discharge for 3 hours. Next, the emission state of each color ink was visually observed to determine the average emission state of each color ink, and the ejection stability was evaluated according to the following criteria.

A: No nozzle missing and exit bending are observed B: No nozzle missing is observed, but nozzles with exiting curvature are recognized in several places C: Clear nozzle missing and exit bending occur, Table 2 shows the results obtained as described above.

  As is apparent from the results shown in Table 2, the ink jet printers 5 and 9 in which the filter of the filter box and the filter adjacent portion are formed of different conductive members are in contact with the ink containing the cationic polymerizable composition for a long period of time. Thus, it can be seen that the generation of precipitates is observed and the discharge stability is poor. On the other hand, the inkjet printers 6 to 8 made of the same kind of metal, the inkjet printer 10 using copper and silver having a smaller ionization tendency than the hydrogen element, and made of different metals, but the ink contact portion is made of an insulating material. It can be seen that the coated ink jet printer 11 prevents electron transfer with the ink, suppresses the generation of precipitates, does not cause nozzle clogging during continuous emission, and provides good emission stability.

Example 3
<Inkjet printer>
Prepare the ink jet printers 12 to 18 having the ink supply line having the configuration including the intermediate tank unit described in FIG. 2B and having the components of the filter 107 and the filter adjacent portion 109 as described in Table 3. did. As the insulating member shown in Table 3, oleethylene resin was used, and the entire surface of the ink contact portion adjacent to the filter was covered to obtain an insulating state. Further, the ink supply path 102 is formed by covering an ink-resistant Teflon (registered trademark) tube, which is an insulating member, with a black polyolefin tube, and each joint is made the same as the filter adjacent portion material.

<< Evaluation of deposition resistance and ejection stability of inkjet printer >>
In the same manner as in the method described in Example 2, the precipitation resistance and discharge stability inside the intermediate tank unit were evaluated, and the obtained results are shown in Table 3.

  As is apparent from the results shown in Table 3, the ink jet printers 12 and 16 in which the filter of the intermediate tank unit and the filter adjacent portion are made of different conductive members are in contact with the ink containing the cationic polymerizable composition for a long period of time. By doing so, it can be seen that the generation of precipitates is observed and the discharge stability is poor. In contrast, the inkjet printers 13 to 15 made of the same type of metal, the inkjet printer 17 using copper and silver having a smaller ionization tendency than the hydrogen element, and made of different metals, but the ink contact portion is made of an insulating material. It can be seen that the coated ink jet printer 18 prevents electron transfer with the ink, suppresses the generation of precipitates, does not cause nozzle clogging during continuous emission, and provides good emission stability.

Example 4
In Examples 1 to 3, in place of the photopolymerization initiator 1 used for the preparation of each ink, except that the following photopolymerization initiator 2 was used, the preparation of each ink and the ink jet using the ink were similarly performed. As a result of evaluating the printer, the same results as in Tables 1 to 3 were obtained.

Example 5
In Examples 1 to 3, instead of the alicyclic epoxy compound 1 used for the preparation of each ink, Cel2021P (manufactured by Daicel Chemical Industries) was used in the same manner, and the preparation of each ink and the ink were used. As a result of evaluating the ink jet printer, the same results as in Tables 1 to 3 were obtained.

Example 6
In Examples 1 to 3, the water content of each ink (the water content of the ink used in Examples 1 to 3 is 0.9%) is 0.1%, 0.3%, 0.5%, 1. Each ink was prepared in the same manner except that it was changed to 5%, 2.0%, 2.5%, 3.0%, 3.5%, 5.0%. As a result of the same evaluation using an ink jet printer, it was confirmed that better results were obtained when the water content of the ink was in the range of 0.5 to 3.0%.

1 is a diagram illustrating an overall configuration of an ink jet printer including a filter and an intermediate tank according to an embodiment of the present invention. It is a schematic block diagram which shows an example of the ink supply path structure of the inkjet printer of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Ink tank 2,104 Recording head 3 Energy ray source 4,103 Carriage 6,110 Filter box 7,108 Intermediate tank 8,102 Ink supply path 105 Intermediate tank unit 106 Intermediate tank front chamber 107 Filter 109, 111 Adjacent to filter Part J1-J6 Joint L Active energy source N Nozzle

Claims (5)

In an ink jet printer that emits an ink containing a cationic polymerizable composition onto a recording medium,
There are a plurality of ink contact members constituting an ink supply path from the ink tank for storing the ink to the nozzle for emitting the ink from the ink tank,
Each of the plurality of contact ink member is formed of a different conductive material from each other, and by providing the insulating material between the contact inking member between the plurality of, the contact inking member between the plurality of the insulating state, it Inkjet printer characterized by. In an ink jet printer that emits an ink containing a cationic polymerizable composition onto a recording medium,
A filter in an ink tank that stores the ink or an ink supply path from the ink tank to a nozzle that emits ink; and a filter adjacent portion that holds and holds the filter.
The filter and the filter adjacent portion are made of different conductive materials, and an insulating material is provided between the filter and the filter adjacent portion , so that the filter and the filter adjacent portion are in an insulated state. Inkjet printer featuring. The ink-jet printer according to claim 1 or 2, wherein the ink containing the cationic polymerizable composition contains a photoacid generator. The water content of the ink containing a cationically polymerizable composition, 0.5 wt% or more, the ink-jet printer according to any one of claims 1 to 3, characterized in that at most 3.0 wt% . Using an ink jet printer according to any one of claims 1 to 4, an image forming method and forming an image by emitting ink containing a cationically polymerizable composition onto a recording medium.

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