JP2006169345A - Inkjet pigment ink, ink set, image formation method and image recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain pigment ink useful for inkjet recording and having high discharge stability from an inkjet head and an ink set and to provide an image formation method and an image recording apparatus. <P>SOLUTION: In the inkjet pigment comprising at least pigment, a dispersant, a water-soluble organic solvent and water, the dispersant is a polymer containing a phenylalkyl group at the end. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pigment ink used in ink jet printing and an ink set having a combination of the ink and a reaction liquid, and in particular, a pigment ink, an ink set, an image forming method, and an image recording having high ejection stability from an ink jet head. Relates to the device.

  In the ink jet recording method, recording is performed by causing a droplet of a recording liquid (ink) to fly and adhere to a recording medium such as paper. In particular, according to the method disclosed in Patent Documents 1 to 3, an electrothermal converter is used as an ejection energy supply unit, and droplets are ejected by generating bubbles by applying thermal energy to ink. High-density multi-orifice can be easily realized, and high-resolution and high-quality images can be recorded at high speed.

  Ink used for conventional inkjet recording is generally water as a main component and generally used as a coloring material dye that dissolves in water, but in order to improve the weather resistance and water resistance of the recorded matter, Development using pigments for color materials is in progress. However, the pigment fine particles dispersed in the ink, in the method of recording by discharging from the ink jet head by adding the thermal energy to the ink and foaming as described above, in the vicinity of the electrothermal converter when discharged Because very large thermal energy is instantaneously applied and the ink physical properties change abruptly, the dispersion state of the pigment fine particles tends to become very unstable, and as a result, aggregates precipitate and block the vicinity of the nozzle. In some cases, the ink is deposited on the electrothermal converter to form a kogation, thereby impairing the ejection stability of the ink from the inkjet head.

Japanese Patent Publication No. 61-59911 Japanese Patent Publication No. 61-59912 Japanese Examined Patent Publication No. 61-59914

  Accordingly, an object of the present invention is suitable for inkjet recording, can form high-quality images, and is particularly a pigment ink with high ejection stability from an inkjet head, or an ink comprising a combination of a pigment ink and a reaction liquid. It is to provide a set, an image forming method, and an image recording apparatus.

  The above object is achieved by the present invention described below. That is, the present invention relates to an inkjet pigment ink comprising at least a pigment, a dispersant, a water-soluble organic solvent, and water, wherein the dispersant is a polymer having a phenylalkyl group at a terminal. Ink.

Another aspect of the present invention is an ink set comprising a pigment ink and a reaction liquid containing at least a compound having an action of increasing an average particle size of pigment particles contained in the ink when brought into contact with the ink. The pigment ink is the above-described pigment ink for inkjet.
Another aspect of the present invention is an image recording method comprising a step of applying the inkjet pigment ink to a recording medium.

  According to the present invention, there is provided an inkjet pigment ink (hereinafter referred to as ink) that has high ejection stability and can produce a high-quality printed matter with high printing resolution when an image is formed. When the ink is used in combination with a reaction liquid containing at least a compound having an action of increasing the average particle size of pigment particles contained in the ink when it comes into contact with the ink, printing with particularly high color density and high color development is performed. An object can be produced.

  Hereinafter, the present invention will be described in more detail with reference to the best mode for carrying out the invention. The ink according to the present invention is characterized in that the dispersant contained in the ink is a polymer and has a phenylalkyl group at the polymer terminal.

  As a method for introducing a phenylalkyl group into the polymer terminal as described above, (1) a method of preparing a polymer from a polymerization reaction solution containing a monomer having a phenylalkyl group and introducing it into the polymer terminal, or (2 ) A method of preparing a polymer using a polymerization initiator or a chain transfer agent having a phenylalkyl group and introducing it to the polymer terminal is mentioned.

  Specific examples of the above (1) include, for example, a radical polymerization method and a living polymerization method from a polymerization reaction solution comprising a benzyl (meth) acrylate monomer having a phenylalkyl group and a plurality of vinyl monomers containing the same. There is a method of synthesizing by a known polymerization method. Among these, the living polymerization method is preferable because a phenylalkyl group can be easily introduced into the polymer terminal.

  Specific examples of the above (2) include a polymerization initiator having a phenylalkyl group such as 1,1′-azobis (1-acetoxy-1-phenylethane), and a phenylalkyl group such as α-methylstyrene dimer. Examples thereof include a method of introducing a phenylalkyl group into a polymer terminal by synthesizing by a known method such as a radical polymerization method using a chain transfer agent having

  The dispersant for the pigment used in the present invention obtained by the method as listed above is preferably a polymer having a weight average molecular weight in the range of 1,000 to 30,000, and more preferably 3,000 to 3,000. A polymer in the range of 15,000 is preferred.

  Specific examples of the dispersant composed of a polymer having a phenylalkyl group at the terminal used in the present invention include, for example, styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, α , Β-ethylenically unsaturated carboxylic acid aliphatic alcohol ester, (meth) acrylic acid, (meth) acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, fumaric acid derivative, At least one selected from vinyl compounds having an acidic functional group such as vinyl sulfonic acid and vinyl phosphonic acid, vinyl acetate, vinyl acetate derivatives, vinyl pyrrolidone, vinyl pyrrolidone derivatives, acrylamide, acrylamide derivatives and the like, or two or more Monomer (at least one of which is hydrophilic heavy) (Co) polymer composed of a compatible monomer), and the form of the (co) polymer is a copolymer such as a random copolymer, a block copolymer, or a graft copolymer, or these Examples include salts.

  Among the above-mentioned dispersants, a particularly preferable dispersant is a graft copolymer (graft copolymer) having a phenylalkyl group at the terminal, one of the main chain unit or the side chain unit is a hydrophilic segment, and the other is a hydrophobic segment. ). Here, when the graft copolymer is described as a graft copolymer composed of two types of monomers A and B, it is composed of a homopolymer (main chain unit) composed only of the monomer A and another monomer B. It is a copolymer in which blocks are linked like branches (side chain units). When the graft copolymer having the structure as described above is used as a pigment dispersant, it adsorbs to the surface of the pigment particles on the hydrophobic segment side of the copolymer, and the hydrophilic segment side spreads in the ink. This is because it can be imparted to the pigment particles and the dispersion stability can be improved.

  Here, "one of the main chain unit or the side chain unit is a hydrophilic segment and the other is a hydrophobic segment" means that the segment constituting either the main chain unit or the side chain unit is Any (co) polymer composed mainly of a monomer having a hydrophilic functional group and the other being a (co) polymer of a monomer mainly having a hydrophobic functional group may be used. In the present invention, the graft copolymer is dissolved or stably dispersed at a concentration of 10% by mass or more in an aqueous solution to which an alkali compound corresponding to 80% or more of the acid value of the graft copolymer is added. Those that can achieve the state are particularly preferred.

  Examples of a monomer having a preferable hydrophilic functional group that can be used in forming the graft copolymer include acrylic acid, methacrylic acid, 2-hydroxy (meth) acrylate, EO addition (meth) acrylate, and EO. Addition methyl (meth) acrylate, EO addition ethyl (meth) acrylate, EO addition butyl (meth) acrylate, (meth) acrylamide, etc. are mentioned. In the graft copolymer that can be suitably used in the present invention, the proportion of the monomer having the hydrophilic functional group in the hydrophilic segment (hydrophilic portion) in the graft copolymer is 30% by mass or more, and further 50% by mass. % Or more is preferable.

  Moreover, as a monomer having a preferable hydrophobic functional group used in the graft copolymer used in the present invention, styrene, α-methylstyrene, benzyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, alicyclic (Meth) acrylate, C1-C21 alkyl (meth) acrylate, N-alkyl substituted (meth) acrylamide, etc. are mentioned. The monomers having these hydrophobic functional groups are used in the graft copolymer that can be suitably used in the present invention. The monomers having these hydrophobic functional groups occupy the hydrophobic segment (hydrophobic part) in the graft copolymer. The proportion is preferably 30% by mass or more, and more preferably 50% by mass or more.

  The graft copolymers used in the present invention are in particular graft copolymers by means of (co) polymers consisting of one or more monomers selected from acrylic acid, acrylate esters, acrylamides and acrylamide N-substituted products. When the hydrophilic side chain unit is formed, it is preferable because the dispersion stability of the ink can be further improved.

  The graft copolymer used in the present invention is, for example, a polymerization method in which a monomer is polymerized from a polymerization starting point on a main chain unit to grow a side chain unit, or a side chain unit synthesized in advance is converted into a main chain. It can be obtained by a known synthesis method such as a macromonomer method for binding to a unit.

  The dispersant as mentioned above used in the present invention preferably has an acid value of 50 mgKOH / g to 300 mgKOH / g, more preferably 80 mgKOH / g to 300 mgKOH / g. When a dispersant having an acid value in the above range is used, the solubility of the dispersant in the dispersion medium can be increased when the pigment is dispersed in the preparation of the pigment dispersion used for preparing the ink. A solution (dispersion slurry) in which pigment particles having relatively low viscosity are suspended in a dispersion medium can be prepared. As a result, when preparing an ink, it is possible to easily disperse the pigment dispersion in an aqueous medium, and it is easy to produce a pigment ink having stable ink properties, which is preferable.

  In the ink according to the present invention, the dispersant only needs to contain at least the polymer having the above-described configuration, and the dispersant may be composed of one or a plurality of the polymers. In addition, a polymer other than the above may be incorporated into the dispersant as long as the polymer having the above-described configuration is included. As polymers other than the above, various vinyl (co) polymers, or acrylic resins, and natural resins such as rosin, shellac and starch can be preferably used.

  In the ink according to the present invention, the polymer used as a pigment dispersant is preferably contained in a total amount of 0.1 to 15% by mass with respect to the total mass of the ink. The polymer having a phenylalkyl group at the terminal is preferably contained in the range of 0.5 to 10% by mass with respect to the total mass of the ink.

  In order to increase the solubility of the dispersant, the dispersion slurry or pigment ink is preferably adjusted to be neutral or alkaline. In other words, this is preferable because the solubility of the polymer used as the dispersant is improved, so that fine particles can be easily formed by dispersion, and the long-term storability of the produced pigment ink is further improved. However, in this case, since it may cause corrosion of various members used in the ink jet recording apparatus, it is desirable that the pH range is 7-10. Examples of the pH adjuster used in this case include various organic amines such as diethanolamine and triethanolamine, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide, Examples include organic acids and mineral acids.

  The ink according to the present invention includes at least a pigment, a water-soluble organic solvent, and water in addition to the dispersant described above. Hereinafter, these components will be described.

The ink according to the present invention preferably contains a pigment in a mass ratio of 1 to 20 mass%, more preferably 2 to 12 mass% with respect to the total mass of the ink. In the present invention, the following pigments can be used. First, examples of black pigments that can be used in the present invention include carbon black. For example, carbon black produced by a furnace method or a channel method having a primary particle size of 15 to 40 mμm (nm), Those having characteristics such as a specific surface area by the BET method of 50 to 400 m ² / g, a volatile content of 0.5 to 10% by mass, and a pH value of 2 to 10 can be preferably used. Examples of commercially available products having such characteristics include No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical), RAVEN1255 (manufactured by Colombia), REGAL330R, 400R, 660R, MOGUL L (manufactured by Cabot), There are Color Black FW1, FW18, S160, S170, Printex 35, Printex U (manufactured by Degussa) and the like, and any of them can be preferably used.

  Examples of yellow pigments that can be used in the present invention include C.I. I. Pigment Yellow 1, 2, 3, 13, 16, 74, 83, 109, 128, 155, and the like. Examples of magenta pigments include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, quinacridone solid solution, C.I. I. Pigment Violet 19 etc. are mentioned. Examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 16, 22, C.I. I. Vat Blue 4, 6 etc. are mentioned. Of course, the present invention is not limited to these. In addition to the above, newly manufactured pigments such as self-dispersing pigments can also be used.

  An aqueous medium suitable for forming the ink according to the present invention is a mixed solvent of water and a water-soluble organic solvent. However, water is not general water containing various ions but ion-exchanged water (dehydrated water). It is preferred to use ionic water).

  Examples of the water-soluble organic solvent used by mixing with water include carbon atoms of 1 such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like. Alkyl alcohols of -4; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, 1,2-hex Alkylene glycols having 2 to 6 carbon atoms such as ethylene diol and diethylene glycol; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of polyhydric alcohols; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Among the water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferable.

  The content of the water-soluble organic solvent in the ink as described above is generally in the range of 3 to 50% by mass, more preferably in the range of 3 to 40% by mass with respect to the total mass of the ink. The water content is 10 to 90% by mass, more preferably 30 to 80% by mass, based on the total mass of the ink.

  In addition to the above-described components, the ink according to the present invention may be appropriately added with additives such as surfactants, antifoaming agents, preservatives, etc. in order to obtain inks having desired physical properties as required. can do. As an example of the addition amount, 0.05 to 10% by mass, preferably 0.2 to 5% by mass is suitable with respect to the total mass of the ink.

  As a method for producing an ink according to the present invention comprising the above-described components, first, a pigment is added to an aqueous medium in which at least a polymer as a dispersant and water are mixed, and after mixing and stirring, A dispersion process is performed using a dispersion means, and a centrifugal separation process is performed as necessary to obtain a desired pigment dispersion. Next, if necessary, an aqueous medium, a sizing agent, or appropriately selected additive components such as those mentioned above are added to the pigment dispersion and stirred to obtain an ink according to the present invention.

  When a polymer having an acidic functional group is used as the dispersant, the dispersion stability of the ink can be improved by adding a base when preparing the pigment dispersion in order to dissolve the polymer. Examples of bases that can be preferably used in this case include organic amines such as monoethanolamine, diethanolamine, triethanolamine, amine methylpropanol, and ammonia, or inorganic bases such as potassium hydroxide and sodium hydroxide. It is done.

  In the method for preparing the ink containing the pigment, as described above, the pigment dispersion obtained by performing the dispersion treatment is used for the preparation of the ink, but the dispersion performed during the preparation of the pigment dispersion is used. Before the treatment, it is effective to add a pigment to the dispersant and the aqueous medium for premixing. That is, the premixing operation is preferable because it improves wettability of the pigment surface and promotes adsorption of the dispersant onto the pigment surface.

  The disperser used in the pigment dispersion treatment may be any commonly used disperser, and examples thereof include a ball mill, a roll mill, a sand mill, and a nanomizer (trade name). Among them, a high-speed sand mill is preferably used, and examples thereof include a super mill, a sand grinder, a bead mill, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  In order to enable the ink containing the pigment to be suitably used in the ink jet recording method, it is preferable to use an ink having an optimum particle size distribution from the request of clogging resistance and the like. As a method for obtaining a pigment having a desired particle size distribution, it is possible to reduce the size of the grinding media of the disperser as mentioned above, increase the filling rate of the grinding media, increase the processing time, and discharge speed. For example, a method of slowing down, classifying with a filter or a centrifuge after pulverization, and a combination of these methods.

  The ink containing the pigment having the above-described constitution according to the present invention is combined with a reaction liquid containing at least a compound having an action of increasing the average particle size of the pigment particles contained in the ink when in contact with the ink. When used as a set, it is possible to give a good printed matter with higher printing density and high color development.

Hereinafter, the reaction solution used in the present invention will be described. As the compound (reactant) having the effect of increasing the average particle size of the pigment particles contained in the ink contained in the reaction liquid, a polyvalent metal salt can be mentioned. The polyvalent metal salt is composed of divalent or higher polyvalent metal ions and anions that bind to these polyvalent metal ions. Specific examples of the polyvalent metal ion include, for example, divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ and Zn ²⁺ , or trivalent such as Fe ³⁺ and Al ^3+. A metal ion is mentioned. Further, examples of the anion bonded to these include Cl ⁻ , NO ₃ ⁻ , SO ₄ ^{2− and the} like. These reactants preferably react with the pigment in the ink instantaneously to produce an action of increasing the average particle size of the pigment particles. In order to do this, it is desirable that the total charge concentration of polyvalent metal ions in the reaction solution be at least twice the total charge concentration of reverse polarity ions in the ink.

  The reaction liquid used in the present invention is composed of a composition containing at least the above-mentioned reactant and an aqueous medium. As the aqueous medium, it is preferable to use a mixed medium of water and a water-soluble organic solvent. As the water-soluble organic solvent, any of those which can be contained in the ink described above can be used. Although there is no restriction | limiting in particular about content of the water-soluble organic solvent in the reaction liquid in this invention, 5-60 mass% of the reaction liquid total mass, More preferably, 5-40 mass% is suitable.

  In the reaction solution used in the present invention, additives such as a viscosity adjusting agent, a pH adjusting agent, a preservative, and an antioxidant may be appropriately blended as necessary, but it functions as a penetration accelerator. The selection and addition amount of the surfactant to be used must be careful in order to suppress the permeability of the reaction liquid to the recording medium. Furthermore, the reaction liquid used in the present invention is more preferably colorless, but it may be a light color in a range that does not change the color tone of each color ink when mixed with ink on the recording medium. Furthermore, the reaction solution used in the present invention having the above-described configuration has a viscosity of 1 to 30 cps. It is preferably adjusted so as to be in the range.

  The recording medium used for carrying out the image forming method according to the present invention is not particularly limited, and so-called plain papers such as copy papers and bond papers conventionally used are preferably used. Of course, a coated paper specially prepared for ink-jet recording and a transparent film for OHP are also preferably used, and can also be suitably used for general high-quality paper and glossy paper.

  The image recording method using the ink set according to the present invention may be any method that allows the reaction liquid and the ink to contact and coexist on the recording medium, but after applying the reaction liquid to the recording medium in advance. Therefore, it is necessary to apply ink to the recording medium.

  As a method of preliminarily applying the reaction liquid to the recording medium, a method of adhering to the entire surface of the recording medium with a spray, a roller, or the like can be considered, but only in the vicinity of the image forming area where the ink adheres and the image forming area. It is preferable to carry out by an ink jet system capable of selectively and uniformly attaching. Further, the time from when the reaction liquid is attached to the recording medium to when the ink is attached is not particularly limited, but in order to carry out the present invention more effectively, within a few seconds, especially Preferably, it is within 1 second. As a method for attaching the reaction liquid to the recording medium, various ink jet recording methods can be used. Particularly preferred is a so-called on-demand type in which droplets are ejected using bubbles generated by thermal energy. It is a thermal ink jet system. The image forming area referred to in the present invention is an area to which ink dots adhere, and the vicinity of the image forming area is separated by about 1 to 5 dots outside the area to which ink dots adhere. Refers to an area.

  Next, an ink jet recording method suitable for using the ink set according to the present invention will be described. In addition, specific examples of the configuration of a cartridge, a recording unit, an ink jet recording apparatus, and a liquid discharge head preferably used in these apparatuses, to which the reaction liquid and ink constituting the ink set according to the present invention are preferably applied, will be described. .

  FIG. 1 is a schematic perspective view showing an essential part of an example of an ink jet recording head of a discharge type that is suitable for an image recording apparatus according to the present invention and that communicates air bubbles with the atmosphere during discharge, and an ink jet printer having this head. In FIG. 1, an ink jet printer includes a transport device 1030 that intermittently transports a paper 1028 as a recording medium provided in a casing 1008 along a longitudinal direction in a direction indicated by an arrow P shown in the drawing, A recording unit 1010 that is reciprocated along a guide shaft 1014 substantially parallel to an arrow S direction substantially orthogonal to the conveyance direction P of the paper 1028 by the conveying device 1030, and a moving drive as a driving unit that reciprocates the recording unit 1010. Part 1006. Reference numeral 1020 denotes a driving unit.

  The moving drive unit 1006 is arranged substantially in parallel with pulleys 1026a and b arranged on rotating shafts opposed to each other with a predetermined interval, belt 1016 wound around the two pulleys, roller units 1022a and b, and the roller units. And a motor 1018 that drives a belt 1016 coupled to the carriage member 1010a of the recording unit 1010 in the forward direction and the reverse direction.

  When the motor 1018 is activated and the belt 1016 rotates in the direction of arrow R in FIG. 1, the carriage member 1010a of the recording unit 1010 is moved by a predetermined amount of movement in the direction of arrow S in FIG. When the motor 1018 is activated and the belt 1016 rotates in the direction opposite to the arrow R direction shown in the figure, the carriage member 1010a of the recording unit 1010 is in the direction opposite to the arrow S direction in FIG. Is moved by a predetermined amount. Further, a recovery unit 1026 for performing an ejection recovery process of the recording unit 1010 is disposed at one end portion of the movement driving unit 1006 at a position serving as a home position of the carriage member 1010a so as to face the ink ejection port array of the recording unit 1010. Is provided.

  The recording unit 1010 includes ink jet cartridges (hereinafter sometimes simply referred to as cartridges) 1012Y, 1012M, 1012C, and 1012B. Each of the inks contains, for example, yellow, magenta, cyan, and black pigments. The carriage member 1010a is detachably provided.

  FIG. 2 shows an example of an ink jet cartridge that can be mounted on the above-described ink jet recording apparatus. The cartridge 1012 in this example is of a serial type, and a main part is composed of an ink jet recording head (also referred to as a liquid discharge head) 100 and a liquid tank 1001 that stores liquid such as ink or reaction liquid.

  The inkjet recording head 100 is formed with a large number of ejection ports 832 for ejecting liquids such as ink and reaction liquid, and these liquids are ejected from the liquid tank 1001 through a liquid supply passage (not shown). To the common liquid chamber (see FIG. 3). A cartridge 1012 shown in FIG. 2 is formed by integrally forming an ink jet recording head 100 and a liquid tank 1001 so that liquid can be supplied into the liquid tank 1001 as necessary. A structure in which a liquid tank 1001 is connected to 100 in a replaceable manner may be adopted.

  A specific example of the above-described liquid discharge head that can be mounted on the ink jet printer having such a configuration will be described in more detail below. FIG. 3 is a schematic perspective view schematically showing a main part of a liquid discharge head suitable for the ink jet recording apparatus of the present invention. In the figure, electrical wiring for driving the electrothermal transducer is omitted.

  In the liquid discharge head 100 used in the present invention, for example, a substrate 934 made of glass, ceramics, plastic, metal, or the like as shown in FIG. 3 is used. The material of the substrate 934 is not the essence of the present invention, but functions as a part of the flow path component, and serves as a support for the material layer that forms the ink discharge energy generating element and the liquid flow path and discharge port described later. As long as it can function, it is not particularly limited. Therefore, in this example, a case where a Si substrate (wafer) is used will be described. Ink ejection openings are formed on such a substrate 934. In addition to the formation method using laser light, for example, MPA (Mirror Projection) using an orifice plate (ejection opening plate) 935 described later as a photosensitive resin. A method of forming the discharge port by an exposure apparatus such as Aliner may also be mentioned.

  In FIG. 3, reference numeral 934 denotes a substrate including an electrothermal conversion element (hereinafter also referred to as a heater) 931 and an ink supply port 933 including a long groove-like through-hole as a common liquid chamber portion. On both sides of the mouth 933 in the longitudinal direction, heaters 931 serving as thermal energy generating means are arranged in a staggered pattern, one row at a time, and the distance between the electrothermal conversion elements is, for example, 300 dpi. The substrate 934 is provided with an ink flow path wall 936 for forming an ink flow path. The ink flow path wall 936 is further provided with a discharge port plate 935 having a discharge port 832.

  In FIG. 3, the ink flow path wall 936 and the ejection port plate 935 are shown as separate members. However, the ink flow path wall 936 is placed on the substrate 934 by a technique such as spin coating. By forming the same, the ink flow path wall 936 and the discharge port plate 935 can be simultaneously formed as the same member. Here, the discharge port surface (upper surface) 935a side is further subjected to water repellent treatment. In the illustrated apparatus, a serial type head that performs recording while scanning in the direction of arrow S in FIG. 1 is used, for example, recording is performed at 1,200 dpi. The drive frequency is 10 kHz, and one discharge port performs discharge at the shortest time interval of 100 μs.

  The liquid discharge operation by the ink jet recording head having the above-described configuration is described in, for example, FIGS. 16 to 23 of JP-A-2002-201390 and the description thereof. In the liquid discharge head of the example shown in the above Japanese Patent Application Laid-Open No. 2002-201390, a plurality of grooves dispersed with respect to the center of the discharge port when discharging the liquid in the volume reduction stage after the bubbles grow to the maximum volume. As a result, the direction of the main droplet at the time of ejection can be stabilized. As a result, it is possible to provide a liquid ejection head with no landing deviation and high landing accuracy. In addition, high-speed and high-definition printing can be realized by being able to stably perform ejection even with respect to variation in foaming at a high driving frequency.

  In particular, in the liquid discharge head of the example shown in the above-mentioned Japanese Patent Application Laid-Open No. 2002-201390, the bubbles are communicated with the atmosphere by discharging the liquid by first communicating the bubbles with the atmosphere at the bubble volume reduction stage. Since mist generated when ejecting droplets can be prevented, it is possible to suppress a state where droplets adhere to the ejection port surface, which is a cause of sudden non-ejection. As another embodiment of a recording head of the above-described ejection type that allows air bubbles to communicate with the atmosphere during ejection as described above, which can be suitably used in the present invention, for example, as described in Japanese Patent No. 2783647, so-called edge shooter type Is mentioned.

  The image recording method according to the present invention is particularly effective in inkjet recording heads and recording apparatuses that perform recording by forming flying droplets using thermal energy, even among inkjet recording methods. is there. As for the typical configuration and principle, for example, those performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 are preferable. .

  This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it corresponds to a sheet or a liquid path that holds liquid (ink). By applying at least one drive signal that corresponds to the recorded information and gives a rapid temperature rise exceeding film boiling to the arranged electrothermal transducer, thermal energy is generated in the electrothermal transducer, and recording is performed. This is effective because film boiling occurs on the heat acting surface of the head, and as a result, bubbles in the liquid (ink) corresponding to this drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, since the bubble growth and contraction is performed immediately and appropriately, and thus it is possible to achieve discharge of liquid (ink) having particularly excellent responsiveness.

  As the pulse-shaped drive signal at this time, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by adopting the conditions described in US Pat. No. 4,313,124 related to the invention concerning the temperature rise rate of the heat acting surface.

  The configuration of the recording head that constitutes the ink cartridge, the recording unit, and the ink jet recording apparatus used when realizing the image recording method according to the present invention is the ejection as disclosed in each of the above-mentioned specifications. U.S. Pat. No. 4,558 which discloses a configuration in which the heat acting portion is bent in addition to the combined configuration (straight liquid channel or right angle liquid channel) of the outlet, the liquid channel and the electrothermal transducer , 333 and US Pat. No. 4,459,600 are also preferably used.

  In addition, for a plurality of electrothermal transducers, Japanese Patent Application Laid-Open No. 59-123670 that discloses a configuration in which a common slit is used as a discharge portion of the electrothermal transducer, or an aperture that absorbs pressure waves of thermal energy is provided. It is also effective as a configuration based on Japanese Patent Application Laid-Open No. 59-138461 which discloses a configuration corresponding to the discharge unit.

  Furthermore, as a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length of the recording head is a combination of a plurality of recording heads as disclosed in the above specification. Either a configuration that satisfies the above requirements or a configuration as a single recording head that is integrally formed may be used.

  In addition, by mounting on the apparatus main body, the ink can be integrated with the replaceable chip type recording head that can be electrically connected to the apparatus main body and supplied with ink from the apparatus main body, or the recording head itself. A cartridge type recording head provided with a tank can also be used.

  In addition, it is preferable to add a recovery means for the recording head, a preliminary auxiliary means, etc. provided in the ink jet type image recording apparatus according to the present invention, since the effects of the present invention can be further stabilized. . Specifically, capping means for the recording head, cleaning means, pressurization or suction means, electrothermal converter or a heating element different from this, or preheating means by a combination of these, recording and In order to perform stable recording, it is also effective to perform a preliminary discharge mode in which another discharge is performed.

  Hereinafter, it demonstrates still more concretely using an Example and a comparative example. In the following description, “part” and “%” are based on mass unless otherwise specified.

[Example 1]
<Preparation of dispersant>
(Preparation of Dispersant A1)
In this example, first, 1,1′-azobis (1-acetoxy-1-phenylethane) having a phenylalkyl group was used as a polymerization initiator, and acrylic acid as a monomer having a hydrophilic functional group was used. Then, benzyl acrylate and n-butyl methacrylate, which are monomers having a hydrophobic functional group, were used as synthetic raw materials, and polymerization was performed as follows to obtain Dispersant A1.

A mixture of 40 parts of benzyl acrylate, 20 parts of n-butyl methacrylate, 40 parts of acrylic acid and 6 parts of a polymerization initiator 1,1′-azobis (1-acetoxy-1-phenylethane) was added to 500 parts of 2-propanol, and the polymerization temperature. The solution was added dropwise at 75 ° C. under a N ₂ stream for 3 hours. After the dropwise addition, the polymerization reaction was completed by keeping the temperature at 75 ° C. for 2 hours. Thereafter, the reaction product was developed in 1,000 parts of hexane, unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain dispersion resin A1. The obtained dispersion resin A1 had a weight average molecular weight of 5,000 and an acid value of 200 mgKOH / g. When structural analysis was performed on the dispersant A1 obtained above with an NMR apparatus, it was confirmed that a phenylalkyl group derived from a polymerization initiator was introduced into the terminal portion.

<Preparation of pigment dispersion K1>
・ Dispersant A1 5 parts ・ Potassium hydroxide 1 part ・ Diethylene glycol 20 parts ・ Ion-exchanged water 59 parts

The above components containing the dispersant A1 obtained above are mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component. To this solution, 15 parts of carbon black pigment Printex 90 (manufactured by Degussa) and 1 part of isopropyl alcohol were added, premixed for 30 minutes, and then dispersed under the following conditions.
・ Disperser: Sand grinder (Igarashi Machine)
・ Crushing media: Zirconium beads, 1 mm diameter ・ Filling rate of grinding media: 70% (volume ratio)
-Grinding time: 3 hours Further, centrifugal separation (12,000 rpm, 20 minutes) was performed to remove coarse particles to obtain a pigment dispersion K1.

<Preparation of ink k1>
Using the pigment dispersion K1 obtained above, components having the following composition ratio were mixed, and then filtered to prepare an ink containing a pigment by a conventional method, which was designated as ink k1.
-Pigment dispersion K1 30.0 parts-Glycerol 10.0 parts-Ethylene glycol 5.0 parts-N-methylpyrrolidone 5.0 parts-Acetylenol EH (manufactured by Kawaken Fine Chemicals)
1.0 part ・ Ion-exchanged water 49.0 parts

<Evaluation of ink (continuous printing durability test)>
The ink was evaluated as follows. The ink k1 produced as described above was filled in an ink cartridge, and continuous printing was performed using a commercially available inkjet printer BJF890 (manufactured by Canon). At this time, it was checked at what number the ink non-ejection occurred, and the determination was made according to the following criteria. The obtained evaluation results are shown in Table 1 below.

(Evaluation criteria)
◎: Not generated at 1,000 sheets ○: Generated at 100 or more and less than 1,000 sheets ×: Generated at less than 100 sheets

(Comparative Example 1)
<Preparation of dispersant>
(Preparation of Dispersant A)
In this comparative example, azobisisobutyronitrile that does not have a phenylalkyl group is used as a polymerization initiator, and acrylic acid that is a monomer having a hydrophilic functional group and a monomer that has a hydrophobic functional group are used. Dispersant A was obtained by polymerization as follows using a certain styrene and n-butyl methacrylate as a synthetic raw material.

A mixture of 40 parts of styrene, 20 parts of n-butyl methacrylate, 40 parts of acrylic acid and 6 parts of a polymerization initiator azobisisobutyronitrile is added to 500 parts of 2-propanol at a polymerization temperature of 75 ° C. under an N ₂ stream for 3 hours. It was dripped over. After the dropwise addition, the polymerization reaction was completed by keeping the temperature at 75 ° C. for 2 hours. Thereafter, the reaction product was developed in 1,000 parts of hexane, unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain dispersion resin A. The obtained dispersion resin A had a weight average molecular weight of 6,000 and an acid value of 190 mgKOH / g. The structural analysis of the dispersant A obtained above was performed with an NMR apparatus, and no phenylalkyl group was introduced into the terminal portion.

<Preparation of pigment dispersion K2>
-Dispersant A 5 parts-Potassium hydroxide 1 part-Diethylene glycol 20 parts-Ion-exchanged water 59 parts Pigment dispersion K2 having the above composition was subjected to the same dispersion treatment as in the preparation of pigment dispersion K1 in Example 1. Obtained.

<Production and Evaluation of Ink k2>
Ink k2 was prepared in the same manner as ink k1, except that pigment dispersion K1 used in the preparation of ink k1 in Example 1 was changed to pigment dispersion K2 prepared above. The obtained ink k2 was evaluated by conducting a continuous printing durability test in the same manner as the ink k1 prepared in Example 1. The evaluation results are shown in Table 1 below.

[Example 2]
<Production of Dispersant A2>
(Preparation of macromonomer B1)
A mixture of 40 parts of acrylic acid having a hydrophilic functional group, 10 parts of α-methylstyrene dimer which is a chain transfer agent having a phenylalkyl group, and 6 parts of azobisisobutyronitrile which is a radical polymerization initiator is 1-methoxy- The mixture was added dropwise to 500 parts of 2-propanol at a polymerization temperature of 75 ° C. under a N ₂ stream over 3 hours. After the dropwise addition, the polymerization reaction was completed by keeping the temperature at 75 ° C. for 2 hours. Thereafter, the reaction product was developed in 1,000 parts of hexane, the unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain a macromonomer B1 having a hydrophilic functional group.

(Preparation of dispersant A2)
40 parts of the macromonomer B1 having a hydrophilic functional group obtained above was previously dissolved in 500 parts of 1-methoxy-2-propanol, 40 parts of benzyl methacrylate, 20 parts of n-butyl methacrylate and azobisisobutyronitrile 6 Part of the mixture was added dropwise to 1-methoxy-2-propanol in which the macromonomer B1 was dissolved over 3 hours at a polymerization temperature of 75 ° C. under a N ₂ stream. After the dropwise addition, the polymerization reaction was completed by keeping the temperature at 75 ° C. for 2 hours. Thereafter, the reaction product was developed in 1,000 parts of hexane, the unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain Dispersant A2.

  The obtained dispersant A2 had a weight average molecular weight of 7,500 and an acid value of 180 mgKOH / g. Further, structural analysis of the dispersant A2 produced above with an NMR apparatus confirmed that an α-methylstyrene dimer-derived phenylalkyl group was introduced into the terminal portion. Further, the dispersant A2 was a graft copolymer having a structure in which the main chain unit is a hydrophobic part and the side chain unit is a hydrophilic part.

<Preparation of pigment dispersion C1>
-Dispersant A2 5 parts-Potassium hydroxide 1 part-Diethylene glycol 20 parts-Ion-exchanged water 59 parts Pigment dispersion C1 having the above composition was subjected to the same dispersion treatment as in the preparation of pigment dispersion K1 in Example 1. Obtained. At this time, 15 parts of phthalocyanine pigment Irgalite Blue GLNF (manufactured by Ciba Specialty Chemicals) was used instead of 15 parts of carbon black pigment Printex 90 (manufactured by Degussa).

<Production and Evaluation of Ink c1>
Ink c1 was prepared in the same manner as in ink k1, except that pigment dispersion K1 used in the preparation of ink k1 in Example 1 was changed to pigment dispersion C1 prepared above. The obtained ink c1 was evaluated by conducting a continuous printing durability test in the same manner as the ink k1 prepared in Example 1. The evaluation results are shown in Table 1 below.

Example 3
<Production of Dispersant A3>
(Preparation of macromonomer B2)
A mixture of 40 parts of benzyl acrylate having a hydrophobic functional group, 10 parts of α-methylstyrene dimer which is a chain transfer agent having a phenylalkyl group and 6 parts of azobisisobutyronitrile is added to 500 parts of 1-methoxy-2-propanol. The polymerization temperature was dropped at 75 ° C. for 3 hours under a N ₂ stream. After dropping, the polymerization reaction was completed by maintaining at 75 ° C. for 2 hours. Thereafter, the reaction product was developed in 1,000 parts of hexane, the unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain a macromonomer B2 having a hydrophobic functional group.

(Preparation of Dispersant A3)
50 parts of the macromonomer B2 having a hydrophobic functional group obtained above was previously dissolved in 500 parts of 1-methoxy-2-propanol, and 30 parts of acrylic acid, 20 parts of ethyl acrylate and 6 parts of azobisisobutyronitrile. The mixture was added dropwise to 1-methoxy-2-propanol in which the macromonomer B2 was dissolved over a period of 3 hours at a polymerization temperature of 75 ° C. under a N ₂ stream. After the dropwise addition, the polymerization reaction was completed by keeping the temperature at 75 ° C. for 2 hours. Thereafter, the reaction product was developed in 1,000 parts of hexane, unreacted product was removed by precipitation purification, and dried under reduced pressure to obtain Dispersant A3.

  The obtained dispersant A3 had a weight average molecular weight of 7,500 and an acid value of 220 mgKOH / g. Furthermore, structural analysis of the dispersant A3 produced above with an NMR apparatus confirmed that a phenylalkyl group derived from α-methylstyrene dimer was introduced into the terminal portion. Furthermore, the dispersant A3 was a graft copolymer having a structure in which the main chain unit is a hydrophilic part and the side chain unit is a hydrophobic part.

<Preparation of pigment dispersion M1>
A pigment dispersion K1 was prepared except that, in the pigment dispersion K1 prepared earlier, the dispersant A1 was changed to the dispersant A3 obtained above, and the pigment was replaced with the quinacridone pigment Chrophtal Pink PT (manufactured by Ciba Specialty Chemicals). In the same manner as described above, a pigment dispersion M1 was prepared.

<Production and Evaluation of Ink m1>
Ink m1 was prepared in the same manner as ink k1 except that pigment dispersion K1 was changed to pigment dispersion M1 obtained above in the preparation of ink k1 of Example 1. The obtained ink m1 was evaluated by performing a continuous printing durability test in the same manner as in the case of the ink k1. The evaluation results are shown in Table 1 below.

[Examples 4 to 8]
<Preparation of dispersants A4 to A8>
First, in the synthesis of the dispersant A1 performed in Example 1, the dispersants A4 to A8 having different acid values used in Examples 4 to 8 were used in the same manner except that the raw material compositions shown in Table 2 below were used. Each was produced.

<Preparation of pigment dispersions K4 to K8>
Pigment dispersions K4 to K8 were prepared in the same manner as in the pigment dispersion K1 prepared in Example 1, except that the dispersants A4 to A8 obtained above were used instead of the dispersant A1.

<Production and Evaluation of Inks k4 to k8>
Inks k4 to k8 were prepared in the same manner as in the case of the ink k1 except that the pigment dispersion K1 was changed to the pigment dispersions K4 to K8 obtained above in the preparation of the ink k1 of Example 1. Then, for each of the obtained inks k4 to k8, a continuous printing durability test was performed and evaluated in the same manner as in the case of the ink k1. The obtained evaluation results are shown in Table 3 below.

Example 9
This embodiment relates to an ink set composed of a combination of a reaction liquid s1 having an action of increasing the average particle diameter of pigment particles contained in ink and inks k1, c1, m1, and y1 when coming into contact with ink.

<Preparation of ink y1>
(Preparation of pigment dispersion Y1)
A pigment dispersion Y1 was prepared in the same manner as in the pigment dispersion C1 prepared in Example 2, except that the phthalocyanine pigment was changed to the azo pigment Irgaphor GELB 8G-CF (manufactured by Ciba Specialty Chemicals).

(Preparation of ink y1)
An ink y1 was prepared in the same manner as in the ink c1 prepared in Example 2, except that the pigment dispersion C1 was changed to the pigment dispersion Y1 obtained above.

<Preparation of reaction solution s1>
Components having the following composition were mixed and then filtered to prepare a reaction solution s1.
・ Diethylene glycol 10.0 parts ・ Methyl alcohol 5.0 parts ・ Magnesium nitrate 3.0 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals)
0.1 part, 81.9 parts of ion-exchanged water

<Creation and evaluation of ink set>
The reaction liquid s1 obtained above and the inks k1, c1, m1, and y1 were combined to obtain the ink set of this example. The inks k1, c1, and m1 prepared in Examples 1 to 3 were used. Using the ink set obtained in this manner, the reaction liquid s1 is first applied to PB paper (manufactured by Canon), which is plain paper, and then the ink k1 so that the reaction liquid s1 and each ink come into contact with each other. , C1, m1, and y1 were applied to produce a printed matter 1A.

  The recording head used here had a recording density of 1,200 dpi, and the driving condition was a driving frequency of 15 kHz. Further, a 4 pl head was used for the ejection volume per dot. The environmental conditions for the print test are unified at 25 ° C./55% RH.

  The printed matter 1A produced had good bleeding, and there was no bleeding between colors. When the printed part was rubbed with an edge part of another paper after about 5 seconds from printing, the printed image did not flow. Further, when the optical density of the portion produced by the ink k1 of the printed portion of the printed matter 1A and the saturation of the portion produced by the ink c1, m1, y1 were measured with a reflection densitometer RD-19I (manufactured by GretagMacbeth), The optical density of the portion prepared with the ink k1 was 1.5, and the saturations of the portions prepared with the ink c1, the ink m1, and the ink y1 were 54, 65, and 82, respectively.

[Reference Example 1]
A printed matter 2A was produced on PB paper (manufactured by Canon), which is plain paper, using the inks k1, c1, m1, and y1 in the same manner as in Example 9 except that the reaction liquid s1 was not used. The produced printed matter 2A was slightly bleeding as compared with the printed matter 1A, and bleeding between colors was observed. When the printed part was rubbed with an edge part of another paper after about 5 seconds from the printing, the printed image did not flow. Further, when the optical density and saturation of the printing part were measured with a reflection densitometer RD-19I (manufactured by GretagMacbeth) in the same manner as in Example 9, the optical density of the part produced with the ink k1 was 1.2. The saturation of the part produced by c1, m1, and y1 obtained values of 44, 61, and 74 in order. As a result, it was confirmed that by using the reaction solution s1, a printed matter having excellent color developability and higher image quality can be obtained.

1 is a schematic perspective view illustrating an example of an ink jet printer that is an image recording apparatus of the present invention. It is a schematic perspective view which shows an example of an inkjet cartridge. It is a typical schematic perspective view which shows an example of a liquid discharge head.

Explanation of symbols

100: inkjet recording head 832: discharge port 931: electrothermal conversion element (heater, ink discharge energy generating element)
933: Ink supply port (opening)
934: Substrate 935: Orifice plate (discharge port plate)
935a: discharge port surface 936: ink channel wall 940: discharge port portion 1001: liquid tank 1006: movement drive unit 1008: casing 1010: recording unit 1010a: carriage member 1012: cartridge 1012Y, M, C, B, S: inkjet Cartridge 1014: Guide shaft 1016: Belt 1018: Motor 1020: Drive unit 1022a, 1022b: Roller unit 1026: Recovery unit 1026a, 1026b: Pulley 1028: Paper 1030: Transport device P: Paper transport direction R: Belt rotation direction S : Direction substantially orthogonal to the paper transport direction

Claims (9)

  An inkjet pigment ink comprising an inkjet pigment ink containing at least a pigment, a dispersant, a water-soluble organic solvent, and water, wherein the dispersant is a polymer having a phenylalkyl group at a terminal.   The inkjet pigment ink according to claim 1, wherein the dispersant is a graft copolymer in which one of a main chain unit or a side chain unit is composed of a hydrophilic segment and the other is composed of a hydrophobic segment.   The side chain unit of the graft copolymer is formed from one or more monomers having a phenylalkyl group at the terminal and selected from acrylic acid, acrylate ester, acrylamide, and acrylamide N-substituted product. The inkjet pigment ink according to claim 2.   The inkjet pigment ink according to any one of claims 1 to 3, wherein the dispersant has an acid value of 50 mgKOH / g to 300 mgKOH / g.   An ink set comprising a pigment ink and a reaction liquid containing at least a compound having an action of increasing an average particle diameter of pigment particles contained in the ink when brought into contact with the ink, wherein the pigment ink comprises: Item 5. An ink set, which is the inkjet pigment ink according to any one of Items 1 to 4.   An image recording method comprising a step of applying the inkjet pigment ink according to any one of claims 1 to 4 to a recording medium.   Before applying the inkjet pigment ink to the recording medium, when the ink comes into contact with the recording medium, a reaction liquid containing at least a compound having an action of increasing the average particle diameter of the pigment particles contained in the ink is recorded on the recording medium. The image recording method according to claim 6, further comprising a step of applying to a medium.   An image recording apparatus comprising means for applying the inkjet pigment ink according to claim 1 to a recording medium. Before applying the inkjet pigment ink to the recording medium, when the ink comes into contact with the recording medium, a reaction liquid containing at least a compound having an action of increasing the average particle diameter of the pigment particles contained in the ink is recorded on the recording medium. The image recording apparatus according to claim 8, further comprising means for applying to a medium.

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