JP5346725B2 - Inkjet recording method using a treatment liquid for inkjet recording - Google Patents

Description

  The present invention relates to a processing liquid that can be used in an ink jet recording method for forming an image on a recording medium by discharging ink containing at least water and a pigment toward a recording medium such as PPC paper, and an ink jet using the processing liquid. It relates to a recording method.

  Conventionally, based on image information read by itself or image information transmitted from another device, ink containing at least water and pigment is ejected from an ink discharge port (nozzle) of an inkjet recording head, such as PPC (Plain Paper Copier) paper. 2. Related Art There is known an ink jet recording apparatus that forms an image by discharging ink toward a recording medium so that ink adheres to the recording surface of the recording medium. The ink jet recording apparatus generally includes an endless transport belt for transporting a recording medium, and an ink jet recording head disposed so as to face the transport belt. An image is formed on the recording medium by ejecting ink from a plurality of ink ejection openings arranged in the ink jet recording head toward the recording medium while the recording medium is conveyed by traveling of the conveying belt. The recording medium on which the ink is adhered and the image is formed is continuously conveyed by the conveyor belt, transferred to the discharge roller at the end of the conveyor belt, and discharged from the conveyor belt.

  In such an ink jet recording apparatus, in order to perform mass high-speed printing such as 100 to 150 sheets / minute, in addition to increasing the driving frequency of the recording head that ejects ink, is it the same as the width of the recording medium? It is proposed to use a line type recording head having a longer length. That is, when a long line type recording head is used instead of a serial type recording head that ejects ink while scanning the recording head in a direction perpendicular to the conveyance direction of the recording medium, the line type recording head is attached to the main body of the apparatus. Since it is fixed, ink can be ejected simultaneously over the entire width of the recording medium, and a much faster processing can be realized as compared with a serial type recording head.

  By the way, in the case of plain paper such as PPC paper, not the recording medium whose recording surface is coated with resin, such as coated paper such as photographic paper, the pigment contained in the ink ejected to the recording medium is inside the recording medium. As a result, there is a problem that the density of the image formed on the recording surface is reduced and the image quality is deteriorated as a result of the excessive penetration (there is another problem that the image shows through). In order to cope with this problem, for example, as disclosed in Patent Document 1, before the ink is attached to the recording medium, a treatment liquid containing polyvalent metal ions such as calcium ions and magnesium ions is previously applied to the recording medium. It is known to be attached (see paragraph 0072 and the like). By doing so, the pigment contained in the ink discharged onto the recording medium reacts with the polyvalent metal ions on the recording surface to promote aggregation, and the excessive penetration of the pigment into the recording medium is suppressed. Is likely to remain on the recording surface, and as a result, a decrease in image density is avoided even with plain paper, and high image quality is achieved (in addition, the problem of image back-through is also solved).

  However, when the remaining amount of the pigment on the recording surface increases, a new problem arises that the pigment on the recording surface easily adheres to the discharge roller that receives the recording medium on which the image is formed at the end of the conveying belt. In particular, when high-speed processing of an ink jet recording apparatus is achieved, the time from when the ink is ejected to the recording medium until the discharge roller comes into contact with the recording medium is shortened, and before the ink moisture penetrates into the recording medium. Since the possibility that the discharge roller comes into contact with the recording medium (in other words, while the ink is insufficiently dried) increases, the pigment remaining on the recording surface is more likely to adhere to the discharge roller. . As a result, the image formed on the recording medium may be chipped or disturbed.

  Furthermore, when the pigment adhering to the discharge roller is transferred to the non-image forming portion of the recording medium and stains the recording medium, or when images are continuously formed on a plurality of recording media, the pigment adheres to the discharge roller. There may be a problem in that the pigment is transferred to a subsequent recording medium and soils a plurality of recording media.

  In this regard, Patent Document 2 discloses an unnecessary solvent for the recording liquid remaining on the recording medium after the recording liquid is discharged to the recording medium and before the recording medium is transferred to the conveying roller at the end of the conveying belt. A technique of absorbing and removing by a solvent absorbing roller is disclosed (see paragraphs 0004 and 0064, FIG. 1).

JP 2002-79740 A JP 2006-263984 A

  However, since the technique disclosed in Patent Document 2 attempts to remove only moisture by bringing the solvent absorption roller into contact with the recording medium immediately after the recording liquid is discharged, the conveyance speed of the recording medium and the absorption roller If the rotation speed is not well synchronized, there is a possibility that the image formed on the recording medium is displaced or disturbed. Further, as the speed is increased, the time during which the absorbing roller can absorb the solvent becomes shorter, so that the absorbing roller may not be able to absorb the solvent completely. Therefore, not only high-speed processing is difficult, but it is necessary to periodically clean or replace the solvent absorbing roller, and the size of the apparatus is increased by the amount of the solvent absorbing roller.

  The present invention addresses the above-described problem in the ink jet recording method in which a treatment liquid is attached to a recording medium and then ink is attached to the recording medium, and achieves high image quality when forming an image on plain paper such as PPC paper. For this reason, the remaining amount of pigment on the recording surface of the recording medium is increased, and in order to realize high-speed processing, the time from when the ink is ejected to the recording medium until the discharge roller contacts the recording medium is shortened. Another object is to suppress the pigment on the recording surface of the recording medium from adhering to the discharge roller.

  That is, the present invention relates to a treatment liquid used in an ink jet recording method in which a treatment liquid is attached to a recording medium, and then ink is attached to the recording medium, comprising a polyvalent metal salt, an emulsion of a cationic polymer compound, It is characterized by containing. According to the present invention, a large amount of pigment remaining on the recording surface of the recording medium is quickly fixed on the recording medium by the action of the emulsion of the cationic polymer compound contained in the treatment liquid, and is coated with the polymer compound. It will be in the state. As a result, the pigment on the recording surface of the recording medium is protected by the coating film of the polymer compound, and even if the discharge roller comes into contact, the discharge roller comes into contact with the coating film, The pigment does not adhere to the discharge roller.

  In this case, the treatment liquid preferably contains 10 to 40% by mass of the polyvalent metal salt and 1 to 10% by mass of the emulsion of the cationic polymer compound. When the composition of the treatment liquid is within this range, the effects of the present invention are exhibited to the maximum and no adverse effects occur.

  The present invention also provides an ink jet recording method in which a treatment liquid is attached to a recording medium, and then ink is attached to the recording medium, the treatment comprising a polyvalent metal salt and an emulsion of a cationic polymer compound. It is characterized by using a liquid. Also according to the present invention, a large amount of pigment remaining on the recording surface of the recording medium is fixed on the recording medium at an early stage and coated with the polymer compound by the action of the emulsion of the cationic polymer compound contained in the treatment liquid. As a result, the pigment on the recording surface of the recording medium is protected by the coating film of the polymer compound, and even if the discharge roller contacts, the discharge roller contacts the coating film. As a result, the pigment does not adhere to the discharge roller.

In this case, 0.2 to 1.8 mg of a treatment liquid containing 10 to 40% by mass of the polyvalent metal salt and 1 to 10% by mass of the emulsion of the cationic polymer compound may be adhered per 1 cm ² of the recording medium. preferable. When the composition of the treatment liquid is in the above range, the effects of the present invention are maximized and no adverse effects occur. And when such a processing liquid is used in the said range, the effect of this invention is exhibited more fully and a bad effect does not arise.

  Since the treatment liquid contains an emulsion of a cationic polymer compound, the treatment liquid itself becomes an emulsion. In that case, since the content of the cationic polymer compound emulsion in the treatment liquid is relatively small, the emulsion as the treatment liquid is an O / W type (oil-in-water type) emulsion.

  The present invention increases the residual amount of pigment on the recording surface of the recording medium in order to achieve high image quality when forming an image on plain paper such as PPC paper, and ink is applied to the recording medium in order to realize high-speed processing. Even when the time from the ejection to the time when the discharge roller contacts the recording medium is shortened, there is a remarkable effect that the pigment on the recording surface of the recording medium is prevented from adhering to the discharge roller.

1 is a schematic configuration diagram of an ink jet recording apparatus suitable for carrying out an ink jet recording method according to the present invention. FIG. 3 is an enlarged vertical sectional view of a dot forming portion provided in an ink jet recording head of the ink jet recording apparatus.

(Processing liquid)
The treatment liquid according to the present invention is characterized in that it contains a polyvalent metal salt and an emulsion of a cationic polymer compound.

  As the solvent of the treatment liquid that can be used in the present invention, a solvent similar to the solvent conventionally used as a solvent for ink is used. For example, a purification agent to which a drying inhibitor, a pH adjuster, an antifoaming agent, or the like is added. Water or the like can be preferably used.

The polyvalent metal salt that can be used in the present invention is composed of divalent or higher polyvalent metal ions (positively charged cations) and anions (negatively charged anions) that bind to these polyvalent metal ions. The polyvalent metal ions are dissolved in the solvent of the treatment liquid to produce the polyvalent metal ions in the treatment liquid. Specific examples of the polyvalent metal ions include, for example, divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , and Ba ²⁺ , and trivalent such as Al ³⁺ , Fe ³⁺ , and Cr ^3+. Metal ions and the like. Specific examples of the anion include Cl ⁻ , NO ₃ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , CH ₃ COO ^{− and the} like. In particular, a polyvalent metal salt composed of Ca ²⁺ or Mg ²⁺ can be preferably used from the two viewpoints of the pH of the treatment liquid and the quality of the image formed on the recording medium. A polyvalent metal salt can be used individually by 1 type or in combination of 2 or more types according to a condition.

  In the treatment liquid of the present invention, the content of the polyvalent metal salt may be changed according to the type of the metal salt and the like, but is generally in the range of 10 to 40% by mass, preferably in the range of 20 to 35% by mass. More preferably, it is the range of 25-30 mass%. When the content of the polyvalent metal salt is excessively small, the effect of promoting the aggregation of the pigment in the ink tends to be insufficient. When the content of the polyvalent metal salt is excessively large, the polyvalent metal salt tends to precipitate without being completely dissolved in the solvent.

  Examples of the cationic polymer compound emulsion that can be used in the present invention include acrylic resin emulsions, N, N-dimethylaminoethyl methacrylic resin emulsions, urethane acrylic resin emulsions, and styrene butadiene resin emulsions. Used. In particular, N, N-dimethylaminoethyl methacrylic resin emulsion can be preferably used from the viewpoint of the effect of promoting the aggregation of the pigment in the ink, the effect of early fixing of the aggregated pigment particles, and the effect of coating the pigment particles on the recording surface. . The emulsion of the cationic polymer compound can be used alone or in combination of two or more depending on the situation.

  In the treatment liquid of the present invention, the content of the emulsion of the cationic polymer compound may be changed according to the type of the emulsion and the like, but is generally in the range of 1 to 10% by mass, preferably 2 to 8% by mass. More preferably, it is the range of 4-6 mass%. If the content of the cationic polymer compound emulsion is too small, the effect of promoting the aggregation of the pigment in the ink, the effect of fast fixing the aggregated pigment particles, and the effect of covering the pigment particles on the recording surface tend to be insufficient. If the emulsion content of the cationic polymer compound is excessively large, the viscosity of the treatment liquid becomes too high, and it becomes difficult to handle the treatment liquid and attach (apply) to the recording medium, or the treatment liquid may be dried. It becomes faster, and problems such as the solidification of the treatment liquid easily and the decrease in the solubility of the polyvalent metal salt in the treatment liquid tend to occur.

  The treatment liquid of the present invention may contain, for example, a drying inhibitor, a pH adjuster, an antifoaming agent and the like in addition to the emulsion of the polyvalent metal salt and the cationic polymer compound.

  Moreover, since the treatment liquid of the present invention contains an emulsion of a cationic polymer compound, the treatment liquid itself is also an emulsion. In that case, in order to stabilize the emulsion as the treatment liquid, the treatment liquid may further contain a conventionally known emulsifier. In particular, since the content of the emulsion of the cationic polymer compound in the treatment liquid is relatively small, the emulsion as the treatment liquid is an O / W type (oil-in-water type) emulsion. Therefore, the emulsifier to be contained in the treatment liquid is one having a relatively large HLB value (for example, any one having an HLB value of 8 to 16).

  The treatment liquid of the present invention can be adjusted by mixing the raw materials as described above and sufficiently stirring them using a homomixer or the like while controlling the temperature. However, if the polyvalent metal salt and the cationic polymer compound emulsion are mixed together in a short period of time, there may be a problem that the resin component in the emulsion will precipitate. Depending on the situation, a solution containing only the polyvalent metal salt and a solution containing only the emulsion of the cationic polymer compound are prepared separately, and the homomixer is used while slowly controlling the temperature of these two types of solutions. Etc. are preferably used as a final treatment liquid. By doing so, the problem that the resin component in the emulsion is precipitated does not occur.

The coating amount of the treatment liquid of the present invention on the recording medium may be changed according to the content of the polyvalent metal salt in the treatment liquid and the content of the cationic polymer compound emulsion in the treatment liquid. When the content of the polyvalent metal salt is in the range of 10 to 40% by mass and the content of the emulsion of the cationic polymer compound is in the range of 1 to 10% by mass, the content is generally 0.2 to 1 per 1 cm ² of the recording medium. The range is 1.8 mg, preferably 0.4 to 1.5 mg, and more preferably 0.6 to 1.2 mg. When the coating amount of the treatment liquid on the recording medium is excessively small, the effect of promoting the aggregation of the pigment in the ink, the effect of early fixing of the aggregated pigment particles, and the effect of covering the pigment particles on the recording surface tend to be insufficient. If the amount of the treatment liquid applied to the recording medium is excessively large, cockling (a phenomenon in which the surface of the paper that is the recording medium becomes wavy as a result of the liquid) and curling of the paper that is the recording medium are likely to occur.

(ink)
The ink that can be used in the present invention contains at least water and a pigment, and, if necessary, for example, a polymer dispersant, a surfactant (as a wetting agent or a surface tension adjusting agent), a water-soluble organic solvent (penetration) Etc.) can be added as accelerators or drying inhibitors.

  Examples of pigments that can be used in the present invention include insoluble azo pigments, soluble azo pigments, phthalocyanine blue, isoindolinone, quinacridone, dioxazine violet, organic pigments such as verinone / betalin, and inorganic pigments such as carbon black and titanium dioxide. Examples thereof include colorant pigment components and extender pigments such as white clay, talc, clay, diatomaceous earth, calcium carbonate, barium sulfate, titanium oxide, alumina white, silica, kaolin, and aluminum hydroxide.

  More specifically, black (K) pigments include furnace black, lamp black, acetylene black, channel black and other carbon blacks (CI Pigment Black 7), copper oxide, iron oxide (CI pigment black 11) or metals such as titanium oxide, and organic pigments such as aniline black (CI pigment black 1) can be mentioned. The above can be used in combination.

  Examples of yellow (Y) pigments include C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 74, 81, 83 (Disazo Yellow HR), 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, etc. Or two or more types can be used in combination.

  Examples of magenta (M) pigments include C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48 : 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G lake), 83, 88, 92, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (Dimethylquinacridone), 123,146,149,166,168,170,172,177,178,179,185,190,193,209,2 9 and the like can be mentioned, depending on the situation, can be used in combination either singly or in combination.

  Examples of cyan (C) pigments include C.I. I. Pigment Blue 1, 2, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63, etc. can be mentioned, According to the situation, it can be used individually by 1 type or in combination of 2 or more types.

  The pigment content in the total ink liquid varies depending on the purpose of use, but from the balance between the coloring power and the viscosity of the ink (the higher the pigment content, the higher the viscosity of the ink and the more difficult it is ejected). 0.1 to 20% by mass, preferably 1 to 10% by mass, and more preferably 3 to 7% by mass.

  A water-soluble resin may be added as a polymer dispersant for dispersing the pigment in the ink solvent. Preferred examples of the polymer dispersant include styrene-acrylic-acrylic acid alkyl ester copolymers, styrene-acrylic acid copolymers, styrene-maleic acid copolymers, and styrene-maleic acid-acrylic acid alkyl ester copolymers. Styrene-methacrylic acid copolymer, styrene-methacrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, etc. Water-soluble resin is mentioned.

  The content of the water-soluble resin (as a polymer dispersant) in the total ink liquid is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass. Two or more of these water-soluble resins can be used in combination.

  As a method for dispersing the pigment, a ball mill, a sand mill, a roll mill, an agitator, an ultrasonic homogenizer, a wet jet mill, a paint shaker, or the like can be used.

  A high-concentration pigment dispersion that is separately prepared in advance to prepare the ink of the present invention uses a centrifugal separator to remove foreign matters, dust, coarse particles, and the like during dispersion. Is preferred. And when preparing the ink of this invention finally, it is preferable to filter using a filter.

  The average particle diameter of the pigment particles usable in the present invention is preferably 30 to 300 nm, more preferably 50 to 150 nm. The average particle diameter can be measured using, for example, a dynamic light scattering particle size distribution measuring apparatus (“LB-550” manufactured by Horiba, Ltd.).

  As the surfactant (wetting agent or surface tension adjusting agent) used in the ink of the present invention, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks are used. Nonionic surfactants such as copolymers are preferably used.

  In the present invention, the ink can obtain a desired surface tension by adjusting the addition amount of the surfactant (wetting agent or surface tension adjusting agent).

  Examples of the water-soluble organic solvent (penetration accelerator or anti-drying agent) used in the ink in the present invention include ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol monomethyl ether, Triethylene glycol, hexylene glycol, octanediol, thiodiglycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-methyl-1 , 3-propanediol, 2,4-pentanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol trimethylolpropane, 2-methyl-1,3-propanediol, diethyl Glycol, propylene glycol, 1,3-butanediol, ethylene glycol, glycerine, 2-pyrrolidone, and the like.

  In the present invention, the ink can have a desired viscosity by adjusting the amount of the water-soluble organic solvent (penetration accelerator or anti-drying agent) added. The viscosity of the ink can be measured using a viscometer such as a vibration type viscometer (“SV-10” manufactured by A & D).

  The ink of the present invention may further contain, for example, a pH adjusting agent, an antifoaming agent, an antiseptic or the like.

  The ink of the present invention can be prepared by mixing the raw materials as described above, sufficiently stirring, and then filtering.

The ink jet recording treatment liquid of the present invention is considered to exert the following action on the ink as described above. First, in general, in an inkjet recording ink, a pigment is composed of, for example, a styrene-acrylic acid copolymer or the like regardless of whether it is black (K), yellow (Y), magenta (M), or cyan (C). As a pigment particle having a particle diameter of about 30 to 300 nm, it is stably dispersed by electrostatic repulsion between particles. On the other hand, in the treatment liquid of the present invention, polyvalent metal ions (positively charged cations) such as calcium ions (Ca ²⁺ ) and magnesium ions (Mg ²⁺ ) are ^generated from polyvalent metal salts such as calcium nitrate and magnesium nitrate. Is generated. When such a treatment liquid and the ink are mixed, an electric double layer on the surface of the pigment particles dispersed in the ink (more specifically, a solid-liquid contact interface between the surface of the pigment particles and the water in the ink) In this case, the negative charge on the pigment particle surface side and the positive charge on the ink moisture side are continuously distributed, and as a whole, an electrically neutral boundary layer) is caused by the positive charge of the polyvalent metal ions in the treatment liquid. The surface of the pigment particle reaches the isoelectric point (in other words, the electric charge of the entire pigment particle becomes zero), the electrostatic repulsive force between the pigment particles disappears, and the aggregation of the pigment particles occurs (this In the present specification, for the sake of convenience, it is referred to as “the effect of promoting the aggregation of the pigment in the ink” by the polyvalent metal salt).

  Also, since the surface of the pigment particles dispersed in the ink has a negative zeta (ζ) potential (electrokinetic potential), this pigment molecule and the positively charged cationic polymer contained in the treatment liquid By the interaction with the compound, the aggregation of the pigment particles is promoted, and the aggregated pigment particles and the polymer compound are in a bonded state (this is referred to as “by the cationic polymer compound for convenience in this specification”). The effect of promoting the aggregation of pigments in the ink ”).

  In this case, since the cationic compound is a polymer, the conjugate of the pigment particles and the polymer compound has a high binding property to the recording medium and does not penetrate into the recording medium. The pigment particles bonded to the cationic polymer compound are stably and quickly fixed on the recording surface of the recording medium (this is referred to as “aggregated pigment particles by the cationic polymer compound for convenience in this specification. , Etc.) ”.

  In addition, since the cationic polymer compound is in the form of an emulsion (emulsion) in which water and oil do not mix, the cationic polymer compound and the pigment particles bonded to the polymer compound are contained in the ink. The water easily separates from the water in the processing liquid and the water in the processing liquid and reliably remains on the recording surface of the recording medium separately from the water that penetrates into the recording medium. As a result, the pigment particles bonded to the cationic polymer compound are quickly and stably fixed on the recording surface of the recording medium, and are covered with the cationic polymer compound. Even if the discharge roller comes into contact with the cover film from the outside, the discharge roller comes into contact with the coating film, and pigment particles do not adhere to the discharge roller (this is For convenience, it may be described as “the effect of coating the pigment particles on the recording surface” by the emulsion of the cationic polymer compound).

  As a result of the combined effects of the above effects, in the ink jet recording method in which the treatment liquid is adhered to the recording medium and then the ink is adhered to the recording medium, the image forming on the plain paper such as PPC paper is highly effective. In order to achieve image quality, the remaining amount of pigment on the recording surface of the recording medium is increased, and in order to realize high-speed processing, the time from when the ink is ejected to the recording medium until the discharge roller contacts the recording medium is short. Even in this case, the pigment on the recording surface of the recording medium is prevented from adhering to the discharge roller.

(Inkjet recording device)
Next, an example of a specific configuration of an ink jet recording apparatus suitable for carrying out the ink jet recording method of the present invention using the processing liquid for ink jet recording of the present invention will be described.

  As shown in FIG. 1, an ink jet recording apparatus 1 is an ink jet printer that forms an image on a recording medium using an ink composition for ink jet recording based on image information transmitted from another device.

  The ink jet recording apparatus 1 includes a paper storage unit that stores recording media X such as PPC paper in a stacked state in a paper feeding cassette (not shown). The recording medium X is fed one by one from the uppermost one by the rotation of the paper feed roller 2 and is supplied to the paper transport unit by the transport rollers 3.

  The paper transport unit includes an endless transport belt 6 wound horizontally between a pair of rollers. The recording medium X supplied by the conveying rollers 3... 3 is conveyed to the image forming unit with the recording surface facing upward by the traveling of the conveying belt 6.

  The image forming unit includes a long line-type inkjet recording head 5 having a length equal to or greater than the width of the recording medium X conveyed by the conveyance belt 6 above the conveyance belt 6. The recording head 5 is fixed to the main body of the inkjet recording apparatus 1 over a direction orthogonal to the conveyance direction of the recording medium X. As will be described later, the recording head 5 has a large number of ink discharge ports (nozzles) of the dot forming portion arranged on the lower surface facing the conveyance belt 6 or the recording medium X, and ink is simultaneously applied over the entire width of the recording medium X. By discharging, an image can be formed on the recording medium X at high speed. The distance between the lower surface (nozzle surface) of the recording head 5 and the recording medium X on the conveying belt 6 is set to about 1 mm.

  A recording medium detection sensor 4 for detecting the leading end of the recording medium X conveyed by the conveying belt 6 is provided above the conveying belt 6 and upstream of the inkjet recording head 5 in the conveying direction of the recording medium X. Yes. An ink discharge command is output to the inkjet recording head 5 with reference to the detection time of the sensor 4.

  A processing liquid roll coater 9 for attaching the processing liquid to the recording medium X is provided above the conveying belt 6 and upstream of the recording medium detection sensor 4 in the conveying direction of the recording medium X. The roll coater 9 includes a container 10 for storing the processing liquid, a pumping roller 11 for pumping the processing liquid from the container 10, an intermediate roller 12 for receiving the processing liquid from the pumping roller 11, and a processing liquid from the intermediate roller. An application roller 13 for applying the treatment liquid onto the recording surface of the recording medium X on the conveyor belt 6, and a control blade 14 for controlling the amount of the treatment liquid adhering to the surface of the application roller 13. Yes. The roll coater 9 adjusts the amount of the drawing roller 11 immersed in the container 10, the contact pressure between the rollers 11, 12, 13, the position of the control blade 14 with respect to the application roller 13, and the like, thereby adjusting the unit area of the recording medium X. The amount of the applied treatment liquid can be adjusted.

  While being transported by the transport belt 6, the recording medium X on which the processing liquid is deposited by the processing liquid roll coater 9 and then the ink is deposited by the ink jet recording head 5 to form an image on the recording surface is continuously transported. It is conveyed by the belt 6, transferred to a pair of upper and lower discharge rollers 7, 8 at the end of the conveyor belt 6, and discharged from the conveyor belt 6. At this time, since the upper discharge roller 7 is in contact with the recording surface of the recording medium X on which an image is formed, there is a possibility that the pigment on the recording surface adheres to the upper discharge roller 7 and becomes dirty. .

  FIG. 2 is an enlarged longitudinal sectional view showing one of the dot forming portions 50 arranged in a large number on the ink jet recording head 5 of the ink jet recording apparatus 1.

  The recording head 5 is a long line type recording head 5 extending in the width direction of the recording medium X. Although not shown in detail, the recording head 5 has a structure in which three sub heads (divided heads) are sequentially connected in a direction orthogonal to the conveyance direction of the recording medium X. Each of the sub-heads has a trapezoidal discharge port collecting area on the lower surface (nozzle surface) in the order of four in the direction perpendicular to the conveyance direction of the recording medium X (the upper and lower trapezoids have a trapezoidal shape). (Arranged so that they are alternately reversed). In each discharge port assembly area, the dot forming section 50 and the nozzles (ink discharge ports) 53 shown in FIG. 2 are arranged in four rows in the transport direction of the recording medium X. By setting the pitch between adjacent nozzles 53, 53 in the same row to 150 dpi, and shifting the position of the nozzle 53 between adjacent rows by a quarter pitch in the direction perpendicular to the conveyance direction of the recording medium X, 600 dpi is obtained. It has been realized. Since the number of dot forming portions 50 and nozzles 53 per row is 166, 664 nozzles 53 are arranged in one discharge port aggregate area (four rows). Accordingly, 7968 (664 × 4 × 3) nozzles 53 are provided in the entire recording head 5.

  The dot forming unit 50 includes an oval pressurizing chamber 52 in plan view, and one end of the pressurizing chamber 52 is connected to a nozzle 53 formed on the lower surface of the recording head 5 via a nozzle channel 54. The other end portion communicates with the common ink supply path 56 via the throttle path 55. The nozzle 53 has an inverted truncated cone shape in which the diameter of the upper opening 53b is larger than the diameter of the lower opening 53a.

  The dot forming unit 50 includes a first substrate 51a in which a pressurizing chamber 52 is formed, a second substrate 51b in which an upper portion 54a of a nozzle channel 54 and a throttle passage 55 are formed, a lower portion 54b of the nozzle channel 54, and ink. The third substrate 51c on which the common supply path 56 is formed and the fourth substrate 51d on which the nozzle 53 is formed are stacked. A substrate 51 of the recording head 5 is provided by the laminated first to fourth substrates 51a to 51d.

  A piezoelectric actuator AC having a configuration in which a thin plate-like piezoelectric element 58 having a common electrode 57 therein and an individual electrode 59 corresponding to the pressurizing chamber 52 of each dot forming unit 50 are stacked on the upper surface of the substrate 51. It has been. By driving the piezoelectric actuator AC, a pressure wave is transmitted to the ink in the pressurizing chamber 52, and the ink in the nozzle channel 54 and the nozzle 53 is vibrated by the pressure wave, so that the ink flows from the lower opening 53a of the nozzle 53. The ink is discharged toward the recording medium X.

Here, an example of a preferable specific numerical value regarding the specification of the dot forming portion 50 is shown below.
・ Area of pressurizing chamber 52: 0.2 mm 2
・ Pressure chamber 52 width: 200 μm
-Depth of pressurizing chamber 52: 100 μm
・ Length of nozzle 53: 30 μm
The radius of the lower opening 53a of the nozzle 53: 10 μm
-Diameter of nozzle channel 54: 200 μm
・ Length of nozzle channel 54: 800 μm
-Diameter of throttle passage 55: 30 μm
・ Length of throttle passage 55: 40 μm

  The inkjet recording apparatus 1 illustrated in FIG. 1 has a single recording head 5 and forms an image in a single color. However, the present invention is not limited to this, and for example, K (black) ink, Y ( For each of yellow (yellow) ink, M (magenta) ink, and C (cyan) ink, a plurality (four) of the recording heads 5 may be arranged in the conveyance direction of the recording medium X to form an image in full color. In that case, the ink (one of the four types) is discharged from the last head (the most downstream head) to the recording medium X after the discharge roller 7 comes into contact with the recording medium X due to high-speed processing. This becomes a problem because the time of the system becomes shorter.

  In addition, the inkjet recording apparatus 1 may include a serial recording head instead of a line recording head as long as high-speed processing is realized. In that case, from the time when ink is ejected from the recording head to the recording medium X in one or two recording head scans performed at the end in accordance with high-speed processing, the discharge roller 7 comes into contact with the recording medium X. This becomes a problem because the time of the system becomes shorter.

(Inkjet recording method)
Using the inkjet recording apparatus 1 configured as described above, a treatment liquid containing a polyvalent metal salt and an emulsion of a cationic polymer compound is charged into the roll coater 9 and ink containing a pigment is charged into the recording head 5. Then, while conveying the recording medium X by the conveying belt 6, a treatment liquid containing a polyvalent metal salt and an emulsion of a cationic polymer compound is adhered to the recording surface of the recording medium X by a roll coater 9, and thereafter An ink jet recording method in which an ink containing a pigment is attached to the recording medium X by the recording head 5 can be performed.

  EXAMPLES Hereinafter, although the Example of this invention is given with a comparative example and this invention is demonstrated further more concretely, this invention is not limited by a following example.

<Preparation of ink>
First, a high-concentration pigment dispersion used for ink preparation was prepared with the following composition.
Pigment: C.I. I. 20% by mass of pigment blue 15: 3 (cyan phthalocyanine compound)
Polymer dispersant: 5% by mass of a styrene-acrylic acid copolymer (“John Crill 683” manufactured by Johnson)
-Anti-drying agent: 10% by mass of glycerin
・ Solvent: 65% by mass of ion-exchanged water

  These raw materials were charged into a batch type vertical sand mill (manufactured by Imex Co., Ltd.), filled with zirconia beads (diameter 0.5 mm) as a medium, and sufficiently dispersed while being cooled with water. After the dispersion treatment, the zirconia beads are removed, and a centrifuge is used to remove foreign substances and coarse particles during dispersion. The pigment concentration is 20% by mass and the average particle size of the dispersed pigment particles is 50 to 150 nm. Got. The average particle size of the dispersed pigment particles is obtained by diluting the obtained pigment dispersion five times with ion-exchanged water and using a dynamic light scattering particle size distribution measuring device (“LB-550” manufactured by Horiba, Ltd.). Confirmed.

Next, an ink was prepared using the obtained pigment dispersion with the following composition.
-25% by mass of the above cyan pigment dispersion
Surfactant (or wetting agent or surface tension adjusting agent): 2,4,7,9-tetramethyl-5-decyne-4,7-diol di [polyoxyethylene] ether (manufactured by Nissin Chemical Industry Co., Ltd. Olfin (registered trademark) E1010 ") 0.5% by mass
・ Penetration enhancer: 5% by mass of 1,3-butanediol
・ Penetration enhancer: 5% by mass of triethylene glycol monobutyl ether
-Anti-drying agent: 5% by mass of 2-pyrrolidone
-Anti-drying agent: 15% by mass of glycerin
・ Solvent: 44.5% by mass of purified water

  These raw materials were sufficiently stirred at room temperature and then filtered under pressure with a filter having a pore size of 5 μm to obtain an ink for ink jet recording.

<Preparation of treatment solution>
First, two types of polyvalent metal ion solutions A-1 and A-2 used for preparation of the treatment liquid were prepared with the following composition.
(Multivalent metal ionic liquid A-1)
・ Polyvalent metal salt: 50% by mass of calcium nitrate (Ca (NO3) 2)
-Anti-drying agent: 40% by mass of glycerin
・ Solvent: 10% by mass of purified water
(Multivalent metal ionic liquid A-2)
-Multivalent metal salt: 50% by mass of magnesium nitrate (Mg (NO3) 2)
-Anti-drying agent: 40% by mass of glycerin
・ Solvent: 10% by mass of purified water

  These raw materials were sufficiently dissolved at room temperature using a propeller type stirrer to obtain polyvalent metal ionic liquids A-1 and A-2.

Moreover, five types of resin emulsions B-1, B-2, B-3, B-4 and B-5 used for preparation of the treatment liquid were prepared with the following composition.
(Resin emulsion B-1)
8% by mass of an anionic acrylic resin emulsion (“Boncoat (registered trademark) TA-96” manufactured by DIC Corporation)
・ 92% by mass of purified water
(Resin emulsion B-2)
8% by mass of an anionic acrylic resin emulsion (“Boncoat (registered trademark) SFA-33” manufactured by DIC)
・ 92% by mass of purified water
Note that “Boncoat (registered trademark) TA-96” and “Boncoat (registered trademark) SFA-33” differ in non-volatile content (%), viscosity, pH, and the like.
(Resin emulsion B-3)
8% by mass of cationic acrylic resin emulsion (“Boncoat (registered trademark) SFC-571” manufactured by DIC Corporation)
・ 92% by mass of purified water
(Resin emulsion B-4)
Water-soluble cationic resin: 4% by mass of a copolymer of vinylpyrrolidone and N, N-dimethylaminoethylmethacrylic acid (“HC Polymer 11” manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ Oil content: 1% by mass of coconut fatty acid ("Lunac L-55" manufactured by Kao Corporation)
-Surfactant (or emulsifier): 1% by mass of octadecyloxypropyltrimethylammonium chloride (“Cootamine E-80K” manufactured by Kao Corporation)
-Surfactant (or emulsifier): 2% by mass of stearyl alcohol
・ 92% by mass of purified water
(Resin emulsion B-5)
Water-soluble cationic resin: 4% by mass of a copolymer of vinylpyrrolidone and N, N-dimethylaminoethyl methacrylic acid (“HC Polymer 5” manufactured by Osaka Organic Chemical Industry Co., Ltd.)
・ Oil content: 1% by mass of coconut fatty acid ("Lunac L-55" manufactured by Kao Corporation)
-Surfactant (or emulsifier): 1% by mass of octadecyloxypropyltrimethylammonium chloride (“Cootamine E-80K” manufactured by Kao Corporation)
-Surfactant (or emulsifier): 2% by mass of stearyl alcohol
・ 92% by mass of purified water
The “HC polymer 11” and the “HC polymer 5” have different degrees of polymerization, monomer composition ratios, and the like.

  These raw materials are charged into a 1 L container so that the total amount is 250 g, and stirred for 5 minutes at 8000 rpm under a liquid temperature of 40 ° C. using a homomixer (“HM-310” manufactured by ASONE). Emulsions B-1, B-2, B-3, B-4 and B-5 were obtained.

  Here, while stirring at 8000 rpm, the polyvalent metal ionic liquid A-1 or A-2 was gradually added until the total amount became 500 g (that is, the polyvalent metal ionic liquid A and the resin emulsion B were added at a mass ratio). 1: 1 (mixed at 250 g: 250 g), and further stirred at 8000 rpm for 5 minutes under the condition of a liquid temperature of 40 ° C. to obtain a liquid for inkjet recording. Table 1 shows combinations of the polyvalent metal ion solution and the resin emulsion in each treatment solution.

  Treatment liquids 8 to 10 and 13 to 15 containing a polyvalent metal ion and a cationic resin emulsion are examples of the present invention, treatment liquids 1 to 5 containing only a resin emulsion and no cationic resin emulsion. Instead, treatment liquids 6, 7, 11, and 12 containing an anionic resin emulsion are comparative examples.

  And the following evaluation was performed using the obtained processing liquid and ink for inkjet recording.

(Image density (ID: Image Density) evaluation)
In order to confirm the image quality stability, the image density was evaluated. First, A4 size plain paper, that is, PPC paper ("V938" manufactured by Fuji Xerox Co., Ltd.) is used as a recording medium, and a strip-shaped resin film having a length of 21 cm and a width of 3 cm is formed on the short side of the short side. And a predetermined amount of the processing solution was dropped linearly over the entire length of the film. A bar coder having a plurality of grooves formed on the lower edge was moved from the resin film side to the other short side of the PPC paper at a constant speed, and the treatment liquid on the film was uniformly applied onto the PPC paper. The central part of the PPC paper coated with the treatment liquid was cut out to A6 size (14.8 cm × 10.5 cm) to obtain a test piece. 2 from the weight difference before and after application of the treatment liquid, determined the treatment liquid application amount per unit area of the PPC paper to (mg / cm ^2), the coating amount of the 0.6 mg / cm ² and 1.2 mg / cm ² Different types of specimens were prepared.

  Images were formed as follows using an ink jet printer having the structure shown in FIGS. 1 and 2 (an ink jet printer manufactured by Kyocera Mita Co., Ltd. modified for this experiment). The recording head of the ink jet printer was filled with ink, and excess liquid coming out from the lower surface of the nozzle was scraped off with a wipe blade. The distance between the nozzle surface of the recording head and the recording medium on the conveying belt was about 1 mm. A rectangular solid image of 30 mm × 30 mm was formed on the test piece with the maximum density at a driving frequency of 20 kHz in a normal temperature and humidity environment with a temperature of 20 ° C. and a humidity of 65%. At this time, the treatment liquid was not attached using a roll coater.

The density of the formed solid image was measured using a reflection densitometer (“TC-6D” manufactured by Tokyo Denshoku Co., Ltd.), and the average value was obtained several times and evaluated according to the following criteria. The results are shown in Table 1.
○: Image density is 1.3 or more Δ: Image density is 1.1 or more and less than 1.3 ×: Image density is less than 1.1

(Roller dirt prevention evaluation)
Images were formed as follows using an ink jet printer having the structure shown in FIGS. 1 and 2 (an ink jet printer manufactured by Kyocera Mita Co., Ltd. modified for this experiment). The recording head of the ink jet printer was filled with ink, and excess liquid coming out from the lower surface of the nozzle was scraped off with a wipe blade. The position of the recording head was adjusted so that the distance between the nozzle surface of the recording head and the recording medium on the conveying belt was 1 mm, and the recording head was fixed. On the other hand, filled with the process liquid in a roll coater, the treatment liquid application amount per unit area of the recording medium was adjusted to a roll coater so that 0.6 mg / cm ² or 1.2 mg / cm ^2. Continuously print a 30mm x 30mm square solid image on A4 size PPC paper ("V938" manufactured by Fuji Xerox Co., Ltd.) at a maximum frequency of 20mm at a driving frequency of 20kHz in a room temperature and humidity environment of 20 ° C and 65% humidity. 10 sheets were formed. At this time, the conveyance speed of the recording medium was 847 mm / second.

The state of the surface of the discharge roller after image formation and the state of the recording medium on which the image was formed were visually confirmed and evaluated according to the following criteria. The results are shown in Table 1.
○: Ink pigment does not adhere to the discharge roller or the non-image forming part of the recording medium. Δ: Ink pigment adheres to the discharge roller but does not adhere to the non-image forming part of the recording medium. No ×: The ink pigment adheres to both the discharge roller and the non-image forming portion of the recording medium.

The results of image density evaluation will be considered from Table 1. When using the treatment liquid 8～10,13～15 an embodiment of the present invention, the reflection of both the image even when the coating amount of the treatment liquid is also 1.2 mg / cm ² when a 0.6 mg / cm ² The density was 1.3 or more, and the image density evaluation was good. This is because the treatment liquids 8 to 10 and 13 to 15 contain a polyvalent metal salt, so that the effect of promoting aggregation of the pigment in the ink by the polyvalent metal salt is exhibited, and a large amount of the pigment is formed on the recording surface of the recording medium. As a result, and the treatment liquids 8 to 10 and 13 to 15 contain emulsions of the cationic polymer compound, the aggregation effect of the pigment in the ink by the cationic polymer compound is increased, and the cationic high The effect of early fixing of aggregated pigment particles by molecular compounds and the coating effect of pigment particles on the recording surface by the emulsion of cationic polymer compound are exerted, and the pigment remaining on the recording surface does not adhere to the discharge roller, and the image density This is thought to be due to the fact that the decline in sales was avoided.

  On the other hand, since the treatment liquids 6, 7, 11, and 12 which are comparative examples include an anionic resin emulsion instead of a cationic resin emulsion, the effect of facilitating the aggregation of the pigment is weakened, and as a result, the effect of early fixing and covering the pigment particles It is considered that the image density is lowered when the effect is weakened, particularly when the amount of treatment liquid applied is small.

  Furthermore, the treatment liquids 1 to 5, which are comparative examples containing no polyvalent metal salt, did not exhibit the effect of promoting aggregation of the pigment in the ink by the polyvalent metal salt, and the image density was generally poor. However, a slight improvement in image density can be seen when the coating amount of the treatment liquids 4 and 5 is large. From this, the cationic resin emulsions B-4 and B-5 used in the treatment liquids 4 and 5 are more effective in promoting the aggregation of the pigment than the cationic resin emulsion B-3 used in the treatment liquid 3, and thus the pigment. It can be seen that the early fixing effect and covering effect of the particles are slightly superior.

Next, the results of the roller dirt prevention evaluation will be considered from Table 1. When using the treatment liquid 8～10,13～15 an embodiment of the present invention, the coating amount of the treatment liquid are both the recording medium also in the case of 0.6 mg / cm ² of 1.2 mg / cm ² Adhesion of the pigment to the non-image forming part was not observed. In particular, when the cationic resin emulsions B-4 and B-5 were used and the application amount was large, the adhesion of the pigment to the discharge roller was not observed. These are the effect of promoting the aggregation of pigments in ink by cationic polymer compounds, the effect of early fixing of aggregated pigment particles by cationic polymer compounds, and the effect of coating pigment particles on the recording surface by emulsions of cationic polymer compounds This is thought to be because of

  On the other hand, the treatment liquids 6, 7, 11, and 12, which are comparative examples including an anionic resin emulsion, are weak in the early fixing effect and covering effect of the pigment particles, so that the pigment adheres to the discharge roller and the recording medium. ing.

  In addition, in the treatment liquids 4 and 5 which are comparative examples, the roller dirt prevention evaluation is good, for example, the cationic resin emulsions B-4 and B-5 used in the treatment liquids 4 and 5 are pigment aggregations. It is thought that this is because of excellent acceleration effect, early fixing effect of pigment particles and coating effect, but the treatment liquids 4 and 5 containing no polyvalent metal salt have the effect of promoting aggregation of the pigment in the ink by the polyvalent metal salt. It is thought that a major factor is that the amount of the residual pigment on the recording surface was originally small and was not exhibited. Therefore, the roller contamination prevention evaluation is not necessarily the same for the processing liquids 4 and 5 and the processing liquids 8 to 10 and 13 to 15. That is, in the treatment liquids 8 to 10 and 13 to 15 containing the polyvalent metal salt, the effect of promoting aggregation of the pigment in the ink by the polyvalent metal salt is exhibited, and the amount of the residual pigment on the recording surface is originally large. Regardless, the pigment is not attached to the recording medium.

  In addition, at the time of the above image density evaluation, the state of the surface of the discharge roller was visually observed. However, the treatment liquids 8 to 10 and 13 to 15 as examples were generally good results as in the above-described evaluation for preventing roller contamination. Met. In addition, the state of the image formed on the recording medium was visually observed at the time of the above-described evaluation for prevention of roller contamination, but the treatment liquids 8 to 10 and 13 to 15 as examples were generally good as in the above image density evaluation. It was a result.

  Furthermore, using other types of pigments, other types of polyvalent metal salts, and emulsions of other types of cationic polymer compounds, ink jet recording inks and treatment liquids were prepared in the same manner as described above, and similar evaluations were made. The results were similar.

  As described above in detail with reference to specific examples, the present invention provides high-quality, high-speed processing, but a large amount of pigment remaining on the recording surface of the recording medium after image formation is present on the recording surface. Since it is fixed at an early stage and coated with a cationic polymer compound, the above-mentioned pigment does not adhere to and contaminate the non-image forming part of the discharge roller or the recording medium. It is what you have.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 5 Inkjet recording head 6 Conveying belt 7 Discharge roller 9 Treatment liquid roll coater X Recording medium

Claims (2)

An inkjet recording method in which a treatment liquid is attached to a recording medium, and then ink is attached to the recording medium,
Using a treatment liquid containing a polyvalent metal salt and an emulsion of a cationic polymer compound ,
When attaching the processing liquid to the recording medium, a container for storing the processing liquid, a pumping roller for pumping up the processing liquid from the container, an intermediate roller for receiving the processing liquid from the pumping roller, and the intermediate roller Using a processing liquid roll coater comprising: an application roller that receives the processing liquid and applies the processing liquid to the recording medium; and a control blade that controls the amount of the processing liquid adhering to the intermediate roller, By adjusting the immersion amount of the pumping roller into the container, the contact pressure between the pumping roller and the intermediate roller, the contact pressure between the intermediate roller and the application roller, and the position of the control blade with respect to the intermediate roller, The amount of the treatment liquid applied to the recording medium is 0.2 to 1 per cm ^{2 of the} recording medium. Adjust the amount to be 8 mg,
An ink jet recording method comprising: an ink jet recording apparatus including a long line type ink jet recording head having a length equal to or greater than a width of the recording medium when the ink is attached to the recording medium . A polyvalent metal salt 10 to 40% by mass, the ink jet recording method according to claim 1, characterized in that to with wearing a treatment liquid containing 1 to 10 wt% emulsion of a cationic polymer compound.

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