JP2010090191A - Water-based ink for use in inkjet printing, ink tank, recording unit, device and method for inkjet recording, and method for manufacturing water-based ink for inkjet printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink for use in inkjet printing which satisfies both scratch resistance and luster property. <P>SOLUTION: This water-based ink for use in inkjet printing, includes at least a pigment and two kinds of resins, wherein one resin relatively contributing to pigment-dispersion does not deposit over a pH range of 4.0 or above to 6.0 or below, and the other relatively non-contributing to pigment-dispersion resin deposits over a pH range of 4.0 or above to 6.0 or below. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aqueous inkjet ink, an ink tank, a recording unit, an inkjet recording apparatus, an inkjet recording method, and a method for producing an inkjet aqueous ink.

  Conventionally, dyes have been used as ink coloring materials in ink jet recording methods. Dyes are easy to handle as water-based inks and have the advantage of high color developability, but have the problem that the recorded images have poor light resistance. As a means for improving the weather resistance of the recorded image, there is a technique in which a pigment is used as an ink coloring material and the pigment is dispersed in water with a water-soluble resin to obtain a pigment ink. However, many problems exist when pigment ink is used as an ink-jet ink. Typical examples are scratch resistance and gloss.

Many means have been proposed for improving the problems such as scratch resistance and gloss of a recorded image formed using a pigment ink as an inkjet ink. For example, as a technique for improving scratch resistance, a pigment ink containing resin emulsion particles in an aqueous medium has been proposed (see Patent Document 1). As a technique for improving glossiness, a technique has been proposed in which a treatment liquid containing fine resin particles is applied to a recorded matter after printing with pigment ink (see Patent Document 2).
JP 2004-026947 A JP 2004-330554 A

  In order to solve the problems such as scratch resistance and glossiness of a recorded image formed using a pigment ink, the inventors of the present invention have made studies focusing on Patent Documents 1 and 2 described above. However, the ink does not satisfy the scratch resistance and glossiness required by the present inventors. This is considered to be due to the trade-off relationship between scratch resistance and glossiness. In order to improve the scratch resistance, the water-soluble resin contained in the ink needs to be deposited on the recording medium after the ink is applied to the recording medium. However, the water-soluble resin that easily deposits on the recording medium causes unevenness due to precipitation on the surface of the recording medium, resulting in a decrease in gloss.

  The present invention solves the above-mentioned problems and provides an aqueous inkjet ink, an ink tank, a recording unit, an inkjet recording apparatus, an inkjet recording method, and an inkjet aqueous ink manufacturing method that satisfy both scratch resistance and glossiness. The purpose is to provide.

The present invention is an inkjet water-based ink containing at least a pigment, a resin A, and a resin B,
The resin A contributes to the dispersion of the pigment, the resin B does not contribute to the dispersion of the pigment compared to the resin A,
The resin A is a copolymer that does not precipitate over the range of pH 4.0 or more and pH 6.0 or less, and includes a copolymer having a vinyl alcohol monomer unit, a copolymer containing a monomer unit having a sulfonic acid group, The monomer unit contributing as a functional group is at least one copolymer selected from the group consisting of a copolymer having only a (meth) acrylic acid unit, and the resin B has a pH of 4.0 or more and pH 6.0 or less. An aqueous inkjet ink characterized by being a copolymer having a (meth) acrylic acid monomer unit precipitated over a range.

  In addition, the present invention is an ink tank that accommodates the above-described inkjet ink.

  In addition, the present invention is a recording unit including an ink tank that stores the above-described inkjet ink, and a recording head for ejecting the ink.

  In addition, the present invention is an ink jet recording apparatus including an ink tank that accommodates the above water-based ink for ink jet and a recording head for ejecting ink.

  Further, the present invention is an ink jet recording method using the above water-based ink for ink jet. The present invention also provides a method for producing the above-described water-based ink for ink jet.

  By using the present invention, it is possible to provide a water-based ink for ink jet, an ink tank, a recording unit, an ink jet recording apparatus, an ink jet recording method, and a method for producing the water-based ink for ink jet satisfying both scratch resistance and glossiness. It becomes.

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

  First, the background to the present invention will be described. The inventors searched for a resin that imparts excellent gloss to the ink. As a result, it has been found that excellent glossiness is exhibited if the resin can improve the leveling property between the inks on the recording medium and smooth the surface of the recording medium provided with the ink (FIG. 2). ). Specifically, it has been found effective to contain in the ink a resin that does not precipitate over the range of pH 4.0 to pH 6.0 (hereinafter also referred to as resin A). However, the resin A has high water solubility. A resin having high water solubility hardly causes solid-liquid separation from the liquid component of the ink after the ink is applied to the recording medium. That is, the resin contained in the ink is likely to penetrate into the recording medium after the ink is applied to the recording medium. As a result, an effective amount of resin hardly remains on the recording medium. Therefore, the pigment ink having the resin A is an unfavorable ink from the viewpoint of scratch resistance.

  Therefore, the present inventors have made a detailed study paying attention to the difference in the state of the pigment and resin on the image surface from the viewpoint of scratch resistance. As a result, it has been found that a resin that can form a strong film on the recording medium and firmly bind the pigment and the recording medium exhibits excellent scratch resistance (FIG. 3). Specifically, it was obtained that the copolymer (hereinafter also referred to as resin B) having a (meth) acrylic acid monomer unit precipitated was effective over the range of pH 4.0 to pH 6.0. In the present invention, (meth) acrylic acid is methacrylic acid or acrylic acid. However, by using the ink containing the resin B, although the scratch resistance is improved, the glossiness is impaired.

  The inventors have characteristics that change depending on the pH responsiveness of the resin, such as a resin that precipitates over a range of pH 4.0 to pH 6.0 and a resin that does not precipitate over a range of pH 4.0 to pH 6.0. I guess it is due to the following mechanism.

  Most of the recording media, especially so-called glossy paper, have an acidic surface, and a cationic component is present in such recording media. It is considered that the resin B in the solution applied on the recording medium reacts with a cation component present in the recording medium, so that the solubility is quickly reduced and precipitates on the recording medium. In addition, since the resin A in the solution hardly reacts with the cation component present in the recording medium, it is considered that the precipitation on the recording medium is suppressed and the penetration into the recording medium without lowering the solubility.

  Based on the above estimation, the present inventors have further studied the best mode in which the advantages of the two types of resins having different properties are simultaneously established. As a result, the resin A contributes to the pigment dispersion, and the resin B does not contribute to the pigment dispersion compared to the resin A, that is, the resin B is present in the ink in a free manner, so that the scratch resistance and glossiness are increased. We found that we can be satisfied at the same time. The reason is considered as follows.

  First, the pigment dispersed by the resin A and the ink in which the resin B is present are applied to the recording medium. Thereafter, the resin B quickly undergoes solid-liquid separation and forms a film in the recording medium or on the surface of the recording medium. Thereafter, the pigment dispersed by the resin A is deposited on the recording medium whose pores are blocked by the resin B, and a smooth film having excellent glossiness can be formed (FIG. 1). Normally, the resin A that permeates into the recording medium together with the solution in the ink also remains on the recording medium. Therefore, the water-based ink for ink-jet has a scratch resistance higher than the scratch resistance improving ability by the action of the resin B. It becomes possible to grant. Specifically, since the resin A acts as a dispersant, the pigment and the resin A are dispersed in advance to form a dispersion. Thereafter, the resin of the present invention can be obtained by adding resin B as an external additive into the ink containing the dispersion. By performing the above operation, it is possible to produce an ink in which the type of resin that is more adsorbed by the pigment is controlled.

  When both of the two types of resins are added in the step of dispersing the pigment, the resin having a relatively low water solubility is more easily adsorbed on the pigment surface than the resin having a relatively high water solubility. Therefore, in the ink obtained by such a manufacturing method, the resin A is liberated in the ink, and the resin B contributes to the dispersion of the pigment. When such an ink is used, it has been confirmed that although improvement in scratch resistance can be expected, no improvement in glossiness is observed.

  In the present invention, it can be determined by the following method whether the resin A contributes more to the pigment dispersion in the ink than the resin B. That is, the ink is centrifuged under a condition of 20000 rpm for 2 hours to separate the color material component as a sediment component and the water-soluble component as a supernatant component. Thereafter, the colorant component separated by centrifugation is subjected to Soxhlet extraction with an organic solvent such as tetrahydrofuran to separate the resin component. About the obtained resin component, the resin component which adsorb | sucked to the pigment relatively much is discriminate | determined by quantifying each resin by NMR measurement.

  In the present invention, it is preferable that the resin A is adsorbed on the pigment surface and the resin B is not adsorbed on the pigment surface, but the resin A only needs to be adsorbed on the pigment more than the resin B.

  Further, whether or not the resin is precipitated in the range of pH 4.0 to pH 6.0 is determined by the following method. First, 40.0 mL of dilute acetic acid aqueous solution whose pH is adjusted to 6.0 with acetic acid is added to a 50.0 mL beaker, and this is stirred with a stirrer. 0.5 mL of a resin aqueous solution adjusted to 15% by mass is added dropwise to this aqueous solution. And after stirring for 1 minute, stirring is stopped. If a white or light yellow precipitate can be confirmed at this time, it is determined that the resin is precipitated at pH 6.0. On the other hand, if no precipitate can be confirmed, it is determined that the resin dissolves at pH 6.0. Similarly, by adjusting the pH of acetic acid to be adjusted to 4.0 or pH 5.0, it can be determined whether or not the resin is precipitated at pH 4.0 and pH 5.0.

  Next, each component constituting the water-based ink of the present invention will be described in detail.

(Resin that improves glossiness)
The resin (resin A) for improving the gloss in the present invention will be described.

  It is required that the resin A does not precipitate over a range of pH 4.0 or more and pH 6.0 or less. Resin A is a copolymer having a vinyl alcohol monomer unit, a copolymer containing a monomer unit having a sulfonic acid group, and a copolymer in which the monomer unit contributing as a hydrophilic group is only a (meth) acrylic acid unit. It is required to be at least one copolymer selected from the group consisting of:

  Specific examples of preferable monomers constituting the resin A include the following. For example, styrenes such as styrene and o-methylstyrene, (meth) acrylic acid esters such as methyl methacrylate and benzyl methacrylate, and unsaturated groups having an anionic group such as acrylic acid, methacrylic acid and maleic acid. And monomers. The monomer unit having a monomer unit having a sulfonic acid group includes styrene sulfonic acid, sulfonic acid-2-propylacrylamide, acrylic acid-2-ethyl sulfonate, methacrylic acid-2-ethyl sulfonate, butylacrylamide sulfonic acid. Monomers having a sulfonic acid group such as methacrylic acid-2-ethyl phosphonate, monomers having a phosphonic acid group such as ethyl acrylate-2-phosphonate.

  The method for synthesizing the resin A is not particularly limited, and examples thereof include a method in which the above monomer and radical polymerization initiator are added to an organic solvent such as xylene and polymerized. Examples of the polymerization initiator include azo initiators and peroxides.

  When a copolymer having a vinyl alcohol monomer unit is used as the resin A, the content (% by mass) of the vinyl alcohol monomer unit is 30% by mass to 60% with respect to the total mass of the copolymer having the vinyl alcohol monomer unit. It is preferable to set it as mass% or less. Further, when a copolymer containing a monomer unit having a sulfonic acid group is used as the resin A, the monomer unit having a sulfonic acid group with respect to the total mass of the copolymer containing the monomer unit having a sulfonic acid group. It is preferable to make content (mass%) into 10 mass% or more and 50 mass% or less. Further, when a copolymer containing only (meth) acrylic acid as a hydrophilic group is used as the resin A, the resin A preferably has an acid value of 250 mgKOH / g or more and 400 mgKOH / g or less.

  When a copolymer containing a vinyl alcohol monomer unit or a copolymer containing a monomer unit having a sulfonic acid group is used as the resin A, the copolymer is a copolymer with (meth) acrylic acid. Is more preferable.

  According to further studies by the present inventors, the weight average molecular weight of the resin A is preferably in the range of 5000 to 15000 from the viewpoint of improving discharge stability. Moreover, it is more preferable that it is the range of 6000 or more and 9000 or less.

(Resin that improves scratch resistance)
Next, the resin (resin B) that improves the scratch resistance will be described.

  The resin B in the present invention is not particularly limited as long as it is a copolymer having a (meth) acrylic acid monomer unit that precipitates over a range of pH 4.0 or more and pH 6.0 or less. In the present invention, it is necessary that the resin B does not function as a resin for dispersing the pigment than the resin A. As the monomer component constituting the resin B, the following can be used. For example, preferable monomer components include monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, styrenesulfonic acid, sulfonic acid-2 -Monomers having a sulfonic acid group such as propylacrylamide, ethyl acrylate-2-sulfonate, methacrylic acid-2-ethyl sulfonate, butyl acrylamide sulfonic acid, etc., ethyl methacrylate-2-phosphonate, acrylate-2-phosphone And monomers having a phosphonic acid group such as ethyl acid. The resin B is preferably a copolymer having an acid value of 90 mgKOH / g or more and 150 mgKOH / g or less and having a (meth) acrylic acid monomer unit from the viewpoint of improving glossiness and water resistance.

  According to further studies by the present inventors, the weight average molecular weight of the resin B is preferably in the range of 5000 to 15000 from the viewpoint of improving discharge stability. Moreover, it is more preferable that it is the range of 6000 or more and 9000 or less.

  As a method for synthesizing the acrylic resin, there can be mentioned a method obtained by adding a monomer and a radical polymerization initiator as described above into an organic solvent such as xylene and polymerizing it. Examples of the polymerization initiator include azo initiators and peroxides.

  The mass ratio of the resin A and the resin B in the ink (resin A: resin B) is preferably 1.0: 0.5 to 1.0: 5.0. When the ratio of the resin B is smaller than 1.0: 0.5, the water resistance is lower than that in the range, and conversely, the ratio of the resin B is larger than 1.0: 5.0. In this case, the glossiness is lower than that when the gloss is within this range.

  The total amount of the resin A and the resin B is preferably 0.5% by mass or more and 10.0% by mass or less with respect to the total amount of the ink. If the resin content is less than this range, the scuffing property is poor compared to the case where the resin content is within this range, and if the resin content is more than this range, the ejection property may be lowered.

(Pigment)
The pigment that can be used in the water-based ink according to the present invention is not particularly limited, and any of the following carbon blacks and organic pigments can be used. Carbon black is suitable as the pigment used in the black ink. For example, carbon black such as furnace black, lamp black, acetylene black and channel black can be used. Specifically, for example, Raven 7000, Rayvan 5750, Rayvan 5250, Rayvan 5000ULTRA, Rayvan 3500, Rayvan 2000, Rayvan 1500, Rayvan 1250, Rayvan 1200, Rayvan 1190ULTRA-II, Rayvan 1170, Rayvan 1255 (and above) Colombia), Black Pearls L, Regal 400R, Legal 330R, Legal 660R, Mogul L, Monarch 700, Monak 800, Monak 880, Monak 900, Monak 1000, Monak 1100, Monak 1300, Monak 1400, Monak 2000, Vulcan XC-72R (above, Ki Manufactured by Cabotte), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. Commercial products such as 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical Corporation) can be used.

  Carbon black newly prepared for the present invention can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used. Further, the material is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used as a black pigment.

  Specific examples of the organic pigment include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red, and soluble azo pigments such as ritole red, heliobordeaux, pigment scarlet, and permanent red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, and perylene pigments such as perylene red and perylene scarlet , Isoindolinone yellow, isoindolinone pigments such as isoindolinone orange, benzimidazolone yellow, benzimidazolone orange, benzimidazolone red Imidazolone pigments, pyranthrone pigments such as pyranthrone red, pyranthrone orange, indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel Azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like can be mentioned. Of course, it is not limited to these, Other organic pigments may be used.

  The organic pigment that can be used in the present invention is represented by a color index (CI) number. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272, C.I. I. Pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment green 7, 36, C.I. I. Examples thereof include CI Pigment Brown 23, 25, 26, and the like. The ratio of the pigment to the total amount of ink is preferably 0.1% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less.

(Other ingredients)
Next, other components that can be used in the aqueous ink according to the present invention will be described. The aqueous ink according to the present invention may contain a mixed solvent of water and a water-soluble organic solvent. The water-soluble organic solvent can be selected from those listed below. Specific examples of the water-soluble organic solvent include those having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol. Alkyl alcohols; 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, diethylene glycol Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene Lower alkyl ethers of polyhydric alcohols such as glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Moreover, it is preferable to use deionized water as water.

  The content of the water-soluble organic solvent in the aqueous ink according to the present invention is not particularly limited, but is preferably in the range of 3.0% by mass to 50.0% by mass with respect to the total mass of the ink. The amount of water contained in the ink is preferably in the range of 50.0% by mass or more and 95.0% by mass or less with respect to the total mass of the ink.

  The water-based ink according to the present invention may use a moisturizing solid content such as urea, urea derivative, trimethylolpropane, trimethylolethane or the like as an ink component in addition to the above-described components in order to maintain the moisture retention. In general, the content of moisturizing solids such as urea, urea derivatives, and trimethylolpropane in the ink is preferably in the range of 0.1% by mass to 20.0% by mass with respect to the ink. A range of 3.0% by mass or more and 10.0% by mass or less is more preferable.

  In addition to the above components, the ink for an inkjet recording apparatus of the present invention includes a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, and the like as necessary. Various additives may be contained.

(recoding media)
In the recording method of the present invention, it is preferable to use a recording medium having an acidic pH. This is because the amount of the cation component in the recording medium has a correlation with pH. Specifically, a recording medium having a surface pH of 4.0 or more and 6.0 or less is preferable. When the pH of the surface of the recording medium is 4.0 or more and 6.0 or less, the resin A and the resin B of the present invention can effectively express the respective properties. The pH of the recording medium surface can be measured by the following method. 40 μl of pure water is dropped on the surface of the recording medium to be measured. Then leave it for 1 minute. After leaving for 1 minute, a pH electrode is attached to the area where pure water is dropped, and the pH is measured.

(Recording method)
An ink jet recording method in which ink is ejected from an orifice according to a recording signal and recording is performed on a recording medium can be preferably used. In particular, an ink jet recording method for recording on a recording medium by applying thermal energy to the ink can be more preferably used.

(Recording device)
Hereinafter, an example of a recording apparatus that can be used in the present invention will be described with reference to the drawings. FIG. 4 is a perspective view of the recording apparatus according to the present invention as viewed from the left front. FIG. 5 is a longitudinal sectional view of the recording apparatus. The recording apparatus according to the present embodiment includes a feeding unit 1, a transport unit 2, a carriage unit 3, a paper discharge unit 4, and a control board 6. In the present embodiment, an ink jet recording apparatus that performs recording by discharging ink from a discharge port of the recording head 5 to a sheet based on image information will be described as an example.

  The feeding unit 1 is configured by attaching a pressure plate 8 on which sheets P are stacked, a feeding roller 9 for feeding sheets P, a separation roller 17 for separating sheets P, and the like to a feeding base 7.

  The operation of the feeding unit 1 will be described. In the standby state, the pressure plate 8 and the separation roller 17 are released. Next, the pressure plate 8 contacts the feeding roller 9. Thereafter, the sheet is fed toward the conveyance unit 2 by the feeding roller 9.

  The conveying roller 11 is provided with a plurality of pinch rollers 12 that are driven to rotate. Each pinch roller 12 is brought into pressure contact with the conveying roller 11 by a pinch roller spring, thereby generating a conveying force of the sheet P.

  The sheet P sent to the conveyance unit 2 is nipped between the conveyance roller 11 and the pinch roller 12 and conveyed along the upper surface of the platen 10.

  The carriage unit 3 includes a carriage 15 that carries the recording head 5 and moves back and forth. The recording head 5 is positioned and fixed to the carriage 15 by a head set lever 16 pivotally supported on the carriage 15. The recording head 5 records the image on the sheet P by ejecting ink from each ejection port by driving a heater (heat generating element) in each ejection port based on the recording data. An ink tank that stores ink to be supplied to the recording head is replaceably attached to the recording head 5.

  The carriage substrate is also provided with contacts for electrical connection with the recording head 5. The carriage substrate and the control substrate 6 on the apparatus main body side are connected by a flexible substrate for transmitting a head signal to the recording head 5.

  When recording an image in the above configuration, first, the sheet P is transported to the row position for recording by driving the transport roller 11. Then, the carriage 15 is moved, the recording head 5 is driven based on the recording information in synchronization with the movement of the carriage, and an image is recorded by ejecting ink from the ejection port of the recording head 5.

  The paper discharge unit 4 is provided with two paper discharge rollers 13 and 14 attached to the platen 10. By rotating the paper discharge rollers 13 and 14 in synchronization with the transport roller 11, the recorded sheet P is discharged out of the apparatus main body.

  Although a thermal jet recording head that discharges ink based on recording data has been described here as an embodiment of the recording head, the recording method that can be used in the recording apparatus of the present invention is not limited to this. Specifically, a recording apparatus equipped with a piezo jet recording head that ejects ink using a piezoelectric element may be used.

  Further, here, a recording apparatus using a recording unit in which an ink tank is replaceably mounted on the recording head has been described. However, the recording head and the ink tank are integrated, and the recording head and the ink tank are replaced at the same time. It may be a recording device using a recording unit capable of recording.

  Hereinafter, although it demonstrates more concretely using an Example and a comparative example, this invention is not limited to these.

  In the following description, “%” is based on mass unless otherwise specified. In the examples, THF represents tetrahydrofuran, and AIBN represents azobisisobutyronitrile.

Example 1
Ink 1 used in Example 1 was prepared in the following manner.

  A dispersion resin 1KOH made of vinyl alcohol-styrene-acrylic acid was mixed with 37.5 parts by mass of a 20% by mass resin aqueous solution neutralized with 1 equivalent, 15 parts by mass of carbon black, and 47.5 parts by mass of water. The dispersion resin 1 has vinyl alcohol / styrene / acrylic acid = 0.30 / 0.60 / 0.10 (weight ratio), an acid value of 70, and a weight average molecular weight of 7000. The obtained mixture was dispersed in a bead mill using zirconia beads to obtain a carbon black dispersion 1 (pigment concentration 15 mass%, resin concentration 7.5 mass%, average particle diameter 105 nm).

  15 parts by mass of the additive resin 1 composed of styrene-ethyl acrylate-acrylic acid, 1 equivalent of potassium hydroxide with respect to the carboxylic acid are added, the remainder is adjusted to 100 parts by mass with water, and stirred at 80 ° C. The resin was dissolved. After the resin was dissolved, the solid content concentration was adjusted to 15% by mass with water to obtain an aqueous resin solution 1 for addition. The additive resin 1 has an acid value of 120, styrene / ethyl acrylate / acrylic acid = 0.23 / 0.60 / 0.17 (weight ratio), an acid value of 120, and a weight average molecular weight of 7000.

  16.7 parts of carbon black dispersion liquid 1, 16.7 parts by weight of aqueous resin solution 1 for addition, 5.0 parts by weight of glycerin, 9.0 parts by weight of ethylene glycol, 1.0 part by weight of acetylene E100 (manufactured by Kawaken Fine Chemicals) Part and the rest were adjusted to 100 parts by mass with water (51.6 parts by mass of water was added). Thereafter, further filtration was performed to obtain ink 1.

  The ink was centrifuged (20,000 rpm, 2 hours) to separate the color material, and the sediment was collected. The sediment was subjected to Soxhlet extraction with THF, THF was distilled off, and a resin component was obtained from the sediment. NMR measurement of the obtained resin was carried out, and more copolymer of vinyl alcohol-styrene-acrylic acid was detected than water-soluble resin consisting of ethyl acrylate and acrylic acid.

  In addition, the acrylic acid copolymer consisting of vinyl alcohol-styrene-acrylic acid was polymerized at a reflux temperature by dropping a mixed solution of vinyl alcohol / styrene / acrylic acid / polymerization initiator AIBN in a toluene solvent.

(Example 2)
Ink 2 was obtained in the same manner as in Example 1 except that Dispersing Resin 2 was used instead of Dispersing Resin 1 used in Example 1. The dispersion resin 2 has vinyl alcohol / styrene / acrylic acid = 0.60 / 0.30 / 0.10 (weight ratio), an acid value of 70, and a weight average molecular weight of 7500. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 2 was detected than the additive resin 1.

(Example 3)
Ink 3 was obtained in the same manner as in Example 1 except that the dispersion resin 3 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 3 has a styrenesulfonic acid / styrene / acrylic acid = 0.10 / 0.80 / 0.10 (weight ratio), an acid value of 95, and a weight average molecular weight of 7,500. Further, when NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of a-dispersed resin 3 was detected than in the additive resin 1.

Example 4
An ink 4 was obtained in the same manner as in Example 1 except that the dispersion resin 4 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 4 has styrene sulfonic acid / styrene / acrylic acid = 0.50 / 0.40 / 0.10 (weight ratio), an acid value of 205, and a weight average molecular weight of 7800. Further, when NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 4 was detected than the additive resin 1.

(Example 5)
Ink 5 was obtained in the same manner as in Example 1 except that Dispersing Resin 5 was used instead of Dispersing Resin 1 used in Example 1. The dispersion resin 5 has vinyl alcohol / styrene / acrylic acid = 0.45 / 0.45 / 0.10 (weight ratio), an acid value of 70, and a weight average molecular weight of 7600. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 5 was detected than the additive resin 1.

(Example 6)
An ink 6 was obtained in the same manner as in Example 1 except that the dispersion resin 6 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 6 has a styrene sulfonic acid / styrene / acrylic acid = 0.30 / 0.60 / 0.10 (weight ratio), an acid value of 150, and a weight average molecular weight of 7500. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 6 was detected than the additive resin 1.

(Example 7)
Example 1 except that dispersion resin 6 was used instead of dispersion resin 1 used in Example 1, and addition resin 2 consisting of styrene-ethyl acrylate-acrylic acid was used instead of addition resin 1 The same operation was performed to obtain ink 7. The additive resin 2 has styrene / ethyl acrylate / acrylic acid = 0.23 / 0.56 / 0.21 (weight ratio), an acid value of 150, and a weight average molecular weight of 7000. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 6 was detected than the additive resin 2.

(Example 8)
Example 1 except that the dispersion resin 6 was used instead of the dispersion resin 1 used in Example 1, and the addition resin 3 made of styrene-ethyl acrylate-acrylic acid was used instead of the addition resin 1. The same operation was performed to obtain ink 8. The additive resin 3 has styrene / ethyl acrylate / acrylic acid = 0.23 / 0.64 / 0.13 (weight ratio), an acid value of 90, and a weight average molecular weight of 6500. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 6 was detected than the additive resin 3.

Example 9
Ink 9 was obtained in the same manner as in Example 1 except that Dispersing Resin 7 was used instead of Dispersing Resin 1 used in Example 1. The dispersion resin 7 has a styrene sulfonic acid / styrene / acrylic acid = 0.25 / 0.65 / 0.10 (weight ratio), an acid value of 135, and a weight average molecular weight of 7000. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 7 was detected than the additive resin 1.

(Example 10)
An ink 10 was obtained in the same manner as in Example 1 except that the dispersion resin 8 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 8 has a styrenesulfonic acid / styrene / acrylic acid = 0.55 / 0.35 / 0.10 (weight ratio), an acid value of 220, and a weight average molecular weight of 7200. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 8 was detected than the additive resin 1.

(Example 11)
Example 1 except that dispersion resin 6 was used instead of dispersion resin 1 used in Example 1, and addition resin 4 made of styrene-ethyl acrylate-acrylic acid was used instead of addition resin 1. The same operation was performed to obtain ink 11. The additive resin 4 has styrene / ethyl acrylate / acrylic acid = 0.23 / 0.55 / 0.22 (weight ratio), an acid value of 155, and a weight average molecular weight of 7800. Further, when NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 6 was detected than additive resin 4.

Example 12
Example 1 except that the dispersion resin 6 was used instead of the dispersion resin 1 used in Example 1, and the addition resin 5 made of styrene-ethyl acrylate-acrylic acid was used instead of the addition resin 1. The same operation was performed to obtain ink 12. The additive resin 5 has styrene / ethyl acrylate / acrylic acid = 0.23 / 0.65 / 0.12 (weight ratio), an acid value of 85, and a weight average molecular weight of 7100. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 6 was detected than the additive resin 5.

(Example 13)
Ink 13 was obtained in the same manner as in Example 1 except that Dispersing Resin 9 was used instead of Dispersing Resin 1 used in Example 1. The dispersion resin 9 has styrene / acrylic acid = 0.65 / 0.35 (weight ratio), an acid value of 250, and a weight average molecular weight of 7500. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 9 was detected than the additive resin 1.

(Example 14)
An ink 14 was obtained in the same manner as in Example 1 except that the dispersion resin 10 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 10 has a styrene / acrylic acid = 0.42 / 0.58 (weight ratio), an acid value of 400, and a weight average molecular weight of 7100. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 10 was detected than the additive resin 1.

(Example 15)
An ink 15 was obtained in the same manner as in Example 1 except that the dispersion resin 11 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 11 has styrene / acrylic acid = 0.58 / 0.42 (weight ratio), an acid value of 300, and a weight average molecular weight of 7300. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 11 was detected than the additive resin 1.

(Example 16)
An ink 16 was obtained in the same manner as in Example 1 except that the dispersion resin 12 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 12 has styrene sulfonic acid / styrene / acrylic acid = 0.05 / 0.85 / 0.10 (weight ratio), an acid value of 81, and a weight average molecular weight of 7,300. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 12 was detected than the additive resin 1.

(Example 17)
An ink 17 was obtained in the same manner as in Example 1 except that the dispersion resin 13 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 13 has vinyl alcohol / styrene / acrylic acid = 0.20 / 0.70 / 0.10 (weight ratio), an acid value of 70, and a weight average molecular weight of 7800. Further, when NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 13 was detected than in the additive resin 1.

(Example 18)
An ink 18 was obtained in the same manner as in Example 1 except that the dispersion resin 14 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 14 has vinyl alcohol / styrene / acrylic acid = 0.70 / 0.20 / 0.10 (weight ratio), an acid value of 70, and a weight average molecular weight of 7100. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 14 was detected than the additive resin 1.

(Example 19)
An ink 19 was obtained in the same manner as in Example 1 except that the dispersion resin 15 was used instead of the dispersion resin 1 used in Example 1. The dispersion resin 15 has styrene / acrylic acid = 0.38 / 0.62 (weight ratio), an acid value of 450, and a weight average molecular weight of 7000. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, more dispersion resin 15 was detected than the additive resin 1.

(Comparative Example 1)
Ink 20 was obtained in the same manner as in Example 1 except that the addition resin 1 made of styrene-ethyl acrylate-acrylic acid was used as the dispersion resin instead of the dispersion resin 1 used in Example 1. .

(Comparative Example 2)
An ink 21 was obtained in the same manner as in Example 1 except that the dispersion resin 1 was used as the additive resin instead of the additive resin 1 used in Example 1.

(Comparative Example 3)
Similar to Example 1 except that the additive resin 1 was used as the dispersion resin instead of the dispersion resin 1 used in Example 1, and that the dispersion resin 1 was used as the additive resin instead of the addition resin 1. Ink 22 was obtained. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the additive resin 1 was detected than the dispersion resin 1.

(Comparative Example 4)
Ink 23 was obtained in the same manner as in Example 1 except that the dispersion resin 11 was used as the additive resin instead of the additive resin 1 used in Example 1. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of the dispersed resin 1 was detected than the dispersed resin 11.

(Comparative Example 5)
The same operation as in Example 1 was performed except that the additive resin 1 was used as the dispersion resin instead of the dispersion resin 1 used in Example 1, and the additive resin 3 was used instead of the additive resin 1. Ink 24 was obtained. Further, when the NMR measurement of the resin in the sediment was performed in the same manner as in Example 1, a larger amount of addition resin 1 was detected than addition resin 3.

  Table 1 summarizes the resin compositions of Examples and Comparative Examples.

<Evaluation>
<Precipitation test of various copolymers in the range of pH 4.0 to pH 6.0>
The dispersion resins 1 to 15 used in the inks 1 to 24 and the 15% by mass aqueous solutions of the addition resins 1 to 5 (one equivalent neutralization with KOH) were prepared. After dropping 0.5 mL of a resin aqueous solution adjusted to 15% by mass into a dilute acetic acid aqueous solution adjusted to pH 6.0 prepared in advance in a 50 mL beaker, the mixture was stirred for 1 minute, and the presence or absence of precipitates at that time was evaluated. The results are shown in Table 1. Similarly, the presence or absence of precipitation at pH 5.0 was confirmed using a dilute acetic acid aqueous solution adjusted to pH 5.0, and the presence or absence of precipitation at pH 4.0 was confirmed using a dilute acetic acid aqueous solution adjusted to pH 4.0. The presence or absence of precipitation at pH 6.0 is shown in Table 2, the presence or absence of precipitation at pH 5.0 is shown in Table 3, and the presence or absence of precipitation at pH 4.0 is shown in Table 4, respectively.

<Printing the evaluation image>
Each of the inks 1 to 23 was injected into an ink jet ink tank and mounted at the cyan position of the ink jet recording apparatus PIXUS990i. Thereafter, a solid patch having a printing area of 2 cm × 8 cm was printed on a glossy recording medium for inkjet GL-101 (manufactured by Canon Inc.) with a printing duty of 150%. The pH of the surface of GL-101 was pH 5.2 when measured by attaching a pH electrode after dropping 40 μl of pure water on the surface and allowing it to stand for 1 minute.

<Evaluation of scratch resistance>
Scratch resistance was evaluated by scratching the solid patch shown above with a nail and visually observing the state of scratches on the printed matter.
The evaluation criteria for scratching are as follows. The results are shown in Table 5.
◯: Scratches are hardly noticeable.
Δ: Scratches are visible, but the white background of the recording medium is not visible.
X: The scratch is so large that the white background part of a recording medium appears.

<Evaluation of glossiness>
The 20 ° gloss of the solid patch shown above was measured using a Gardner glossiness meter.
The evaluation criteria for glossiness are as follows. The results are shown in Table 5.
A: Glossiness is 40 or more.
Δ: Glossiness is 20 or more and less than 40.
X: Glossiness is less than 20.

<Evaluation of water resistance>
The solid patch shown above was allowed to stand for 10 minutes after printing, and then placed on a 45 ° tilt table, and 2 cc of pure water was dropped onto the printed matter. The water resistance was evaluated by visually observing the ink flow after dropping.
The evaluation criteria for water resistance are as follows. The results are shown in Table 5.
◯: No ink flow out.
Δ: Some ink flow out.
X: The ink is flowing out clearly.

In Table 1, each monomer unit is expressed as follows.
AA: acrylic acid, VA: vinyl alcohol, StSO: styrene sulfonic acid, St: styrene, EA: ethyl acrylate, BzMA: benzyl methacrylate

It is the figure which showed typically the mode on the recording medium of the ink used by embodiment of this invention. FIG. 6 is a diagram schematically illustrating a state on a recording medium when ink having excellent scratch resistance is used. It is the figure which showed typically the mode on a recording medium at the time of using the ink excellent in glossiness. It is the perspective view which looked at the recording device in the embodiment of the present invention from the left front. 1 is a longitudinal sectional view of a recording apparatus according to an embodiment of the present invention.

Explanation of symbols

a Pigment b Glossy ink (Resin A)
c Ink with excellent abrasion resistance (resin b)
DESCRIPTION OF SYMBOLS 1 Feeding part 2 Conveying part 3 Carriage part 4 Paper discharging part 5 Recording head 6 Control board 7 Feeding base 8 Pressure plate 9 Feeding roller 10 Platen 11 Carrying roller 12 Pinch roller 13 Paper discharge roller 14 Paper discharge roller 15 Carriage 16 Head Set lever 17 Separation roller P sheet

Claims (14)

An aqueous inkjet ink containing at least a pigment, a resin A, and a resin B,
The resin A contributes to the dispersion of the pigment, the resin B does not contribute to the dispersion of the pigment compared to the resin A,
The resin A is a copolymer that does not precipitate over the range of pH 4.0 or more and pH 6.0 or less, and includes a copolymer having a vinyl alcohol monomer unit, a copolymer containing a monomer unit having a sulfonic acid group, A monomer unit that contributes as a functional group is at least one copolymer selected from the group consisting of a copolymer having only a (meth) acrylic acid unit,
The water-based ink for ink jet according to claim 1, wherein the resin B is a copolymer having a (meth) acrylic acid monomer unit that is precipitated over a pH range of 4.0 to 6.0.   The aqueous ink for inkjet according to claim 1, wherein the resin B has an acid value of 90 mgKOH / g or more and 150 mgKOH / g or less.   The aqueous inkjet ink according to claim 1 or 2, wherein the resin A is a copolymer of a vinyl alcohol monomer unit and a (meth) acrylic acid monomer unit.   The aqueous ink for inkjet according to claim 3, wherein the content (% by mass) of the vinyl alcohol monomer unit is 30% by mass or more and 60% by mass or less with respect to the total mass of the resin A.   The aqueous ink for inkjet according to claim 1 or 2, wherein the resin A is a copolymer of a monomer unit having a sulfonic acid group and a (meth) acrylic acid monomer unit.   6. The aqueous inkjet ink according to claim 5, wherein the content (% by mass) of the monomer unit having the sulfonic acid group is 10% by mass to 50% by mass with respect to the total mass of the resin A.   The aqueous inkjet ink according to claim 1 or 2, wherein the monomer unit in which the resin A contributes as a hydrophilic group is a copolymer having only (meth) acrylic acid.   The aqueous ink for inkjet according to claim 7, wherein the resin A has an acid value of 250 mgKOH / g or more and 400 mgKOH / g or less.   9. An ink tank for storing ink, wherein the ink is the inkjet water-based ink according to any one of claims 1 to 8.   9. A recording unit comprising an ink tank for containing ink and a recording head for discharging ink, wherein the ink is the inkjet water-based ink according to claim 1.   9. An ink jet recording apparatus comprising an ink tank for containing ink and a recording head for ejecting ink, wherein the ink is the water-based ink for ink jet according to any one of claims 1 to 8. apparatus.   9. An ink jet recording method for applying ink to a recording medium, wherein the ink is the water-based ink for ink jet according to any one of claims 1 to 8.   The inkjet recording method according to claim 12, wherein the recording medium has a surface pH of 4.0 or more and 6.0 or less.   A copolymer that does not precipitate over the range of pH 4.0 or more and pH 6.0 or less, and has a copolymer having vinyl alcohol, a copolymer having a monomer unit having a sulfonic acid group, and a monomer that contributes as a hydrophilic group A step of mixing at least one copolymer selected from the group consisting of a copolymer whose unit is only (meth) acrylic acid and a pigment to form a dispersion; and pH 4.0 or more in the dispersion and a step of adding a (meth) acrylic acid copolymer that precipitates over a pH of 6.0 or less.

Images