JP2005330309A - Water-based ink-jet ink and method for ink-jet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink-jet ink carrying out printing on various kinds of recording media, especially having excellent resistance to strike-through and printed image quality in recording on plain paper and excellent printed image quality and fixing properties on coated paper for printing without an ink absorbing layer and further improved preservation stability of the ink itself and jetting stability and to provide a method for ink-jet recording using the ink. <P>SOLUTION: The water-based ink-jet ink is characterized as comprising a compound represented by general formula (I) [wherein, R<SB>1</SB>denotes a hydrogen atom, a straight-chain or a branched alkyl group or a straight-chain or a branched alkenyl group; and R<SB>2</SB>denotes a straight-chain or a branched alkyl group or a group of (CH<SB>2</SB>)<SB>n1</SB>-COOR<SB>3</SB>(wherein, R<SB>3</SB>denotes a straight-chain or a branched alkyl group; and n1 denotes 1 or 2)]. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel aqueous inkjet ink and an inkjet recording method using the same.

  In recent years, the inkjet recording method can easily and inexpensively create an image, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as a color filter. In particular, the recording device that emits and controls fine dots, and the ink with improved color reproduction range, durability, and emission suitability, and the ink absorbability, the coloring property of the coloring material, and the surface gloss are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper.

  The image quality improvement of today's ink jet recording system is achieved only when all of the ink jet recording apparatus, ink jet ink, and special paper are available.

  However, in an inkjet system that requires special paper, there is a problem that the recording medium that can be used is limited, the cost of the recording medium is increased, and the like.

  On the other hand, in the office, there is an increasing need for a system that can perform high-speed full-color printing without being restricted by a recording medium (for example, plain paper, coated paper, art paper, plain paper double-sided printing, etc.). In the electrophotographic system, there is a high-speed type capable of printing 100 sheets at an A4 size per minute, but the printing is limited to monochrome images, and the printing speed is increased in color printing, the simplicity of the apparatus, the cost, In order to satisfy any requirement such as power consumption, there are still many technical problems, and the user's request has not been satisfied.

  For example, in a printing method using plain paper, a method using oil-based ink is performed. Oil-based inks have the advantage that curling and cockling are unlikely to occur even when recorded on plain paper. However, the permeability to plain paper is large and the back-through to the back side is large. Further, since the non-volatile oily solvent is present in the paper, the opacity of the paper is reduced, and characters on the back surface are easily seen through the surface. Therefore, when performing double-sided printing, special paper with controlled ink permeability and special paper with increased opacity of the paper by increasing the amount of inorganic compound added are used. There is a problem that it is expensive compared to plain paper. Also, it is possible to reduce the strikethrough by limiting the amount of ink shot, but if the amount of ink shot is reduced until the strikethrough is sufficiently improved, the surface density will be significantly reduced and it is not always a good solution. It was not a solution.

  On the other hand, in the recording method for printing on plain paper, when a general water-based dye ink or water-based pigment ink is used, it is relatively easy to adjust the surface tension and the like, unlike oil-based ink. The penetrability is easy to control, and even when recording on plain paper, it is possible to suppress ink back-through. However, recent printers have been increased in speed, and accordingly, from the viewpoint of ink drying, it is required that the ink absorption speed on paper is also high. Particularly in the case of a high-speed printer equipped with a line head, a high ink absorption speed is required. Here, when adjusting the penetrability by the surface tension of the ink, the absorption speed and penetrability of plain paper are in a trade-off relationship, making it difficult to satisfy both drying and back-through performance during high-speed recording. ing. Regarding this permeability control, there is known a method in which a normal temperature solid ink containing a low melting point wax is heated (for example, 120 ° C. or more), melted, ejected in the melted state, and instantly solidified on a recording medium. . According to this method, it is possible to obtain an image having a moderate quality even with a recording medium having ink absorbing ability such as plain paper, but in order to increase the scratch resistance of the formed image, the hardness of the solidified ink is reduced. Although it is necessary to increase, it is necessary to use a wax having a high melting point in order to obtain a desired hardness. For example, when a wax having a melting point of 120 ° C. or higher is used, the head is heated to a high temperature of 120 ° C. or higher, so that the heat resistance of the head of the ink jet printing apparatus and the members of the ink supply system are overloaded, making it difficult to maintain the durability of the printing apparatus. There is a problem that the apparatus must be large. In particular, in a system using a piezo element for the recording head, there is a Curie temperature as a high temperature limit point, and there is an upper limit on the temperature that can be heated by itself.

  Furthermore, the water-based ink has a big problem that curling and cockling are likely to occur when recording on plain paper. In particular, when performing double-sided printing on plain paper, the process of printing the second side after printing the first side is often used, but when curling or cockling occurs immediately after printing the first side, During paper transport for printing the second side or during printing on the second side, the paper surface may become dirty due to poor paper transport, rubbing with the head, or the paper itself may jam and cannot be printed. Met.

As a method for improving curling and cockling that occurs when water-based ink is recorded on plain paper, a technique for containing casein resin in the ink is disclosed (for example, see Patent Document 1). However, this technology is said to be due to the flexible resin entering between the paper fibers, and a large amount of resin is required to suppress curling and cockling, increasing the ink viscosity and thixotropy, and further the colorant In the case of using a pigment, there is a problem that the dispersion stability of the pigment is remarkably lowered. In addition, a technique for improving curling and cockling by incorporating a specific diol into an aqueous ink is disclosed (for example, see Patent Document 2 and Patent Document 3). However, when an amount of diol necessary for preventing curling and cockling is contained, ink separation or solid precipitation may occur during ink storage. Such a phenomenon is likely to occur particularly when stored at a low temperature of 0 ° C. Furthermore, a technique for improving curling and cockling by incorporating saccharides in aqueous ink is disclosed (for example, see Patent Document 4). However, with this technique, the problem is that the viscosity of the ink increases when a necessary amount of sugar is added to prevent curling and cockling. Furthermore, it has a problem that solid content tends to precipitate during low-temperature storage.
JP-A-5-208547 JP-A-6-157955 Japanese Patent Laid-Open No. 11-12520 JP 2001-98193 A

  The present invention has been made in view of the above-mentioned problems, and its purpose is to enable printing on various recording media, in particular, excellent print-through resistance and print image quality in plain paper recording, and occurrence of curling and cockling. In addition, the present invention provides a water-based ink-jet ink in which the storage stability and emission stability of the ink itself are improved and an ink-jet recording method using the same.

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

(Claim 1)
A water-based inkjet ink comprising a compound represented by the following general formula (I):

[Wherein, R ₁ represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkenyl group, R ₂ represents a linear or branched alkyl group, or — (CH ₂ ) _n1 —COOR ₃ Represent. R ₃ represents a linear or branched alkyl group, and n1 represents 1 or 2. ]
(Claim 2)
A water-based inkjet ink comprising a compound represented by the following general formula (II):

[Wherein, R ₃ and R ₄ each independently represents a linear or branched alkyl group or a linear or branched alkenyl group capable of containing a cyclic structure. ]
(Claim 3)
A water-based inkjet ink comprising a compound represented by the following general formula (III):

[Wherein, R ₅ represents a benzyl group which may have a substituent, R ₆ represents a linear or branched alkyl group, or a linear or branched alkenyl group, and A represents one having 1 to 4 carbon atoms. Represents a linear or branched alkyl group. n2 represents 1 or 2. ]
(Claim 4)
A water-based inkjet ink comprising a compound represented by the following general formula (IV):

[Wherein, R ₇ represents a linear or branched alkyl group or a linear or branched alkenyl group, and R ₈ and R ₉ represent a linear, branched or cyclic alkyl group, or a linear, branched or cyclic group, respectively. Represents an alkenyl group. n3 represents 2, 3 or 4. ]
(Claim 5)
A water-based inkjet ink comprising a compound represented by the following general formula (V):

[Wherein, R ₁₀ represents a linear or branched alkyl group or a linear or branched alkenyl group, and R ₁₁ and R ₁₂ represent a linear, branched or cyclic alkyl group, or a linear, branched or cyclic group, respectively. Represents an alkenyl group. n4 represents 2, 3 or 4. ]
(Claim 6)
Containing at least one compound selected from the general formulas (I) to (V), wherein the content of the water-soluble organic solvent is 50% by mass or more and less than 95% by mass with respect to the total mass of the ink; Content is 1 mass% or more and less than 45 mass%, The water-based inkjet ink of any one of Claims 1-5 characterized by the above-mentioned.

(Claim 7)
The water-based inkjet ink according to claim 6, wherein the water-soluble organic solvent having the highest content in the water-soluble organic solvent has a solubility in water of 10% or more.

(Claim 8)
The addition amount of at least one compound selected from the general formulas (I) to (V) with respect to the total mass of the ink is 0.1% by mass or more and less than 20% by mass. The water-based inkjet ink of any one of these.

(Claim 9)
The water-based inkjet ink according to claim 1, further comprising a pigment as a colorant.

(Claim 10)
The water-based inkjet ink according to any one of claims 1 to 9, wherein the sol-gel phase transition is reversibly caused by temperature.

(Claim 11)
11. The aqueous inkjet ink according to claim 10, wherein a temperature at which the sol-gel phase transition is 30 ° C. or more and less than 100 ° C. 11.

(Claim 12)
An inkjet recording method for recording on a recording medium using the aqueous inkjet ink according to any one of claims 1 to 11, wherein the temperature of the aqueous inkjet ink in a recording head, and the recording medium An ink jet recording method, wherein a temperature difference from the temperature is 10 ° C. or more.

(Claim 13)
An inkjet recording method for recording on a recording medium using the aqueous inkjet ink according to any one of claims 1 to 11, wherein the aqueous inkjet ink in the recording head is heated to thereby record the recording head. A temperature difference between the temperature of the water-based inkjet ink and the temperature of the recording medium is 10 ° C. or more.

(Claim 14)
An inkjet recording method for performing recording on a recording medium using the water-based inkjet ink according to claim 1, wherein the recording head is a line head.

  According to the present invention, it is possible to print on various recording media, in particular, excellent resistance to show-through in plain paper recording, excellent print image quality, less curling and cockling, and storage stability of the ink itself and Provided are an aqueous inkjet ink having improved emission stability and an inkjet recording method using the same.

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

  As a result of intensive studies in view of the above problems, the present inventors can print on various recording media with the aqueous inkjet ink containing the compounds represented by the general formulas (I) to (V). In particular, resistance to show-through in plain paper recording, excellent print image quality, excellent print image quality and fixability on coated paper for printing without an ink absorbing layer, and dispersion stability and emission stability of the ink itself. Was found to be able to realize an improved water-based inkjet ink.

  The present inventors have increased the content of a water-soluble solvent in a water-based ink, which has been generally used in the past, and reduced the content of water in the ink, thereby reducing the content of water in a plain paper while being a water-based ink. A technical disclosure has been made by finding an ink capable of remarkably reducing curling and cockling during recording (for example, Japanese Patent Application No. 2004-31738). The present inventors have further developed this technique, and by using the water-based inkjet ink constitution or inkjet recording method of the present invention, the surface paper has excellent resistance to see-through on plain paper, excellent print image quality, and sufficient surface drying for high-speed printing. Further, it has been found that the occurrence of curling and cockling is extremely reduced.

  The aqueous inkjet ink of the present invention containing the compounds represented by the general formulas (I) to (V) has a low viscosity and good fluidity when emitted. However, the landing on the recording medium is an ink with a low surface tension, mainly due to a rapid increase in ink viscosity or a phase transition from sol to gel due to a decrease in ink temperature, resulting in a significant decrease in fluidity. It is thought that the feathering and back-through in plain paper recording could be improved drastically.

  Details of the present invention will be described below.

  The water-based inkjet ink of the present invention (hereinafter also simply referred to as ink) is characterized by containing at least one compound selected from the general formulas (I) to (V).

  By adding the compound selected from the general formulas (I) to (V) according to the present invention to the ink, it becomes possible to increase the viscosity or gel the ink with a temperature drop.

  Whether the ink is thickened or gelled can be adjusted by the amount of the compound selected from the general formulas (I) to (V) to the ink. In order to maximize the print quality and back-through performance on the recording medium, the ink is preferably gelled on the recording medium. Gelation as used in the present invention refers to an independent movement of a substance due to an interaction such as a lamellar structure, a polymer network formed by covalent bonding or hydrogen bonding, a polymer network formed by a physical aggregation state, or an aggregation structure of fine particles. It has a structure that is aggregated by losing and solidified with a sudden increase in viscosity or elasticity, or semi-solidified.

  When the ink of the present invention causes a sol-gel phase transition depending on the temperature, the sol-gel transition temperature is arbitrarily set, but is preferably 30 ° C. or higher and lower than 100 ° C. When the phase transition temperature of the ink is less than 30 ° C., it is difficult to obtain a stable ejection property due to the influence of the printing environment temperature when ejecting ink droplets from the recording head. As a result, it is necessary to heat the printer to an excessively high temperature, which imposes a load on the head of the ink jet recording apparatus and the members of the ink supply system, causing a problem in durability, and increasing the overall size of the apparatus and resulting cost increase. It becomes. The phase transition temperature by the sol-gel referred to in the present invention means a temperature at which the viscosity suddenly changes from a fluid solution state to a gel state, and the gel transition temperature, gel dissolution temperature, gel softening temperature, It is synonymous with terms called sol-gel transition point and gel point.

  The method for measuring the phase transition temperature in ink is, for example, placing a gel-like test piece on a heat plate, heating the heat plate, measuring the temperature at which the shape of the test piece collapses, and using this as the sol-gel phase transition It can be determined as temperature. The sol-gel transition temperature is preferably between the ink temperature in the head and the temperature of the recording medium. The sol-gel transition temperature of the ink of the present invention can be adjusted by the amount of the compound selected from the general formulas (I) to (V) according to the present invention.

  In the ink of the present invention, the penetration at a load of 10 g measured according to the method defined in JIS K 2207-1996 at 20 ° C. is preferably 1 or more and 100 or less.

  The penetration (20 ° C.) in the present invention is a value measured according to the method defined in JIS K 2207-1996 except that only the load is changed to 10 g.

  As a specific measuring method, 10 g is applied to the needle having the shape shown in FIG. 2 in which the balance is maintained under a load of 0 g using the penetration test apparatus shown in FIG. 1 of JIS K 2207-1996. Apply a load of ± 0.1 g. On the other hand, after placing the ink-jet ink as a specimen in a glass container and keeping the temperature at 20 ± 0.1 ° C., the needle is vertically penetrated into the ink-jet ink surface together with the holding device and the weight, and the tip of the needle and the ink surface The penetration distance (mm) 5 seconds after the contact with is measured with a displacement difference meter (dial gauge), and a value obtained by multiplying the obtained value by 10 is defined as penetration (20 ° C.).

  When the penetration (20 ° C.) specified in the present invention exceeds 100, sufficient character quality and back-through resistance cannot be obtained when recording on plain paper. It is not preferable because it breaks down.

  In the ink of the present invention, the method for achieving the penetration (20 ° C.) specified above is not particularly limited, but in the present invention, the method is selected from the general formulas (I) to (V) according to the present invention. By selecting the type of compound (melting point, etc.) and adjusting the addition amount, an ink having a desired penetration can be obtained.

  Next, specific examples of the compounds represented by the general formulas (I) to (V) according to the ink of the present invention are shown, but the present invention is not limited to these compounds.

  The amount of the compound represented by the general formulas (I) to (V) according to the present invention added to the ink is arbitrarily adjusted depending on the object effect of the present invention. It is preferably 1% by mass or more and less than 20% by mass, more preferably 1.0% by mass or more and less than 20% by mass, and particularly preferably 3.0% by mass or more and less than 15% by mass. .

  The ink of the present invention is characterized by being thickened or gelled when landed on a recording medium, and it is particularly preferable that the ink is gelled.

  The compounds represented by the general formulas (I) to (V) according to the present invention may be used alone or in combination of two or more. When two or more types are used, the total amount is preferably less than 20% by mass with respect to the total mass of the ink.

  In the ink of the present invention, when the amount of the compound represented by the general formulas (I) to (V) is less than 0.1% by mass with respect to the total mass of the ink, Since the thickening and gelation of the ink becomes insufficient, the printing quality on the recording medium and the through-through performance are not sufficiently satisfied. Further, when the amount of the compound represented by the general formulas (I) to (V) is 20% by mass or more with respect to the total mass of the ink, the emission may be unstable, and the coloring material may be a pigment. When used, the dispersion stability of the pigment may be impaired.

  Next, the components of the ink of the present invention excluding the above items will be described.

  In the ink of the present invention, a dye or a pigment can be used without limitation as a color material constituting the ink, but a pigment having good dispersion stability with respect to the ink component and excellent weather resistance is used. It is preferable. Although it does not necessarily limit as a pigment, For example, the organic or inorganic pigment of the following number described in a color index can be used for this invention.

  Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, and 53: 1. 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13 16, 20, 36, blue or cyan pigments include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 1 7-1, 22, 27, 28, 29, 36, 60, as green pigment, Pigment Green 7, 26, 36, 50, as yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193, and black pigments such as Pigment Black 7, 28, 26 can be used depending on the purpose.

  Specific product names include, for example, chromofine yellow 2080, 5900, 5930, AF-1300, 2700L, chromofine orange 3700L, 6730, chromofine scarlet 6750, chromofine magenta 6880, 6886, 6891N, 6790, 6887. , Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Ku Mofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Red 8040 , C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870 , Seika Fast Bordeaux 10B-430, Seica Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C7 18, A612, cyanine blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seika Kogyo), KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302 , 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (large Nippon Ink Chemical Co., Ltd.), Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pi gment Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, C USN, Colortex Maroon 601, Colortex Brown B610N, Colortex violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403B, Col. , Lionol lue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink), Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, Black Bumpy Carbon G2 , # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, MA11, MA100, MA100R , MA77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, And the like, such as F9 (manufactured by Mitsubishi Chemical).

  Further, it is also possible to use a dispersion liquid in which the pigment is dispersed in high concentration in advance in water, a solvent, a polymerizable monomer or the like.

  In the ink of the present invention, it is preferable to use a pigment dispersant for dispersing the pigment. Examples of the dispersant that can be used in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, and polyoxyalkylene alkyls. Activators such as ether phosphate, polyoxyalkylene alkylphenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivatives, vinyl naphthalene derivatives, Block copolymer consisting of two or more monomers selected from acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, random copolymer Body and the like, and salts thereof.

  For the dispersion of the pigment, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the pigment.

  In the present invention, the addition amount of the pigment dispersant is preferably 10 to 100% by mass with respect to the pigment.

  The average dispersed particle size of the pigment obtained by the above method is preferably 50 nm or more and 150 nm or less. If the average dispersed particle diameter of the pigment is within the range specified above, the dispersion stability of the ink can be improved. As a result, clogging of the head nozzle is suppressed, and the emission stability is further improved. In the ink of the present invention, the means for adjusting the average dispersed particle size of the pigment to the range specified above is achieved by, for example, appropriately selecting or combining pigment, dispersant, dispersion medium selection, dispersion conditions, and filtration conditions. can do.

  In the ink of the present invention, a conventionally known dye, preferably a water-soluble dye, can be used as required. Examples of water-soluble dyes that can be used in the present invention include azo dyes, eye dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the like. Examples of the compound include dyes exemplified in JP-A No. 2002-264490.

  The amount of the pigment or water-soluble dye added is preferably 0.1 to 20% by mass, more preferably 0.4 to 10% by mass. If it is 0.1% by mass or more, good image quality can be obtained, and if it is 20% by mass or less, an appropriate ink viscosity in ink ejection can be obtained. In addition, two or more kinds of colorants can be mixed as appropriate for color adjustment.

  The water-based ink of the present invention comprises at least water and a water-soluble solvent. Furthermore, it is preferable that the solubility of water-soluble organic solvent having the highest content in water among water-soluble organic solvents in ink is 10% or more.

  Examples of water-soluble solvents preferably used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), many Monohydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), multivalent Alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl) Ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol Ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethyl) Morpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide) Etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (for example, dimethyl sulfoxide, etc.) ), Sulfones (for example, sulfolane), urea, acetonitrile, acetone and the like.

  The solvent content in the aqueous ink of the present invention is not particularly limited, but is 50% by mass or more and 95% by mass or less with respect to the total mass of the ink, and the content of water with respect to the total mass of the ink is 1% by mass or more. , Less than 45% by mass is preferable from the viewpoint of preventing curling and cockling in recording on plain paper.

  In this invention, you may contain surfactant as needed. Surfactants preferably used in the ink of the present invention include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers. Nonionic surfactants such as acetylene glycols and polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, it is preferable to use an anionic surfactant and a nonionic surfactant.

  In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as a viscosity modifier, a specific resistance modifier, a film forming agent, an ultraviolet absorber, an antioxidant, a discoloration inhibitor, an antibacterial agent, and a rust inhibitor can be appropriately selected and used.

  As a recording medium that can be used for image formation with the ink of the present invention, various papers widely used in the ink jet system can be used. For example, glossy paper for ink jet, ink jet coated paper, and plain paper. In particular, by using the ink and the recording method of the present invention, it is possible to drastically improve the recording characteristics for inexpensive plain paper. Examples of plain paper include electrophotographic paper, electrophotographic and ink jet common paper, high-quality paper for printing, and medium-quality paper.

  Next, the ink jet recording method of the present invention will be described.

  In a preferred embodiment of the ink jet recording method of the present invention, an ink temperature in a recording head and a temperature of a recording medium are obtained using an ink containing a compound selected from the general formulas (I) to (V) according to the present invention. An ink jet recording method for forming an image with a difference between the two, and a method using a solidifying means for thickening or gelling the ink of the present invention landed on a recording medium by lowering the temperature. The temperature difference between the temperature of the water-based inkjet ink and the temperature of the recording medium is 10 ° C. or more.

  As the fixing means by the above thickening or gelling, for example, an inkjet recording apparatus used for inkjet recording is heated to a predetermined temperature in a relatively low temperature environment such as room temperature and then landed on a recording medium. The method of natural cooling by the ambient temperature and fixing, the method of cooling the recording medium in advance, or the method of fixing by blowing cold air to the landing part can be appropriately selected and used. A method of heating the ink in the recording head higher than the room temperature is simple and preferable. Examples of the method for heating the ink in the recording head include a method for heating the ink directly or indirectly by attaching a heater inside or outside the recording head, a method for utilizing heat generated when the recording head is driven, and the like. it can.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording medium and cured by irradiation with actinic rays is preferably 2 to 25 μm. Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording medium, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

(Ink ejection conditions)
As the ink ejection conditions, it is preferable from the viewpoint of ejection stability that the recording head and ink are heated to 35 to 100 ° C. and ejected. The ink of the present invention has a large viscosity fluctuation range due to temperature fluctuation, and the viscosity fluctuation directly affects the droplet size and droplet ejection speed, causing image quality degradation. It is preferable to keep in and emit in that state. The predetermined temperature range is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C. The set temperature here refers to a reference temperature set as the temperature of ink when ink is ejected.

  In the present invention, the amount of liquid droplets ejected from each nozzle of the recording head is preferably 2 to 15 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe. According to the present invention, even when the ink is ejected with a small droplet amount such as 2 to 15 pl, the ejection stability is improved, and a high-definition image can be stably formed.

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

Example 1
<Preparation of ink>
[Preparation of Ink 1]
The following additives were sequentially mixed, heated to 80 ° C. and stirred, and then the obtained liquid was filtered with a # 3000 metal mesh filter under heating and cooled to prepare ink 1 as a cyan ink. .

Water-soluble solvent: Dipropylene glycol monomethyl ether 64 parts Water-soluble solvent: 1,2-hexanediol 10 parts Ion-exchanged water 15 parts Surfactant: Orphine E1010 (manufactured by Nissin Chemical) 1 part Pigment dispersion 1 (below) 10 parts <Preparation of pigment dispersion 1>
Pigment: Black pigment (carbon black MA100, manufactured by Mitsubishi Chemical Corporation) 20 parts Pigment dispersant: Solsperse 20000 (Avecia) 5 parts Water-soluble solvent: Dipropylene glycol monomethyl ether 30 parts Ion-exchanged water 45 parts After mixing the above additives Pigment dispersion 1 was prepared by kneading using a bead mill. It was 85 nm as a result of measuring the volume average particle diameter of the pigment particle of the pigment dispersion liquid 1 containing this black pigment using a Zetasizer 1000 (manufactured by Malvern).

[Preparation of inks 2 to 4]
Inks 1 to 4 were prepared in the same manner as in the preparation of ink 1 except that 12-hydroxystearic acid (abbreviated as 12-HSA in Table 1) was added as shown in Table 1. . In Table 1, compound names are abbreviated as follows.

DPGME: Dipropylene glycol monomethyl ether (optionally mixed with water)
TPGME: Tripropylene glycol monomethyl ether (optionally mixed with water)
TEGME: Triethylene glycol monomethyl ether (mixed arbitrarily with water)
DMI: 1,3-dimethyl-2-imidazolidinone (optionally mixed with water)
HDO: 1,2-hexanediol (optionally mixed with water)
[Preparation of inks 5 to 24]
Inks 5 to 24 were prepared in the same manner as in the preparation of the ink 1 except that various additives and addition amounts were changed as shown in Table 1.

<Measurement of each characteristic value of ink>
For the inks 1 to 24 prepared as described above, the phase transition temperature was measured by the following method. The obtained results are shown in Table 1.

(Measurement of phase transition temperature)
Place each gel-like ink test piece on a melting point measuring machine (ATM-01 ATM-01), heat at a heating rate of 5 ° C / min or less, measure the temperature at which the test piece melts, and repeat this operation three times. The average value was calculated repeatedly, and the first decimal place was rounded off to obtain the ink phase transition temperature.

<< Inkjet image formation >>
Each of the inks prepared above is loaded into a line head type ink jet recording apparatus equipped with a piezo type ink jet nozzle, and 4, 5, 6 points MS Mincho on PPC paper (first class paper manufactured by Konica Minolta Business Technology) The characters “Mouth, Four, Day, Time, Cause, Trouble, Solid, Country, Eye, Figure, Country” and black solid images were printed on the body to obtain images 1 to 24. The ink supply system consists of an ink tank, a supply pipe, a front chamber ink tank immediately before the print head, a pipe with a filter, and a piezo head. The ink is insulated from the front chamber tank to the print head and heated to the ink phase transition temperature + 20 ° C. did. The piezo head also has a built-in heater, and the ink temperature in the recording head is heated to the phase transition temperature + 20 ° C. For the ink that does not cause gelation, the ink was uniformly heated to 80 ° C. The piezo head has a nozzle diameter of 25 μm, 256 nozzles (128 nozzles × 2 rows, staggered arrangement, 1 row nozzle pitch 360 dpi), and a droplet speed of about 8 m / droplet under the condition that the amount of each droplet is 4 pl. It was emitted in sec and printed with a recording resolution of 1440 dpi × 1440 dpi. The temperature of each recording medium was 23 ° C. The above image formation was performed in an environment of 23 ° C. and 55% RH. In the present invention, dpi represents the number of dots per 2.54 cm.

<Evaluation of formed image>
About the created images 1-24, according to the following method, evaluation of character quality, back-through resistance, ink thixotropy, ink storability, and emission stability was performed.

[Evaluation of character quality]
By the above method, the resolution of 1400 dpi x 1400 dpi on a PPC paper (first class paper manufactured by Konica Minolta Business Technology) with a 3 point, 4 point and 5 point MS Mincho style kanji "mouth, four, day, times, The characters “Cause, Difficulty, Solid, Country, Eye, Figure, Country” were printed, the printed character image was visually observed, and the character quality was evaluated according to the following evaluation criteria.

◎: All four-point characters are clearly recorded in detail ○: All four-point characters are legible △: Only four-point characters are legible, but all five-point characters ×: Only a part of 4, 5 point characters can be read, but all 6 point characters can be read. ××: Some 6 point characters cannot be read. Resistance evaluation)
By the above method, the back surface density of the black solid image portion created on PPC paper (first class paper manufactured by Konica Minolta Business Technology) was measured using an optical densitometer (938 spectral densitometer manufactured by X-Rite). Further, the density of the non-recorded portion of the paper was measured in the same manner. Next, (the density of the back surface of the black solid image portion) − (the density of the non-image portion) was determined, and the strike through resistance was evaluated according to the following evaluation criteria.

A: Density difference is less than 0.05. O: Density difference is 0.05 or more and less than 0.08. Δ: Density difference is 0.08 or more and less than 0.12. 12 or more and less than 0.15 XX: Density difference is 0.15 or more [Evaluation of ink thixotropy]
The viscoelasticity measuring device (UDS-300; manufactured by Paar Physica) was used to measure the viscosity of inks 1 to 24 at a share rate of 1 sec and 1000 sec. The ink temperature at the time of measurement was set to the phase transition temperature + 20 ° C. for the ink that gels, and uniformly 80 ° C. for the ink that does not gel. Next, the thixotropy of the ink was determined using the thixo index calculated by the following equation.

Thixo index = (viscosity at 1 sec share rate) / (viscosity at 1000 sec share rate)
A: The thixo index is 0.98 or more and less than 1.02. B: The thixo index is 0.95 or more and less than 0.98, or 1.02 or more and less than 1.05. Δ: The thixo index is 0.00. 90 or more, less than 0.95, or 1.05 or more, and less than 1.10 x: Thixo index is 0.75 or more, less than 0.90, or 1.10 or more, less than 1.25 xx: Thixo index is less than 0.75 or 1.25 or more [Evaluation of ink storage stability]
Inks 1 to 24 were placed in glass sample bottles, sealed, and stored at 0 ° C. and 23 ° C. for 14 days. After storage, the one stored at 0 ° C. was returned to room temperature, the two ink states were compared and observed, and the ink storage stability was evaluated according to the following criteria.

A: No difference is observed between the two inks. O: A slightly separated liquid is observed on the surface of the ink stored at 0.degree. C. A: A slight separation is observed in the entire ink stored at 0.degree. C.:0 Separation is observed in the entire ink stored at ℃ [Evaluation of emission stability]
The printer equipped with each of the inks prepared above was changed in a temperature range of 10 to 40 ° C. for 12 hours, and after repeating this for 3 cycles, the image was emitted and visually observed for the presence of nozzle missing and emission bending. The emission stability was evaluated according to the following criteria.

◎: No nozzle missing was observed. ○: Out of all nozzles 256, 1 to 5 nozzles were bent in the exit direction. Δ: Out of all nozzles 256, exit direction was from 6 to 10 nozzles. Xx: Out of all nozzles 256, one or two nozzles showed defective emission. Xx: All of nozzles 256, three or more nozzles showed defective emission. The results are shown in Table 2.

  As is clear from the results in Table 2, the aqueous inkjet ink of the present invention containing the compounds represented by the general formulas (I) to (V) according to the present invention is better than the comparative example in the character quality of the formed image. It can be seen that the ink has excellent anti-through-through resistance and has almost no thixotropy as an ink, and has excellent emission stability and storage stability. Further, curling and cockling were good for all printed materials.

Example 2
<< Preparation of pigment dispersion >>
[Preparation of Yellow Pigment Dispersion 1]
Pigment: Yellow pigment (manufactured by Novoperm P-HG Clariant) 15 parts Pigment dispersant: Solsperse 20000 (Avecia) 5 parts Triethylene glycol monomethyl ether 60 parts Ion-exchanged water 20 parts After mixing the above additives, a bead mill is used. The mixture was kneaded to prepare a yellow pigment dispersion 1. As a result of measuring the volume average particle diameter of the pigment particles of this yellow pigment dispersion 1 using a Zetasizer 1000 (manufactured by Malvern), it was 125 nm.

[Preparation of magenta pigment dispersion 1]
Pigment: Magenta pigment (Hostperm Pink E, manufactured by Clariant) 15 parts Pigment dispersant: Solsperse 20000 (Avecia) 5 parts Triethylene glycol monomethyl ether 60 parts Ion-exchanged water 20 parts After mixing the above additives, a bead mill was used. The magenta pigment dispersion 1 was prepared by kneading. As a result of measuring the volume average particle diameter of the pigment particles of this magenta pigment dispersion 1 using a Zetasizer 1000 (manufactured by Malvern), it was 110 nm.

[Preparation of Cyan Pigment Dispersion 1]
Pigment: Cyan pigment (made by Hostperm Blue B2G Clariant)
20 parts Pigment dispersant: Solsperse 20000 (manufactured by Avecia) 5 parts Triethylene glycol monomethyl ether 60 parts Ion-exchanged water 15 parts After mixing the above additives, the mixture is kneaded using a bead mill to prepare cyan pigment dispersion 1 did. It was 85 nm as a result of measuring the volume average particle diameter of the pigment particle of this cyan pigment dispersion liquid 1 using Zetasizer 1000 (made by Malvern).

[Black pigment dispersion 1]
The black pigment dispersion 1 described in Example 1 was used.

<Preparation of ink set>
An ink set comprising the following color inks was prepared.

[Preparation of yellow ink]
The following additives were sequentially mixed, heated and stirred at 80 ° C., and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a yellow ink.

Water-soluble solvent: Triethylene glycol monomethyl ether 29 parts Water-soluble solvent: 1,3-dimethyl-2-imidazolidinone 10 parts Water-soluble solvent: 1,2-hexanediol 5 parts Surfactant: Olphine E1010 (Nisshin Chemical) 1 part Ion-exchanged water 15 parts Yellow pigment dispersion 1 30 parts Illustrative compound (III-1) 10 parts [Preparation of magenta ink]
The following additives were sequentially mixed, heated and stirred at 80 ° C., and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a magenta ink.

Water-soluble solvent: 41 parts of triethylene glycol monomethyl ether Water-soluble solvent: 10 parts of 1,3-dimethyl-2-imidazolidinone Water-soluble solvent: 3 parts of 1,2-hexanediol Surfactant: Olphine E1010 (Nisshin Chemical) 1 part Deionized water 15 parts Magenta pigment dispersion 1 20 parts Illustrative compound (III-1) 10 parts [Preparation of cyan ink]
The following additives were mixed in sequence, heated and stirred at 80 ° C., and the resulting liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a cyan ink.

Water-soluble solvent: Triethylene glycol monomethyl ether 39 parts Water-soluble solvent: 1,3-dimethyl-2-imidazolidinone 15 parts Water-soluble solvent: 1,2-hexanediol 5 parts Surfactant: Olphine E1010 (Nisshin Chemical) 1 part Ion-exchanged water 20 parts Cyan pigment dispersion 1 10 parts Illustrative compound (III-1) 10 parts [Preparation of black ink]
The following additives were sequentially mixed, heated and stirred at 80 ° C., and then the obtained liquid was filtered with a # 3000 metal mesh filter under heating and then cooled to prepare a black ink.

Water-soluble solvent: Triethylene glycol monomethyl ether 32 parts Water-soluble solvent: 1,3-dimethyl-2-imidazolidinone 15 parts Water-soluble solvent: 1,2-hexanediol 2 parts Surfactant: Olfine E1010 (Nisshin Chemical) 1 part Deionized water 20 parts Black pigment dispersion 2 20 parts Illustrative compound (III-1) 10 parts [Preparation of light magenta ink]
The following additives were sequentially mixed, heated and stirred at 80 ° C., and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a light magenta ink.

Water-soluble solvent: Triethylene glycol monomethyl ether 49 parts Water-soluble solvent: 1,3-dimethyl-2-imidazolidinone 10 parts Water-soluble solvent: 1,2-hexanediol 5 parts Surfactant: Olphine E1010 (Nisshin Chemical) 1 part Ion-exchanged water 20 parts Magenta pigment dispersion 1 5 parts Illustrative compound (III-1) 10 parts [Preparation of light cyan ink]
The following additives were sequentially mixed, heated and stirred at 80 ° C., and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a light cyan ink.

Water-soluble solvent: Triethylene glycol monomethyl ether 52 parts Water-soluble solvent: 1,3-dimethyl-2-imidazolidinone 10 parts Water-soluble solvent: 1,2-hexanediol 5 parts Surfactant: Olphine E1010 (Nisshin Chemical) 1 part Ion-exchanged water 20 parts Cyan pigment dispersion 1 2 parts Exemplary compound (III-1) 10 parts << Measurement of each characteristic value of ink >>
For each color ink prepared as described above, the phase transition temperature was measured in the same manner as in the method described in Example 1, and the obtained results are shown in Table 3.

<< Formation and evaluation of inkjet image >>
Using the line head type ink jet printer of the first embodiment, the above-mentioned six colors of ink are packed in a line head printer arranged in six rows in the paper transport direction, and the recording conditions are the same as in the first embodiment. PPC paper (Konica Minolta Business Technology) A 3P Mincho character image and a JIS / SCID N5 “bicycle” image were printed on the first class paper), and the character quality evaluation and the strikethrough resistance evaluation were performed in the same manner as described in Example 1. As a result of evaluating high-temperature bleeding resistance and ink transfer resistance, excellent effects could be confirmed in all evaluation items. Moreover, as a result of visually observing the created JIS / SCID N5 “bicycle” image, it was confirmed that the image was excellent in sharpness and high optical density was obtained.

Claims (14)

A water-based inkjet ink comprising a compound represented by the following general formula (I):

[Wherein, R ₁ represents a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkenyl group, R ₂ represents a linear or branched alkyl group, or — (CH ₂ ) _n1 —COOR ₃ Represent. R ₃ represents a linear or branched alkyl group, and n1 represents 1 or 2. ] A water-based inkjet ink comprising a compound represented by the following general formula (II):

[Wherein, R ₃ and R ₄ each independently represents a linear or branched alkyl group or a linear or branched alkenyl group capable of containing a cyclic structure. ] A water-based inkjet ink comprising a compound represented by the following general formula (III):

[Wherein, R ₅ represents a benzyl group which may have a substituent, R ₆ represents a linear or branched alkyl group, or a linear or branched alkenyl group, and A represents one having 1 to 4 carbon atoms. Represents a linear or branched alkyl group. n2 represents 1 or 2. ] A water-based inkjet ink comprising a compound represented by the following general formula (IV):

[Wherein, R ₇ represents a linear or branched alkyl group or a linear or branched alkenyl group, and R ₈ and R ₉ represent a linear, branched or cyclic alkyl group, or a linear, branched or cyclic group, respectively. Represents an alkenyl group. n3 represents 2, 3 or 4. ] A water-based inkjet ink comprising a compound represented by the following general formula (V):

[Wherein, R ₁₀ represents a linear or branched alkyl group or a linear or branched alkenyl group, and R ₁₁ and R ₁₂ represent a linear, branched or cyclic alkyl group, or a linear, branched or cyclic group, respectively. Represents an alkenyl group. n4 represents 2, 3 or 4. ] Containing at least one compound selected from the general formulas (I) to (V), wherein the content of the water-soluble organic solvent is 50% by mass or more and less than 95% by mass with respect to the total mass of the ink; Content is 1 mass% or more and less than 45 mass%, The water-based inkjet ink of any one of Claims 1-5 characterized by the above-mentioned. The water-based inkjet ink according to claim 6, wherein the water-soluble organic solvent having the highest content in the water-soluble organic solvent has a solubility in water of 10% or more. The addition amount of at least one compound selected from the general formulas (I) to (V) with respect to the total mass of the ink is 0.1% by mass or more and less than 20% by mass. The water-based inkjet ink of any one of these. The water-based inkjet ink according to claim 1, comprising a pigment as a colorant. The water-based inkjet ink according to claim 1, wherein the sol-gel phase transition is reversibly changed depending on a temperature. 11. The aqueous inkjet ink according to claim 10, wherein a temperature at which the sol-gel phase transition is 30 ° C. or more and less than 100 ° C. 11. An inkjet recording method for recording on a recording medium using the aqueous inkjet ink according to any one of claims 1 to 11, wherein the temperature of the aqueous inkjet ink in a recording head, and the recording medium An ink jet recording method, wherein a temperature difference from the temperature is 10 ° C. or more. An inkjet recording method for recording on a recording medium using the aqueous inkjet ink according to any one of claims 1 to 11, wherein the aqueous inkjet ink in the recording head is heated to thereby record the recording head. A temperature difference between the temperature of the water-based inkjet ink and the temperature of the recording medium is 10 ° C. or more. An inkjet recording method for performing recording on a recording medium using the water-based inkjet ink according to claim 1, wherein the recording head is a line head.