JP4998048B2 - Inkjet recording method - Google Patents

Description

  The present invention relates to an inkjet recording method and recorded matter. More specifically, the present invention relates to an ink jet recording method and recorded matter excellent in cockling or curling characteristics.

  The ink jet recording method is a printing method in which printing is performed by ejecting ink droplets from a printer head and landing on a recording medium such as paper. The ink used in this ink jet recording method needs to have low viscosity in order to fly from the printer head, and ink with a high water content is used. Therefore, inkjet recording paper with high ink absorbability is used as the recording medium.

  According to the inkjet dedicated paper, a high-quality image can be realized. However, if the absorbing layer for absorbing ink is not provided thick, the amount of absorption is reduced, and the amount of coating is increased. In addition, since powdered silica, alumina or the like is used as a raw material to make the absorption layer transparent, the cost has been high. This high cost has become a barrier that narrows the user's applications.

  Although plain paper such as copy paper and coated paper for printing (also referred to as coated paper or main printing paper) are inexpensive, they have lower ink absorbency than ink-jet dedicated paper. For this reason, plain paper is essentially unsuitable as a recording medium for the ink jet recording method. In recent years, various ink-jet recording inks have been developed that guarantee high-quality images even on inexpensive plain paper, but it is extremely difficult to achieve image quality on ink-jet dedicated paper.

  Since the coated paper for printing has a lower ink absorbability than the plain paper, it has been considered to be more inappropriate than the plain paper as a recording medium for the ink jet recording method. However, since the image quality of coated paper is extremely high, a technique for using this as a recording medium for an ink jet recording method has also been proposed.

For example, the print areas P1 and P2 that can be printed in one pass are divided into a plurality of passes for printing, and paper feeding is not performed while printing of the print region is completed in the plurality of passes. There has been proposed an ink jet recording method capable of producing a high-quality image without using additional equipment in a conventional apparatus and using a coated paper for printing having low water absorption and excellent printability (Patent Document 1). .
JP 2006-272732 A

  As described above, combining the advantage of the ink jet recording method, which is simple and small, with the coated paper for printing having low cost and excellent printability has been studied from the viewpoint of the ink jet recording method. There is room for improvement.

  Also, when printing on a coated paper for printing using a conventional ink composition having a high water content, wrinkles such as wrinkling of the coated paper after the ink is ejected are generated. There is a problem that a phenomenon such as so-called “curl” occurs in which the coated paper itself warps.

  However, simply reducing the water content of the ink composition increases the viscosity of the ink composition. When such high-viscosity ink is ejected by an ink jet recording head, it is difficult to ensure high-speed ejection and stable ejection, and thus there is a problem that high-speed printing cannot be supported.

  Accordingly, an object of the present invention is to prevent cockling and curling even when a printing paper having a low ink absorbency is used as a recording medium, and to discharge stability even in high-speed printing. It is to provide a technology capable of ensuring the above.

The present invention achieves the above object by providing the following invention (1). (1) An ink jet recording method for performing printing by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the ink composition includes a pigment, a water-soluble organic solvent, and a surfactant. An ink composition comprising at least an agent and 60 to 50 % by weight of water, the ink composition is heated, and droplets of the ink composition having a viscosity of 2 to 5 mPa · s are ejected. An inkjet recording method.

Preferred embodiments of the invention are as follows. (2) The inkjet recording method according to (1), wherein the water-soluble organic solvent includes at least polyhydric alcohols and butyl ethers of glycol ethers;
(3) the surfactant is an acetylene glycol based surfactant and / or poly-modified siloxane-based surfactant, an inkjet recording how according to (1) or (2).

[Inkjet recording method]
Next, the ink jet recording method of the present invention will be described based on preferred embodiments. As described above, the ink jet recording method of the present invention is an ink jet recording method in which droplets of an ink composition are ejected, and the droplets are attached to a recording medium to perform printing. And an ink composition comprising at least a water-soluble organic solvent, a surfactant, and 60 to 10% by weight of water, and the ink composition is heated to have a viscosity of 2 to 5 mPa · s. A droplet of the ink composition is ejected.

  By using an ink composition in which the water content is specified in the above range, the amount of water absorbed by the cellulose in the coated paper is less than that of the conventional ink composition, resulting in cockling and curling. The thought swelling of cellulose can be suppressed. Therefore, the ink composition of the present embodiment is also useful for a recording medium having an absorbent layer of a paper support having poor ink absorbability, such as plain paper or coated paper for printing (printing paper).

  When the water content is less than 10% by weight, the fixability to the recording medium may be lowered. In addition, it becomes difficult to ensure high-speed ejection and stable ejection of ink, making it difficult to support high-speed printing. On the other hand, when the water content of the ink composition exceeds 60% by weight, as in the case of the conventional aqueous ink composition, when printing on a recording medium having an absorbent layer of a paper support with poor ink absorbability, Rings and curls are likely to occur.

  In the present embodiment, “plain paper” generally refers to paper that uses pulp as a main raw material and is used in a printer or the like, and is defined by JIS P 0001 number 6139. Specific examples include high-quality paper, PPC copy paper, and non-coated printing paper. As the plain paper, those commercially available from various companies can be used. For example, various papers such as Xerox 4200 (manufactured by Xerox), GeoCycle (Georgia-Pacific), and the like can be used.

In the present embodiment, “a recording medium having a paper support absorbing layer with poor ink absorption” means that the water absorption within 30 msec ^1/2 from the start of contact in the Bristow method is 30 ml / m ² or less. A recording medium having an absorption layer of a paper support. In the present embodiment, any coated coated paper (printing paper) conventionally used as printing paper for letterpress printing, flat printing (for example, offset printing), or intaglio printing (for example, gravure printing). Can also be used. The printing coated paper includes ordinary coated paper, cast coated paper, and matte coated paper. Also included are printing paper defined by JIS P 0001 number 6122, coated paper defined by JIS P 0001 number 6059 (for example, OK top coat N), and the like.

  The colorant of the ink composition used in the present invention uses a pigment from the viewpoint of light resistance. As the pigment, both inorganic pigments and organic pigments can be used.

  As inorganic pigments, carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, iron oxide, titanium oxide, and the like can be used.

  Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments Polycyclic pigments, dye chelates (for example, basic dye chelates, acid dye chelates, etc.), dye rakes (basic dye rakes, acid dye rakes), nitro pigments, nitroso pigments, aniline black, daytime Examples thereof include photofluorescent pigments. The above pigments can be used alone or in combination of two or more.

  Carbon black is preferred as the pigment used in the black ink composition. Specific examples of carbon black include # 2300, # 900, HCF88, # 33, # 40, # 45, # 52, MA7, MA8, MA100, # 2200B manufactured by Mitsubishi Chemical, Raven 5750, 5250 , 5000, 3500, 1255, 700, etc., Regal 400R, 330R, 660R, Mogu L, 700, Monarch 800, 880, 900, 1000, 1100, 1300, manufactured by Cabot Corporation , 1400, etc. Color Black FW1, FW2V, FW18, FW200, Color Black S150, S160, S170, Printex 35, U, V, 140U, Special Black 6, 5 4A, same Etc. can be mentioned, may be used as these one or a mixture of.

  The color ink composition used in this embodiment preferably includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition. Examples of the pigment of the color ink composition include pigment yellow, pigment red, pigment violet, pigment blue and the like described in the color index.

  Specifically, for example, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 147, 150, 153, 155, 174, 180, 188, 198; I. Pigment red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184,202,207,209; I. Pigment Bio Red 1,3,5: 1, 16, 19, 23, 38; I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16; I. Pigment Black 1, 7, etc., and an ink composition can also be formed using a plurality of pigments.

  In particular, the organic pigment contained in the yellow ink composition is C.I. I. Pigment Yellow 74, 109, 110, 128, 138, 147, 150, 155, 180, and 188, and the organic pigment contained in the magenta ink composition includes C.I. I. Pigment red 122, 202, 207, 209, C.I. I. An organic pigment containing at least one selected from pigment violet 19 and contained in the cyan ink composition is C.I. I. It is preferable to include at least one selected from CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, and 16.

  Further, any pigment not described in the color index can be used as long as it is insoluble in water.

  According to the embodiment of the present invention, the content of the pigment contained in the ink composition may be appropriately determined, but is preferably 0.5 to 10% by weight.

  The ink composition of this embodiment contains a water-soluble organic solvent from the viewpoint of preventing clogging of the nozzles of the inkjet printer.

  Examples of the water-soluble organic solvent include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2 -Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol Polyhydric alcohols such as 1,5-pentanediol and 4-methyl-1,2-pentanediol; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol; ethylene glycol monomethyl Ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso- Propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monobutyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl Ether, propire Glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene Glycol ethers such as glycol mono-iso-propyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone; formamide, acetamide; dimethyl sulfoxide; sorbitol, sorbitan; acetin, diacetin , Triacetin; sulfolane and the like, and one or more of these can be used.

  These water-soluble organic solvents are preferably contained in the ink composition in an amount of 10 to 90% by weight from the viewpoint of ensuring appropriate physical properties (such as viscosity) of the ink composition, printing quality, and reliability.

  Furthermore, in the present embodiment, at least polyhydric alcohols and butyl ethers of glycol ethers are used in combination as the water-soluble organic solvent, so that reliability such as print quality, ejection stability, clogging recovery properties, etc. Can provide an ink composition having excellent resistance. This is because polyhydric alcohols are suitable for controlling water retention (humidity) and penetrability of the ink composition into recording media such as plain paper, and glycol butyl ethers are suitable for ejection stability and ink for recording media. The ink composition is suitable for controlling the penetrability of the composition. By using these in combination, it is possible to provide a highly reliable ink composition such as print quality, ejection stability, and clogging recovery.

  As a particularly preferred water-soluble organic solvent, the polyhydric alcohol is a combination of two or more selected from glycerin, diethylene glycol, triethylene glycol, 1,5-pentanediol and 1,2-hexanediol, and butyl glycols Examples include diethylene glycol monobutyl ether or triethylene glycol monobutyl ether.

  The ink composition of the present embodiment contains a surfactant from the viewpoint of storage stability. As the surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant can be contained. A nonionic surfactant is particularly preferable from the viewpoint of obtaining an ink composition with less foaming and foaming.

  Further specific examples of nonionic surfactants include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl Ethers such as allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether; polyoxyethylene oleic acid, polyoxyethylene oleic acid ester, polyoxyethylene distearic acid ester , Sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxy Esters such as ethylene monooleate and polyoxyethylene stearate; polyether-modified siloxane surfactants such as dimethylpolysiloxane; fluorine-containing surfactants such as fluorine alkyl esters and perfluoroalkyl carboxylates Can be mentioned. The nonionic surfactant can be used alone or in combination of two or more.

  Among the above nonionic surfactants, acetylene glycol surfactants and / or polyether-modified siloxane surfactants are particularly preferable in that they have little foaming and have excellent antifoaming performance.

  Further specific examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol. 3,5-dimethyl-1-hexyne-3ol, etc., but are also available commercially, for example, Surfynol 104, 82, 465, 485 manufactured by Air Products, manufactured by TG and Nisshin Chemical Co., Ltd. Olfin STG, Olfin E1010 and the like. Specific examples of the polyether-modified siloxane surfactant include BYK-345, BYK-346, BYK-347, BYK-348, UV3530, and the like manufactured by Big Chemie Japan. A plurality of these may be used in the ink composition.

  The water contained in the ink composition of the present invention is preferably pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide in order to prevent the generation of mold and bacteria and enable long-term storage of the ink composition.

  A pH adjuster can be added to the ink composition of the present embodiment. As the pH adjuster, alkali hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide and / or alkanolamines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine can be used. . In particular, it is preferably adjusted to pH 6 to 10 including at least one pH adjusting agent selected from alkali metal hydroxide, ammonia, triethanolamine, and tripropanolamine. If the pH is within this range, the clogging recoverability can be maintained without causing deterioration of the materials constituting the ink jet printer.

  If necessary, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid and the like can be used as a pH buffering agent.

  The trialkanolamine can be suitably used as a gloss-imparting agent for ink compositions. In order to form a uniform glossy image on a glossy recording medium, yellow, magenta and cyan inks are used. It can be added to the composition.

  The content of trialkanolamine used as the gloss imparting agent of the ink composition is 10 to 50% by weight with respect to 100% by weight of the pigment from the viewpoints of erosion to members used in the printer, ink viscosity and gloss. %, More preferably 12 to 45% by weight, more preferably 1% by weight or more based on the total amount of the ink composition, and more preferably the upper limit is 3% by weight, The lower limit is 1% by weight.

  The trialkanolamine is not particularly limited, but triethanolamine and / or tripropanolamine are preferable from the viewpoint of improving printing stability and glossiness.

  Furthermore, an antifoaming agent, an antioxidant, an ultraviolet absorber, an antiseptic / antifungal agent, and the like can be added to each ink composition used in the present embodiment as necessary.

  Examples of the antioxidant and the ultraviolet absorber include allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, L-ascorbic acid and its salts, etc. Tinuvin 328 manufactured by Ciba Geigy 900, 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or the like, or a lanthanide oxide or the like is used.

  Examples of the antiseptic / antifungal agent include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one ( Avecia's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  The ink composition of the present embodiment can be prepared in the same manner as the conventional ink composition using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, a roll mill, or the like. In the preparation, it is preferable to remove coarse particles from the viewpoint of preventing nozzle clogging. The coarse particles are removed by, for example, filtering the ink obtained by mixing the above components using a filter such as a membrane filter or a mesh filter, and removing particles of preferably 10 μm or more, more preferably 5 μm or more. Done.

  In the ink jet recording method of this embodiment, the ink composition is ejected as droplets from a fine nozzle by an ink jet recording apparatus, and the droplets are attached to a recording medium.

  At this time, the ink composition described above is heated, and droplets of the ink composition having a viscosity of 2 to 5 mPa · s are ejected.

  The ink composition whose water content is limited to 60 to 10% by weight has a higher viscosity than the conventional ink composition. Such a high-viscosity ink composition is advantageous in suppressing curling and cockling, but tends to lack ejection stability when the ink composition is ejected as droplets from a fine nozzle of an inkjet recording apparatus. Therefore, it is disadvantageous for high-speed printing. Therefore, by heating at least a part of the ink composition described above and setting the viscosity to 2 to 5 mPa · s, the ejection stability of the liquid droplets ejected from the nozzle can be improved.

  The heating may be performed by heating the entire ink composition or only a part thereof. The object of the present invention can be achieved if the viscosity of the droplets discharged from the nozzle is at least 2 to 5 mPa · s.

  The heated ink composition is held at a constant temperature in the inkjet recording head, and has a viscosity of 2 to 5 mPa · s until it is discharged from the nozzle.

  The means for heating the ink composition is not particularly limited, and a conventionally known heater can be used. The heating is preferably performed in the range of 50 ° C. to 70 ° C. in consideration of the influence on the composition of the ink composition.

  Specific examples of the method for ejecting the ink composition as droplets from the fine nozzles of the ink jet recording apparatus include the following methods.

  As the first method, there is an electrostatic suction method, this method applies a strong electric field between the nozzle and the acceleration electrode placed in front of the nozzle, and continuously ejects ink from the nozzle in the form of droplets, This is a method in which a print information signal is applied to the deflection electrode while the ink droplet is flying between the deflection electrodes for recording, or a method in which the ink droplet is ejected in response to the print information signal without being deflected.

  The second method is a method in which ink droplets are forcibly ejected by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. The ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is given to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which a pressure and a print information signal are simultaneously applied to an ink liquid using a piezoelectric element, and ink droplets are ejected and recorded.

  The fourth method is a method in which the ink liquid is rapidly expanded in volume by the action of thermal energy, and the ink liquid is heated and foamed with a microelectrode in accordance with a print information signal, and ink droplets are ejected and recorded.

  Any of the above methods can be used in the ink jet recording method using the ink composition of the present embodiment.

  According to the ink jet recording method of the present embodiment, cockling and curling can be prevented by the above ink jet recording method even when a printing coated paper with low ink absorbability is used as a recording medium. At the same time, ejection stability can be ensured even in high-speed printing.

[Recordings]
The recorded matter of this embodiment is recorded on a recording medium using at least the above-described inkjet recording method. By using the above-described inkjet recording method, the recorded matter can prevent cockling and curling even when a printing coated paper with low ink absorbency is used as a recording medium.

1. Preparation of Ink Composition An ink composition containing a pigment, a water-soluble organic solvent, a surfactant, and water was prepared using the combinations shown in Table 1.

2. Evaluation Test (1) Printing Method An evaluation machine capable of heating the ink compositions shown in Table 1 (Examples 1 to 4 and Comparative Examples 1 to 4) is prepared and filled. A 100% duty patch pattern of each color was printed. As recording media, OK topcoat N (produced by Oji Paper Co., Ltd.), which is a type of coated paper for printing (printing paper), Xerox P (produced by Fuji Xerox Co., Ltd.), and Xerox 4200 (Xerox Co), which are types of plain paper. .)It was used. Then, each evaluation test described later was performed using the obtained patch pattern as a sample.

(2) Evaluation of optical density (OD value) The OD value of the patch portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). And the average value for every sample was calculated | required and the optical density value (OD value) was evaluated by the following evaluation criteria about the calculated average OD value. The results are shown in Table 3.
A: OD value is 1.2 or more B: OD value is 1.0 or more and less than 0.9 C: OD value is less than 0.9

(3) Evaluation of printing quality The image quality of each sample was visually observed and evaluated according to the following evaluation criteria. The results are shown in Table 3.
A: Color development is good and no color unevenness is observed. B: Color unevenness is slightly observed, but there is no practical problem. C: Color unevenness is conspicuous and impractical.

(4) Evaluation of cock ring The unevenness (cock ring) of each sample was measured using a laser displacement meter (LK-010, manufactured by Keyence Corporation). And the average value for every sample was calculated | required and the cockling was evaluated on the following evaluation criteria based on the calculated average value. The results are shown in Table 3.
A: Unevenness is less than 1.0 mm B: Unevenness is not less than 1.0 mm and less than 2.0 mm C: Unevenness is not less than 2.0 mm

Claims (3)

An ink jet recording method for performing printing by discharging a droplet of an ink composition and attaching the droplet to a recording medium,
As the ink composition, an ink composition comprising at least a pigment, a water-soluble organic solvent, a surfactant, and 60 to 50% by weight of water is used.
Heating the ink composition and discharging droplets of the ink composition having a viscosity of 2 to 5 mPa · s;
Inkjet recording method.   The inkjet recording method according to claim 1, wherein the water-soluble organic solvent contains at least polyhydric alcohols and butyl ethers of glycol ethers.   The ink jet recording method according to claim 1, wherein the surfactant is an acetylene glycol surfactant and / or a poly-modified siloxane surfactant.