JP2009269964A - Ink composition for inkjet recording - Google Patents

Abstract

[PROBLEMS] To achieve high-quality images without white streaks or roughness even with low resolution when using art paper or other printing paper. An ink composition that can be suppressed is provided.
An ink composition for ink-jet recording comprising at least a colorant, water, an alcohol solvent, and a surfactant, wherein the alcohol solvent comprises a slightly water-soluble alkanediol and a water-soluble 1. , 2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol is used in an inkjet recording method.
[Selection figure] None

Description

Background of the Invention

Field of the Invention The present invention is capable of obtaining a high-quality recorded product free from printed spots even on various recording media, particularly recording media with low water absorption, such as synthetic paper and printing paper, and a thin recording medium. The present invention relates to an ink composition for ink-jet recording that hardly causes curling even when used.

BACKGROUND ART An ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. Due to recent advances in inkjet recording technology, inkjet recording methods have been used in the field of high-definition printing that has been realized only by silver salt photography and offset printing. Along with that, high gloss recording media comparable to photographic paper and art paper used in the field of silver salt photography and offset printing, so-called special paper, is used for inkjet recording, and glossiness equivalent to silver salt photography. Ink for ink jet recording that can realize an image having the above has been developed. Ink-jet recording inks have been developed that can achieve image quality comparable to that of silver halide photographs even when plain paper is used.

  By the way, with recent spread of image forming technology from digital data, desktop publishing (DTP) is becoming widespread, especially in the printing field. Even when printing is performed by DTP, a color proofing proof is produced in advance in order to confirm glossiness and color feeling with an actual printed matter. An inkjet recording method is applied to the output of this proof, and in DTP, color reproduction and stability reproduction of printed matter are required. Therefore, dedicated paper for inkjet recording is usually used as a recording medium. Has been.

  The dedicated paper for ink-jet recording is prepared so that the gloss and color feel are the same as the output actually printed on the printing paper. As described above, the material of the special paper is appropriately adjusted according to the type of the printing paper, but producing the special paper corresponding to all of the various printing papers causes an increase in manufacturing cost. Thus, in color proofing applications, there is a desire to perform ink jet recording on printed paper rather than dedicated paper. In addition, if the final calibration sample can be obtained by performing inkjet recording directly on the main printing paper without using dedicated paper, it is considered that the cost for calibration can be greatly reduced. Synthetic paper, which is widely used in the printing field and is formed into a film by mixing an inorganic filler or the like with polyethylene resin or polyester resin, has recently attracted attention as an environmentally friendly material that is excellent in recyclability.

  The main printing paper is a coated paper provided with a coating layer for receiving oil-based ink on its surface, but has a feature that the ink absorption capability of the coating layer is poor. For this reason, when water-based pigment ink generally used for ink jet recording is used, the permeability of the ink into the recording medium (printing paper) is low, and blurring and uneven aggregation may occur in the image.

  In response to the above problem, for example, in Japanese Patent Application Laid-Open No. 2005-194500 (Patent Document 1), a polysiloxane compound is used as a surfactant, and alkanediol such as 1,2-hexanediol is added as a dissolution aid. Thus, a pigment-based ink is disclosed that has improved bleeding and excellent gloss for special paper. JP-A 2003-213179 (Patent Document 2), JP-A 2003-253167 (Patent Document 3), and JP-A 2006-249429 (Patent Document 4) disclose glycerin and 1,3-butane. It has been proposed that by adding a diol such as a diol or a triol alcohol solvent such as pentanetriol into the ink, the penetrability of the ink into the recording medium can be controlled and a high-quality image can be obtained.

JP 2005-194500 A JP 2003-213179 A JP 2003-253167 A JP 2006-249429 A

Summary of the Invention

  The present inventors now have a slightly water-soluble alkanediol, a water-soluble alkanediol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, By using an alcohol solvent containing water-soluble alkanetriol, high-quality images without white streaks or graininess even when printed at low resolution on low-absorbent recording media such as printing paper The knowledge that it can be realized. The present invention is based on this finding.

  Accordingly, an object of the present invention is to provide an ink composition capable of realizing a high-quality image without white streak or roughness even when printed at a low resolution on a low liquid-absorbing recording medium such as printing paper. Is to provide.

The ink composition for ink jet recording according to the present invention is an ink composition for ink jet recording comprising at least a colorant, water, an alcohol solvent, and a surfactant,
The alcohol solvent comprises a slightly water-soluble alkanediol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol. , That is.

  According to the present invention, there is provided an ink composition capable of realizing a high-quality image without white streak or roughness even when printed at a low resolution on a low liquid-absorbing recording medium such as printing paper. That is.

Detailed description of the invention

  An ink composition for ink jet recording according to the present invention is an ink composition for ink jet recording comprising at least a colorant, water, an alcohol solvent, and a surfactant, wherein the alcohol solvent is a slightly water-soluble alkane. It comprises a diol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol. Hereinafter, each component will be described.

<Definition>
In the present specification, the alkanediol, dialkylene glycol, and alkanetriol may be either linear or branched.

  Water-soluble means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is 10.0 g or more, and poorly water-soluble means the solubility in water (100 g of water). It means that the amount of solute relative to 1.0 g is less than 1.0 g.

<Alcohol solvent>
The alcohol solvent used in the ink composition for ink-jet recording according to the present invention includes an alkanediol having a water-soluble alkanediol, a water-soluble 1,2-alkanediol, and a side chain on any one carbon having a hydroxyl group. And at least four kinds of organic solvents including water-soluble alkanetriol. By including these four kinds of alcohol solvents as essential components, printing paper, especially art paper, POD application paper (for example, Ricoh Business Coat Gloss 100 manufactured by Ricoh Co., Ltd.), laser printer, etc., which have a relatively high ink absorption capacity. With special paper (for example, Seiko Epson Corporation, LPCCTA4), ink agglomeration is suppressed, and even when printed at low resolution, a high-quality image free of white streaks or roughness can be realized, and ejection stability In addition, an excellent ink composition can be realized. In this specification, “aggregation” means local density variation of similar colors that occurs when printed as a surface (for example, when printed in a single color (not the number of ink colors) on a 6-inch square). This does not mean that a portion of the surface of the recording medium that is not covered with ink remains. White streaks mean that when printed as a surface (for example, when printed in a single color on a 6-inch square), there is no local color density unevenness, and the surface of the recording medium moves in the drive direction of the recording head. It means a phenomenon in which a portion not covered with ink remains on the streaks. Further, the rough feeling or poor filling means that, when printed as a surface in the same manner as described above, there is no local color density unevenness and the surface of the recording medium is not covered with ink. This means a phenomenon in which the surface of the material has a grainy texture.

Further, in the present invention, even in the case where a thin printing paper having a basis weight of 73.3 to 104.7 g / m ² is used in the recording medium as described above, the printing surface is warped inward so-called curl. Can be suppressed.

  As described above, in addition to the poorly water-soluble alkanediol and the water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group and a water-soluble alkanetriol are essential. The reason why a high-quality image without white streaks or roughness can be realized by adding it as a component is not clear, but is considered as follows.

  The agglomeration of ink that occurs when recording on printing paper is due to the fact that the printing paper repels ink because of the high surface tension of the ink dots and the high contact angle between the printing paper surface and the ink droplets. it is conceivable that. Even when white streaks or filling defects occur when recording at low resolution, aggregation of ink is suppressed by reducing the surface tension of the ink adhering to the surface of printing paper.

  Also, white streaks and poor filling in low-resolution recording are caused by ink dots adhering to the surface of printing paper coming into contact with adjacent ink dots, spreading each other, and causing undried ink to flow with each other. Conceivable. This mutual ink flow is considered to be due to the difference in the drying time of the ink dots depending on the difference in the adhesion time between adjacent ink dots and the size of the droplets at the time of adhesion. Therefore, in order to realize a high-quality image without white streak or roughness even when printing at low resolution, ink aggregation is suppressed, and ink with low surface tension and low fluidity is printed. It is considered preferable to adhere to the paper.

  However, if a permeable wetting agent is not used to reduce the fluidity of the ink, the ink dots adhering to the surface of the printing paper will dry faster and the ink will be absorbed faster, so that the adhering ink dots will get wet. It is considered that the spreading time is lost, and as a result, white streaks and poor filling occur in low resolution recording.

  The alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol used in the present invention are substances exhibiting viscosity such as glycerin. Further, alkanediol having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriol are penetrating wetting agents having a lower surface tension than glycerin. For example, the surface tension of 3-methyl-1,3,5-pentanetriol in the case of 10% aqueous solution is 47.5 mN / m, and 3-methyl-1,3-3-in the case of 10% aqueous solution. The surface tension of butanediol is 52.6 mN / m.

  An alkanediol having a side chain on one of the carbons having a hydroxyl group having such properties and a water-soluble alkanetriol are combined with the above-mentioned poorly water-soluble alkanediol and water-soluble 1,2-alkanediol. By using it, discharge stability is also improved. The discharge stability is better as the alkyl chain length of the alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol is shorter.

  In addition to poorly water-soluble alkanediols and water-soluble 1,2-alkanediols, alkanediols and alkanetriols having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriols as essential components The reason why curling can be suppressed when it is added onto thin printing paper is not clear, but is considered as follows.

  Water-soluble 1,2-alkanediol is a polar solvent and a resin film-forming aid. By inhibiting this effect, it is considered that film shrinkage of the resin is prevented. In order to inhibit this effect, a weakly polar solvent is preferable. It is considered that the nonpolar solvent has a weak affinity with the resin, and an inhibitory effect cannot be obtained. As a weakly polar solvent, it is considered preferable to simultaneously have a + I effect alkyl group and a −I effect hydroxyl group on the same carbon. Alkanediol having a side chain on one of the carbons having a hydroxyl group inhibits film-forming shrinkage of water-soluble 1,2-alkanediol, and under these conditions, the curling effect of water-soluble alkanetriol causes curling. It is thought that the occurrence of is suppressed.

  In the present invention, the slightly water-soluble alkanediol is preferably an alkanediol having 7 or more carbon atoms, more preferably an alkanediol having 7 to 10 carbon atoms, such as 1,2-heptanediol, 1,2 -Octanediol, 5-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, 4,4-dimethyl-1,2-pentanediol and the like. Among these, 1,2-octanediol is more preferable.

  The water-soluble 1,2-alkanediol is preferably an alkanediol having 6 or less carbon atoms, such as 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, 4-methyl- 1,2-pentanediol, 3,3-dimethyl-1,2-butanediol and the like can be mentioned. Among these, a water-soluble alkanediol having a surface tension of 28 mN / m or less in the case of a 15% aqueous solution is more preferable. 1,2-hexanediol (surface tension: 26.7 mN / m), 4-methyl 1,2 -Pentanediol (surface tension: 25.4 mN / m) and 3,3-dimethyl-1,2-butanediol (surface tension: 26.1 mN / m) are particularly preferred. From the viewpoint of odor during printing, 1,2-hexanediol is preferred.

  Examples of the alkanediol having a side chain on any one carbon having a hydroxyl group used in the present invention include 3-methyl-1,3-butanediol.

  Furthermore, in the present invention, examples of the water-soluble alkanetriol include 1,2,6-hexanetriol and 3-methyl-1,3,5-pentanetriol.

  Further, as a solubilizing aid for the slightly water-soluble alkanediol, an alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol can be used in combination.

  In the four types of alcohol solvents described above, the content ratio of the slightly water-soluble alkanediol to the water-soluble 1,2-alkanediol is preferably 6: 1 to 1: 3, more preferably 6: 1. ~ 1: 1. By setting it within this range, the slightly water-soluble alkanediol can be stably dissolved in the ink, and the ejection stability is improved. On the other hand, when the proportion of the water-soluble 1,2-alkanediol is larger than the above range, it is difficult to achieve both reduction of the initial ink viscosity and reduction of aggregation spots. In addition, when the ratio of the water-soluble 1,2-alkanediol is less than the above range, it becomes difficult to stably dissolve the poorly water-soluble alkanediol in the ink, and the viscosity change during the course is suppressed or stored. It becomes difficult to maintain stability.

  The content ratio of the slightly water-soluble alkanediol to the total amount of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is 1: 1 to 1:18. Is more preferable, and 1: 1 to 1: 6 is more preferable. By setting it within this range, the initial viscosity of the ink can be lowered and good clogging recovery can be realized. On the other hand, when the ratio of the total amount of alkanediol having a side chain on any one carbon having a hydroxyl group and water-soluble alkanetriol is larger than the above range, the ink initial viscosity is increased and drying property is lowered. In addition, if the ratio of the total amount of alkanediol having a side chain on one of the carbons having a hydroxyl group and the water-soluble alkanetriol is less than the above range, the clogging recovery property is deteriorated and the drying property is increased. As a result, it becomes impossible to secure the time for spreading the ink, so that the recording medium cannot be covered with ink, and white streaks are likely to occur.

  The content ratio of the water-soluble 1,2-alkanediol to the total amount of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is 1: 1 to 1:36. Is preferable, and 1: 1 to 1:18 is more preferable. By setting it within this range, white streaks and roughness can be further suppressed when printing is performed on the printing paper at a low resolution. On the other hand, when the proportion of the water-soluble 1,2-alkanediol is larger than the above range, the ink initial viscosity becomes high and the drying property is lowered. In addition, if the ratio of the total amount of alkanediol having a side chain on one of the carbons having a hydroxyl group and the water-soluble alkanetriol is less than the above range, the clogging recovery property is deteriorated and the drying property is increased. As a result, it becomes impossible to secure the time for spreading the ink, so that the recording medium cannot be covered with ink, and white streaks are likely to occur.

  Furthermore, the content ratio of the alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol is preferably 3: 1 to 1: 3, and 2: 1 to 1: 2 is more preferable. By setting this range, the occurrence of curling can be further suppressed. When the proportion of alkanediol having a side chain on any one of the carbons having a hydroxyl group is larger than the above range, the initial viscosity becomes lower, so that the flying speed of the ink is increased, so that the droplet deposition accuracy is improved, More preferred. Moreover, it is more preferable from the viewpoint that the slightly water-soluble 1.2-alkanediol can be stably dissolved. On the other hand, if the proportion of alkanediol having a side chain on any one carbon having a hydroxyl group is less than the above range, the effect of inhibiting the film-forming shrinkage of the water-soluble 1,2-alkanediol becomes poor. It is difficult to obtain the effect of suppressing the occurrence of

  Further, the content ratio of the water-soluble 1,2-alkanediol and the alkanediol having a side chain on any one carbon having a hydroxyl group is preferably 1: 1 to 1:12, preferably 1: 1. More preferably, it is ˜1: 6. By setting it within this range, white streaks and roughness can be further suppressed when printing is performed on the printing paper at a low resolution. On the other hand, when the proportion of the water-soluble 1,2-alkanediol is larger than the above range, the ink initial viscosity becomes high and the drying property is lowered. Also, if the proportion of alkanediol having a side chain on any one of the carbons having a hydroxyl group is less than the above range, clogging recoverability deteriorates and drying properties increase, so that it becomes impossible to secure time for ink to spread. The recording medium cannot be covered with ink, and white streaks are likely to occur.

  Furthermore, in the present invention, the sum of the contents of the slightly water-soluble alkanediol and the water-soluble 1,2-alkanediol is preferably 6% by weight or less based on the ink composition. By setting it within this range, a recording medium having a low ink absorbency such as printing paper does not cause aggregation spots and is excellent in ejection stability.

  In the present invention, the sum of the contents of the slightly water-soluble alkane diol, the alkane diol having a side chain on any one of the carbons having a hydroxyl group, and the water-soluble alkane triol is added to the ink composition. On the other hand, it is preferably 21% by weight or less. By setting it within this range, there is no occurrence of agglomeration in a recording medium having low ink absorbency such as printing paper, and ejection stability and curl suppression are good.

  The slightly water-soluble alkanediol is preferably contained in an amount of 1 to 3% by weight, more preferably 1.5 to 2.5% by weight, based on the entire ink composition. If it is less than 1% by weight, printing spots may occur on a recording medium having low ink absorbability such as printing paper. On the other hand, if it exceeds 3% by weight, it may not completely dissolve in the ink.

  The water-soluble 1,2-alkanediol is preferably contained in an amount of 0.5 to 6% by weight, more preferably 0.5 to 3.0% by weight. If it is less than 0.5% by weight, the slightly water-soluble alkanediol may not be dissolved in the ink. On the other hand, if it exceeds 6% by weight, the initial viscosity of the ink may increase, which is not preferable.

  The sum of the contents of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is preferably 3 to 18% by weight based on the whole ink composition. More preferably, it is 4 to 8% by weight. If the amount is less than 3% by weight, white stripes or roughness may occur when printing on a printing paper at a low resolution. On the other hand, if it exceeds 18% by weight, the dryness of the printed material immediately after printing may be inferior.

  The alkanediol having a side chain on any one carbon having a hydroxyl group is preferably contained in an amount of 2 to 12% by weight, more preferably 3 to 6% by weight, based on the entire ink composition.

  The water-soluble alkanetriol is preferably contained in an amount of 2 to 12% by weight, more preferably 3 to 6% by weight, based on the entire ink composition.

<Coloring material>
As the coloring material used in the ink composition for ink jet recording according to the present invention, both dyes and pigments can be used, but pigments can be preferably used from the viewpoint of light resistance and water resistance.

  As the pigment, inorganic pigments and organic pigments can be used, and each can be used alone or in combination. As the inorganic pigment, for example, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye-type chelates, acidic dye-type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used.

  Specific examples of the pigment are appropriately given according to the type (color) of the ink composition to be obtained. For example, as a pigment for a yellow ink composition, C.I. I. Pigment Yellow 1, 2, 3, 12, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185 and the like, and one or more of these are used. Of these, C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Yellow 74, 110, 128, and 147. Examples of the pigment for the magenta ink composition include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. Pigment violet 19 and the like, and one or more of these may be used. Of these, C.I. I. Pigment red 122, 202, 209, and C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Violet 19. Examples of the pigment for the cyan ink composition include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60; I. Bat Blue 4, 60 etc. are mentioned, and one or more of these are used. Of these, C.I. I. Pigment Blue 15: 3 and / or 15: 4 are preferably used, especially C.I. I. Pigment Blue 15: 3 is preferably used.

  Examples of the pigment for the black ink composition include lamp black (CI pigment black 6), acetylene black, furnace black (CI pigment black 7), and channel black (CI pigment black). 7), carbons such as carbon black (CI Pigment Black 7), inorganic pigments such as iron oxide pigments, and organic pigments such as aniline black (CI Pigment Black 1). In carbon black, carbon black is preferably used. Specifically, as carbon black, # 2650, # 2600, # 2300, # 2200, # 1000, # 980, # 970, # 966, # 960, # 950, # 900, # 850, MCF-88, # 55, # 52, # 47, # 45, # 45L, # 44, # 33, # 32, # 30 (above, manufactured by Mitsubishi Chemical Corporation), SpecialBlaek4A, 550, Printex95, 90, 85, 80, 75 , 45, 40 (above, Degussa), Regal660, RmogulL, monarch1400, 1300, 1100, 800, 900 (above, Cabot), Raven7000, 5750, 5250, 3500, 3500, 2500 ULTRA, 2000, 1500, 1255 , 1200, 1190 ULTRA, 1170, 1100 ULTRA, Raven5000UIII (above, manufactured by Columbian) and the like.

  The concentration of the pigment is not particularly limited because it may be adjusted to an appropriate pigment concentration (content) when the ink composition is prepared. In the present invention, the solid content concentration of the pigment is set to 6% by weight or more. It is preferable that the content be 12% by weight or more. When ink droplets adhere to the recording medium, the ink spreads wet on the surface of the recording medium. However, by increasing the pigment solid concentration to 6% by weight or more, the fluidity of the ink after the wet spreading stays early. Since the ink is lost, bleeding can be further suppressed when printing is performed on a recording medium such as printing paper at a low resolution. That is, by using a combination of the above four specific alcohol solvents, the ink spreads even on a recording medium with low ink absorbency, and at the same time, by increasing the solid content concentration of the ink, It is considered that bleeding of ink can be suppressed by reducing the fluidity of ink. In particular, the effect of suppressing bleeding is remarkable at the boundary between a portion with a small amount of ink adhesion and a portion with a large amount of ink in the recording medium.

  The pigment is a pigment that has been kneaded with a dispersant, which will be described later, to achieve both the glossiness of the image, the prevention of bronzing, and the storage stability of the ink composition, and to form a color image that is further excellent in glossiness. From the viewpoint of being able to.

<Dispersant>
The ink composition according to the present invention may comprise at least one resin selected from a styrene-acrylic acid copolymer resin, a urethane resin, and a fluorene resin as a dispersant for dispersing the colorant. preferable. These copolymer resins are adsorbed on the pigment to improve dispersibility.

Specific examples of the hydrophobic monomer in the copolymer resin include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso- Octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Sil acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2 -Dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate, noni Phenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butane Diol diacrylate, 1,4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetra Ethylene glycol dimethacrylate, polyethylene glycol di Acrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylol Mention may be made of methylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methylstyrene, vinyltoluene and the like. You may use these individually or in mixture of 2 or more types.

  Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.

  From the viewpoint that the copolymer resin of the hydrophobic monomer and the hydrophilic monomer can form a color image having both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. , Styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic acid ester copolymer resin Or at least one of styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resin.

  The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, a salt such as sodium, potassium, or ammonium may be used.

  The content of these copolymer resins is 100 parts by weight of the pigment from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image with further excellent glossiness. The amount is preferably 20 to 50 parts by weight, and more preferably 20 to 40 parts by weight.

  Further, in the present invention, by using a urethane resin as a pigment dispersant, a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness can be formed. it can. The urethane resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound, but in the present invention, it is a resin having a urethane bond and / or an amide bond and an acidic group. Is preferred.

  Examples of the diisocyanate compound include aromatic aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products thereof. .

  Examples of the diol compound include polyethers such as polyethylene glycol and polypropylene glycol, polyesters such as polyethylene abido and polybutylene abates, and polycarbonates.

  The urethane resin preferably has a carboxyl group.

  In the present invention, a fluorene resin can also be used as the pigment dispersant.

  The weight ratio (the former / the latter) of the copolymer resin and the urethane resin is preferably 1/2 to 2/1. However, the gloss of the color image, the prevention of bronzing, and the storage stability of the ink composition are compatible. From the viewpoint of forming a color image having further excellent glossiness, the ratio is more preferably 1 / 1.5 to 1.5 / 1.

  The weight ratio of the solid content of the pigment to the solid content other than the pigment (the former / the latter) is compatible with the glossiness of the color image, the prevention of bronzing, and the storage stability of the ink composition, and is further excellent in the glossiness. From the viewpoint of forming a color image, it is preferably 100/20 to 100/80.

  The content of the copolymer resin is 100 parts by weight of the pigment from the viewpoint of achieving both color image glossiness, bronzing prevention, and storage stability of the ink composition and at the same time forming a more glossy color image. The amount is preferably 20 to 50 parts by weight, and more preferably 20 to 40 parts by weight.

  The content of the urethane resin is 100 parts by weight of the pigment from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition, and forming a color image with further excellent glossiness. On the other hand, it is preferably 10 to 40 parts by weight, and more preferably 10 to 35 parts by weight.

  The content of the fluorene-based resin is 100 parts by weight of the pigment from the viewpoint of achieving color image glossiness, prevention of bronze, and storage stability of the ink composition and forming a color image having further excellent glossiness. The amount is preferably 20 to 100 parts by weight, and more preferably 20 to 80 parts by weight.

  The total amount of the copolymer resin and the urethane resin is used so as to be 90 parts by weight or less (more preferably 70 parts by weight or less) with respect to 100 parts by weight of the pigment. This is preferable in that it is possible to form a color image having both excellent prevention of bronzing and storage stability of the ink composition and further excellent glossiness.

  The acid value of the copolymer resin is preferably 50 to 320 from the viewpoint of achieving both color image glossiness, bronzing prevention, and storage stability of the ink composition, and forming a color image having further excellent glossiness. More preferably, it is 100-250.

  The acid value of the urethane resin is preferably 10 to 300 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image having further excellent glossiness. Yes, more preferably 20-100. The acid value is the mg amount of KOH required to neutralize 1 g of resin.

  The weight-average molecular weight (Mw) of the copolymer resin is preferable from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is from 2,000 to 30,000, more preferably from 2,000 to 20,000.

  The weight-average molecular weight (Mw) before crosslinking of the urethane resin is compatible from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and at the same time forming a more glossy color image. , Preferably it is 100-200,000, More preferably, it is 1000-50,000. Mw is measured by GPC (gel permeation chromatography), for example.

  The glass transition temperature (Tg; measured in accordance with JISK6900) of the copolymer resin is a viewpoint capable of forming a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is preferably 30 ° C. or higher, and more preferably 50 to 130 ° C.

  The urethane resin has a glass transition temperature (Tg; measured in accordance with JISK6900) from the viewpoint of achieving a color image having excellent glossiness while maintaining the glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. Is preferably −50 to 200 ° C., and more preferably −50 to 100 ° C.

  The copolymer resin has a case where it is adsorbed to the pigment in the pigment dispersion and a case where it is liberated, and achieves both glossiness of color images, prevention of bronzing, and storage stability of the ink composition. In addition, from the viewpoint of forming a color image having further excellent gloss, the copolymer resin preferably has a maximum particle size of 0.3 μm or less, and an average particle size of 0.2 μm or less (more preferably 0.1 μm). The following is more preferable. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

The fluorene resin is not limited as long as it has a fluorene skeleton, and can be obtained, for example, by copolymerizing the following monomer units.
Cyclohexane, 5-isocyanate-1- (isocyanatomethyl) -1,3,3-trimethyl (CAS No. 4098-71-9)
Ethanol, 2,2 ′-[9H-fluorene-9-ylidenebis (4,1-phenyleneoxy)] bis (CAS No. 117344-32-8)
Propionic acid, 3-hydroxy-2- (hydroxymethyl) -2-methyl (CAS No. 4767-03-7)
Ethanamine, N, N-diethyl- (CAS No. 121-44-8)

  A surfactant may be used as the dispersant. Such surfactants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate esters, naphthenates, liquid fats. Anionic surfactants such as oil sulfate esters and alkyl allyl sulfonates; Cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene alkyl ethers and polyoxyethylene alkyls Nonionic surfactants such as esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters and the like can be mentioned. It goes without saying that the surfactant also functions as a surfactant when added to the ink composition.

<Surfactant>
The ink composition for inkjet recording according to the present invention contains a surfactant as an essential component. Glossy recording media such as photographic paper, where glossiness is more important by using a surfactant, compared to a recording medium coated with a resin for receiving ink on the surface. Can be realized. In particular, even when a recording medium having a coating layer for receiving oil-based ink is provided on the surface receiving layer, such as printing paper, bleeding between colors (bleeding) can be prevented. At the same time, it is possible to prevent whitening due to reflected light of light generated with an increase in the amount of ink attached.

  As the surfactant used in the present invention, an organopolysiloxane-based surfactant can be suitably used, and when forming a recorded image, the wettability to the surface of the recording medium can be increased to increase the ink permeability. it can. When an organopolysiloxane-based surfactant is used, it contains three types of alcohol solvent as described above, so that the solubility of the surfactant in the ink is improved and the generation of insoluble matter can be suppressed. An ink composition having more excellent discharge stability can be realized.

  Commercially available surfactants such as those described above may be used, such as Olfine PD-501, Olfine PD-502, Olfine PD-570 (all manufactured by Nissin Chemical Industry Co., Ltd.) and the like. be able to.

（式中、Ｒは水素原子またはメチル基を表し、ａは２〜１１の整数を表し、ｍは２〜５０の整数を表し、ｎは１〜５の整数を表す。）
で表される一種または二種以上の化合物を含んでなるか、または、上記式（I）の化合物において、Ｒが水素原子またはメチル基であり、ａが２〜１３の整数であり、ｍは２〜５０の整数であり、ｎは１〜５の整数である一種または二種以上の化合物を含んでなることがより好ましい。また、上記式（I）の化合物において、Ｒが水素原子またはメチル基であり、ａが２〜１３の整数であり、ｍは２〜５０の整数であり、ｎは１〜８の整数である一種または二種以上の化合物を含んでなることがより好ましい。あるいは、上記式（I）の化合物において、Ｒがメチル基であり、ａが６〜１８の整数、であり、ｍが０であり、ｎが１である一種または二種以上の化合物を含んでなることがより好ましい。このような特定のオルガノポリシロキサン系界面活性剤を使用することにより、記録媒体として印刷本紙に印刷した場合であっても、インクの凝集むらがより改善される。 Further, as the organopolysiloxane surfactant, the following formula (I):

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 11, m represents an integer of 2 to 50, and n represents an integer of 1 to 5).
Or a compound of the above formula (I), wherein R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, and m is More preferably, it is an integer of 2 to 50, and n comprises one or more compounds that are integers of 1 to 5. In the compound of the above formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 8. More preferably, it comprises one or more compounds. Or in the compound of the said formula (I), R is a methyl group, a is an integer of 6-18, m is 0, n is 1 or 1 type, or 2 or more types of compounds are included. More preferably. By using such a specific organopolysiloxane surfactant, unevenness of ink aggregation is further improved even when printing on a printing paper as a recording medium.

  In the compound of the above formula (I), a is an integer of 2 to 5, m is an integer of 20 to 40, n is an integer of 2 to 4, and a is an integer of 7 to 11. M is an integer of 30 to 50, n is an integer of 3 to 5, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 It is more preferable to use a certain compound or a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, the unevenness of ink aggregation can be further improved.

  In the compound of the above formula (I), R is a hydrogen atom, a is an integer of 2 to 5, m is an integer of 20 to 40, and n is an integer of 2 to 4, Alternatively, it is more preferable to use a compound in which a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (I), R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2, Alternatively, it is more preferable to use a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the compound of the above formula (I), it is more preferable to use a compound in which R is a methyl group, a is an integer of 6 to 12, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (I), R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5; , R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, and a is 6 It is most preferable to use a mixture of a compound having an integer of 10 to 10, m being an integer of 10 to 20, and n being an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  The surfactant is preferably contained in the ink composition according to the present invention in an amount of 0.01 to 1.0% by weight, more preferably 0.05 to 0.50% by weight. In addition, it is more preferable to use the surfactant in which R is a methyl group in combination with the surfactant in which R is a hydrogen atom because small font characters are not crushed. In particular, in the case of using the surfactant in which R is a methyl group, the content may be larger than in the case of using the surfactant in which R is H, from the viewpoint of ink aggregation spots. preferable.

  Furthermore, it is more preferable that the content of the surfactant in which R is H is increased with respect to the surfactant in which R is a methyl group. By doing in this way, ink aggregation spots and bleeding can be improved even in printing main paper such as cast-coated paper, which is easy to repel ink and has a low permeation rate.

  Other surfactants, specifically, acetylene glycol surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants and the like may be further added to the ink composition according to the present invention.

  Among these, acetylene glycol surfactants include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Diol, or 3,5-dimethyl-1-hexyn-3ol, 2,4-dimethyl-5-hexyn-3-ol and the like can be mentioned. Commercially available acetylene glycol surfactants can also be used. For example, Olphine E1010, STG, Y (trade name, manufactured by Nissin Chemical Co., Ltd.), Surfynol 61, 104, 82, 465, 485 or TG (Trade name, manufactured by Air Products and Chemicals Inc.).

<Water, other ingredients>
The ink composition for inkjet recording according to the present invention contains the above-mentioned specific alcohol solvent, surfactant, and other various additives, and water as a solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria is prevented for a long period of time.

  The ink composition according to the present invention preferably contains a penetrant in addition to the above components.

  As the penetrant, glycol ethers can be preferably used.

  Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert -Butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-iso-propyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene Glycol mono-n-bu Ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol-iso-propyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-tert-butyl ether, 1-methyl -1-methoxybutanol and the like, and one or a mixture of two or more thereof It can be used.

Among the glycol ethers, alkyl ethers of polyhydric alcohols are preferable, and ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, propylene glycol are particularly preferable. Preference is given to monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether or triethylene glycol mono-n-butyl ether.
More preferred is triethylene glycol mono-n-butyl ether.

  The addition amount of the penetrant may be appropriately determined, but is preferably about 0.1 to 30% by weight, more preferably about 1 to 20% by weight.

  The ink composition according to the present invention preferably contains a recording medium solubilizer in addition to the above components.

  As the recording medium solubilizer, pyrrolidones such as N-methyl-2-pyrrolidone can be preferably used. The addition amount of the recording medium solubilizer may be appropriately determined, but is preferably about 0.1 to 30% by weight, more preferably about 1 to 20% by weight.

  The ink composition for ink jet recording according to the present invention preferably contains substantially no wetting agent. A wetting agent has a function of preventing ink from drying and solidifying in an ink jet nozzle or the like. Therefore, when ink is dropped on synthetic paper having particularly low ink absorption performance, the ink does not dry and high-speed printing is possible. Can be problematic. In addition, when ink containing a wetting agent is used, the next ink adheres to the recording medium in a state where unabsorbed ink exists on the surface of the recording medium, so that aggregation spots may occur.

  Therefore, in the present invention, when such a recording medium having particularly low ink absorption performance is used, it is preferable that the wetting agent is not substantially contained. Even when the ink is dried and solidified in the inkjet nozzle, the solidified ink can be redissolved by applying a solution containing a wetting agent.

  In particular, in the present invention, it is preferable that substantially no wetting agent having a vapor pressure of 2 mPa or less at 25 ° C. is contained. “Substantially free” means that the amount of the wetting agent added is less than 1% by weight based on the ink composition.

  When the content of the wetting agent having a vapor pressure at 25 ° C. of 2 mPa or less is less than 1% by weight with respect to the ink, not only the recording medium having low ink absorbability such as printing paper, but also the ink absorbing ability is completely eliminated. Even for metals and plastics that are not present, printing can be performed by the ink jet recording method. In addition, although it is clear for those skilled in the art that a part of the above-described penetrating solvent also acts as a wetting agent, in the present specification, the above-described penetrating solvent is not included in the wetting agent. . In the present specification, the above alcohol solvent is not included in the wetting agent.

  In the present specification, the wetting agent means a wetting agent used in a normal ink jet recording ink, and specifically, glycerin, ethylene glycol, 1,3-propanediol, 3-methyl-1,3. -Water-soluble alkane diols having 3 to 5 carbon atoms such as butanediol, 1,3-butanediol, 1,2-pentanediol, trimethylolpropane, trimethylolmethane, trimethylolethane and the like. When the recording medium is a printing paper having a low ink absorbency, these wetting agents can be appropriately added.

  The ink composition according to the present invention may further contain a nozzle clogging preventive agent, an antiseptic, an antioxidant, a conductivity adjusting agent, a pH adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen absorber, and the like. it can.

  Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzthiazoline-3-one ( ICI's Proxel CRL, Proxel BND, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  Furthermore, as examples of pH adjusters, other solubilizers or antioxidants, amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, hydroxide Inorganic salts such as lithium, ammonium hydroxide, quaternary ammonium hydroxide (tetramethylammonium, etc.), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate, and other phosphates, or N-methyl-2-pyrrolidone, urea And L-ascorbic acid and salts thereof, such as ureas such as thiourea and tetramethylurea, allophanates such as allophanate and methylallohanate, and biurets such as biuret, dimethylbiuret and tetramethylbiuret.

  In addition, the ink composition according to the present invention may contain an antioxidant and an ultraviolet absorber. Examples thereof include Tinuvin 328, 900, 1130, 384, 292, 123, and 144 manufactured by Ciba Specialty Chemicals. 622, 770, 292, Irgacor 252 153, Irganox 1010, 1076, 1035, MD1024, lanthanide oxide, and the like.

  The ink composition according to the present invention can be produced by dispersing and mixing each of the above components by an appropriate method. Preferably, the pigment, polymer dispersant, and water are first used in a suitable dispersing machine (for example, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ang mill, etc.). Mix to prepare a uniform pigment dispersion, then add separately prepared resin (resin emulsion), water, water-soluble organic solvent, sugar, pH adjuster, preservative, fungicide, etc. An ink solution is prepared. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove the coarse particle diameter and foreign matters that cause clogging.

Inkjet recording method An inkjet recording method according to the present invention performs printing by discharging droplets of the ink composition described above and attaching the droplets to a recording medium. In the recording method according to the present invention, it is preferable to use synthetic paper or main printing paper as a recording medium, and in particular, low-quality paper for art paper, high-quality paper used for POD (print on demand) and dedicated paper for laser printers. Even when printing at a resolution, a high-quality image without white streaks or roughness can be realized. Examples of the high-quality paper for POD use include Ricoh Business Coat Gloss 100 (manufactured by Ricoh Co., Ltd.). Moreover, as an exclusive paper for laser printers, LPCCTA4 (made by Seiko Epson Corporation) is mentioned, for example.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.

<Preparation of ink composition>
Each ink was prepared by mixing each component according to the composition of the following Tables 1-5, and filtering with a 10 micrometer membrane filter. The styrene-acrylic acid resin in the table is a copolymer having a molecular weight of 1600 and an acid value of 150. The urethane resin is a copolymer having a molecular weight of 6000 and an acid value of 50. In addition, fluorene-based resin is CAS No. It is a resin having a molecular weight of 3300, which contains a monomer having a fluorene skeleton represented by 117344-32-8 and a monomer composition ratio of about 50% by weight. Further, the surfactant used is an organopolysiloxane surfactant, and in the above formula (I), R is a methyl group, a is an integer of 9 to 13, and m is 2 to 4. An integer, a compound in which n is an integer of 1 to 2, R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5 Is a surfactant mixed with a compound.

Examples 17-32 and Comparative Examples 5-8
Further, the ink sets of Examples 1 to 16 and the ink sets of Comparative Examples 1 to 4 were similarly replaced with the following surfactants, except that the surfactants of the ink sets 17 to 32 of Examples and Comparative ink sets 5 to 8 were prepared.

  The surfactants used in Examples 17 to 32 and Comparative Examples 5 to 8 are the above formula (I), wherein R is a methyl group, a is an integer of 6 to 10, and m is 10 to 20. It is a surfactant composed of a compound that is an integer and n is an integer of 4 to 8.

Examples 33 to 48 and Comparative Examples 9 to 12
In addition, the ink sets 33 to 48 of the examples and the ink sets of Examples 1 to 16 and the ink sets of Comparative Examples 1 to 4 were similarly used except that the surfactants described below were replaced. Comparative ink sets 9 to 12 were prepared.

  The surfactants used in Examples 33 to 48 and Comparative Examples 9 to 12 have the formula (I), wherein R is a hydrogen atom, a is an integer of 7 to 11, and m is 30 to 50. A compound in which n is an integer of 3 to 5, R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 And a compound in which R is a methyl group, a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. is there.

Examples 49-64 and Comparative Examples 13-16
Further, the ink sets 49 to 64 of the examples and the ink sets of Examples 1 to 16 and the ink sets of Comparative Examples 1 to 4 were similarly replaced with the following surfactants. Comparative ink sets 13 to 16 were prepared.

  The surfactants used in Examples 49 to 64 and Comparative Examples 13 to 16 are the above formula (I), wherein R is a methyl group, a is an integer of 6 to 18, m is 0, A surfactant comprising a compound in which n is 1.

<Evaluation>
Evaluation of initial viscosity of ink The ink viscosity of each ink obtained as described above was evaluated. Using a vibration viscometer (MV100 model, manufactured by Yamaichi Electronics Co., Ltd.), the viscosity of the ink after 1 hour from the preparation of the ink was measured and evaluated according to the following criteria. The measurement temperature was 20 ° C.
S: The viscosity is 4 mPa · s or less.
AA: The viscosity is more than 4 mPa · s and not more than 5 mPa · s.
A: The viscosity exceeds 5 mPa · s and is 6 mPa · s or less.
B: Viscosity exceeds 6 mPa · s and is 7 mPa · s or less.
C: Viscosity exceeds 7 mPa · s and is 8 mPa · s or less.
D: The viscosity exceeds 8 mPa · s.
The evaluation results were as shown in Table 6 below.

Evaluation of Ink Viscosity of Ink After the ink prepared as described above was allowed to stand for 3 days in an environment of 70 ° C., the viscosity of the ink was measured in the same manner as described above and evaluated according to the following criteria.
A: The difference from the initial viscosity is 0.5 mPa · s or less.
B: The difference from the initial viscosity is more than 0.5 mPa · s and 1.0 mPa · s or less.
C: The difference from the initial viscosity is more than 1.0 mPa · s and not more than 2.0 mPa · s.
D: The difference from the initial viscosity exceeds 2.0 mPa · s.
The evaluation results were as shown in Table 6 below.

Evaluation of ink aggregation spots and embedding properties Each ink of Y, M, C, and K obtained above is set as an ink set on an ink cartridge of an ink jet printer (PX-G920, manufactured by Seiko Epson Corporation), and main scanning is performed. Recording was possible at 720 dpi in the (head drive) direction and 360 dpi in the sub-scanning (recording medium conveyance) direction. Next, the voltage of the printer is adjusted so that the dot size upon landing is approximately 7 ng. One drive is 720 × 360 dpi, OKT + (made by Oji Paper Co., Ltd.) of about 128 g / square meter, 720 × 720 dpi solid Images were recorded. Recording was performed in a room temperature and normal humidity environment. The ink adhesion amount was approximately 3.6 mg / inch square meters.
The obtained image was evaluated according to the following criteria.
A: There are no white stripes due to aggregated spots and poor filling.
B: There are no aggregated spots, but there are white streaks due to poor filling.
C: There are white spots due to aggregation spots and poor filling.
D: The ink flow is intense and cannot be determined.
The evaluation results were as shown in Table 6 below.

Printing was performed in the same manner as above except that 104.7 g / square meter of OKT + (manufactured by Oji Paper Co., Ltd.) was used as the curl evaluation recording medium. With the printed surface of the obtained printed matter facing upward, it was allowed to stand for 24 hours in a 40% RH environment at 25 ° C. on a flat desk. After that, the distance between the desk and the four corners of the printed material warped was measured and averaged.
A: Height is less than 5 mm A: Height is 5 mm or more and less than 10 mm B: Height is 10 mm or more and less than 20 mm C: Height is 20 mm or more The evaluation results are as shown in Table 6 below.

Evaluation of Initial Fixability The OKT + printed material was rubbed with a finger after 3 minutes.
A: Color material is not peeled B: Color material is peeled The evaluation results are as shown in Table 6 below.

Evaluation of solubility of poorly water-soluble alkanediol 1,2-octanediol was used as the poorly water-soluble alkanediol, and an aqueous solution having a content of 1,2-octanediol of 10% by weight was prepared. In this aqueous solution, 1,2-octanediol was not completely dissolved and was in a cloudy state.

  To 10 g of the prepared aqueous solution, 1,2-hexanediol (hereinafter abbreviated as HED), 3-methyl-1,3-butanediol (hereinafter abbreviated as 3MBUD), 1,3-butanediol (hereinafter abbreviated as “HED”). 1,3-BUD), 1,2,6-hexanetriol (hereinafter abbreviated as HET), and 3-methyl-1,3,5-pentanetriol (hereinafter abbreviated as 3MPET). Five types of alcohol solvents were added, respectively, until the aqueous solution became transparent.

  Further, instead of the above aqueous solution, an aqueous solution containing 10% by weight of 1,2-octanediol as the hardly water-soluble alkanediol and 10% by weight of 1,2-hexanediol as the water-soluble 1,2-alkanediol was prepared. In the same manner as above, each alcohol solvent was added until the aqueous solution became transparent.

  The addition amount (g) of each alcohol solvent in which the aqueous solution became transparent, that is, the slightly water-soluble alkanediol was completely dissolved was as shown in FIG.

As is clear from FIG. 1, in an aqueous binary alcohol solution containing 1,2-octanediol and 1,2-hexanediol, 3 MBUD, which is an alkanediol having a side chain on any one carbon having a hydroxyl group. Shows that it has a higher ability to dissolve 1,2-octanediol than 1,3-BUD, which is an alkanediol having no side chain on any one carbon having a hydroxyl group. It can also be seen that the ability to dissolve 1,2-octanediol is higher than when only HED is added.
On the other hand, as is clear from FIG. 1, in the aqueous solution containing 1,2-octanediol, HET and 3MPET, which are water-soluble alkanetriols, are compared with the case where only HED is added. It can be seen that the ability to dissolve octanediol is low. Therefore, in an ink composition containing 1,2-octanediol, 3MBUD, which is an alkanediol having a side chain on any one carbon having a hydroxyl group, or 1,2-, which is a water-soluble 1,2-alkanediol. It turns out that it is preferable to contain hexanediol simultaneously.

Evaluation of Clogging Recoverability Using the ink cartridge and ink jet printer described above, the ink replacement button was pressed, and then the outlet was removed. Thus, after the head cap was removed, the printer was left in an environment of 40 ° C. and 15% RH for 1 day. After leaving, the cleaning operation was repeated until all nozzles ejected at the same level as the initial stage, and the ease of recovery was evaluated according to the following criteria.
A: The clogging is recovered by repeating the cleaning operation three times.
B: The clogging is recovered by repeating the cleaning operation six times.
C: The clogging is recovered by repeating the cleaning operation 12 times.
D: The clogging does not recover even if the cleaning operation is repeated 12 times.
The evaluation results were as shown in Table 6 below.

  Moreover, when evaluation similar to the above was performed also about Examples 17-32 and Comparative Examples 5-8, it was the same evaluation result as Examples 1-16 and Comparative Examples 1-4.

  Furthermore, when Examples 33 to 48 and Comparative Examples 9 to 12 were evaluated in the same manner as described above, the evaluation results were the same as those of Examples 1 to 16 and Comparative Examples 1 to 4.

  Moreover, when evaluation similar to the above was performed also about Examples 49-64 and Comparative Examples 13-16, it was the same evaluation result as Examples 1-16 and Comparative Examples 1-4.

  Further, in Examples 1 to 64 and Comparative Examples 1 to 16, the examples were exactly the same except that 3-methyl-1,3,5-pentanetriol was used instead of 1,2,6-hexanetriol. 65-128 were made. When the same evaluation as described above was performed, Examples 1 to 64 and Comparative Examples 1 to 16 were the same evaluation results except for the curl evaluation results. The evaluation result of curl was improved by one level. It can be seen that the alkanetriol having a side chain on any one of the carbons having a hydroxyl group has a higher curl suppressing effect.

It is the graph which showed the solubility of 1,2-octanediol at the time of adding each alcohol solvent to 1,2-octanediol aqueous solution.

Claims (30)

An ink composition for inkjet recording, comprising at least a colorant, water, an alcohol solvent, and a surfactant,
The alcohol solvent comprises a slightly water-soluble alkanediol, a water-soluble 1,2-alkanediol, an alkanediol having a side chain on any one carbon having a hydroxyl group, and a water-soluble alkanetriol. Ink composition for inkjet recording.   The ink composition for inkjet recording according to claim 1, wherein the hardly water-soluble alkanediol is an alkanediol having 7 or more carbon atoms.   The ink composition for inkjet recording according to claim 1 or 2, wherein the water-soluble 1,2-alkanediol is an alkanediol having 6 or less carbon atoms.   The inkjet recording according to any one of claims 1 to 3, wherein a content ratio of the hardly water-soluble alkanediol and the water-soluble 1,2-alkanediol is 6: 1 to 1: 3. Ink composition.   The content ratio of the water-soluble alkanediol to the total amount of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is 1: 1 to 1:18. The ink composition for inkjet recording as described in any one of Claims 1-4.   The content ratio of the water-soluble alkanediol and the alkanediol having a side chain on any one of the carbons having a hydroxyl group is 1: 1 to 1:12. Item 4. An ink composition for ink jet recording according to Item.   The content ratio of the alkanediol having a side chain on any one carbon having a hydroxyl group and the water-soluble alkanetriol is 3: 1 to 1: 3. Item 4. An ink composition for ink jet recording according to Item.   The sum of the contents of the hardly water-soluble alkanediol and the water-soluble 1,2-alkanediol is 6% by weight or less based on the ink composition. The ink composition for inkjet recording as described.   The sum of the contents of the hardly water-soluble alkanediol, the alkanediol having a side chain on any one of the carbons having a hydroxyl group, and the water-soluble alkanetriol is 21% by weight based on the ink composition. The ink composition for inkjet recording according to any one of claims 1 to 8, which is as follows.   The ink composition for inkjet recording according to any one of claims 1 to 9, wherein the hardly water-soluble alkanediol is contained in an amount of 1 to 3% by weight based on the ink composition.   The ink composition for inkjet recording according to any one of claims 1 to 10, wherein the water-soluble 1,2-alkanediol is contained in an amount of 0.5 to 3% by weight based on the ink composition.   The total amount of the alkanediol having a side chain on any one of the carbons having a hydroxyl group and the water-soluble alkanetriol is 3 to 18% by weight based on the ink composition. The ink composition for inkjet recording according to any one of 11.   The ink composition for inkjet recording according to any one of claims 1 to 12, wherein the hardly water-soluble alkanediol is 1,2-octanediol.   The water-soluble 1,2-alkanediol is selected from the group consisting of 1,2-hexanediol, 4-methyl-1,2-pentanediol, and 3,3-dimethyl-1,2-butanediol. The ink composition for inkjet recording according to any one of claims 1 to 13, which is one kind or two or more kinds.   The ink composition for inkjet recording according to any one of Claims 1 to 14, wherein the alkanediol having a side chain on any one carbon having a hydroxyl group is 3-methyl-1,3-butanediol. .   The ink composition for inkjet recording according to any one of claims 1 to 15, wherein the water-soluble alkanetriol is 1,2,6-hexanetriol or 3-methyl-1,3,5-pentanetriol. object.   The ink composition for inkjet recording according to any one of claims 1 to 16, wherein the surfactant is contained in an amount of 0.01 to 1.0% by weight based on the ink composition.   The ink composition for inkjet recording according to claim 17, wherein the surfactant is a polyorganosiloxane surfactant. The polyorganosiloxane has the following formula:

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 11, m represents an integer of 2 to 50, and n represents an integer of 1 to 5).
The ink composition for inkjet recording according to claim 18, comprising one or more compounds represented by: The polyorganosiloxane has the following formula:

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 13, m represents an integer of 2 to 50, and n represents an integer of 1 to 5).
The ink composition for inkjet recording according to claim 18, comprising one or more compounds represented by: The polyorganosiloxane has the following formula:

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 13, m represents an integer of 2 to 50, and n represents an integer of 1 to 8.)
The ink composition for inkjet recording according to claim 18, comprising one or more compounds represented by: The polyorganosiloxane has the following formula:

(In the formula, R represents a methyl group, a represents an integer of 6 to 18, m is 0, and n is 1.)
The ink composition for inkjet recording according to claim 18, comprising one or more compounds represented by:   The ink composition for inkjet recording according to any one of claims 1 to 22, wherein the colorant comprises a pigment and a dispersant capable of dispersing the pigment in the ink.   24. The ink composition for ink jet recording according to claim 23, wherein the dispersant comprises at least one resin selected from styrene-acrylic acid copolymer resins, urethane resins, and fluorene resins.   The ink composition for inkjet recording according to claim 23 or 24, wherein at least one of the dispersants is contained in an amount of 20 to 50% by weight based on the ink composition.   The ink composition for inkjet recording according to any one of claims 1 to 25, wherein the colorant is a pigment, and the solid content concentration of the pigment is 6% by weight or more.   An inkjet recording method for performing printing by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the ink composition for inkjet recording according to any one of claims 1 to 26 is used. An ink jet recording method to be used.   28. The method according to claim 27, wherein the recording medium is a synthetic paper or a printing paper whose main raw material is a synthetic resin. Basis weight of the printing paper is an 73.3~104.7g / ^{m 2,} The method of claim 28. Basis weight of the printing paper is an 104.7~209.3g / ^{m 2,} The method of claim 28.

Images