JP2011168668A - Ink set, inkjet recording method, and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set capable of controlling a discharge failure which remarkably occurs when two or more inks, containing a pigment as a color material, are used as the ink set to expand color reproduction range of an image and to improve an image quality. <P>SOLUTION: The ink set for inkjet is composed of two or more inks that contain the pigment as the color material. The inks are divided into two groups 2A and 2B according to the content of pigment in each ink, and at least one ink of each group contains specific ingredients, respectively. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink set composed of a plurality of inks containing a pigment, an ink jet recording method, and an ink jet recording apparatus.

  In the ink jet system, ink is ejected from the ejection port of the recording head toward the recording medium. The ink ejected from the recording head may hit the recording medium and bounce off, or fine ink droplets (satellite) may be generated in addition to the main ink droplets during ejection, and may drift in the atmosphere. These may become ink mist and adhere to the periphery of the ejection port of the recording head. In addition, dust in the air may adhere to the periphery of the recording head. Then, the main ink droplets are pulled by these deposits, so that the ink ejection direction changes, and the straightness of the main ink droplets may be hindered. In order to solve such a problem, an inkjet recording apparatus wipes a surface (hereinafter referred to as an ejection port surface) having an ejection port of a recording head with a wiper member made of an elastic material such as rubber at a predetermined timing. Then, the deposit is removed (wiping operation).

  In recent years, in order to improve image characteristics such as the density (image density), water resistance, and light resistance of an image recorded with ink, pigment ink containing a pigment as a coloring material has been increasingly used. ing. The pigment ink is obtained by dispersing a color material that is originally solid by introducing a functional group on the surface of a resin dispersant or pigment particles. Therefore, when the liquid component in the ink evaporates and the dried pigment ink produced by drying adheres to the discharge port surface, it is compared with the dried ink containing the dye in which the coloring material is dissolved at the molecular level. The influence on the discharge port surface is large. In addition, a polymer compound such as a resin dispersant used to disperse the pigment in the ink has a property of being easily adsorbed on the discharge port surface. The problem of such resin adsorption is that when a high molecular compound such as a resin is present in the ink by adding a reactive agent to the ink for the purpose of adjusting the viscosity of the ink or improving the light resistance of the image, It occurs even if it is not a pigment ink. And, when the adsorption of the polymer compound occurs, the pigment or resin dispersant in the ink will adhere to the ejection port surface of the recording head, and the surface characteristics of the ejection port surface are different from the case where it is not adsorbed, In some cases, ejection defects are more likely to occur. Furthermore, when an ejection failure occurs, the ink may land on a position different from the position where the ink is intended, and the image quality may deteriorate.

  In recent years, multicolor pigment inks have been increasingly used for the purpose of expanding the color reproduction range (see Patent Document 1). However, in such a case, it becomes particularly difficult to suppress ejection failure for all inks. This is because the larger the number of inks, the more the characteristics of each ink will vary. Therefore, when an ink set with a large number of inks is used, ejection defects will occur more prominently. Become.

JP 2003-221527 A

  Therefore, the object of the present invention is remarkably generated when a plurality of inks containing a pigment as a color material are used as an ink set in order to increase the color reproduction range of an image and improve the image quality. An object of the present invention is to provide an ink set capable of suppressing ejection failure. Another object of the present invention is to provide an ink jet recording method and an ink jet recording apparatus using each ink constituting the ink set.

The above object is achieved by the present invention described below. That is, the ink set according to the present invention is an ink jet ink set composed of a plurality of inks containing a pigment as a coloring material, and the plurality of inks are Y (yellow) ink and R (red) ink. , G (green) ink, B (blue) ink, four black inks with different pigment contents, two cyan inks with different pigment contents, and two magenta inks with different pigment contents Bk1 ink, Bk2 ink, Bk3 ink, and Bk4 ink in the order of increasing pigment content, the four types of black ink having different pigment contents, and the two types of cyan ink having different pigment contents in order of increasing pigment content C1 ink and C2 ink, and the two types of magenta inks having different pigment contents in this order. When 1 ink and M2 ink are used, at least one of the Y ink, the R ink, the G ink, the B ink, the Bk1 ink, the Bk2 ink, the Bk3 ink, the C1 ink, and the M1 ink is used. The ink is at least one modified siloxane compound selected from the group consisting of a compound represented by the following formula (1), a compound represented by the following formula (2), and a compound represented by the following formula (3) As well as
The acid value is 90 mgKOH / g or more and 150 mgKOH / g or less, and the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is 1.0 cal ^0.5 / cm ^1.5 or more and 3.7 cal ^{0 .5} / ^{cm 1.5} or less is a resin a, and an acid value of not more than 200 mg KOH / g exceeds the 150 mgKOH / g, and hydrogen bond of the resin obtained by the solubility parameters of monomers constituting the polymer 1.0 cal ^0.5 / cm ^1.5 or more and ^1.5 cal ^0.5 / cm ^1.5 or less of resin B, containing at least one kind of resin, the Bk4 ink, the C2 ink, and At least one of the M2 inks includes a nonionic unit represented by the following general formula (I) and a unit having a polysiloxane structure. Characterized in that it contains a non-graft polymer.

(The weight average molecular weight of the compound represented by Formula (1) is 8,000 or more and 30,000 or less. In Formula (1), R ₁ is an alkylene group having 1 to 20 carbon atoms, and R ₂ is A hydrogen atom or an alkyl group having 1 to 20 carbon atoms, m is 1 to 250, n is 1 to 100, a is 1 to 100, and b is 0 to 100.

(The weight average molecular weight of the compound represented by Formula (2) is 8,000 or more and less than 50,000. In Formula (2), each R ₃ is independently a hydrogen atom or an alkyl having 1 to 20 carbon atoms. R ₄ is independently an alkylene group having 1 to 20 carbon atoms, p is 1 to 450, c is 1 to 250, and d is 0 to 100.)

(The compound represented by the formula (3) has a weight average molecular weight of 8,000 or more and less than 50,000 and an HLB of 1 or more and less than 7. In the formula (3), each R ₅ is independently a hydrogen atom. Or an alkyl group having 1 to 20 carbon atoms, each R ₆ is independently an alkylene group having 1 to 20 carbon atoms, q is 1 to 100, r is 1 to 100, and e is 1 or more. 100 or less, f is 0 or more and 100 or less.)

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)

  According to the present invention, in order to expand the color reproduction range of an image and improve the image quality, a discharge failure that occurs remarkably when a plurality of inks containing pigments as color materials is used as an ink set. It is possible to provide an ink set capable of suppressing the above. Moreover, according to another embodiment of the present invention, an ink jet recording method and an ink jet recording apparatus using each ink constituting the ink set can be provided.

It is a perspective view of the recording part of an inkjet recording device. It is sectional drawing of a recording head and a recovery unit.

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

  The ink set of the present invention is used for inkjet, and is composed of a plurality of inks containing pigments as color materials. The plurality of inks include yellow ink, red ink, green ink, blue ink, four black inks having different pigment contents, two cyan inks having different pigment contents, and different pigment contents. Contains two types of magenta ink. By using the ink set having such a configuration, the color reproduction range of the image can be expanded, and the image quality can be improved. Hereinafter, each of these inks may be called as described later. Y ink (yellow ink), R ink (red ink), G ink (green ink), B ink (blue ink). Bk1 ink, Bk2 ink, Bk3 ink, and Bk4 ink are used for the four types of black ink having different pigment contents in order of increasing pigment content. C1 ink and C2 ink in order of increasing pigment content of two types of cyan inks having different pigment contents. Two types of magenta inks having different pigment contents are M1 ink and M2 ink in descending order of pigment content.

  Further, the greatest feature of the ink set of the present invention is that the ink group is divided into two groups according to the pigment content in each ink, and each of the inks of each group has a specific component. Containing. That is, an ink group having a relatively high pigment content, that is, at least one of each ink of Y, R, G, B, Bk1, Bk2, Bk3, C1, and M1, includes a specific resin and a specific resin described later. A modified siloxane compound is contained. On the other hand, a specific silicone graft polymer, which will be described later, is contained in at least one of the ink groups having a relatively low pigment content, that is, each of the Bk4, C2, and M2 inks. In addition, by using the ink set having such a configuration, it is possible to suppress the occurrence of ejection failure that becomes particularly noticeable when an ink set including a plurality of inks containing pigments is used.

  Here, the background of finding the configuration of the ink set of the present invention having the above characteristics will be described. As described above, one of the important issues required for ink jet ink sets is to suppress ejection failure. The ejection failure is more likely to occur when the color material of the ink is a pigment, and is particularly noticeable when the number of inks is large. In an ink set having a large number of inks, the performance required for each ink is generally different. For this reason, the types of pigments, resin dispersants, water-soluble organic solvents, and the like are often different depending on the ink, and it becomes difficult to make all the inks constituting the ink set have the same level of reliability. . For example, even when the same resin dispersant is used for each of the two types of inks, the characteristics of the pigments differ depending on the type of pigment. Makes a big difference.

  Thus, as a result of investigations by the present inventors, it has been found that, by adopting the above-described configuration, it is possible to suppress the occurrence of defective ejection as a whole in a plurality of inks constituting an ink set. The present inventors presume the reason why such an effect is obtained as follows.

  One of the causes of ejection failure is a change in surface characteristics of the ejection port surface due to ink adhesion. Here, as described above, when the number of inks constituting the ink set is increased, there is inevitably ink that firmly adheres to the ejection port surface. For this reason, even if a normal wiping operation is performed, it may be difficult to remove the deposits. At this time, it is considered that the presence of a material having a siloxane structure in the ink causes a change in the interface characteristics of the deposit, and the removal is facilitated by the elasticity that is a characteristic of the siloxane structure.

  In the present invention, in the plurality of inks constituting the ink set, the ink group having a relatively high pigment content and the ink group having a relatively low pigment content are configured to use different materials having a siloxane structure. It is possible to suppress the occurrence of defective discharge as a whole. The fact that such a configuration is effective is a fact found by the study of the present inventors, and the reason why such a configuration is effective is not clear at present, but the inclusion of the pigment in the ink is not clear. It is presumed that it largely depends on the relationship with quantity. In addition, it is considered that the balance between the change in the interface characteristics and the elasticity can be efficiently expressed by combining the specific resin to be included in the ink of the ink group having a relatively high pigment content and the specific modified siloxane compound. . On the other hand, the silicone graft polymer contained in the ink of the ink group having a relatively low pigment content has a nonionic unit and a unit having a polysiloxane structure, and has a graft structure. For this reason, functional separation is performed, and it is considered that the balance between the change in the interface characteristics of the deposit and the elasticity is efficiently expressed.

  In view of the above-described mechanism, it can be assumed that a material having a siloxane structure can have a higher effect by being included in all inks constituting the ink set. However, it has been found that since ink can adhere to the discharge port surface even by ink mist or the like, sufficient effects can be obtained if it is contained in at least one kind of ink in each group.

<Ink set>
The ink set in the present invention includes a plurality of inks, and may further include other inks. The form of the ink set in the present invention is integrally configured by combining a set of a plurality of ink cartridges each containing the above inks independently and a plurality of ink containing portions each containing a plurality of inks. Ink cartridge status. Further, an ink cartridge having a configuration in which the recording head is integrally formed may be used. Furthermore, the ink set of the present invention also includes a state in which the ink cartridges that individually contain the plurality of inks are configured to be detachable from one ink jet recording apparatus. The ink set of the present invention is not limited to the above form as long as it can be used in combination with at least a yellow ink and a magenta ink, and may take any form.

  An ink cartridge that contains ink constituting the ink set of the present invention includes an ink containing portion that contains ink, and each of the inks constituting the ink set of the present invention described above is contained in the ink containing portion. It has been made. As for the structure of the ink cartridge, the ink storage portion includes an ink storage chamber that stores liquid ink and a negative pressure generation member storage chamber that stores a negative pressure generation member that holds the ink therein by a negative pressure. Things. Alternatively, the ink cartridge may be an ink container that does not have an ink storage chamber for storing liquid ink and is configured to hold the entire storage capacity by a negative pressure generating member. Further, the ink cartridge may be configured to have an ink storage portion and a recording head.

  Of the inks that make up the ink set, for inks that do not contain a material having a siloxane structure, the ink composition can be determined by appropriately selecting the components described below. In the present invention, it is particularly preferable that all inks in the ink group having a relatively low pigment content contain a specific silicone graft polymer described later. Further, it is particularly preferable that at least two kinds of inks in the ink group having a relatively high pigment content contain a specific resin and a specific modified siloxane compound described later.

  Hereinafter, components that can be contained in each ink constituting the ink set of the present invention will be described. In the present invention, (meth) acryl means acryl or methacryl. In the following description, for the sake of simplicity, at least one ink in an ink group having a relatively high pigment content is referred to as dark ink, and at least one ink in an ink group having a relatively low pigment content is used. The ink is described as light ink.

(Modified siloxane compound)
The modified siloxane compound used for the dark ink is at least one selected from the group consisting of a compound represented by the following formula (1), a compound represented by the following formula (2), and a compound represented by the following formula (3). It is a seed.

In the compounds represented by the following formulas (1), (2), and (3), (C ₂ H ₄ O) is an ethylene oxide unit, and (C ₃ H ₆ O) is propylene oxide. Each unit is shown. Moreover, in each modified siloxane compound, the form in which the ethylene oxide unit and the propylene oxide unit are present in the structure may be any form. However, in the present invention, these are preferably present in a random form or a block form. Here, the presence of each unit in a random state means that ethylene oxide units and propylene oxide units are irregularly arranged. Further, the presence of each unit in the form of a block means that the repeating unit of the ethylene oxide unit or the propylene oxide unit constitutes a block, and the blocks configured in this way are regularly arranged. Means.

  [Compound represented by Formula (1)]

(The weight average molecular weight of the compound represented by Formula (1) is 8,000 or more and 30,000 or less. In Formula (1), R ₁ is an alkylene group having 1 to 20 carbon atoms, and R ₂ is A hydrogen atom or an alkyl group having 1 to 20 carbon atoms, m is 1 to 250, n is 1 to 100, a is 1 to 100, and b is 0 to 100.

R ₁ is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an ethylene group, a propylene group, a butylene group, or the like. R ₂ is preferably an alkyl group having 1 to 10 carbon atoms, more preferably an ethyl group or a propyl group. m is preferably 1 or more and 250 or less, more preferably 1 or more and 100 or less, and particularly preferably 1 or more and 50 or less. n is preferably 1 or more and 100 or less, and more preferably 1 or more and 50 or less. a is preferably 1 or more and 100 or less, and more preferably 1 or more and 50 or less. b is preferably 0 or more and 100 or less, and more preferably 1 or more and 50 or less.

  The compound represented by the above formula (1) that can be used in the present invention is obtained by an addition reaction of two kinds of compounds represented by the following formulas. That is, it can be obtained by an addition reaction between a polysiloxane having n hydrogen atoms bonded to n Si and a compound having a structure having one alkene group and an ethylene oxide unit and / or a propylene oxide unit at the terminal. Specifically, it can be obtained by adding an alkene group to a hydrogen atom of polysiloxane. In the following formula, m is 1 to 250, n is 1 to 100, a is 1 to 100, and b is 0 to 100. R is an alkene group having 1 to 20 carbon atoms.

  [Compound represented by Formula (2)]

(The weight average molecular weight of the compound represented by Formula (2) is 8,000 or more and less than 50,000. In Formula (2), each R ₃ is independently a hydrogen atom or an alkyl having 1 to 20 carbon atoms. R ₄ is independently an alkylene group having 1 to 20 carbon atoms, p is 1 to 450, c is 1 to 250, and d is 0 to 100.)

R ₃ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom, an ethyl group, or a propyl group. R ₄ is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an ethylene group, a propylene group, or a butylene group. p is preferably 1 or more and 450 or less, more preferably 1 or more and 100 or less, and particularly preferably 1 or more and 50 or less.

  The compound represented by the above formula (2) that can be used in the present invention is obtained by an addition reaction of two kinds of compounds represented by the following formulas. That is, it can be obtained by an addition reaction between a polysiloxane having a hydrogen atom in Si at both ends and a compound having a structure having one alkene group and an ethylene oxide unit and / or a propylene oxide unit at the ends. Specifically, it can be obtained by adding an alkene group to a hydrogen atom of polysiloxane. In these formulas, p is from 1 to 450, c is from 1 to 250, and d is from 0 to 100. R is an alkene group having 1 to 20 carbon atoms.

  [Compound represented by Formula (3)]

(The compound represented by the formula (3) has a weight average molecular weight of 8,000 or more and less than 50,000 and an HLB of 1 or more and less than 7. In the formula (3), each R ₅ is independently a hydrogen atom. Or an alkyl group having 1 to 20 carbon atoms, each R ₆ is independently an alkylene group having 1 to 20 carbon atoms, q is 1 to 100, r is 1 to 100, and e is 1 or more. 100 or less, f is 0 or more and 100 or less.)

R ₅ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom, an ethyl group, or a propyl group. R ₆ is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an ethylene group, a propylene group, or a butylene group. e is preferably 1 or more and 100 or less, and more preferably 1 or more and 50 or less. f is preferably 1 or more and 100 or less, more preferably 1 or more and 50 or less.

  The compound represented by the above formula (3) which can be used in the present invention is obtained by an addition reaction of two kinds of compounds represented by the following formula. That is, it can be obtained by an addition reaction between a polysiloxane having hydrogen atoms in Si at both ends, an alkene group at both ends, and a compound having a structure having an ethylene oxide unit and / or a propylene oxide unit. Specifically, it can be obtained by adding an alkene group to a hydrogen atom of polysiloxane. In these formulas, q is from 1 to 100, r is from 1 to 100, e is from 1 to 100, and f is from 0 to 100. R is an alkene group having 1 to 20 carbon atoms.

  As a result of the study by the present inventors, the following weights are given as at least one modified siloxane compound selected from the group consisting of the compounds represented by formula (1), formula (2), and formula (3). It is particularly preferable to use a modified siloxane compound having an average molecular weight. Specifically, in the case of the compound represented by the above formula (1), the weight average molecular weight (MW) is 8,000 or more and 30,000 or less, and further, 8,500 or more and 30,000 or less. It is particularly preferred that In the case of the compound represented by the above formula (2) or the above formula (3), these weight average molecular weights (MW) are 8,000 or more and less than 50,000, and further, 8,500 or more, 30, 000 or less is particularly preferable. In addition, the said weight average molecular weight (MW) is a weight average molecular weight of polystyrene conversion in the molecular weight distribution measured by gel permeation chromatography (GPC). The compounds represented by formula (1), formula (2), and formula (3) that can be used in the present invention can be obtained as described above. A compound having an alkene group is a mixture of compounds having various molecular weights. For this reason, the molecular weight of these modified siloxane compounds is determined as an average molecular weight.

  As a result of the study by the present inventors, it was found that among the compounds represented by the above formula (1), it is preferable to use a modified siloxane compound having a specific HLB (value calculated by the Griffin method). . That is, the compound represented by the formula (1) preferably has an HLB of 1 to 11 and more preferably 5 to 11.

  In the present invention, when the compound represented by the above formula (1) is used in the dark ink, the surface characteristics can be efficiently changed by setting the weight average molecular weight and further the HLB in the above range. Therefore, even when the content of the compound represented by the above formula (1) in the ink is small, the effect of suppressing ejection failure is sufficiently exerted. Examples of the compound represented by the above formula (1) that satisfies the above conditions and can be particularly preferably used in the present invention include the following. For example, FZ-2104, FZ-2130, FZ-2191 (above, manufactured by Toray Dow Corning), KF-615A (manufactured by Shin-Etsu Chemical), TSF4452 (manufactured by Momentive Performance Materials Japan) and the like can be mentioned. Of course, the present invention is not limited to these.

  In the present invention, when the compound represented by the above formula (2) is used in the dark ink, the surface characteristics can be efficiently changed by setting the weight average molecular weight within the above range. Therefore, even when the content of the compound represented by the above formula (2) in the ink is small, the effect of suppressing ejection failure is sufficiently exerted. Examples of the compound represented by the above formula (2) that satisfies the above conditions and can be particularly preferably used in the present invention include BYK333 (manufactured by BYK Chemie). Of course, the present invention is not limited to these.

  As a result of the study by the present inventors, it was found that it is preferable to use a modified siloxane compound having a specific HLB (value calculated by the Griffin method) as the compound represented by the above formula (3). That is, as the compound represented by the above formula (3), a compound whose HLB is 1 or more and less than 7 is used.

  In the present invention, when the compound represented by the above formula (3) is used in the dark ink, the surface characteristics can be efficiently changed by setting the weight average molecular weight and the HLB in the above range. Therefore, even when the content of the compound represented by the above formula (3) in the ink is small, the effect of suppressing ejection failure is sufficiently exerted. Examples of the compound represented by the above formula (3) that satisfies the above conditions and can be particularly preferably used in the present invention include the following. Examples thereof include FZ-2203, FZ-2207, FZ-2222, FZ-2231 (manufactured by Toray Dow Corning). Of course, the present invention is not limited to these.

  As described above, the weight average molecular weight (MW) of the modified siloxane compound can be measured by gel permeation chromatography (GPC) using tetrahydrofuran as a mobile phase. The measuring method used in the present invention is as follows. However, measurement conditions such as filters, columns, standard polystyrene samples and their molecular weights that can be applied to the present invention are not limited to the following.

  First, a sample to be measured is placed in tetrahydrofuran and allowed to stand for several hours to dissolve to prepare a solution. Thereafter, the solution is filtered with a solvent-resistant membrane filter having a pore size of 0.45 μm (for example, trade name: TITAN2 Syringe Filter, PTFE, 0.45 μm; manufactured by SUN-SRi) to obtain a sample solution. In addition, the density | concentration of the sample in a sample solution is adjusted so that content of a modified siloxane compound may be 0.1 to 0.5 mass%.

For the GPC, an RI detector (Refractive Index Detector) is used. In order to accurately measure a molecular weight range of 10 ^{3 to} 2 × 10 ⁶ , it is preferable to combine a plurality of commercially available polystyrene gel columns. For example, four Shodex KF-806M (manufactured by Showa Denko) can be used in combination, or a corresponding one can be used. Tetrahydrofuran is allowed to flow as a mobile phase at a flow rate of 1 mL / min through a column stabilized in a 40.0 ° C. heat chamber, and about 0.1 mL of the above sample solution is injected. The weight average molecular weight of the sample is determined using a molecular weight calibration curve prepared with a standard polystyrene sample. As the standard polystyrene sample, one having a molecular weight of about 10 ^{2 to} 10 ⁷ (for example, manufactured by Polymer Laboratories) is used, and it is appropriate to use at least about 10 kinds of standard polystyrene samples.

  In the present invention, the content (% by mass) of the compound represented by the above formula (1), formula (2), and formula (3) in the dark ink is 0. It is preferable that they are 2 mass% or more and 5.0 mass% or less. Furthermore, it is more preferable that it is 0.5 mass% or more and less than 3.0 mass%.

(Resin used in combination with modified siloxane compounds)
As a result of the study by the present inventors, it is necessary to use at least one kind of resin A and resin B having the following characteristics for the dark ink because of the balance with the modified siloxane compound. all right. That is, the resin to be contained in the dark ink in combination with the compounds represented by the above formulas (1), (2), and (3) is at least selected from the following resin group A and resin group B: One type of resin may be mentioned. Resin Group A: The acid value is 90 mgKOH / g or more and 150 mgKOH / g or less, and the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is 1.0 cal ^0.5 / cm ^1.5 or more Resin which is 3.7 cal ^0.5 / cm ^1.5 or less. Resin group B: The acid value is more than 150 mgKOH / g and not more than 200 mgKOH / g, and the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is 1.0 cal ^0.5 / cm1 ^. Resin having ⁵ or more and ^1.5 cal ^0.5 / cm ^1.5 or less. Hereinafter, a resin corresponding to the resin group A is referred to as a resin A, and a resin corresponding to the resin group B is referred to as a resin B.

  The “hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin” that defines the resin that can be used in the present invention is specifically a value obtained as follows. First, for each monomer constituting the target resin, the hydrogen bond term of each monomer constituting the resin is calculated from the solubility parameter specific to the monomer. Next, the value obtained by multiplying the hydrogen bond term of each monomer constituting the resin obtained above by the composition (mass) ratio of each monomer constituting the resin (composition ratio with the sum being 1) was obtained, respectively. The hydrogen bond term of the resin can be obtained by adding the obtained values.

When the acid value of the resin to be contained in the dark ink is less than 90 mgKOH / g, the resin may precipitate when the resin cannot be dissolved with an alkali or when the ink is stored for a long period of time. For this reason, it is preferable that the acid value of resin is 90 mgKOH / g or more. On the other hand, when the acid value of the resin exceeds 150 mgKOH / g, the hydrophilicity increases, and it may be difficult to change the surface properties of the ink due to the relationship with the siloxane compound. Therefore, when the acid value of the resin exceeds 150 mgKOH / g, it is preferable that the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is ^1.5 cal ^0.5 / cm ^1.5 or less. . However, if the acid value of the resin exceeds 200 mgKOH / g, the effect of suppressing ejection failure, which is the target of the present invention, may not be exhibited regardless of how the hydrogen bond term of the resin is defined. For this reason, it is preferable that the acid value of resin is 200 mgKOH / g or less.

Further, the resin A and the resin B contained in the dark ink are caused by the resin when the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is less than 1.0 cal ^0.5 / cm ^1.5. As a result, the sticking resistance may be lowered. Therefore, hydrogen bond of polymer obtained by the solubility parameters of monomers constituting the resin A and resin B is preferably set to ^{1.0 cal} 0.5 ^{/ cm 1.5} or more. On the other hand, when the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin exceeds 3.7 cal ^0.5 / cm ^1.5 , the hydrophilicity of the resin becomes too high. In this case, no matter how the acid value of the resin is defined, there are cases where the effect of suppressing the ejection failure targeted by the present invention is not exhibited.

In summary, as the resin to be contained in the dark ink, at least one kind of resin A and resin B having the characteristics of combining the acid value and the hydrogen bond term within the following ranges is used. Resin A has an acid value of 90 mgKOH / g or more and 150 mgKOH / g or less. In addition to this, the resin A has a hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin of 1.0 cal ^0.5 / cm ^1.5 or more and 3.7 cal ^0.5 / cm ^{1. .5} or less. As a more preferable resin A, the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is 1.0 cal ^0.5 / cm ^1.5 or more and 3.2 cal ^0.5 / cm ^1.5 or less. Can be mentioned. In particular, the resin A has a hydrogen bond term of 1.2 cal ^0.5 / cm ^1.5 or more and 1.8 cal ^0.5 / cm ^1.5 or less calculated from the solubility parameter of the monomer constituting the resin. It is preferable. On the other hand, the resin B has an acid value exceeding 150 mgKOH / g and not more than 200 mgKOH / g. Further, in addition to this, the resin B has a hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin of 1.0 cal ^0.5 / cm ^1.5 or more and ^1.5 cal ^0.5 / cm ^{1. .5} or less. As a more preferable resin B, the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is 1.2 cal ^0.5 / cm ^1.5 or more and ^1.5 cal ^0.5 / cm ^1.5 or less. Can be mentioned.

  Any monomer can be used as the monomer constituting the resin to be included in the dark ink as long as the acid value of the resin and the value of the hydrogen bond term of the resin can be a resin having the characteristics described above. it can. Specifically, the monomers listed below can be used as the monomer constituting the resin. Hydrophobic monomers such as styrene, α-methylstyrene, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, methyl methacrylate, and benzyl methacrylate. (Meth) acrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid, styrene sulfonic acid, sulfonic acid-2-propylacrylamide, acrylic acid-2-ethyl sulfonate, methacrylic acid Hydrophilic monomers such as ethyl-2-sulfonic acid, butylacrylamidesulfonic acid, methacrylic acid-2-ethylphosphonate, and acrylic acid-2-ethylphosphonate;

  In the present invention, when the resin A is used, it is preferable to include at least one monomer selected from the group consisting of styrene, n-butyl acrylate, and benzyl methacrylate among the monomers listed above. Furthermore, it is more preferable that the monomer constituting the resin A has both styrene and n-butyl acrylate. At this time, among the monomers constituting the resin A, the mass ratio of n-butyl acrylate based on styrene (n-butyl acrylate / styrene) is particularly preferably more than 0.2 and less than 0.35. preferable. Moreover, when using the said resin B, it is preferable that the monomer mentioned above contains at least 1 sort (s) of monomer chosen from the group which consists of styrene and (alpha) -methylstyrene. Furthermore, it is more preferable that the monomer constituting the resin B has both styrene and α-methylstyrene. At this time, among the monomers constituting the resin B, the mass ratio of α-methylstyrene (α-methylstyrene / styrene) based on styrene is particularly preferably 0.90 or less.

  The weight average molecular weight of the resin (at least one kind of resin A and resin B) contained in the dark ink is preferably 5,000 or more and 15,000 or less, and more preferably 6,000 or more and 9,000 or less. In a resin having a weight average molecular weight outside the above range, the modified siloxane compound is susceptible to steric hindrance. For this reason, it becomes difficult to cause changes in interface characteristics, and the effect of suppressing ejection failure may not be sufficiently exhibited.

  In the present invention, the content (% by mass) of the resin contained in the dark ink is 0.5% by mass or more and 5.0% by mass or less, and further 2.5% by mass or more and 4.0% by mass based on the total mass of the ink. It is preferable that it is below mass%.

  The resin A and the resin B mentioned above can also be used as a pigment dispersant (resin dispersant). However, in the present invention, the resin used as the dispersant is more preferably a resin other than those listed above. At this time, any dispersant can be used as long as it is applicable to general ink jet ink. Specific examples of the monomer constituting the dispersant include the following, and examples thereof include a resin composed of at least two monomers. At this time, at least one is preferably a hydrophilic monomer. Styrene, vinyl naphthalene, aliphatic alcohol ester of α, β-ethylenically unsaturated carboxylic acid, acrylic acid, maleic acid, itaconic acid, fumaric acid, vinyl acetate, vinyl pyrrolidone, acrylamide, or derivatives thereof. Examples of the resin include a block copolymer, a random copolymer, a graft copolymer, or a salt thereof. Furthermore, natural resins such as rosin, shellac and starch may be used. These resins are soluble in an aqueous solution in which a base is dissolved, and are alkali-soluble resins. The resin (dispersant) preferably has a weight average molecular weight of 1,000 to 30,000, more preferably 3,000 to 15,000. The content (% by mass) of the resin (dispersant) in the ink is preferably 0.1% by mass or more and 10.0% by mass or less based on the total mass of the ink.

(Silicone graft polymer)
The silicone graft polymer contained in the light ink has at least a nonionic unit represented by the following general formula (I) and a unit having a polysiloxane structure. In the present invention, hereinafter, “unit” includes both cases in which one or a plurality of repeating units are included in the unit.

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)

  The graft polymer in the present invention is “a polymer having a structure in which a branch polymer (side chain) is bonded to one trunk polymer (main chain)”. And as a method of discriminating whether the structure of a certain polymer is a graft polymer, the following methods are mentioned, for example. That is, it is possible to determine that the structure of a certain polymer is a graft polymer by measuring the absolute molecular weight and the molecular size in combination with gel permeation chromatography and a multi-angle light scattering detector. Specifically, the greater the difference between the absolute molecular weight and molecular size measured by these methods, the higher the degree of branching of the polymer, and in the form of a graft polymer. Judgment can be made.

  The graft polymer to be included in the light ink has a structure in which the functions of the unit having a polysiloxane structure and the nonionic unit are effectively separated in the molecule in order to efficiently perform each function. Is preferred. Specifically, in order to further clarify the functional separation of these units, the graft polymer preferably has a structure in which a side chain includes a unit having a nonionic unit and a polysiloxane structure. That is, it is preferable that one end of the nonionic unit or the unit having a polysiloxane structure constitutes a part of the main chain of the graft polymer. Furthermore, it is more preferable that the side chain is a graft polymer composed only of the nonionic unit and a unit having a polysiloxane structure. By using the graft polymer having such a structure, the effect of suppressing ejection failure is sufficiently exhibited. Further, as the nonionic unit, it is preferable to use a low molecular weight unit instead of a high molecular weight unit. Specifically, the molecular weight of the nonionic unit is preferably 70 or more and 190 or less, and more preferably 110 or more and 190 or less in terms of weight average molecular weight. In this case, the nonionic units can be evenly branched from the main chain of the graft polymer, that is, the nonionic units branched from the main chain can be delocalized, and the effects of the present invention can be obtained. In particular, it is particularly suitable. In the present invention, the content (% by mass) of the graft polymer in the light ink is 0.1% by mass or more and 10.0% by mass or less, further 0.1% by mass or more and 5% by mass or more based on the total mass of the ink. It is preferable that it is 0.0 mass% or less. Hereinafter, each unit constituting the graft polymer contained in the light ink will be described in more detail.

[Nonionic unit]
The nonionic unit constituting the graft polymer contained in the light ink has a structure represented by the following general formula (I). The nonionic unit having this structure is obtained by copolymerizing a monomer represented by the following general formula (I ′) having 1 or 2 repeating units of an ethylene oxide group and having a polymerizable functional group at the terminal. is there. Furthermore, in the graft polymer used in the present invention, the vinyl group or vinylidene group of the monomer represented by the following general formula (I ′) is a part of the main chain of the graft polymer, and the portion from R ₃ to R ₁ is branched. Thus, a structure that is a side chain of the graft polymer is preferable.

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)

(In general formula (I ′), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. _{When 2} is a methyl group, R ₃ is not an ether bond.)

  In the present invention, in the nonionic unit represented by the general formula (I), the number of repeating units of the ethylene oxide group is 1 or 2, that is, x in the general formula (I) is 1 or 2. It is necessary to use something. When x in the general formula (I) is 3 or more, in the case where the nonionic unit branches from the main chain of the graft polymer, the tendency of localized nonionic sites to increase is increased, and the graft polymer The hydrophilicity as a whole becomes high. For this reason, the effect which suppresses discharge defect may not be exhibited. In addition, as described above, when the hydrophilicity of the graft polymer as a whole becomes high, the graft polymer has an action like a surfactant in the ink, and the interface characteristics of the ink cannot be changed. .

  In addition, when the graft polymer further includes a unit having an ethylene oxide group having a structure different from that of the nonionic unit represented by the general formula (I), the number of repeating units of the ethylene oxide group in the unit is determined. 1 or 2 is preferable.

  Further, as a result of the study by the present inventors, even if a silicone graft polymer containing an ionic unit as a constituent component is contained in the ink instead of the nonionic unit, the effect of suppressing ejection failure may not be exhibited. all right. The present inventors presume this reason as follows. For example, in the case of an ink that does not have the nonionic unit and instead contains a silicone graft polymer having an anionic unit, the following phenomenon occurs. That is, in the process of evaporating the aqueous medium or the like in the ink, salting out or the like occurs, resulting in extremely low hydrophilicity of the silicone graft polymer and aggregation. In such a case, it is considered that the interface characteristics cannot be changed, and the effect of suppressing ejection failure cannot be obtained.

  Specific examples of the nonionic unit represented by the general formula (I) include those obtained by copolymerization of (meth) acrylate monomers and vinyl ether monomers. Moreover, in the graft polymer to be contained in the light ink, the nonionic unit may be configured by combining one type or two or more types.

  Examples of (meth) acrylate monomers include 2-hydroxyethyl methacrylate, diethylene glycol monomethacrylate, 2-hydroxyethyl acrylate, diethylene glycol monoacrylate, methoxydiethylene glycol-monomethacrylate, methoxydiethylene glycol-monoacrylate, and the like. As such a (meth) acrylate monomer, for example, commercially available products such as BLEMMER PE-90, AE-90, PME-100 (above, NOF Corporation), BHEA, HEMA (manufactured by Nippon Shokubai Co., Ltd.) are used. it can. Examples of vinyl ether monomers include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and the like. As such a vinyl ether monomer, for example, commercially available products such as HEVE and DEGV (manufactured by Maruzen Petrochemical Co., Ltd.) can be used. In the present invention, among these monomers, it is particularly preferable to use 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or methoxydiethylene glycol-monomethacrylate.

[Units having a polysiloxane structure]
As the unit having a polysiloxane structure constituting the graft polymer to be contained in the light ink, any unit having a polysiloxane structure may be used. In the present invention, it is particularly preferable to use a unit represented by the following general formula (II) among units having a polysiloxane structure. The unit represented by the general formula (II) is obtained by copolymerization of a monomer represented by the following general formula (II ′) having a polymerizable functional group at one end. Further, in the graft polymer, the vinyl group or vinylidene group of the monomer represented by the following general formula (II ′) becomes a part of the main chain of the graft polymer, and the portion from the ester bond to R ₁₁ is branched. It is preferable that the structure be a side chain. Moreover, in the graft polymer to be contained in the light ink, the unit having a polysiloxane structure may be constituted by one kind or a combination of two or more kinds.

(In General Formula (II), R ₈ is a hydrogen atom or a methyl group, R ₉ is an alkylene group having 1 to 6 carbon atoms, R ₁₀ is independently a methyl group or a phenyl group, and R ₁₁ is (It is a C1-C6 alkyl group or a phenyl group, and m is 1 or more and 150 or less.)

(In General Formula (II ′), R ₈ is a hydrogen atom or a methyl group, R ₉ is an alkylene group having 1 to 6 carbon atoms, R ₁₀ is independently a methyl group or a phenyl group, and R ₁₁ Is an alkyl group having 1 to 6 carbon atoms or a phenyl group, and m is 1 or more and 150 or less.)

  In the present invention, as the monomer represented by the general formula (II ′), for example, commercially available products such as Silaplane FM-0711, FM-0721, FM-0725 (manufactured by Chisso) and the like are used. it can.

[Other units]
The graft polymer contained in the light ink preferably has at least the above-described nonionic unit represented by the general formula (I) and a unit having a polysiloxane structure, and further has a unit having an acidic group. The graft polymer contained in the light ink may further include other units in addition to these units. Examples of other units include acid monomers, monomers having a carboxyl group, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and copolymers of monomers such as anhydrides, salts, and ester compounds thereof. Moreover, in the graft polymer used in the present invention, the other units may be configured by combining one type or two or more types.

  Specific examples of the monomer constituting the other unit include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, 2- (meth) acryloyloxymethyl succinic acid, and the like. (Meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. Styrene sulfonic acid, maleic anhydride, 2- (meth) acrylamide-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester and the like. Vinylphosphonic acid, vinyl phosphate, bis ([meth] acryloxyethyl) phosphate, diphenyl-2- (meth) acryloyloxyethyl phosphate, and the like. Further, dibutyl-2- (meth) acryloyloxyethyl phosphate, dibutyl-2- (meth) acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate and the like can be mentioned. Among these, (meth) acrylic acid, methyl (meth) acrylate, and butyl (meth) acrylate are preferable.

(Pigment)
Each ink constituting the ink set of the present invention includes a resin dispersion type pigment (resin dispersion type pigment) in which a pigment is dispersed using a dispersant, or a self-dispersion type in which a hydrophilic group is introduced on the surface of pigment particles. A pigment (self-dispersing pigment) can be used. In addition, pigments (resin-bonded self-dispersing pigments) in which organic groups containing polymers are chemically bonded to the surface of the pigment particles, microcapsule type that increases the dispersibility of the pigment and enables dispersion without using a dispersant Pigments can also be used. Of course, these pigments having different dispersion methods may be used in combination. The content (% by mass) of the pigment in the ink is 0.1% by mass to 15.0% by mass and more preferably 1.0% by mass to 10.0% by mass based on the total mass of the ink. preferable. Examples of the pigment include inorganic pigments such as organic pigments and carbon black, which can be appropriately selected from those applicable to general ink jet inks according to the color tone of the ink. Further, in addition to the pigment to be mainly contained, toning may be performed by using one or more other pigments in combination.

(Aqueous medium)
Each ink constituting the ink set of the present invention may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water (ion exchange water) as water. The content (% by mass) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of alcohols, glycols, glycol ethers, nitrogen-containing compounds, and the like that can be used for ink-jet inks can be used, and one kind or two or more kinds are contained in the ink. Can be made.

(Other ingredients)
In addition to the above components, each ink constituting the ink set of the present invention may contain a water-soluble organic compound that is solid at room temperature, such as urea, urea derivatives, trimethylolpropane, and trimethylolethane. The content (% by mass) of such a water-soluble organic compound in the ink is 0.1% by mass or more and 20.0% by mass or less, and further 3.0% by mass or more and 10.0% by mass based on the total mass of the ink. It is preferable that it is below mass%. In addition, various inks such as salts, surfactants, pH adjusters, rust preventives, antiseptics, antifungal agents, antioxidants, anti-reduction agents, etc. are used in order to obtain inks having desired physical property values. An additive may be contained.

<Inkjet recording method, inkjet recording apparatus>
The inkjet recording method of the present invention is an inkjet recording method in which a plurality of inks are ejected from an inkjet recording head to perform recording on a recording medium. And each ink which comprises the ink set of this invention demonstrated above as said several ink is used. In the present invention, thermal energy can be particularly preferably used as the energy for ejecting ink.

  The ink jet recording apparatus of the present invention is an ink jet recording apparatus provided with an ink containing portion that contains a plurality of inks and a recording head for ejecting each of the plurality of inks. And each ink which comprises the ink set of this invention demonstrated above as said several ink is used. In the present invention, a recording head using thermal energy can be particularly preferably used as means for ejecting ink.

  Hereinafter, the main structure of the ink jet recording apparatus of the present invention that can suitably carry out the ink jet recording method of the present invention will be described. FIG. 1 is a perspective view of a recording unit of the ink jet recording apparatus, and FIG. 2 is a cross-sectional view of a recording head and a recovery unit. First, the overall configuration of the ink jet recording apparatus will be briefly described. The main body of the ink jet recording apparatus is mounted on a stand, in which a transport unit for transporting the recording medium, a carriage unit 1 for performing predetermined recording on the recording medium, and the functions of the recording heads 2A and 2B are restored. Has a recovery unit and so on.

  In the ink jet recording apparatus of the present invention, the recording unit is configured by mounting the two recording heads 2 of the first recording head 2A and the second recording head 2B on the carriage unit 1. In FIG. 1, the first recording head 2A is mounted on the first head holder 5A, and the second recording head 2B is mounted on the second head holder 5B. Hereinafter, since the two recording heads can have the same configuration, the first recording head will be described. The first recording head 2A is configured to be detachable from the head holder 5A by opening and closing the first head lever 3A and the second head lever 4A. The carriage unit 1 reciprocates in the main scanning direction along the first rail 6A and the second rail 6B, and a recording medium in a sub scanning direction orthogonal to the main scanning direction by a recording medium transport unit (not shown). Is conveyed, image recording is performed.

  In the present invention, an inkjet recording apparatus having a configuration in which two recording heads capable of ejecting six types of ink per recording head are used and an image is recorded by an ink set composed of 12 types of ink is used. Can do. In FIG. 2, the recording head 2 is provided with a recording element 21 and an ink supply coupling portion 22n. The recording element 21 has ejection openings (not shown) for ejecting each ink as an ejection opening array. . Then, ink is ejected from each ejection port by the action of thermal energy generated by the electrothermal conversion element. An ink supply coupling unit 22n is coupled to an ink cartridge (not shown) installed inside the main body of the ink jet recording apparatus via a tube (not shown), and is accommodated in the ink storage unit of the ink cartridge. Ink is supplied to the recording head 2. Further, a passage (not shown) for supplying ink to the recording element 43n is provided for each ink type inside the recording head 2 and communicates with the ejection port 44n. In addition, the member which attached | subjected the code | symbol n means that it is comprised by the some member group which has the same structure.

  In the above description, the configuration in which two recording heads that discharge six types of ink are used to record an image using the 12 types of inks included in the ink set of the present invention has been described. The number and the configuration of the carriage are not limited to this. That is, any configuration may be used as long as recording can be performed using 12 types of ink.

  When recording is not performed, the carriage unit 1 in FIG. 1 is located at the home position, and at that position, the ejection port of the recording head 2 faces the surface (ejection port surface) where the ejection port is opened, that is, A recovery unit (FIG. 2) is provided below FIG. The recovery unit is provided to perform cleaning such as cleaning of ink adhering to the discharge port surface of the recording head 2 provided in the carriage unit 1 and eliminating clogging of the discharge port. Also, when filling the recording head with ink stored in the ink cartridge, it is used for avoiding ejection failure due to the presence of air bubbles in advance. For this reason, the ink jet recording apparatus of the present invention includes a recovery unit including the wiper 71 and the suction cap 72n.

  Hereinafter, the configuration and operation of the recovery unit will be described with reference to FIG. FIG. 2 is a cross-sectional view of the recording head 2 and the recovery unit as viewed from the right in FIG. Reference numeral 71 denotes a wiper, which has a configuration in which a wiper member made of an elastic member such as rubber is provided on a support member (not shown) movable in the direction of an arrow. The wiper 71 is in a state like 71A and moves in the direction of the arrow, thereby wiping the discharge port surface of the recording head 2 and performing a wiping operation to remove the deposits. Reference numeral 73n denotes a suction cap, which moves so as to approach the discharge port surface of the recording head 2, and covers the discharge port surface when its outer peripheral portion comes into contact with the recording element 43n (discharge port surface). A suction mechanism (not shown) is connected to the suction tube 53n. The ink stored in the ink cartridge is filled to the vicinity of the discharge port of the recording head by the suction pressure of the suction mechanism, and the ink is discharged from discharge failure due to bubbles in the ink or clogging of the discharge port. A suction operation is performed to obtain a normal state.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples as long as the gist thereof is not exceeded. “Part” or “%” is based on mass unless otherwise specified.

<Synthesis of silicone graft polymer>
According to the following procedure, graft polymers 1 to 3 which are silicone graft polymers were synthesized by the following polymerization methods, respectively. First, in a flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, each monomer having a composition shown in Table 1 below and a polymerization initiator are charged, and 500 parts of 1-methoxy-2-propanol is used as a solvent, and nitrogen gas is used. The polymerization reaction was performed at a temperature of 110 ° C. for 4 hours under reflux. The solution containing the copolymer thus obtained was dried under reduced pressure to obtain a copolymer. To the obtained copolymer, 25 parts of methyl ethyl ketone as a solvent was added and dissolved, and then 2 parts of 30% aqueous potassium hydroxide solution was added to neutralize some of the salt-forming groups of the copolymer. 300 parts of exchange water was added and stirred. Thereafter, the solvent was removed under reduced pressure at a temperature of 60 ° C., and further concentrated by removing a part of water to obtain an aqueous solution of a graft polymer having a solid content of 20.0%. With respect to the graft polymers 1 to 3 thus obtained, the absolute molecular weight and the molecular size were measured by combining gel permeation chromatography (manufactured by Shimadzu Corporation) and a multi-angle light scattering detector (manufactured by Shoko Tsusho). . As a result, the measured values of the absolute molecular weight and the molecular size were greatly different, and it was confirmed that they had a graft polymer structure.

In Table 1 below, (* 1) to (* 3) represent the following monomers, respectively.
(* 1): Silaplane FM-0711 (manufactured by Chisso; monomer having polysiloxane structure represented by the general formula (V ′), number average molecular weight of about 1,000)
(* 2): HEMA (product name: manufactured by Nippon Shokubai; nonionic monomer in which R ₁ in the general formula (I ′) is a hydrogen atom, R ₂ is a methyl group, R ₃ is an ester bond, and x is 1)
(* 3): Blemmer PME-100 (product name: manufactured by NOF; R ₁ and R ₂ in the general formula (I ′) are methyl groups, R ₃ is an ester bond, and x is 2)

<Preparation of pigment dispersion>
First, resins 1 and 2 having the following characteristics were synthesized by a conventional method and neutralized with a 10.0% aqueous potassium hydroxide solution.
Resin 1: Styrene / n-butyl acrylate / acrylic acid, composition (mass) ratio = 18: 68: 14, weight average molecular weight 6,000, acid value 109 mgKOH / g, resin hydrogen bond term 3.2 cal ^0.5 / cm ^1.5
Resin 2: Styrene / α-methylstyrene / acrylic acid, composition (mass) ratio = 48: 34: 18, weight average molecular weight 9,000, acid value 140 mgKOH / g, hydrogen bond term of resin 1.0 cal ^0.5 / cm ^1.5 .

  A pigment of the type shown in Table 2 below: 10.0 parts, resin: 5.0 parts, and ion-exchanged water: 85.0 parts were mixed and dispersed in a batch type vertical sand mill for 3 hours. Pressure filtration was performed with a filter (product name: HDCII; manufactured by Nihon Pall) which is 5 μm. Ion exchange water was added thereto to obtain each pigment dispersion having a pigment content of 10.0% and a resin content of 5.0%.

<Preparation of ink>
Each component shown in Tables 3 and 4 below was mixed and stirred sufficiently, and then pressure filtration was performed with a polypropylene filter (manufactured by Pall) having a pore size of 1.2 μm to prepare each ink. In Tables 3 and 4 below, the graft polymer and the resin are shown as solid content values, and the polyethylene glycol has an average molecular weight of 1,000. Acetylenol E100 is a nonionic surfactant (manufactured by Kawaken Fine Chemicals). Each compound starting with “FZ-” is a modified siloxane compound having the above-described structure, manufactured by Toray Dow Corning, and BYK333 manufactured by BYK Chemie. did.

<Configuration and evaluation of ink set>
The inks obtained above were combined as shown on the left side of Table 5 to obtain an ink set. An ink cartridge filled with each ink constituting the ink set was set in a modified large-format ink jet recording apparatus (trade name: iPF5000; manufactured by Canon Inc.). On an office planner (manufactured by Canon), 50,000 images of a recording duty of 10% and 18 cm × 24 cm were recorded in the default mode. At this time, each time 20 sheets were recorded, the discharge port surface was cleaned with a wiper at a rate of once. The state of the discharge port surface at this time was visually confirmed, and the state of the discharge port surface was evaluated. The evaluation criteria for the state of the discharge port surface are as follows. The evaluation results are shown in Table 5. Also, after recording 50,000 sheets, a nozzle check pattern of iPF5000 was recorded. The obtained nozzle check pattern was visually confirmed, and the discharge stability was evaluated. The evaluation criteria for ejection stability are as follows. The evaluation results are shown in Table 5. When any of the following evaluation criteria is B or more, it indicates that the occurrence of ejection failure is suppressed, and when there is C in any one of the items, the ejection failure is not suppressed and is an unacceptable level. It was.

(Evaluation criteria for the condition of the discharge port surface)
A: Almost no ink was present around the ejection port B: A little ink was present around the ejection port C: Ink was present around the ejection port in a band shape.

[Evaluation criteria for ejection stability]
A: Nozzle check pattern was not disturbed and recording was normal B: Nozzle check pattern was slightly disturbed, but there was no non-ejection C: Nozzle check pattern was clearly unejected or disturbed, It was not possible to record normally.

Claims (3)

An ink-jet ink set composed of a plurality of inks containing a pigment as a coloring material,
The plurality of inks are Y (yellow) ink, R (red) ink, G (green) ink, B (blue) ink, four types of black ink having different pigment contents, and two types having different pigment contents. Cyan ink, two magenta inks having different pigment contents, and four black inks having different pigment contents, in order of increasing pigment content, Bk1 ink, Bk2 ink, Bk3 ink and Bk4 ink, Two kinds of cyan inks having different pigment contents are designated as C1 ink and C2 ink in order of increasing pigment content, and two kinds of magenta inks having different pigment contents are designated as M1 ink and M2 ink in order of increasing pigment content. When
At least one of the Y ink, R ink, G ink, B ink, Bk1 ink, Bk2 ink, Bk3 ink, C1 ink, and M1 ink is represented by the following formula (1). At least one modified siloxane compound selected from the group consisting of a compound represented by the following formula (2), a compound represented by the following formula (3), and
The acid value is 90 mgKOH / g or more and 150 mgKOH / g or less, and the hydrogen bond term of the resin calculated from the solubility parameter of the monomer constituting the resin is 1.0 cal ^0.5 / cm ^1.5 or more and 3.7 cal ^{0 .5} / ^{cm 1.5} or less is a resin a, and an acid value of not more than 200 mg KOH / g exceeds the 150 mgKOH / g, and hydrogen bond of the resin obtained by the solubility parameters of monomers constituting the polymer 1.0 cal ^0.5 / cm ^1.5 or more and ^1.5 cal ^0.5 / cm ^1.5 or less of resin B,
At least one of the Bk4 ink, the C2 ink, and the M2 ink contains a graft polymer including a nonionic unit represented by the following general formula (I) and a unit having a polysiloxane structure. An ink set characterized by

(The weight average molecular weight of the compound represented by Formula (1) is 8,000 or more and 30,000 or less. In Formula (1), R ₁ is an alkylene group having 1 to 20 carbon atoms, and R ₂ is A hydrogen atom or an alkyl group having 1 to 20 carbon atoms, m is 1 to 250, n is 1 to 100, a is 1 to 100, and b is 0 to 100.

(The weight average molecular weight of the compound represented by Formula (2) is 8,000 or more and less than 50,000. In Formula (2), each R ₃ is independently a hydrogen atom or an alkyl having 1 to 20 carbon atoms. R ₄ is independently an alkylene group having 1 to 20 carbon atoms, p is 1 to 450, c is 1 to 250, and d is 0 to 100.)

(The compound represented by the formula (3) has a weight average molecular weight of 8,000 or more and less than 50,000 and an HLB of 1 or more and less than 7. In the formula (3), each R ₅ is independently a hydrogen atom. Or an alkyl group having 1 to 20 carbon atoms, each R ₆ is independently an alkylene group having 1 to 20 carbon atoms, q is 1 to 100, r is 1 to 100, and e is 1 or more. 100 or less, f is 0 or more and 100 or less.)

(In General Formula (I), R ₁ and R ₂ are each independently a hydrogen atom or a methyl group, R ₃ is an ester bond or an ether bond, and x is an integer of 1 or 2. However, R ₂ When R is a methyl group, R ₃ is not an ether bond.)   An ink jet recording method for recording on a recording medium by discharging a plurality of inks from an ink jet recording head, wherein each of the inks constituting the ink set according to claim 1 is used as the plurality of inks. Inkjet recording method.   The ink set according to claim 1, comprising: an ink storage portion that stores a plurality of inks; and a recording head that discharges each of the plurality of inks. The ink set according to claim 1. An ink jet recording apparatus using each ink.