Oil-based inkjet ink

Abstract

To provide an oil-based inkjet ink that has improved dischargeability, prevents a printed material including the ink from degrading or deforming a resin product in contact therewith, and also prevents toner transfer to the printed material.SOLUTION: An oil-based inkjet ink contains a diester solvent (A) with a dispersion term δD of 15.7 MPa1 / 2 or less in Hansen solubility parameters, a monoester solvent (B) with a boiling point of 300°C or higher, and a colorant. In one example, the mass ratio between the diester solvent (A) and the monoester solvent (B) preferably satisfies A / B=3 / 7-3 / 2.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an oil-based ink-jet ink. [Background technology]

[0002] Inkjet recording is a method of ejecting highly fluid inkjet ink as droplets from a fine nozzle to record an image on a recording medium placed opposite the nozzle. This method has been rapidly spreading in recent years because it allows low-noise, high-speed printing. Inks used in such inkjet recording methods include aqueous inks containing water as the main solvent, ultraviolet-curable inks (UV inks) containing a high content of polymerizable monomers as the main component, and hot-melt inks (solid inks) containing a high content of wax as the main component, as well as so-called non-aqueous inks containing a non-aqueous solvent as the main solvent. Non-aqueous inks can be classified into solvent inks (solvent-based inks) whose main solvent is a volatile organic solvent, and oil-based inks (oil-based inks) whose main solvent is a low-volatility or non-volatile organic solvent. Solvent inks dry on the recording medium mainly by the evaporation of the organic solvent, whereas oil-based inks mainly penetrate into the recording medium.

[0003] Patent Document 1 (JP 2014-15491 A) proposes a non-aqueous pigment ink containing a pigment, a non-aqueous solvent, a non-water-soluble resin, and a water-soluble resin, in which the non-water-soluble resin is an acrylic polymer and the water-soluble resin is polyethyleneimine. This ink has the advantages of being able to suppress strike-through while realizing low ink viscosity and excellent storage stability, and being able to achieve high print density. This ink also has the advantage of being able to suppress the occurrence of satellites.

[0004] On the other hand, if a printed matter with an image formed using oil-based inkjet ink is stored in a clear file made of polypropylene (PP) or the like, there is a problem that the clear file will warp and become deformed. One of the reasons for this is thought to be that when the clear file comes into contact with the printed surface, one side of the clear file swells due to the ink components. In this way, when the printed surface comes into contact with a resin product, the resin product may be altered, and in the case of film-like resin products, deformation may occur. It has become clear that the impact of such printed matter on resin products is greatly influenced by the solvent, one of the ink components. Furthermore, if a printed item printed with ink that contains a large amount of highly polar solvent is placed on top of a printed item printed using an electrophotographic method that uses toner, the highly polar solvent may dissolve the toner, causing the printed items to stick together.

[0005] Patent Document 2 (JP 2013-166813 A) proposes a non-aqueous inkjet ink that suppresses deformation of clear files, reduces toner solubility, and improves ejection performance. The ink contains a pivalic acid ester having 25 or more carbon atoms and an ethylene glycol monoalkyl ether as an organic solvent. Patent Document 3 (JP 2018-141123 A) proposes an oil-based inkjet ink that contains a specific modified silicone oil as a non-aqueous solvent, preventing deformation of clear files, improving the wettability of the ink to the nozzle plate, and improving ejection performance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-15491 A [Patent Document 2] JP 2013-166813 A [Patent Document 3] JP 2018-141123 A Summary of the Invention [Problem to be solved by the invention]

[0007] Although the inks disclosed in Patent Documents 2 and 3 are effective in suppressing deformation of clear files, there is room for improvement in the ejection performance during printing. Furthermore, if a highly polar solvent is used to prevent deformation of a clear file, when a printed matter on which an oil-based ink image is formed comes into contact with a printed matter on which a toner image is formed, the toner image may be more likely to dissolve due to the oil-based ink image, which may cause toner transfer.

[0008] An object of the present invention is to improve the ejection properties, suppress the occurrence of deterioration or deformation of a resin product due to a printed matter, and prevent the transfer of toner to the printed matter. [Means for solving the problem]

[0009] In one aspect of the present invention, the dispersion term δ in the Hansen solubility parameter D is 15.7MPa 1 / 2 The oil-based inkjet ink contains a diester solvent (A) as shown below, a monoester solvent (B) having a boiling point of 300° C. or higher, and a coloring material. Effect of the Invention

[0010] According to one embodiment of the present invention, it is possible to improve the ejection properties, suppress the occurrence of deterioration or deformation of a resin product due to a printed matter, and prevent the toner from being transferred to the printed matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described below using an embodiment. The following embodiment is not intended to limit the present invention.

[0012] The oil-based inkjet ink according to one embodiment (hereinafter, simply referred to as oil-based ink or ink) has a dispersion term δ D is 15.7MPa 1 / 2The present invention is characterized in that it contains a diester solvent (A) having a boiling point of 300° C. or higher, a monoester solvent (B) having a boiling point of 300° C. or higher, and a colorant. This oil-based inkjet ink can improve the ejection properties, suppress the deterioration or deformation of resin products caused by printed matter, and prevent toner transfer to printed matter. For example, deformation of a thin resin film such as a clear file can be prevented when the printed matter comes into contact with the printed matter. In addition, this oil-based inkjet ink can prevent the printed surface of the printed matter from being soiled. Hereafter, the dispersion term δ in the Hansen solubility parameters D is 15.7MPa 1 / 2 The diester solvent (A) below is also referred to as diester solvent (A), and the monoester solvent (B) having a boiling point of 300° C. or higher is also referred to as monoester solvent (B).

[0013] When storing printed material in a polypropylene (PP) clear file folder, if the ink on the surface of the printed material comes into contact with the inside of the clear file and the inside of the clear file swells due to the effects of the ink components, the clear file may deform and warp outward. This can also occur with thin resin products such as clear files. In addition, the surface of strong resin products may change, for example reducing weather resistance and durability. On the other hand, in printed matter formed using a toner, the toner often exhibits high polarity, and therefore when a printed matter on which a toner image is formed comes into contact with a high polarity component, the toner image may dissolve and transfer to a mating material. When a high polarity component remains on a printed matter on which an oil-based ink image is formed by oil-based ink, the toner may easily dissolve when the oil-based ink image comes into contact with a toner image, and the toner image may be transferred to the oil-based ink image. This phenomenon is also called toner transfer. Even if the toner image is not transferred, the toner image may be altered by the high polarity component of the oil-based ink image, resulting in a decrease in image quality. Toner transfer is particularly likely to occur in printed matter formed using a styrene-acrylic copolymer type toner.

[0014] There is a concept called Hansen solubility parameter for predicting interactions between substances. The cohesive energy density of a substance is expressed as δ D (dispersion term), δ P (polar term), and δ H (hydrogen bond term), and the interaction can be predicted from the parameter distance between substances. Since clear files and toner, which are polymers, also have this parameter, the interaction with a solvent (solubility) can be expressed as a numerical value. δ D is the size or weight of the molecule, δ P is the charge imbalance in the molecule, δ H is influenced by the presence or absence of hydrogen bonds.

[0015] δ solubility D , δ P , and δ H When the polymer is divided into three components and expressed three-dimensionally, a solvent with parameters outside the range of the three-dimensional space represented by the three components of the polymer is a solvent that has a weak interaction with the polymer. D Therefore, in order for the solvent to suppress the interaction with the polymer, the δ D It is important to keep δ low. P and δ H It is important to select a solvent that has The polymer components of the clear file and the toner have parameters outside the three-dimensional space, so δ P and δ H From this viewpoint, it was found that the diester structure is suitable. However, the diester structure is generally D Since is large, δ D In terms of the three-dimensional space of the polymer component, many of them fall within the range of the three-dimensional space. Therefore, among the solvents having a diester structure, δ D By selecting a solvent with a small δ, it is possible to suppress the interaction with the polymer component. DSolvents with small molecular weights are less likely to interact with clear files and therefore can prevent deformation of the clear files, and are also less likely to interact with the polymer components of the toner, thereby suppressing toner dissolution and preventing toner transfer.

[0016] However, δ D A diester solvent having a small δ has a relatively low solubility in a toner image by itself, but dissolves the toner to some extent. D A diester solvent with a small δ is combined with a monoester solvent. D , δ P , and δ H The three components of this solvent are small. By combining these two solvents, it is possible to reduce the interaction with the polymer components of the toner, improving the problem of the solubility of the toner image due to the ink components. Another problem is that the monoester solvent interacts with the clear file. Therefore, a high boiling point solvent is selected from among the monoester solvents to prevent the monoester solvent from volatilizing from the printed matter, suppressing contact between the clear file and the monoester solvent, and preventing deformation of the clear file. Although not bound by the above theory, the dispersion term δ in the Hansen solubility parameter is calculated based on the above theory. D is 15.7MPa 1 / 2 By combining the diester solvent (A) below with the monoester solvent (B) having a boiling point of 300° C. or higher, deformation of the clear file and toner transfer can be prevented.

[0017] Furthermore, the monoester solvent (B) tends to have a high surface tension due to its ester structure. By using an ink containing the monoester (B) with high surface tension, the surface tension of the ink droplets ejected from the nozzles is increased, making it possible to prevent the generation of satellite droplets as minute droplets from the main ink droplet. In the inkjet recording method, ink droplets ejected from the nozzle fly with a trailing tail, and there is a time and speed difference between the leading and trailing parts of the flying droplets. This can cause unwanted tiny droplets (satellites) to be generated in addition to the leading main droplet. When ink droplets are ejected from the nozzle and adhere to the recording medium, if the satellites land on the recording medium at a position different from the main ink droplets, they can cause the printed surface to be soiled. In addition, the satellites turn into mist and float in the space between the nozzle face of the inkjet head and the transport path, and can adhere to the recording medium at a position different from the ink droplets, reducing the print quality, or can adhere to the inside of the device and soil it.

[0018] Oil-based ink has a dispersion term δ D is 15.7MPa 1 / 2 It may comprise a diester solvent (A) which is:

[0019] In terms of Hansen solubility parameters, the diester solvent (A) preferably has the following properties: Dispersion term δ of diester solvent (A) D is 15.7MPa 1 / 2 The following is preferable: 15.6MPa 1 / 2 The following is more preferable. This makes it difficult for the polymer component of the clear file and the toner to interact with each other, and makes it possible to prevent deformation of the clear file and toner transfer. Dispersion term δ of diester solvent (A) D From the viewpoint of preventing a decrease in surface tension, 1 / 2 More than 14MPa is preferable. 1 / 2 More preferably, 14.5MPa or more 1 / 2 The above is even more preferable. By including a solvent with high surface tension in the ink, it is possible to prevent satellites from being generated from the ink droplets ejected from the nozzles, and to prevent staining of the printed surface. From the viewpoint of suppressing the generation of satellites, the dispersion term δ of the diester solvent (A) is D is 15.0MPa 1 / 2 The above is preferred.

[0020] Polarity term δ of diester solvent (A) P and hydrogen bond term δ H are components that are affected by the charge imbalance in the molecule and the presence or absence of hydrogen bonds, and are specified within the following ranges depending on the diester structure. Since these ranges fall outside the three-dimensional space of the polymer components of the clear file and toner, the diester solvent (A) acts to help prevent deformation of the clear file and toner transfer. Polarity term δ of diester solvent (A) P 1.0~5.0MPa 1 / 2 is preferably 1.0 to 4.0 MPa 1 / 2 More preferably, 1.5 to 3.0 MPa 1 / 2 is more preferred. Hydrogen bond term δ of diester solvent (A) H 1.0 to 10.0 MPa 1 / 2 is preferably 1.5 to 6.0 MPa 1 / 2 More preferably, 2.0 to 4.0 MPa 1 / 2 is more preferred.

[0021] A method for calculating the Hansen solubility parameter (HSP value) is described below. In this disclosure, the three-dimensional Hansen solubility parameter proposed by Hansen in 1967 is used. The Hansen solubility parameter was introduced by Hildebrand and is expressed as the dispersion term δ D , polarity term δ P , hydrogen bond term δ H It is divided into three components and expressed in three-dimensional space. The dispersion term indicates the effect due to dispersion forces, the polar term indicates the effect due to dipole-dipole forces, and the hydrogen bond term indicates the effect of hydrogen bonding forces. More details are explained in POLYMER HANDBOOK, FOURTH EDITION (Editors: J. BRANDRUP, EHIMMERGUT, and E.A. GRULKE), etc. Specifically, the calculation was performed using the Hansen solubility parameter calculation software "HSPiP: Hansen Solubility Parameters in Practice" ver. 5.3 by Charles M. Hansen et al. The same applies below.

[0022] The boiling point of the diester solvent (A) is not particularly limited, but is preferably less than 360° C. A low boiling point solvent has a relatively low viscosity, and therefore the ink can be more improved in ejection properties by including a low boiling point solvent in the ink. The diester solvent (A) has a dispersion term δ in the above range. D By providing the above, deformation of the clear file and toner transfer can be prevented even in the case of a low boiling point and low viscosity. The boiling point of the diester solvent (A) is preferably less than 360° C., and more preferably 300° C. or lower. In order to prevent the solvent from volatilizing from the inkjet nozzle, the boiling point of the diester solvent (A) is preferably 150° C. or higher, more preferably 200° C. or higher, and more preferably 250° C. or higher. In this disclosure, the boiling point of a solvent refers to the boiling point at 1 atmospheric pressure. The boiling point of a solvent can be measured in accordance with the (1) initial boiling point method of JIS K2254 "Petroleum products - Distillation test method". The same applies below.

[0023] The surface tension of the diester solvent (A) is preferably 20 mN / m or more at 23°C. The diester solvent (A) has a dispersion term δ in the above range. D By including a solvent with high surface tension in the ink, it is possible to prevent satellites from being generated from the ink droplets ejected from the nozzles, and thus prevent the printing surface from being soiled. The surface tension of the diester solvent (A) is preferably 20 mN / m or more, more preferably 22 mN / m or more, and even more preferably 26 mN / m or more at 23° C. This can further prevent the generation of satellites. The surface tension of the diester solvent (A) is not particularly limited, but from the viewpoints of solvent miscibility and pigment affinity, it is preferably 40 mN / m or less, and more preferably 35 mN / m or less at 23°C. In the present disclosure, the surface tension of a solvent is a value measured by a maximum bubble pressure method under the measurement conditions of 23°C and 0.05Hz. For example, a surface tension measuring device (SITA Messtechnik GmbH science line t60 (product name) manufactured by SITA Process Solutions) can be used as the measuring device. The same applies below.

[0024] The viscosity of the diester solvent (A) at 23° C. is preferably from 1 to 20 mPa·s, more preferably from 1 to 10 mPa·s, and even more preferably from 2 to 8 mPa·s. In the present disclosure, the solvent viscosity is a value measured at 23° C. using a rotational viscometer. For example, a "Rheometer MCR302" manufactured by Anton Paar Japan Co., Ltd. can be used as the viscosity measuring device. The same applies below.

[0025] The diester solvent (A) is a compound having two ester bonds in one molecule. The diester solvent (A) is preferably in a liquid state at 23°C. The diester solvent (A) may be an ester of a dicarboxylic acid having two carboxy groups and a monohydric alcohol, an ester of a monocarboxylic acid and a diol having two hydroxyl groups, a carbonic acid diester, etc. Among these, a dicarboxylic acid diester, a diol diester, or a combination thereof is preferred. In the diester solvent (A), the hydrocarbon groups contained in the units derived from the acid component and the units derived from the alcohol component may each independently be saturated or unsaturated hydrocarbon groups, and may be chain hydrocarbon groups, alicyclic hydrocarbon groups, or aromatic hydrocarbon groups. If the chain hydrocarbon group is a chain hydrocarbon group, it may be linear or branched. Preferably, in the diester solvent (A), the units derived from the acid component and the units derived from the alcohol component each independently have a saturated chain hydrocarbon group, which may be linear or branched.

[0026] In the diester solvent (A), some or all of the hydrogen atoms may be substituted. In view of the Hansen solubility parameter and the stability as a solvent, the substituents are preferably fluorine atoms. When the diester solvent (A) has a substituent, it is preferable that the substituent is introduced to the carbon atom between two ester bonds rather than to the terminal group of the ester bond. This allows the dispersion term δ to be reduced while maintaining the solvent miscibility. D can be set to a more preferable range.

[0027] The diester solvent (A) preferably has 6 to 30 carbon atoms in one molecule, more preferably 8 to 22, and even more preferably 8 to 20. Within this range, the boiling point and viscosity of the diester solvent (A) become more appropriate, and the dischargeability can be further improved.

[0028] An example of the diester solvent (A) may include a diester represented by the following general formula (1): [ka] In the general formula (1), R 1 and R 2 are each independently an isopropyl group, a sec-butyl group, or a tert-butyl group.

[0029] The diester represented by the general formula (1) is an ester of 2,2,4-trimethyl-1,3-pentanediol with a monocarboxylic acid, such as isobutyric acid, 2-methylbutanoic acid, or pivalic acid. The diester represented by the general formula (1) is R 1 and R 2 may be different from each other, but are preferably the same from each other. By increasing the symmetry of the molecular structure, the polarity of the molecule is decreased, which reduces the solubility of the toner image by the ink components, and makes it possible to more effectively prevent toner transfer.

[0030] In the diester represented by the general formula (1), some or all of the hydrogen atoms may be substituted with fluorine atoms. For example, the hydrogen atoms at the site derived from 2,2,4-trimethyl-1,3-pentanediol may be substituted with fluorine atoms, the hydrogen atoms at the site derived from monocarboxylic acid may be substituted with fluorine atoms, or all of the hydrogen atoms contained in one molecule may be substituted with fluorine atoms. This allows the dispersion term δ of the Hansen solubility parameter to be D Therefore, it is possible to prevent the staining of the printed surface caused by satellites.

[0031] Other examples of the diester solvent (A) may include fluorine-substituted diesters having 8 to 22 carbon atoms in one molecule, in which 6 or more of the hydrogen atoms are substituted with fluorine atoms. The fluorine-substituted diester may be an esterification product in which at least one of the acid component and the alcohol component has a fluorine atom. For example, in an esterification product of a dicarboxylic acid and a monohydric alcohol, or an esterification product of a monocarboxylic acid and a diol, a compound having a fluorine atom in at least one of the acid component and the alcohol component can be used.

[0032] Examples of dicarboxylic acids having a fluorine atom include hexadecafluorosebacic acid, hexafluoroglutaric acid, dodecafluorosuberic acid, and octafluoroadipic acid.

[0033] Examples of monocarboxylic acids having a fluorine atom include heptafluorobutyric acid, 4,4,4-trifluorobutyric acid, tricosafluorododecanoic acid, 3,3,3-trifluoropropionic acid, tricosafluorododecanoic acid, pentafluoropropionic acid, pentadecafluorooctanoic acid, nonadecafluorodecanoic acid, and nonafluorovaleric acid.

[0034] Examples of monohydric alcohols having fluorine atoms include 4,4,4-trifluoro-1-butanol, 2-(perfluorohexyl)ethanol, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoro-1-propanol, 1H,1H-pentadecafluoro-1-octanol, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 1H,1H-nonadecafluoro-1-decanol, 1H,1H-nonafluoro-1-pentanol, 1H,1H,2H,2H-nonafluoro-1-hexanol, 1H,1H-heptadecafluoro-1-nonanol, and 2,2,3,3,4,4,4-heptafluoro-1-butanol.

[0035] Examples of dihydric alcohols having fluorine atoms include 1H,1H,10H,10H-hexadecafluoro-1,10-decanediol, hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol, 1H,1H,10H,10H-hexadecafluoro-1,10-decanediol, and 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-octanediol.

[0036] The unsubstituted monohydric alcohol, dihydric alcohol, monocarboxylic acid, and dicarboxylic acid may be saturated or unsaturated linear or branched chain monohydric alcohol, dihydric alcohol, monocarboxylic acid, and dicarboxylic acid, each of which has carbon atoms in the range of 8 to 22 in one molecule of the diester. Preferred are saturated linear or branched chain monohydric alcohol, dihydric alcohol, monocarboxylic acid, and dicarboxylic acid.

[0037] The synthesis method of the diester solvent (A) is not particularly limited, and the diester solvent (A) can be obtained by esterification reaction of an acid component and an alcohol component according to a conventional method. An example of the synthesis method of the diester solvent (A) is described below. Note that the diester solvent (A) is not limited to those synthesized by the following synthesis method.

[0038] The ester of a dicarboxylic acid with a monohydric alcohol can be obtained by reacting a dicarboxylic acid or an anhydride thereof with a monohydric alcohol. The dicarboxylic acid and the monohydric alcohol can be the same as those described above. The ester of a monocarboxylic acid and a diol can be obtained by reacting a monocarboxylic acid with a diol. The monocarboxylic acid and the diol can be the same as those described above. In the esterification reaction, the reaction temperature can be adjusted in the range of 80 to 230°C depending on the types of acid and alcohol components. The reaction time can be adjusted in the range of 1 to 48 hours depending on the types of acid and alcohol components and the amount of raw materials used. It is preferable to remove the water generated during the esterification reaction. The reaction can be carried out by putting the two components into a synthesis solvent such as cyclohexane. Dicarboxylic acids and monohydric alcohols react in a molar ratio of 1:2, so it is recommended to feed the raw materials to the synthesis system in this molar ratio. Monocarboxylic acids and diols react in a molar ratio of 2:1, so it is recommended to feed the raw materials to the synthesis system in this molar ratio. In the reaction, a suitable amount of a catalyst such as concentrated sulfuric acid, p-toluenesulfonic acid monohydrate, or methanesulfonic acid may be used.

[0039] Specific examples of the diester represented by the general formula (1) include 2,2,4-trimethyl-1,3-pentanediol diisobutyrate and its fluorine-substituted derivatives, 2,2,4-trimethyl-1,3-pentanediol di-2-methylbutyrate and its fluorine-substituted derivatives, and the like.

[0040] Specific examples of fluorine-substituted diesters include dimethyl octafluoroadipate, bis(2,2,3,3,3-pentafluoro-1-propyl) adipate, bis(4,4,4-trifluoro-1-butyl) adipate, and 1,6-hexanediol bis(pentafluoropropionate). The above diester solvents (A) can be used alone or in combination of two or more kinds. When the oil-based ink contains two or more diester solvents (A), each of the diester solvents (A) has the above δ D It is preferable that the mixed solvent of two or more diester solvents (A) satisfies the above-mentioned δ D It is preferable that the range of physical property values ​​such as the above be satisfied.

[0041] The diester solvent (A) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total amount of the non-aqueous solvent. This allows the diester solvent (A) to exhibit the property of being less likely to interact with the polymer component, and can better prevent deformation of the clear file and toner transfer. In addition, the ink as a whole exhibits high surface tension, and can better prevent staining of the printed surface caused by satellites. The diester solvent (A) is preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 60% by mass or less, based on the total amount of the non-aqueous solvent. By combining the diester solvent (A) with the monoester solvent (B) within a range in which the content of the diester solvent (A) exhibiting high polarity is limited, dissolution of the toner image by the ink components can be suppressed, and toner transfer can be further prevented. For example, the amount of the diester solvent (A) is preferably from 10 to 90 mass %, more preferably from 20 to 80 mass %, and even more preferably from 30 to 60 mass %, based on the total amount of the non-aqueous solvent.

[0042] The amount of the diester solvent (A) is preferably from 5 to 90% by mass, more preferably from 15 to 80% by mass, and even more preferably from 25 to 60% by mass, based on the total amount of the ink.

[0043] The oil-based ink may contain a monoester solvent (B) having a boiling point of 300° C. or higher. The boiling point of the monoester solvent (B) is preferably 300° C. or higher, more preferably 330° C. or higher, and even more preferably 360° C. or higher. By using a combination of the diester solvent (A) and the monoester solvent (B), toner transfer can be more effectively prevented. Furthermore, by using a monoester solvent (B) with a high boiling point, the volatilization of the solvent from the printed matter can be suppressed, the penetration of the solvent into the clear file can be suppressed, and deformation of the clear file can be more effectively prevented. The boiling point of the monoester solvent (B) is not particularly limited, but since a solvent with a high boiling point has a high viscosity and is one of the causes of reduced dischargeability, the boiling point is preferably 450° C. or lower, and more preferably 400° C. or lower.

[0044] In terms of Hansen solubility parameters, the monoester solvent (B) preferably has the following properties: Dispersion term δ of monoester solvent (B) D is 17.0MPa 1 / 2 The following is preferable: 16.5MPa 1 / 2 Less than 16.1MPa is more preferable. 1 / 2 More preferably, the monoester solvent (B) alone has a δ D is in a relatively large range, but when a diester solvent (A) is combined with a monoester solvent (B), the δ D When the δ of the monoester solvent (B) is in this range, the ink component is less likely to interact with the polymer component of the toner, and toner transfer can be more effectively prevented. Since the monoester solvent (B) has a high boiling point, it is possible to prevent deformation of clear files, and the δ of the monoester solvent (B) is D By selecting a size smaller than this range, deformation of the clear file can be prevented more effectively. Dispersion term δ of monoester solvent (B) D From the viewpoint of preventing a decrease in surface tension, 1 / 2 More than 14MPa is preferable. 1 / 2 More preferably, 15MPa or more 1 / 2The above is even more preferable. By including a solvent with high surface tension in the ink, it is possible to prevent satellites from being generated from the ink droplets ejected from the nozzles, and to further prevent staining of the printed surface.

[0045] Polarity term δ of monoester solvent (B) P and hydrogen bond term δ H are components that are affected by the charge imbalance in the molecule and the presence or absence of hydrogen bonds, and are greatly affected by the monoester structure. In many cases, the Hansen solubility parameters of the monoester solvent (B) are outside the three-dimensional space of the toner polymer components, so the monoester solvent (B) acts to help prevent toner transfer. Polarity term δ of monoester solvent (B) P 1.0~5.0MPa 1 / 2 is preferably 1.0 to 4.0 MPa 1 / 2 More preferably, 1.5 to 3.0 MPa 1 / 2 is more preferred. Hydrogen bond term δ of monoester solvent (B) H 1.0~5.0MPa 1 / 2 is preferably 1.0 to 4.0 MPa 1 / 2 More preferably, 1.5 to 3.0 MPa 1 / 2 is more preferred.

[0046] The surface tension of the monoester solvent (B) at 23° C. is preferably 20 mN / m or more, more preferably 25 mN / m or more, and even more preferably 28 mN / m or more. The monoester solvent (B) tends to have a relatively high surface tension. By including a solvent with a high surface tension in the ink, it is possible to prevent satellites from being generated from the ink droplets ejected from the nozzles and to prevent staining of the printed surface. The surface tension of the monoester solvent (B) is not particularly limited, but from the viewpoints of solvent miscibility and pigment affinity, it is preferably 40 mN / m or less, and more preferably 35 mN / m or less at 23°C.

[0047] The viscosity of the monoester solvent (B) is preferably 1 to 30 mPa·s, more preferably 1 to 20 mPa·s, and even more preferably 5 to 15 mPa·s at 23° C. The monoester solvent (B) has a high boiling point and therefore tends to have a high viscosity, but when the viscosity of the monoester solvent (B) is in this range, it is possible to further prevent the decrease in dischargeability by combining it with the diester solvent (A).

[0048] The monoester solvent (B) is a compound having one ester bond in one molecule. The monoester solvent (B) is preferably liquid at 23°C. As the monoester solvent (B), a monocarboxylic acid monoester or the like can be used. In the monoester solvent (B), the hydrocarbon groups contained in the units derived from the acid component and the units derived from the alcohol component may each independently be saturated or unsaturated hydrocarbon groups, and may be chain hydrocarbon groups, alicyclic hydrocarbon groups, or aromatic hydrocarbon groups. If the chain hydrocarbon group is a chain hydrocarbon group, it may be linear or branched. Preferably, in the monoester solvent (B), the unit derived from the acid component and the unit derived from the alcohol component each independently have a saturated chain-like hydrocarbon group, and may be a straight chain or a branched chain. From the viewpoint of preventing a decrease in the solubility of the toner image, the monoester solvent (B) is preferably a monoester of a saturated fatty acid and a saturated alcohol.

[0049] The number of carbon atoms in one molecule of the monoester solvent (B) is preferably 14 to 30, more preferably 18 to 28, and even more preferably 20 to 24. Within this range, the boiling point and viscosity of the monoester solvent (B) become more appropriate, and the dischargeability can be further improved.

[0050] Specific examples of the monoester solvent (B) include isostearyl neopentanoate, isocetyl isooctanoate, isopropyl palmitate, 2-octyldecyl neopentanoate, 2-octyldodecyl neopentanoate, isotridecyl isononanoate, isononyl isononanoate, isodecyl isononanoate, hexyl laurate, butyl stearate, isopropyl isostearate, 5,7,7-trimethyl 2-(1,3,3-trimethylbutyl)octyl 3,5,5-trimethylhexanoate, 1,1,-diethylpropyl 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyloctanoate, 2-hexyldecyl 3,5,5-trimethylhexanoate, 3,7-dimethyloctanol 9,9-dimethyldecanoate, and 3,5,5-trimethylhexyl 9,9-dimethyldecanoate.

[0051] The above monoester solvents (B) can be used alone or in combination of two or more kinds. When the oil-based ink contains two or more monoester solvents (B), it is preferable that each of the monoester solvents (B) satisfies the above-mentioned range of physical property values ​​such as boiling point, etc. More preferably, the mixed solvent of two or more monoester solvents (B) satisfies the above-mentioned range of physical property values ​​such as boiling point, etc.

[0052] The monoester solvent (B) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on the total amount of the non-aqueous solvent. By combining the diester solvent (A) and the monoester solvent (B), the solubility of the toner image by the ink components can be reduced, and toner transfer can be more effectively prevented. The content of the monoester solvent (B) is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, based on the total amount of the non-aqueous solvent, thereby limiting the content of the monoester solvent (B) which exhibits a relatively high viscosity, lowering the viscosity of the ink, and further improving the ejection properties. For example, the amount of the monoester solvent (B) is preferably from 10 to 90 mass %, more preferably from 20 to 80 mass %, and even more preferably from 30 to 70 mass %, based on the total amount of the non-aqueous solvent.

[0053] The amount of the diester solvent (B) is preferably from 5 to 90% by mass, more preferably from 15 to 80% by mass, and even more preferably from 25 to 70% by mass, based on the total amount of the ink.

[0054] The mass ratio A / B of the diester solvent (A) to the monoester solvent (B) is preferably from 1 / 9 to 9 / 1, more preferably from 1 / 4 to 4 / 1, and further preferably from 3 / 7 to 3 / 2. The mass ratio A / B is preferably 3 / 7 or more, more preferably 2 / 3 or more. This ensures a sufficient amount of diester solvent (A) and prevents deformation of the clear file. In addition, by controlling the amount of monoester solvent (B) to an appropriate amount, the ink viscosity can be prevented from increasing, and the ejection properties can be improved. The mass ratio A / B is preferably 3 / 2 or less, and by combining the diester solvent (A) with the monoester solvent (B), the solubility of the toner image by the ink components can be reduced, and toner transfer can be more effectively prevented.

[0055] The total amount of the diester solvent (A) and the monoester solvent (B) is preferably from 10 to 98% by mass, more preferably from 50 to 95% by mass, and even more preferably from 70 to 90% by mass, based on the total amount of the ink.

[0056] In addition to the diester solvent (A) and the monoester solvent (B), the oil-based inkjet ink may contain other non-aqueous solvents as long as the effects of the present invention are not impaired. As the other non-aqueous solvent, either a non-polar organic solvent or a polar organic solvent can be used. Note that, in one embodiment, it is preferable to use a water-insoluble organic solvent that is not uniformly mixed with the same volume of water at 20° C. under 1 atmosphere as the non-aqueous solvent. Examples of other non-aqueous solvents include non-polar organic solvents such as petroleum-based hydrocarbon solvents, such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; polar organic solvents, such as higher alcohol solvents and higher fatty acid solvents. The oil-based ink may also contain other fatty acid ester solvents other than the diester solvent (A) and the monoester solvent (B).

[0057] Examples of aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents include non-aqueous solvents such as paraffin, isoparaffin, and naphthenic solvents. Commercially available products include No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Cactus normal paraffin N-10, Cactus normal paraffin N-11, Cactus normal paraffin N-12, Cactus normal paraffin N-13, Cactus normal paraffin N-14, Cactus normal paraffin N-15H, Cactus normal paraffin YHNP, Cactus normal paraffin SHNP, and Isozol. Preferred examples of the present invention include 300, Isozol 400, Teclain N-16, Teclain N-20, Teclain N-22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No. 7, Naphtesol 160, Naphtesol 200, and Naphtesol 220 (all manufactured by JXTG Nippon Oil & Energy Corporation); Isopar G, Isopar H, Isopar L, Isopar M, Exxor D40, Exxor D60, Exxor D80, Exxor D95, Exxor D110, and Exxor D130 (all manufactured by Exxon Mobil Corporation). Preferred examples of the aromatic hydrocarbon solvent include Grade Alkene L, Grade Alkene 200P (all manufactured by JXTG Nippon Oil & Energy Corporation), Solvesso 100, Solvesso 150, Solvesso 200, and Solvesso 200ND (all manufactured by Exxon Mobil Corporation). The initial distillation point of the petroleum-based hydrocarbon solvent is preferably 100° C. or higher, more preferably 150° C. or higher, and even more preferably 200° C. or higher. The initial distillation point can be measured in accordance with JIS K0066 “Distillation test method for chemical products.”

[0058] Preferred examples of the polar organic solvent include higher alcohol solvents, higher fatty acid solvents, and other fatty acid ester solvents. Examples of higher alcohol solvents include isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, tetradecanol, decyltetradecanol, 1-octadecanol, etc. The number of carbon atoms in one molecule of the higher alcohol solvent is preferably 6 or more, and more preferably 12 to 20. Examples of higher fatty acid solvents include lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, isostearic acid, etc. The number of carbon atoms in one molecule of the higher fatty acid solvent is preferably 12 or more, and more preferably 14 to 20. Examples of other fatty acid ester solvents include 2-ethylhexyl isononanoate, methyl laurate, isopropyl laurate, etc. The number of carbon atoms in one molecule of the other fatty acid ester solvent is preferably 13 or more.

[0059] The boiling point of polar organic solvents such as fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents is preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher. When other non-aqueous solvents are used, they are preferably solvents that can form a single phase with the diester solvent (A) and the monoester solvent (B). As the other non-aqueous solvent, from the viewpoint of suppressing deformation of the clear file, in order to suppress volatilization of the solvent from the printed surface, it is preferable that the non-polar solvent has a high initial distillation point, and that the polar solvent has a high boiling point.

[0060] The ink may include a pigment, a dye, or a combination thereof as the colorant. Examples of the pigment include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments; and inorganic pigments such as carbon black and metal oxides. Examples of the azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of the phthalocyanine pigments include metal phthalocyanine pigments such as copper phthalocyanine pigments, and metal-free phthalocyanine pigments. Examples of the polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). Examples of the carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of the metal oxides include titanium oxide and zinc oxide. These pigments may be used alone or in combination of two or more.

[0061] From the viewpoints of ejection stability and storage stability, the average particle size of the pigment is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and even more preferably 100 nm or less, as a volume-based average value in a particle size distribution measured by a dynamic light scattering method. The amount of the pigment is usually 0.01 to 20% by mass based on the total amount of the ink, and from the viewpoints of print density and ink viscosity, it is preferably 1 to 15% by mass, and more preferably 4 to 10% by mass.

[0062] In order to stably disperse the pigment in the ink, a pigment dispersant can be used together with the pigment. Preferred examples of pigment dispersants include hydroxyl group-containing carboxylates, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, copolymers of vinylpyrrolidone and long-chain alkenes, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, polyoxyethylene alkyl phosphates, and polyester polyamines.

[0063] Examples of commercially available pigment dispersants include "Antaron V216 (vinylpyrrolidone-hexadecene copolymer) and V220 (vinylpyrrolidone-eicosene copolymer)" (all trade names) manufactured by ISP Japan Co., Ltd.; "Solsperse 13940 (polyester amine type), 16000, 17000, 18000 (fatty acid amine type), 11200, 24000, 28000" (all trade names) manufactured by Lubrizol Japan Co., Ltd.; and "EFKA 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)" (all trade names) manufactured by BASF Japan Ltd. "Disparlon KS-860, KS-873N4 (amine salt of polyester)" (all trade names) manufactured by Kusumoto Chemicals Co., Ltd.; "Discol 202, 206, OA-202, OA-600 (multi-chain polymer nonionic)" (all trade names) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; "DISPERBYK2155, 9077" (all trade names) manufactured by BYK Japan KK; "Hypermer KD2, KD3, KD11, KD12" (all trade names) manufactured by Croda Japan Co., Ltd.; and "Solsperse 24000SC, 24000GR, 32000, 33000, 3900, etc." (all trade names) manufactured by Lubrizol Japan Co., Ltd.

[0064] The amount of the pigment dispersant is sufficient so long as it can disperse the pigment sufficiently in the ink, and can be appropriately set. For example, the pigment dispersant can be blended in a mass ratio of 0.1 to 5 parts by mass of pigment per 1 part by mass of pigment, and preferably 0.3 to 1. The pigment dispersant can be blended in an amount of 0.01 to 10% by mass, preferably 0.1 to 8% by mass, and more preferably 1 to 8% by mass, based on the total amount of the ink.

[0065] As the dye, any dye generally used in the art can be used. In the case of oil-based ink, it is preferable to use an oil-soluble dye, since the dye has affinity for the non-aqueous solvent of the ink and thus has better storage stability. Examples of oil-soluble dyes include azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, phthalocyanine dyes, metal phthalocyanine dyes, etc. These may be used alone or in combination. The amount of the dye is usually 0.01 to 20% by mass based on the total amount of the ink, and from the viewpoints of print density and ink viscosity, it is preferably 1 to 15% by mass, and more preferably 5 to 10% by mass.

[0066] In addition to the above components, the oil-based ink may contain various additives as long as they do not impair the effects of the present invention. As additives, nozzle clogging inhibitors, antioxidants, conductivity regulators, viscosity regulators, surface tension regulators, oxygen absorbers, etc. may be appropriately added. The types of these are not particularly limited, and those used in the relevant field may be used.

[0067] The method for producing the oil-based ink is not particularly limited, but one method is to prepare the ink by mixing and stirring each component all at once or in portions. Specifically, the ink can be prepared by dispersing all the components in a dispersing machine such as a bead mill, either all at once or in portions, and passing the mixture through a filtering machine such as a membrane filter, if desired.

[0068] The suitable range of viscosity for an oil-based inkjet ink varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, etc., but in general, it is preferably 5 to 30 mPa·s, more preferably 5 to 15 mPa·s, and even more preferably 8 to 13 mPa·s at 23° C. In the present disclosure, the ink viscosity can be measured by the same measurement method as for the solvent viscosity.

[0069] The printing method using the inkjet ink is not particularly limited, and may be any method such as a piezoelectric method, an electrostatic method, a thermal method, etc. When an inkjet recording device is used, it is preferable to eject the ink according to one embodiment from an inkjet head based on a digital signal, and to cause the ejected ink droplets to adhere to a substrate. The ink according to one embodiment has low viscosity and is suitable for ejection from an inkjet nozzle, so that it can be ejected appropriately at around room temperature (23° C.).

[0070] In one embodiment, the substrate is not particularly limited, and examples thereof include printing paper such as plain paper, coated paper, and special paper, cloth, inorganic sheet, film, OHP sheet, and adhesive sheet having an adhesive layer on the back surface of the substrate, etc. Among these, permeable substrates are preferred from the viewpoint of ink permeability, and printing paper such as plain paper and coated paper can be preferably used.

[0071] Here, plain paper is paper on which no ink receiving layer or film layer is formed on the normal paper. Examples of plain paper include fine paper, medium-quality paper, PPC paper, wood paper, recycled paper, etc. Plain paper is paper into which ink easily penetrates because paper fibers having a thickness of several μm to several tens of μm form voids of several tens to several hundreds of μm.

[0072] As the coated paper, inkjet coated paper such as matte paper, glossy paper, and semi-glossy paper, and so-called coated printing paper can be preferably used. Here, coated printing paper is printing paper that has been used in letterpress printing, offset printing, gravure printing, etc., and is printing paper in which a coating layer is provided on the surface of fine paper or medium-quality paper with a paint containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch. Coated printing paper is classified into lightly coated paper, fine lightweight coated paper, medium lightweight coated paper, fine coated paper, medium coated paper, art paper, cast coated paper, etc., depending on the coating amount of the paint and the coating method. EXAMPLES

[0073] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0074] "Ink Creation" The ink solvent formulations are shown in Tables 1 to 3. In each table, "-" indicates not added or not measured. The ink of Example 1 was prepared by mixing 5% by mass of carbon black ("MA77" (product name) manufactured by Mitsubishi Chemical Corporation), 5% by mass of "Solsperse 18000" (product name, manufactured by Lubrizol Japan, 100% by mass of non-volatile content), and 90% by mass of solvent, and dispersing the pigment sufficiently using a bead mill "Dyno Mill KDL-A" (product name, manufactured by Shinmaru Enterprises Co., Ltd.) for a residence time of 15 minutes. Subsequently, coarse particles were removed using a membrane filter to obtain the ink. The ink of Example 2 was obtained by the same procedure as in Example 1 above, except that 4 mass% of a copper phthalocyanine pigment ("FASTGEN Blue LA5380" (product name) manufactured by DIC Corporation), 3.5 mass% of "Solsperse 13940" (product name, manufactured by Lubrizol Japan Corporation, non-volatile content 40 mass%), and 92.5 mass% of a solvent were mixed. In Examples 3 to 10 and Comparative Examples 1 to 6, inks were obtained in the same manner as in Example 1 above. The solvents were added in the proportions shown in each table. In each table, A and B indicate diester solvent (A) and monoester solvent (B), respectively, A' and B' indicate comparative solvents for diester solvent (A) and monoester solvent (B), respectively, and C indicates other solvents.

[0075] The diester solvents and monoester solvents shown in each table, as well as other solvents, are available from Tokyo Chemical Industry Co., Ltd. or Takakyu Alcohol Kogyo Co., Ltd. In each table, the δ D , δ P , δ H , viscosity, surface tension, and boiling point. δ D , δ P , δ H The unit is MPa 1 / 2 The Hansen solubility parameters of the solvents were calculated using the Hansen solubility parameter calculation software "HSPiP: Hansen Solubility Parameters in Practice" ver. 5.3 by Charles M. Hansen et al. The viscosity was measured using a rotational viscometer at 23°C and is expressed in mPa·s. The surface tension is a value measured using a surface tension measuring device by the maximum bubble pressure method (SITA Messtechnik GmbH science line t60 (product name) manufactured by SITA Process Solutions) under measurement conditions of 23°C and 0.05 Hz, and the unit is mN / m. The boiling point is the boiling point at 1 atmosphere and is expressed in degrees Celsius. The solvent ratio shown in each table indicates the ratio (A / B) of the total amount of diester solvent (A) to the total amount of monoester solvent (B). When comparative solvents were used in the comparative examples, the contents of comparative solvents A' and B' were included in the contents of diester solvent (A) and monoester solvent (B), respectively.

[0076] "evaluation" The inks were evaluated by the following methods, and the results are shown in the tables below. (Prevents deformation of clear files) The deformation of the clear file was evaluated by placing one printed sheet in a polypropylene (PP) clear file and leaving it at room temperature for one week, after which the deformation of the clear file was checked and evaluated according to the following criteria: The thickness of one sheet in the clear file was 0.2 mm. The deformation of the clear file is observed by placing the printed matter inside the clear file flat on a flat surface and bending the top sheet of the clear file outward. The deformation of the clear file is the distance from the flat surface to the maximum height of the top sheet of the clear file when it is bent outward. The prints were produced by loading ink into an “Orphis GD9630” line-type inkjet printer (manufactured by Riso Kagaku Corporation) and printing a solid image measuring approximately 51 mm (600 nozzles) in the main scanning direction and 260 mm in the sub-scanning direction on one side of plain paper “Riso Paper Thin” (manufactured by Riso Kagaku Corporation). S: The deformation of the clear file is less than 1 cm. A: The deformation of the clear file is between 1cm and 3cm. B: The deformation of the clear file is 3 cm or more.

[0077] (Prevention of toner transfer) Using a Canon Inc. laser printer "SateraLBP9100C," a printout of a toner image was produced in which a black solid image was formed on plain paper "Riso Paper Thin" (Riso Kagaku Corporation). 10 minutes after the toner image was formed, 10 μL of the ink obtained in the above examples and comparative examples was dropped onto the solid image of the printout, and plain paper "Riso Paper Thin" was placed on top of it. A PET film was placed on top of this, and a weight was also placed on top. In this state, the paper was left in an environment of 23°C for 3 days, and the degree of adhesion of the toner to the paper after leaving it was examined and evaluated according to the following criteria. S: There is almost no toner adhesion. A: The toner sticks slightly. B: There is a lot of toner sticking.

[0078] (Dischargeability) The ejection property was evaluated by printing a solid image on one side of 100 sheets of plain paper "Riso Paper Thin" (Riso Kagaku Corporation) using a line-type inkjet printer "Orphis GD9630" (Riso Kagaku Corporation) in succession to obtain a print. The printing conditions were the same as those for the evaluation of the deformation of the clear file. Non-ejection of ink from the inkjet nozzle can be confirmed by the appearance of white streaks on the printed matter, which are non-printed areas. The occurrence of these white streaks and the number of streaks that occurred were observed among 100 printed matters. The ejection performance was evaluated based on the total number of white streaks observed among the 100 printed matters. The evaluation criteria are as follows: S: 0 white streaks. A: There are 1 or 2 white streaks. B: There are three or more white streaks.

[0079] (Prevention of stains on the printed surface) The obtained ink was loaded into a line-type inkjet printer "Orphis GD9630" (manufactured by Riso Kagaku Corporation) and printed on plain paper "Riso Paper Multi" and matte paper "Riso Paper Matte IJ (W)" (manufactured by Riso Kagaku Corporation) so that the main droplets were aligned in a line. The obtained images were visually observed for stains on the printed surface due to satellites and evaluated according to the following criteria. S: Almost no staining was observed on the printed surface, even when printed on matte paper. No staining was observed on the printed surface even on plain paper. A: Almost no staining was observed on the printed surface of plain paper. Some staining was observed on the printed surface of matte paper. B: Staining of the printed surface is observed on both plain paper and matte paper.

[0080] [Table 1]

[0081] [Table 2]

[0082] [Table 3]

[0083] As shown in each table, the ink of each example was able to prevent deformation of the clear file, prevent toner transfer, and improve ejection properties. In addition, the ink of each example was able to prevent staining of the printed surface. In addition, although not listed in the table, the ink of each example had good image quality of the printed matter, including print density.

[0084] In Examples 1 to 11, various diester and monoester solvents were combined, and good results were obtained. Examples 4 to 7 are examples in which the solvent ratio between the diester solvent and the monoester solvent is different. Through these examples, it can be seen that when the content of the diester solvent is high and the solvent ratio A / B is 4 / 1, toner transfer occurs slightly. In addition, it can be seen that when the content of the monoester solvent is high and the solvent ratio A / B is 1 / 4, the clear file is slightly deformed and the ejection performance is slightly reduced. In Examples 1 to 3 and 10, a diester solvent represented by the general formula (1) was used, which has a high surface tension and prevents satellites from being generated, and prevents staining of the printed surface. In addition, in Examples 1 to 3 and 10, a monoester solvent with a higher boiling point was used, which prevents deformation of the clear file. In Example 11, good results were obtained even when a certain amount of other solvent was included.

[0085] Comparative Examples 1 and 2 show the δ D The distortion was so large that the clear file was deformed and toner transfer occurred. Comparative Example 3 is an example in which the boiling point of the monoester solvent is low, and deformation of the clear file occurred. Comparative Example 4 is an example in which only a diester solvent was used, and the toner solubility was high, resulting in toner transfer. Comparative Example 5 is an example in which only a monoester solvent having a high boiling point was used, and the ink viscosity increased and the ejection properties decreased. Comparative Example 6 is an example in which only a monoester solvent having a lower boiling point than Comparative Example 5 was used. The ejection properties were improved, but the volatility of the solvent was high, causing deformation of the clear file.

Claims

1. Dispersion term δ in Hansen solubility parameters Ｄ is 15.7MPa １／２ A diester solvent (A), which is A monoester solvent (B) having a boiling point of 300° C. or higher, and An oil-based inkjet ink containing colorants.

2. 2. The oil-based ink-jet ink according to claim 1, wherein a mass ratio of the diester solvent (A) to the monoester solvent (B) satisfies A / B = 3 / 7 to 3 / 2.

3. The oil-based ink-jet ink according to claim 1 , wherein the diester solvent (A) comprises a diester represented by the following general formula (1): 【Chemistry 1】 (In the general formula (1), R １ and R ２ are each independently an isopropyl group, a sec-butyl group, or a tert-butyl group.

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