Aqueous ink, ink cartridge, and inkjet recording method

Abstract

To provide an aqueous ink for inkjet recording which exhibits superior fixation recoverability and is capable of preventing the bronzing phenomenon.SOLUTION: An aqueous ink for inkjet recording contains a pigment. The pigment includes a first pigment being a quinacridone pigment, and a second pigment being a monoazo pigment without a condensed ring in the molecule. The hue angle of a diluted liquid obtained by diluting the ink with water to achieve an absorbance of 1 at the maximum absorption wavelength in the wavelength range of 380 to 780 nm is 330° or more and 345° or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous ink, an ink cartridge, and an inkjet recording method.

Background Art

[0002] In recent years, it has become possible to record high-definition and excellent color-developing images such as those realized by silver halide photography and offset recording by an inkjet recording method. Color materials used in inks include dyes and pigments. Among them, pigments are widely used as color materials from the viewpoint of being able to record images excellent in fastness such as gas resistance, light resistance, and water resistance.

[0003] In the inkjet recording method, usually, an image is recorded with four-color inks obtained by adding black to the three primary colors of cyan, magenta, and yellow. Conventionally, as a magenta-based pigment (hereinafter also referred to as "magenta pigment") used in magenta ink, quinacridone pigment excellent in fastness has been widely used. However, magenta ink using quinacridone pigment has a problem that the fixing recovery property is likely to deteriorate, and an improvement in performance has been desired. The fixing recovery property refers to the performance of being able to eliminate the fixing of ink in the ink flow path and the discharge port and recover to a state where the ink is normally discharged by operating a recovery mechanism even after the ink is filled in the recording head and left for a long time.

[0004] To solve such problems, various proposals have been made so far. For example, an ink has been proposed in which an azo pigment is used together with a quinacridone pigment to suppress the fixing of the quinacridone pigment and keep the discharge property good (Patent Document 1). Also, inks containing a magenta-based pigment and a yellow pigment have been proposed (Patent Documents 2 and 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The inventors of the present invention examined inks containing an azo pigment together with a quinacridone pigment among various inks proposed in Patent Documents 1 to 3. As a result, although the fixing recovery property was good, it was found that a so-called bronze phenomenon, in which light of a color different from the original color of the magenta pigment was observed depending on the angle of observing the image, occurred remarkably.

[0007] Therefore, an object of the present invention is to provide an aqueous ink for inkjet that is excellent in fixing recovery property and capable of suppressing the bronze phenomenon. Another object of the present invention is to provide an ink cartridge using this aqueous ink and an inkjet recording method. [Means for Solving the Problems]

[0008] That is, according to the present invention, there is provided an aqueous ink for inkjet containing a pigment, wherein the pigment includes a first pigment that is a quinacridone pigment and a second pigment that is a monoazo pigment having no condensed ring in the molecule, and the hue angle of a dilution obtained by diluting with water so that the absorbance at the maximum absorption wavelength in the wavelength range of 380 to 780 nm is 1 is 330° or more and 345° or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an aqueous ink for inkjet that is excellent in fixing recovery property and capable of suppressing the bronze phenomenon. Further, according to the present invention, it is possible to provide an ink cartridge using this aqueous ink and an inkjet recording method.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in more detail by giving preferred embodiments. In the description of this specification, "C.I." means an abbreviation of "Color Index". Physical property values are values at normal temperature (25°C) unless otherwise specified.

[0012] First, a method for calculating the hue angle of the ink will be described. In the present invention, in order to define the ink having a hue as magenta ink, the range of the hue angle is utilized. In the present invention, for the sake of convenience, in order to obtain a concentration suitable for measurement with a general spectrophotometer, a diluted solution diluted with water (preferably ion-exchanged water or deionized water) is used to measure the hue angle of the ink. The hue angles of the ink and its diluted solution can be measured and calculated according to the following procedure. First, the ink is diluted with water so that the absorbance at the maximum absorption wavelength in the wavelength range of 380 to 780 nm becomes 1 to obtain a diluted solution. Next, the obtained diluted solution is put into a quartz glass cell with an optical path length of 10 mm, and using a spectrophotometer, the absorption spectrum in the wavelength region of 200 to 800 nm is measured. As the spectrophotometer, for example, a product named "Spectorophotometer U-3900H" (manufactured by Hitachi High-Tech) can be used. Of course, as long as the same measurement is possible, the spectrophotometer is not limited to this. From the measured absorption spectrum of the diluted solution, CIE L * a * b * In the L of the color system * , a * , b* is calculated, and L * C * The hue angle h in the h color space can be calculated.

[0013] The inventors examined an image recorded using an ink containing a quinacridone pigment and an azo pigment. As a result, it was found that a significant bronzing phenomenon occurred in the image. Further analysis of the recorded image revealed the following. The hue of the diffused light of the magenta pigment was in the a * a * b * fourth quadrant (positive value of a * b * and negative value of b) on the a * plane. In contrast, the hue of the specular reflection light that causes the bronzing phenomenon was in the first quadrant (positive value of a * and positive value of b) on the a * b * plane. Generally, in the a * b * plane, the difference in hue between quadrants that straddle the a * axis or the b * axis is easily visible. In the image recorded with the above ink, the b * of the specular reflection light that causes the bronzing phenomenon is located on the plus side across the b * axis with respect to the b * of the diffused light. For this reason, it is considered that the yellowness of the specular reflection light is strongly visible and the bronzing phenomenon becomes more prominent. In order to suppress such a bronzing phenomenon, it is necessary to reduce the value of b * of the specular reflection light. * axis. * of the specular reflection light.

[0014] The inventors examined combinations of pigments that can reduce the value of b * of the specular reflection light of an image while improving the fixing recovery property. As a result, they found that a combination of a quinacridone pigment (first pigment) and a monoazo pigment having no condensed ring in the molecule (second pigment) is effective, leading to the present invention.

[0015] The inventors of the present invention analyzed in detail an image recorded with the ink containing the above-described first pigment and second pigment. As a result, it was found that the specular reflection light of the image recorded with the above-described ink has a higher reflectance of blue light than the specular reflection light of the image in which the bronze phenomenon occurred significantly. As a result of the additive mixing of blue light, which is the complementary color of yellow, and the hue of the specular reflection light approaching white, the value of b * is considered to have decreased and the bronze phenomenon has been suppressed.

[0016] The first pigment and the second pigment are considered to interact specifically. The quinacridone pigment, which is the first pigment, has a carbonyl group (>C=O) and an imino group (>NH), which are polarized groups, and has a crystal plane on which a particularly large number of these polarized groups are present. In addition, the monoazo pigment having no condensed ring in the molecule, which is the second pigment, also has an electron-donating group (donor) that is electrically negative and an electron-accepting group (acceptor) that is electrically positive bonded via an azo group, and is polarized at both ends of the azo bond. In the ink, it is considered that the two pigments exist in a state where they are combined due to a specific interaction in which the polarized monoazo pigment is attracted to the carbonyl group or imino group of the quinacridone pigment.

[0017] On the other hand, it is considered that a disazo pigment or a condensed azo pigment having a plurality of azo bonds does not exhibit a specific interaction with the quinacridone pigment. Disazo pigments and condensed azo pigments usually have a highly symmetric structure represented by the following general formulas (2) and (3). Examples of the pigment composed of the compound represented by the following general formula (2) include C.I. Pigment Yellow: 12, 13, 14, 17, 55, 83, etc. Examples of the pigment composed of the compound represented by the following general formula (3) include C.I. Pigment Yellow: 93, 94, 95, etc.

[0018] TIFF2025100390000001.tif67170(In the above general formulas (2) and (3), X, Y, and Z each independently represent a hydrogen atom or a monovalent substituent)

[0019] In the disazo pigment represented by the general formula (2), the site derived from the diazo component is present in the center of the molecule, and the sites derived from the coupling component are present at both ends of the molecule. In the condensed azo pigment represented by the general formula (3), the site derived from the coupling component is present in the center of the molecule, and the sites derived from the diazo component are present at both ends of the molecule. Both pigments have a symmetrical structure of donor·acceptor·donor or acceptor·donor·acceptor, and polarization within the molecule is easily canceled out. For this reason, disazo pigments and condensed azo pigments hardly interact with quinacridone pigments. Also, among monoazo pigments, monoazo pigments having a condensed ring in the molecule hardly interact with quinacridone pigments due to the steric hindrance of the condensed ring.

[0020] The state (laminated state) of the pigment layer formed using the ink of the present invention containing the first pigment and the second pigment that specifically interact is considered to be different from the laminated state of the pigment layer formed using conventional ink. That is, it is considered that the particles of the two types of pigments do not coexist on the recording medium, but exist on the recording medium in the state of a single particle in which the two types of pigments are adsorbed to each other and complexed. Such a pigment layer, unlike the pigment layer formed using conventional ink, is considered to strongly reflect blue light and exhibit optical characteristics that cancel out the yellowness of the specular reflection light of the quinacridone pigment. Such optical characteristics are considered to be caused by the influence of the refractive index of light in the pigment layer. Generally, when two substances with different refractive indices are in contact with each other, the greater the difference in refractive index, the higher the reflectance of light at the interface. The pigment layer formed using the ink of the present invention has a higher refractive index for blue light than the pigment layer formed using conventional ink, and the difference in refractive index at the interface with air having a low refractive index is large, so it is considered that blue light is particularly strongly reflected.

[0021] The present inventors speculate as follows about the reason why the refractive index of blue light is high in the pigment layer formed using the ink of the present invention. Generally, when light is incident on a certain substance, the electric field of the light traveling through the substance causes the electrons in the substance to oscillate. At this time, an imbalance of electric charges occurs in the substance, and the speed of light traveling through the substance slows down due to the effect of this imbalance of electric charges. The slower the speed of light traveling through the substance, the higher the refractive index of light in the substance. In a pigment layer formed including a state of one particle in which the first pigment and the second pigment are combined, the polarized second pigment attracts the π electrons in the pigment layer, resulting in a state in which the binding of the electrons is strengthened. When light of a yellow wavelength is incident on such a pigment layer, the light of a yellow wavelength has a relatively low energy, so it is difficult to oscillate the π electrons in the pigment layer, and the speed of light is unlikely to slow down in the pigment layer. On the other hand, when light of a blue wavelength is incident, the light has a relatively high energy, so even the π electrons whose binding is strengthened by the combination of the first pigment and the second pigment can be vibrated. At this time, it is believed that the speed of the blue light traveling through the pigment layer slows down due to the action of the vibrating π electrons, resulting in an increase in the refractive index of blue light in the pigment layer.

[0022] The specular reflected light of an image recorded using ink containing only the first pigment as a coloring material and the specular reflected light of an image recorded using ink containing only the second pigment as a coloring material are both measured using the CIE L * a * b * b in color system * In contrast, in the image recorded using the ink containing the first pigment and the second pigment, the intensity of the blue regular reflected light is increased, and b * The value of b in the two images above * That is, by combining the first pigment and the second pigment, it is possible to obtain an effect of suppressing the yellowish tint of the specularly reflected light, but it is difficult to predict this effect from the characteristics of the inks containing the first pigment and the second pigment alone.

[0023] Even if an ink containing a first pigment and another ink containing a second pigment are used, and dots of the two inks are overlapped to record an image, the effect of suppressing the bronze phenomenon cannot be obtained. This is presumably because when the first pigment and the second pigment are not present in a single ink, the two types of pigments do not sufficiently interact with each other. That is, simply overlapping dots of two inks each containing two types of pigments on a recording medium does not form a pigment layer including a state of one particle in which the two types of pigments are combined. For this reason, it is considered that the intensity of the blue specular reflection light does not increase and the bronze phenomenon cannot be suppressed.

[0024] From the above, when an ink in which the first pigment and the second pigment easily interact is applied to a recording medium, a pigment layer including a state of one particle in which the first pigment and the second pigment are combined is formed on the recording medium. Since this pigment layer strongly reflects blue light, it easily cancels out the yellow specular reflection light, and the effect of suppressing the bronze phenomenon can be obtained. Further, when an ink in which the first pigment and the second pigment easily interact is used, since the second pigment easily acts so as to prevent the lamination of the first pigment, the fixing recovery property can be improved.

[0025] <Ink> The ink of the present invention is an aqueous ink for inkjet containing a pigment. The pigment includes a first pigment which is a quinacridone pigment and a second pigment which is a monoazo pigment having no condensed ring in the molecule. And the hue angle of the diluted solution obtained by diluting with water so that the absorbance at the maximum absorption wavelength in the wavelength range of 380 to 780 nm becomes 1 is 330° or more and 345° or less. That is, the ink of the present invention is a magenta ink having a preferable magenta hue.

[0026] With the above configuration, not only can the fixing recovery property and bronze resistance be improved, but it has also been found that an effect such as suppressing a phenomenon (so-called hue shift) in which the hue of an image (magenta hue) differs depending on the type of recording medium on which the image is recorded can be obtained. Among general-purpose recording media for the inkjet recording method, there are those provided with an ink receiving layer for retaining the coloring material in the ink near the surface of the recording medium. There are also recording media such as plain paper that do not have an ink receiving layer. It is considered that hue shift is likely to occur when using conventional inks containing quinacridone pigments and azo pigments because the "aggregation state of the pigments" and the "fixing position of the pigments" differ depending on the presence or absence of the ink receiving layer of the recording medium.

[0027] When ink is applied to a recording medium having an ink receiving layer, the liquid component in the ink rapidly penetrates into the ink receiving layer. As the liquid component penetrates, the pigment concentration of the ink rapidly increases, so the pigments are laminated to form large aggregates and are fixed to the recording medium. On the other hand, when ink is applied to a recording medium without an ink receiving layer, as the liquid component in the ink penetrates into the recording medium, the pigment also sinks into the recording medium. Therefore, the pigment concentration of the ink does not rapidly increase, and the pigment is likely to be fixed without forming aggregates. Thus, even when the same ink is used, it is considered that the hue of the recorded image shifts because the aggregation state of the pigments differs depending on the type of recording medium.

[0028] Furthermore, when an image is recorded on a recording medium having an ink receiving layer, the quinacridone pigment and the azo pigment in the ink are both fixed to the ink receiving layer, so that the fixed positions (positions in the depth direction) of these pigments are generally the same. Therefore, the hue of the recorded image is one in which the hues of the two types of pigments are evenly expressed. In contrast, when an image is recorded on a recording medium having no ink receiving layer, the pigment also sinks into the inside of the recording medium as the liquid components in the ink penetrate. At this time, differences in the fixed positions of the pigments occur depending on the speed of solid-liquid separation of the pigments. Therefore, the hue of the pigment that is fixed at a shallower fixed position and closer to the surface of the recording medium is likely to be strongly expressed. In this way, it is considered that the hue of the recorded image is shifted due to the difference in the fixed positions of the pigments.

[0029] The ink of the present invention uses a monoazo pigment that does not have a condensed ring in the molecule together with a quinacridone pigment, and thus can suppress the hue shift caused by the difference in the "pigment aggregation state" and "pigment fixing position" described above. As described above, among azo pigments, only a monoazo pigment that does not have a condensed ring in the molecule is considered to be capable of specifically interacting with a quinacridone pigment. Due to this interaction, the monoazo pigment that does not have a condensed ring in the molecule enters between the quinacridone pigments, and the aggregation of the quinacridone pigment can be effectively suppressed. As a result, the pigment aggregates are unlikely to be formed even on a recording medium having an ink receiving layer. This state is similar to the fixing state of the pigment on a recording medium without an ink receiving layer, and therefore it is considered that the hue shift caused by the difference in the pigment aggregation state is suppressed.

[0030] Also, as described above, quinacridone pigments and monoazo pigments having no condensed ring in the molecule are considered to form a state of one particle that specifically interacts and complexes. When ink is applied to a recording medium without an ink-receiving layer, the two types of pigments sink into the recording medium and eventually fix while remaining in a state of one particle as if they were complexed. Since the two types of pigments in the state of one particle as if they were complexed fix and remain at the same depth without the complex being dissociated, an image in which the hues of the two types of pigments are evenly represented is recorded. As a result, it is considered that the hue of the image recorded on the recording medium with an ink-receiving layer and the hue of the image recorded on the recording medium without an ink-receiving layer are less likely to deviate. When an ink containing a first pigment and another ink containing a second pigment are used and dots of the two inks are overlapped to record an image, the second pigment cannot sufficiently loosen the aggregation of the first pigment on the recording medium. Therefore, there may be a case where the difference in the aggregation state of the pigments on the recording medium cannot be sufficiently suppressed. Also, it is considered that the two types of pigments are less likely to remain at the same fixing position. As a result, there may be a case where the hue deviation cannot be sufficiently suppressed.

[0031] Hereinafter, each component constituting the ink and the physical properties of the ink will be described.

[0032] (Pigment) The ink contains a pigment as a coloring material. The pigment includes a first pigment and a second pigment. The first pigment and the second pigment can each be used alone or in combination of two or more. The total content (mass %) of the pigment in the ink is preferably 0.10 mass % or more and 15.00 mass % or less, more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the ink. The content (mass %) of the first pigment in the ink is preferably 0.05 mass % or more and 14.50 mass % or less, more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the ink. The content (mass %) of the second pigment in the ink is preferably 0.01 mass % or more and 0.50 mass % or less, more preferably 0.02 mass % or more and 0.20 mass % or less, based on the total mass of the ink. Further, the total content (mass %) of the first pigment and the second pigment in all the pigments in the ink is preferably 95.00 mass % or more, and may be 100.00 mass %.

[0033] 〔First Pigment〕 The first pigment is a quinacridone pigment. The quinacridone pigment is a pigment formed of quinacridone (5,12-dihydro-quino[2,3-b]acridine-7,14-dione) or a quinacridone derivative. Examples of the quinacridone derivative include quinacridone substituted with an alkyl group such as a methyl group or a halogen atom such as a chlorine atom.

[0034] Specific examples of the quinacridone pigment include C.I. Pigment Red 122, 192, 202, 206, 207, 209; C.I. Pigment Violet 19; and the like. A solid solution of two or more quinacridone pigments may be used. The solid solution, also called a mixed crystal, is one in which two or more pigments are mutually dissolved to form a uniform solid phase as a whole, and is different from a simple mixture of two or more pigments.

[0035] Among the above quinacridone pigments, the first pigment is preferably a solid solution of quinacridone pigments (quinacridone solid solution pigment). A quinacridone pigment formed of a single pigment (compound) has high crystal uniformity and is in a state where it is difficult for the second pigment to penetrate. In contrast, a solid solution of quinacridone pigments is a crystal formed by the penetration of two or more pigments (compounds), and distortion occurs in the arrangement during the crystal formation process. Since the second pigment easily penetrates into this distortion, it more easily interacts with the second pigment than a quinacridone pigment formed of a single pigment (compound). Thereby, the effect of suppressing the yellowness of specularly reflected light, the effect of suppressing hue shift due to the recording medium, and the effect of improving the fixing recovery property can be further enhanced.

[0036] Among the solid solutions of quinacridone pigments, a solid solution formed of C.I. Pigment Red 122 in which quinacridone is substituted with a methyl group and C.I. Pigment Violet 19 which is unsubstituted quinacridone is preferable. In this solid solution, the methyl group derived from C.I. Pigment Red 122 is likely to be exposed at the distorted part of the crystal. Since the methyl group has a low electron density, it is easily attracted electrically to the non-bonding electron pair of the azo group in the second pigment, and the two pigments more easily interact with each other. Thereby, the effect of suppressing the yellowness of specularly reflected light, the effect of suppressing hue shift due to the recording medium, and the effect of improving the fixing recovery property can be further enhanced.

[0037] 〔Second Pigment〕 The second pigment is a monoazo pigment having no condensed ring in its molecule. An azo pigment is a pigment formed of a compound having an azo group in its molecule, and the compound forming the azo pigment usually has a structure in which a diazo component obtained by diazotizing an aromatic amine and a coupler component are coupled. A monoazo pigment is a pigment formed of an azo compound having only one azo group in its molecule. A condensed ring means a ring structure in which two or more rings are bonded by sharing two or more atoms.

[0038] Specific examples of the monoazo pigment having no condensed ring in the molecule include C.I. Pigment Yellow: 1, 3, 4, 5, 6, 9, 10, 11, 61, 62, 65, 73, 74, 75, 97, 98, 111, 116, 130, 150, 165, 168, 169, 182, 183, 190, 191, 203; C.I. Pigment Orange 61; and the like.

[0039] The second pigment is preferably a pigment composed of a compound represented by the following general formula (1). Examples of the substituent of the benzene ring include a nitro group; a halogen atom such as a chlorine atom; an alkoxy group having about 1 to 4 carbon atoms such as a methoxy group and an ethoxy group; an anionic group such as a sulfonic acid group (which may be in the form of a salt such as ammonium or an alkali metal); an acetamido group; a sulfonanilide group (-SO2-NH-C6H5); and the like. Specific examples of the compound (pigment) represented by the following general formula (1) include C.I. Pigment Yellow: 1, 3, 4, 5, 6, 9, 61, 62, 65, 73, 74, 75, 97, 98, 111, 116, 130, 168, 169, 203, and the like. The second pigment represented by the following general formula (1) has an amide group (the CONH moiety) in its molecule. This amide group forms a hydrogen bond with the carboxy group or imino group of the quinacridone pigment, making it difficult for the second pigment to detach from the quinacridone pigment. Therefore, more pigment particles of the first pigment and pigment particles of the second pigment are likely to form a state of one particle that is composite with each other. As a result, the effect of suppressing the yellowness of the specularly reflected light, the effect of suppressing the hue shift due to the recording medium, and the effect of improving the fixing recovery property can be enhanced more.

[0040] TIFF2025100390000002.tif30170 (In the general formula (1), R1 and R2 each independently represent a substituted or unsubstituted benzene ring)

[0041] The second pigment is preferably C.I. Pigment Yellow 74. C.I. Pigment Yellow 74 is a pigment with particularly high dispersion stability. When the dispersion stability of the second pigment is high, the interaction between the second pigments is small and they are less likely to aggregate, so they are more likely to interact with the quinacridone pigment. Therefore, it is easy to form a state of one particle that is more complexed with the quinacridone pigment, and the effect of suppressing the yellowness of the specular reflection light can be further improved. In addition, since the two types of pigments are more likely to interact with each other, the effect of suppressing the hue shift due to the recording medium and the effect of improving the fixing recovery can be further enhanced.

[0042] The hue angle of the second pigment is preferably 85° or more and 115° or less, and more preferably 90° or more and 110° or less. The hue of the second pigment with a hue angle less than 85° is approaching red, and the specular reflection light is likely to have a yellowish tint. It is considered that a part of the second pigment exists in the ink in a state where it is not complexed with the first pigment. When the hue angle of the second pigment is less than 85°, the yellowness of the specular reflection light derived from the second pigment that is not complexed with the first pigment may become stronger. For this reason, even if the formed pigment layer strongly reflects blue light, the yellow specular reflection light may not be sufficiently canceled out, and the effect of suppressing the bronzing phenomenon may not be sufficiently obtained.

[0043] On the other hand, the hue of the second pigment with a hue angle exceeding 115° approaches green, which is the complementary color of the quinacridone pigment used as the first pigment. When a second pigment approaching green is mixed with a magenta pigment, it becomes black and absorbs light of all wavelengths, so the color developability of magenta is likely to decrease. In addition, the diffused light of the magenta pigment is absorbed by the second pigment and the diffused light decreases, making the specular reflection light more prominent. For this reason, the yellowness of the specular reflection light cannot be sufficiently suppressed, and the effect of suppressing the bronzing phenomenon may not be sufficiently obtained.

[0044] The hue angle of the second pigment can be measured and calculated in the same procedure as the method for measuring and calculating the hue angles of the ink and its diluent, using as a measurement sample a pigment dispersion prepared by dispersing the second pigment in water. Surfactants and resins do not substantially affect the absorption spectrum to be measured. Therefore, the pigment dispersion used as the measurement sample may contain a dispersant such as a surfactant or a resin, if necessary. When the ink contains two or more types of second pigments, that is, when it contains a plurality of azo pigments having no condensed ring in the molecule, the hue angle of the second pigment is taken as the weighted average value of each second pigment. For example, when the ink contains b mass% of a second pigment with a hue angle of a° and d mass% of a second pigment with a hue angle of c°, the hue angle of the second pigment can be calculated as (a×b + c×d) / (b + d).

[0045] The content (mass%) of the second pigment in the ink is preferably 0.005 times or more and 0.040 times or less, more preferably 0.007 times or more and 0.030 times or less, and particularly preferably 0.010 times or more and 0.020 times or less, in terms of the mass ratio to the content (mass%) of the first pigment. By setting the above mass ratio to 0.005 times or more, the amount of the second pigment that changes the laminated state of the pigments on the recording medium becomes more sufficient, and the effect of suppressing the yellowness of the specular reflection light of the image can be further enhanced. Also, the effect of loosening the aggregation of the first pigment on the recording medium having an ink receiving layer can be further enhanced. As a result, since it approaches the fixing state of the pigments on the recording medium having no ink receiving layer, the effect of suppressing hue shift can be further enhanced. Furthermore, it is easier to suppress the lamination of the quinacridone pigments which are the first pigments, and the effect of improving the fixing recovery property can be further enhanced.

[0046] Also, by setting the above mass ratio to 0.040 times or less, the interaction between the second pigments becomes less likely to occur, and the first pigment and the second pigment can interact more sufficiently. As a result, the effect of suppressing the yellowness of the specular reflection light of the image, the suppression of hue shift due to the recording medium, and the effect of improving the fixing recovery property can be further enhanced.

[0047] 〔Other Pigments〕 The ink can contain other pigments other than the first pigment and the second pigment as long as the effects of the present invention are not impaired. Examples of other pigments include inorganic pigments such as carbon black and organic pigments. The ratio of the total content (mass %) of the first pigment and the second pigment to the total content (mass %) of the pigments in the ink is preferably 95.00 mass % or more, and may be 100.00 mass %.

[0048] 〔Dispersion method of pigment〕 Examples of the dispersion method of the pigment include resin-dispersed pigments using a resin as a dispersant, self-dispersed pigments in which a hydrophilic group is bonded to the particle surface of the pigment, etc. Also, resin-bonded pigments in which an organic group containing a resin is chemically bonded to the particle surface of the pigment, microcapsule pigments in which the surface of the pigment particles is coated or encapsulated with a resin, etc. can be used. It is also possible to use pigments with different dispersion methods in combination.

[0049] (Resin) The ink can contain a resin. The content (mass %) of the resin in the ink is preferably 0.10 mass % or more and 20.00 mass % or less, more preferably 0.50 mass % or more and 15.00 mass % or less, based on the total mass of the ink.

[0050] The resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. Also, (ii) it can be added to the ink to improve various properties of the recorded image. Examples of other forms of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. Also, other resins may be water-soluble resins that can be dissolved in an aqueous medium, or resin particles that are dispersed in an aqueous medium. The resin particles do not need to encapsulate the coloring material.

[0051] As used herein, the term "resin particles" means a resin that exists in a state where it is insoluble in the aqueous medium constituting the ink. More specifically, it means a resin that can exist in the aqueous medium in a state where particles with a particle diameter measurable by the dynamic light scattering method are formed. On the other hand, the "water-soluble resin" means a resin that exists in a state where it is dissolved in the aqueous medium constituting the ink. More specifically, it means a resin that can exist in the aqueous medium in a state where particles with a particle diameter measurable by the dynamic light scattering method are not formed. When expressing the resin particles as a pair with the "water-soluble resin", it becomes "water-dispersible resin (water-insoluble resin)".

[0052] Whether a certain resin is "resin particles" or not can be determined according to the method shown below. First, prepare a liquid (resin solid content: 10% by mass) containing a resin neutralized with an alkali equivalent to the acid value (such as sodium hydroxide, potassium hydroxide, etc.). Next, dilute the prepared liquid 10 times (volume basis) with pure water to prepare a sample solution. Then, when measuring the particle diameter of the resin in the sample solution by the dynamic light scattering method, if particles having a particle diameter are measured, it can be determined that the resin is "resin particles". As a particle size distribution measuring device by the dynamic light scattering method, a particle size analyzer (for example, trade name "UPA-EX150", manufactured by Nikkiso Co., Ltd.) etc. can be used. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3 times, measurement time: 180 seconds, shape: true sphere, refractive index: 1.59. Of course, the particle size distribution measuring device used, the measurement conditions, etc. are not limited to the above. Measuring the particle diameter using the neutralized resin is to confirm that particles are formed even when it is sufficiently neutralized and it is more difficult to form particles. Even under such conditions, a resin having the shape of particles exists in the state of particles in the aqueous ink.

[0053] The acid value of the water-soluble resin is preferably 100 mgKOH / g or more and 250 mgKOH / g or less. The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 2,000,000 or less. The average particle diameter of the resin particles (cumulative 50% particle diameter based on volume (median diameter; D 50 )) is preferably 50 nm or more and 500 nm or less.

[0054] Examples of the resin include acrylic resins, urethane resins, and olefin resins. Among them, acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are more preferable.

[0055] As the acrylic resin, those having a hydrophilic unit and a hydrophobic unit as constituent units are preferable. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one selected from the group consisting of a monomer having an aromatic ring and a (meth)acrylate monomer is preferable. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is preferable. Since these resins are likely to interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

[0056] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of the cation constituting the salt of the acidic monomer include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit having no hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer having no hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, benzyl (meth)acrylate; (meth)acrylate-based monomers such as methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and the like.

[0057] The urethane resin can be obtained, for example, by reacting a polyisocyanate and a polyol. Further, it may be a reaction product with a chain extender. Examples of the olefin resin include polyethylene, polypropylene, and the like.

[0058] (aqueous medium) The ink is an aqueous ink containing an aqueous medium that is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water (ion-exchanged water) is preferably used as the water. The content (% by mass) of water in the ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of those that can be used in inks for inkjet, such as alcohols, glycols, (poly)alkylene glycols, nitrogen-containing compounds, and sulfur-containing compounds, can be used. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink.

[0059] (Other components) In addition to the above-described components, the ink may contain water-soluble organic compounds that are solid at 25°C, such as polyhydric alcohols like trimethylolpropane and trimethylolethane, and urea derivatives like urea and ethylene urea, as required. Further, the ink may contain various additives such as surfactants, pH adjusters, defoamers, rust preventives, antiseptics, fungicides, antioxidants, anti-reduction agents, and chelating agents, as required.

[0060] (Physical properties of the ink) The ink of the present invention is an aqueous ink applicable to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical property values. The dynamic surface tension γ of the ink at a temperature condition of 25°C and a lifetime of 10 milliseconds 10 is preferably 35.0 mN / m or more and 50.0 mN / m or less, and more preferably 40.0 mN / m or more and 50.0 mN / m or less. The dynamic surface tension γ 10Inks with a dynamic surface tension γ of 35.0 mN / m or more take time to penetrate into the recording medium. Therefore, even when ink is applied to a recording medium without an ink receiving layer (a highly permeable recording medium), sufficient time can be ensured for the first pigment and the second pigment to interact. As a result, even when an image is recorded on a recording medium without an ink receiving layer, a difference in the fixing positions of the first pigment and the second pigment is less likely to occur, and a hue shift from the image recorded on a recording medium with an ink receiving layer is less likely to occur.

[0061] On the other hand, when using an ink with a dynamic surface tension γ 10 of 50.0 mN / m or less, the dot height of the pigment layer formed on the recording medium does not become too high, the unevenness on the surface of the pigment layer can be reduced, and light scattering on the surface of the pigment layer can be suppressed. Light scattering is likely to occur with blue light having a short wavelength. The blue specular reflection light that cancels out the yellowish specular reflection light is scattered before reaching the observer if the unevenness of the pigment layer is large, and the effect of suppressing the yellowish bronzing phenomenon may not be sufficiently obtained. Therefore, by using an ink with a dynamic surface tension γ 10 of 50.0 mN / m or less, the blue specular reflection light is less likely to be lost due to scattering, and the effect of suppressing the bronzing phenomenon can be further enhanced.

[0062] The dynamic surface tension of the ink is measured using a dynamic surface tension meter by the maximum bubble pressure method (for example, trade name "BUBBLE PRESSURE TENSIOMETER BP-100", manufactured by KRUSS, etc.). The maximum bubble pressure method is a method of measuring the maximum pressure required to release bubbles generated at the tip of a probe (capillary tube) immersed in the liquid to be measured, and obtaining the surface tension of the liquid from the measured maximum pressure. Specifically, the maximum pressure is measured while continuously generating bubbles at the tip of the probe. The time from when a new bubble surface is generated at the tip of the probe until the maximum bubble pressure (the point at which the radius of curvature of the bubble is equal to the radius of the tip portion of the probe) is reached is called the "lifetime". That is, the maximum bubble pressure method is a method of measuring the surface tension of a liquid in a moving state. The dynamic surface tension γ of the ink at a lifetime of 10 milliseconds 10It can be easily adjusted according to the type and content of the water-soluble organic solvent and surfactant.

[0063] The static surface tension γ of the ink at 25°C s is preferably 25.0 mN / m or more and 40.0 mN / m or less. The static surface tension of the ink is measured using a Wilhelmy type surface tensiometer (for example, trade name "Automatic Surface Tensiometer CBVP-Z", manufactured by Kyowa Interface Science Co., Ltd., etc.).

[0064] The pH of the ink at 25°C is preferably 5.0 or more and 10.0 or less, and more preferably 7.0 or more and 9.5 or less. The pH of the ink is measured using a general pH meter equipped with a glass electrode or the like.

[0065] The viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 5.0 mPa·s or less. The viscosity of the ink is measured using a viscometer (trade name "RE80 type viscometer", manufactured by Toki Sangyo Co., Ltd., etc.).

[0066] <Ink Cartridge> The ink cartridge of the present invention includes ink and an ink storage unit for storing this ink. And the ink stored in this ink storage unit is the aqueous ink of the present invention described above. FIG. 1 is a cross-sectional view schematically showing an embodiment of the ink cartridge of the present invention. As shown in FIG. 1, an ink supply port 12 for supplying ink to the recording head is provided on the bottom surface of the ink cartridge. The inside of the ink cartridge is an ink storage unit for storing ink. The ink storage unit is composed of an ink storage chamber 14 and an absorber storage chamber 16, and these communicate with each other through a communication port 18. Further, the absorber storage chamber 16 communicates with the ink supply port 12. Liquid ink 20 is stored in the ink storage chamber 14, and absorbers 22 and 24 for holding the ink in an impregnated state are stored in the absorber storage chamber 16. The ink storage unit may be in a form that does not have an ink storage chamber for storing liquid ink and holds the entire amount of the stored ink by the absorber. Further, the ink storage unit may be in a form that does not have an absorber and stores the entire amount of the ink in a liquid state. Furthermore, it may be an ink cartridge configured to have an ink storage unit and a recording head.

[0067] <Inkjet recording method> The inkjet recording method of the present invention is a method of discharging the aqueous ink of the present invention described above from an inkjet recording head and recording an image on a recording medium. Examples of the method of discharging ink include a method of applying mechanical energy to the ink and a method of applying thermal energy to the ink. In the present invention, it is particularly preferable to adopt a method of applying thermal energy to the ink to discharge the ink. Except for using the ink of the present invention, the steps of the inkjet recording method may be known ones.

[0068] FIG. 2 is a diagram schematically showing an example of an inkjet recording apparatus used in the inkjet recording method of the present invention, (a) is a perspective view of a main part of the inkjet recording apparatus, and (b) is a perspective view of a head cartridge. The inkjet recording apparatus is provided with a conveying means (not shown) for conveying the recording medium 32 and a carriage shaft 34. A head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 includes recording heads 38 and 40 and is configured such that an ink cartridge 42 can be set. While the head cartridge 36 is conveyed in the main scanning direction along the carriage shaft 34, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32. Then, an image is recorded on the recording medium 32 by conveying the recording medium 32 in the sub-scanning direction by a conveying means (not shown).

Example

[0069] Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Regarding the amounts of components, “parts” and “%” are based on mass unless otherwise specified.

[0070] <Method for Measuring Physical Property Values> (Hue Angle) The hue angle of the diluted ink solution was measured and calculated according to the following procedure. First, the ink was diluted with ion-exchanged water so that the absorbance at the maximum absorption wavelength in the wavelength range of 380 to 780 nm became 1 to obtain a diluted solution. Next, the obtained diluted solution was placed in a quartz glass cell with an optical path length of 10 mm, and an absorption spectrum in the wavelength region of 200 to 800 nm was measured using a spectrophotometer. As the spectrophotometer, the product name “Spectophotometer U-3900H” (manufactured by Hitachi High-Tech) was used. The peak detection conditions when measuring the absorption spectrum were: sampling interval: 0.5 nm, threshold value: 0.01, sensitivity: 1. Also, ion-exchanged water was used as the reference. From the measured absorption spectrum of the diluted solution, under the conditions of light source C and a viewing field of 2°, L * a * b* L in the color system * , a * , b * were calculated, and L * C * The hue angle h in the h color system was calculated from h = tan -1 (b * / a * ).

[0071] <Preparation of Resin> (Aqueous solution of Resin 1) As Resin 1, a styrene / n-butyl acrylate / acrylic acid copolymer synthesized by a conventional method (copolymerization ratio (mass ratio): 60 / 20 / 20) was prepared. This Resin 1 was dissolved in water containing potassium hydroxide equimolar to the acid value to prepare an aqueous solution of Resin 1 with a Resin 1 content of 20.00%.

[0072] (Solution of Resin 2) A flask equipped with a stirrer, a reflux tube, a thermometer, and a dropping funnel was prepared and purged with nitrogen inside. 20 g of styrene, 2 g of acrylic acid, and 10 g of butyl methacrylate were placed in the flask and heated to 70°C. Then, a mixture of 100 g of styrene, 5 g of acrylic acid, 50 g of butyl methacrylate, and 1.5 g of azobisdimethylvaleronitrile was dropped into the flask over 3 hours for polymerization. Further, a mixture of 8 g of azobisisovaleronitrile and 30 g of methyl ethyl ketone was added over 1 hour to accelerate the polymerization. After the reaction was completed, 200 g of methyl ethyl ketone was added to prepare a solution of Resin 2 with a Resin 2 content of 20.00%.

[0073] <Preparation of Pigment> (Pigments 1 to 10) The pigments shown in Table 1 were used as Pigments 1 to 10. The structures of the pigments and whether they are solid solutions or not were summarized and described in Table 1. The "○" shown in the "Solid Solution" column means that this pigment is a solid solution, and the "×" means that this pigment is not a solid solution. Pigments 1 to 4 were prepared by grinding a press cake obtained by mixing C.I. Pigment Red 122 and C.I. Pigment Violet 19 at the ratios (by mass) shown in Table 1, and then treating with an organic solvent according to a conventional method to form a solid solution pigment. As Pigment 7, C.I. Pigment Violet 207, which is a solid solution pigment of C.I. Pigment Violet 19 and 4,11-dichlorokynacridonequinone, was used. As Pigment 8, a commercially available product (trade name "Cromophtal Jet Magenta 2BC", manufactured by Ciba), which is a solid solution pigment of C.I. Pigment Red 202 and C.I. Pigment Violet 19, was used.

[0074] TIFF2025100390000003.tif114170

[0075] (Pigments 11 to 21) The pigments shown in Table 2 were used as Pigments 11 to 21. The hue angle (°), the presence or absence of a condensed ring, and whether it corresponds to the compound represented by General Formula (1) are shown in Table 2. The "○" shown in the "Condensed Ring" column means that the pigment has a condensed ring in the molecule, and the "×" means that the pigment has no condensed ring in the molecule. The "○" shown in the "General Formula (1)" column means that it is a compound represented by General Formula (1), and the "×" means that it is not a compound represented by General Formula (1).

[0076] TIFF2025100390000004.tif94170

[0077] <Preparation of Pigment Dispersion> (Pigment Dispersions 1 to 10, 13 to 22) 10.0 parts of the pigment of the type shown in Table 3, 10.0 parts of the aqueous solution of Resin 1, and 80.0 parts of ion-exchanged water were mixed and dispersed for 3 hours using a batch vertical sand mill to obtain a dispersion. The obtained dispersion was pressure-filtered through a filter with a pore size of 2.5 μm (product name "HDCII", manufactured by Nippon Pall). An appropriate amount of ion-exchanged water was added to prepare Pigment Dispersions 1 to 10 and 13 to 22 with the pigment and resin (resin dispersant) contents shown in Table 3.

[0078] TIFF2025100390000005.tif160170

[0079] (Pigment Dispersion 11) 30.0 parts of the solution of Resin 2, 30.0 parts of Pigment 5 (C.I. Pigment Red 122), and 50.0 parts of 0.1 mol / L aqueous sodium hydroxide solution were stirred using a homogenizer to obtain a mixture. 500 parts of ion-exchanged water was added to the obtained mixture and further stirred. Using an evaporator, a part of methyl ethyl ketone and ion-exchanged water was distilled off to obtain Pigment Dispersion 11 containing the pigment encapsulated by Resin 2, with the pigment content being 20.00% and the Resin 2 content being 4.00%.

[0080] (Pigment Dispersion 12) 15.0 parts of Pigment 5 (C.I. Pigment Red 122), 5.0 parts of ammonium polyoxyethylene lauryl ether sulfate (number of moles of ethylene oxide groups added: 12), 15.0 parts of glycerin, and 65.0 parts of ion-exchanged water were mixed to obtain a mixture. The obtained mixture was put into a wet sand mill using zirconia beads with a diameter of 0.3 mm as the medium for dispersion treatment to obtain Pigment Dispersion 12 with the pigment content being 15.00% and the dispersant (surfactant) content being 5.00%.

[0081] (Pigment Dispersion 23) Except that Pigment 21 (C.I. Pigment Yellow 180) was used instead of Pigment 5, in the same manner as in the case of Pigment Dispersion 11 described above, Pigment Dispersion 23 containing the pigment encapsulated by Resin 2, with the pigment content being 20.00% and the Resin 2 content being 4.00% was obtained.

[0082] (Pigment dispersion 24) A pigment dispersion 24 with a pigment content of 15.00% and a dispersant (surfactant) content of 5.00% was obtained in the same manner as in the case of the aforementioned pigment dispersion 12, except that pigment 12 (C.I. Pigment Yellow 74) was used instead of pigment 5.

[0083] <Preparation of Ink> Each component (unit: %) shown in the middle of Tables 4-1 to 4-4 was mixed and stirred well, and then filtered under pressure through a polypropylene filter with a pore size of 1.0 μm (manufactured by Advantec) to prepare Inks 1 to 42. In the preparation of the ink, the amount of the nonionic surfactant was adjusted so that the dynamic surface tension (γ 10 (mN / m)) at the lifetime of the ink of 10 milliseconds was the value shown in the lower part of Tables 4-1 to 4-4. As the nonionic surfactant, the product named "Acetylenol E100" (manufactured by Kawaken Fine Chemicals) was used. The amount of the nonionic surfactant used is described in the column of "Ion-exchanged water containing Acetylenol E100" in Tables 4-1 to 4-4 as the amount contained in the ion-exchanged water. "Proxel GXL(S)" is the product name of a preservative manufactured by Arch Chemicals.

[0084] The characteristics of the prepared inks are shown in the lower part of Tables 4-1 to 4-4. The dynamic surface tension (γ 10 (mN / m)) of the ink at the lifetime of 10 milliseconds was measured using a dynamic surface tensiometer by the maximum bubble pressure method under the condition of 25°C. As the dynamic surface tensiometer, the product named "BUBBLE PRESSURE TENSIOMETER BP-100" (manufactured by KRUSS) was used. The hue angle of the diluted solution obtained by diluting with water so that the absorbance at the maximum absorption wavelength in the wavelength range of 380 to 780 nm calculated by the above method becomes 1 was described in the column of "Hue angle h (°) of the diluted solution". By preparing such a diluted solution and measuring the hue angle, it is possible to evaluate with the same index even for different pigment types, and by making the absorbance 1, the measurement accuracy can be improved.

[0085] TIFF2025100390000006.tif237170

[0086] TIFF2025100390000007.tif238170

[0087] TIFF2025100390000008.tif254170

[0088] TIFF2025100390000009.tif252170

[0089] <Evaluation> Ink 1 to 40 were respectively filled into ink cartridges and mounted on an inkjet recording apparatus (trade name: "PIXUS PRO - 10S", manufactured by Canon) that discharges ink from a recording head by the action of thermal energy. In this example, the recording duty of a solid image recorded under the condition of applying 8 ink droplets of 4.0 ng per droplet to a unit area of 1 / 600 inch × 1 / 600 inch was defined as 100%. In the present invention, according to the evaluation criteria of each item shown below, "AA", "A", and "B" were set as acceptable levels, and "C" was set as an unacceptable level. The evaluation results are shown in Table 5.

[0090] (Hue angle of magenta ink) The hue angle of magenta ink was evaluated according to the following criteria from the "hue angle h (°) of the diluent" described in Tables 4 - 1 to 4 - 4. A: The hue angle h was 330° or more and 345° or less. C: The hue angle h was less than 330° or more than 345°.

[0091] (Fixing recovery) The following operations were performed using the above inkjet recording apparatus and a recording medium. After performing a recovery process (cleaning operation) from the printer driver, a nozzle check pattern of "PIXUS PRO-10S" was recorded. As the recording medium, a product named "Canon Photo Paper, Glossy Gold GL-101" (manufactured by Canon) was used. Then, while the carriage was operating (when the recording head was at a position other than the home position), the power cable was unplugged to leave the recording head uncapped. And in this state, the inkjet recording apparatus was placed in an environment of 30°C and 10% relative humidity for 14 days. Next, after placing the inkjet recording apparatus in an environment of 25°C for 6 hours, a "PIXUS PRO-10S" nozzle check pattern was recorded while performing a recovery process. The nozzle check pattern 1 recorded before the 14-day placement and the nozzle check pattern 2 recorded after the 14-day placement were visually confirmed, and the fixing recovery property was evaluated according to the following evaluation criteria. The fewer the number of recovery processes required until the nozzle check pattern 2 becomes in the same state as the nozzle check pattern 1 (which can be ejected normally), the better the fixing recovery property. AA: The nozzle check pattern 2 became in the same state as the nozzle check pattern 1 after 1 to 2 recovery processes. A: The nozzle check pattern 2 became in the same state as the nozzle check pattern 1 after 3 to 5 recovery processes. B: The nozzle check pattern 2 became in the same state as the nozzle check pattern 1 after 6 to 10 recovery processes. C: Even after performing the recovery process 10 times, the nozzle check pattern 2 did not become in the same state as the nozzle check pattern 1, and unrecorded portions were confirmed.

[0092] (Bronze resistance) Using the above inkjet recording apparatus, a solid image with a recording duty of 20% was recorded on a recording medium (product name: "Canon Photo Paper, Glossy Gold (GL-101)", manufactured by Canon). After drying the recorded solid image for one day in an environment with a temperature of 23°C and a relative humidity of 55%, using a variable-angle high-speed spectrophotometer (product name: "GCMS-3B type", manufactured by Murakami Color Technology Laboratory), the b * value of the specularly reflected light was measured. The measurement conditions were a light source of D65, a viewing angle of 2°, an incident angle of 45°, a reflection angle of 45°, and a tilt angle of 0°. Then, the bronzing resistance of the image was evaluated according to the following evaluation criteria. A: The b * value was 9 or less. B: The b * value exceeded 9 and was 10 or less. C: The b * value exceeded 10.

[0093] (Suppression of hue angle deviation) Using the above inkjet recording apparatus, solid images with a recording duty of 70% were respectively recorded on the following two types of recording media (recording media 1 and 2). · Recording medium 1: A recording medium having an ink receiving layer, product name: "Canon Photo Paper, Glossy Gold (GL-101)", manufactured by Canon · Recording medium 2: A recording medium without an ink receiving layer, product name: "ECF Bleached Paper (CS-680)

[0094] The recorded solid images were dried for one day in an environment with a temperature of 23°C and a relative humidity of 55%. Then, using a fluorescence spectrophotometer (product name: "FD-7", manufactured by Konica Minolta), under the illumination conditions of M1 (D50), the observation light source: D50, and the field of view: 2°, the L * , a * , b * of the reflected light were measured. Then, the hue angle h1 of the image recorded on recording medium 1 and the hue angle h2 of the image recorded on recording medium 2 were calculated. The deviation of the hue angle (Δh = |h1 - h2|) was calculated, and the suppression of the deviation of the hue angle was evaluated according to the following evaluation criteria. AA: Δh was 0.5 or less. A: The Δh was more than 0.5 and less than or equal to 10. B: The Δh exceeded 10.

[0095] TIFF2025100390000010.tif255162

[0096] Examples 16 to 19 had the same evaluation rank for all of the fixing recovery property, bronze resistance, and suppression of hue angle deviation. However, Examples 16 and 17 were relatively inferior to Examples 18 and 19. Similarly, Examples 24 to 27 had the same evaluation rank for all of the fixing recovery property, bronze resistance, and suppression of hue angle deviation. However, Examples 24 and 25 were relatively inferior to Examples 26 and 27. Furthermore, the suppression of hue angle deviation of Comparative Examples 4 to 6 had the same evaluation rank, but Comparative Example 4 was relatively inferior to Comparative Examples 5 and 6.

[0097] (Comparative Example 14) As Comparative Example 14, using the above inkjet recording apparatus, two types of inks were applied to the recording medium in an overlying manner so that the recording duty of Ink 41 was 10% and the recording duty of Ink 42 was 10% to record a solid image. As the recording medium, the product name "Canon Photo Paper, Glossy Gold (GL-101)" (manufactured by Canon) was used. Then, when the bronze resistance was evaluated according to the above evaluation criteria, it was an unacceptable level of "C" evaluation.

[0098] Using the above inkjet recording apparatus, two types of inks were applied to each of Recording Media 1 and 2 in an overlying manner so that the recording duty of Ink 41 was 35% and the recording duty of Ink 42 was 35% to record a solid image. Then, when the suppression of hue angle deviation was evaluated according to the above evaluation criteria, it was a "B" evaluation.

Claims

1. An aqueous ink for inkjet containing a pigment, wherein the pigment includes a first pigment which is a quinacridone pigment and a second pigment which is a monoazo pigment having no condensed ring in the molecule, the aqueous ink is characterized in that the hue angle of a dilution obtained by diluting with water so that the absorbance at the maximum absorption wavelength in the wavelength range of 380 to 780 nm is 1 is 330° or more and 345° or less.

2. The aqueous ink according to claim 1, wherein the content (% by mass) of the second pigment is 0.005 times or more and 0.040 times or less in terms of the mass ratio to the content (% by mass) of the first pigment.

3. Dynamic surface tension γ at a lifetime of 10 milliseconds １０ The aqueous ink according to claim 1, wherein γ is 35.0 mN / m or more and 50.0 mN / m or less.

4. The aqueous ink according to claim 1, wherein the first pigment is a solid solution of a quinacridone pigment.

5. The aqueous ink according to claim 1, wherein the first pigment is a solid solution of C.I. Pigment Red 122 and C.I. Pigment Violet 19.

6. The aqueous ink according to claim 1, wherein the hue angle of the second pigment is 85° or more and 115° or less.

7. The aqueous ink according to claim 1, wherein the second pigment is a pigment composed of a compound represented by the following formula (1). (In the general formula (1), R １ and R ２ each independently represents a substituted or unsubstituted benzene ring)

8. The aqueous ink according to claim 1, wherein the second pigment is C.I. Pigment Yellow 74.

9. The aqueous ink according to claim 1, wherein the content (% by mass) of the first pigment is 0.05% by mass or more and 14.50% by mass or less based on the total mass of the ink.

10. The aqueous ink according to claim 1, wherein the content (% by mass) of the second pigment is 0.01% by mass or more and 0.50% by mass or less based on the total mass of the ink.

11. An ink cartridge including an ink and an ink containing portion for containing the ink, wherein the ink is the aqueous ink according to any one of claims 1 to 10.

12. An inkjet recording method for recording an image on a recording medium by ejecting an ink from an inkjet recording head, wherein the ink is the aqueous ink according to any one of claims 1 to 10.

Images