JP2012250434A - Image recording method, and ink set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording method where a deep ink and a light ink having small difference in ozone resistance are used, and images having fewer differences in vision depending on the type of recording medium are obtained.SOLUTION: The image recording method has a step of recording an image by applying each of the deep ink and the light ink having the same color phase as the deep ink to the recording medium. The deep ink and the light ink have common a soluble dye. Moreover, the light ink contains a sugar compound having 6 or more carbon numbers, and 5 or more of hydroxyl numbers.

Description

  The present invention relates to an image recording method and an ink set.

  In recent years, in an image recording method using an ink jet method, it is required to output an image having an image quality comparable to a silver salt photograph. In response to such a demand, an image recording method using a dye ink set of dark ink and light ink has been studied. By further using light ink having a low dye concentration in addition to normally used ink (dark ink), for example, graininess in dark areas such as skin color and background is improved, and a higher quality image can be obtained.

  However, when the dark ink and the light ink (hereinafter also referred to as “dark light ink”) contain a common water-soluble dye, the light ink generally has lower ozone resistance than the dark ink. This is because the density of the light ink is lower than that of the dark ink, so there is a higher probability that the dye will be present on the recording medium without agglomeration, and the molecular structure of the dye is broken by direct contact with ozone. Because it is easy to fade. As described above, there is a difference in ozone resistance between dark ink and light ink. Therefore, when an image recorded by the image recording method using dark and light ink is stored for a long period of time, the dark ink use area and the light ink use area are faded. The problem that a difference arises in the degree of was generated. As a method for improving such a problem, there is a method of reducing the difference in ozone resistance between the dark ink and the light ink by improving the ozone resistance of the light ink. As a method for improving the ozone resistance of light ink, a method using a dye having a structure with high ozone resistance different from the dye used for dark ink is disclosed (Patent Documents 1 and 2). Patent Document 1 discloses that an image having a neutral gray color tone that is excellent in ozone resistance and obtained by a gray ink containing a specific dye is disclosed. Patent Document 2 exemplifies a gray ink using a cyan dye, a magenta dye, a yellow dye, and a black dye, and describes that the resistance to a gas containing ozone is high.

JP 2009-062515 A JP 2010-037504 A

  However, as a result of the study by the present inventors, in the methods as described in Patent Documents 1 and 2, the ozone resistance of the light ink is improved and the difference in the ozone resistance performance of the dark and light inks is reduced. It turns out that a problem arises. That is, a phenomenon that the appearance of an image recorded using dark and light inks varies depending on the type of recording medium used (hereinafter also referred to as “recording medium type dependent phenomenon”) has occurred.

  Accordingly, an object of the present invention is to use a dark ink and a light ink that can obtain an image in which the difference in ozone resistance between the dark ink and the light ink is small and the difference in the appearance of the image depending on the type of the recording medium is suppressed. It is to provide an image recording method. Another object of the present invention is to provide an ink set that can be used in the image recording method of the present invention.

  The above object is achieved by the present invention described below. That is, the image recording method according to the present invention is an image recording method including a step of recording an image by applying dark ink and a light ink having the same hue as the dark ink to a recording medium. The dark ink and the light ink contain a common water-soluble dye, and the light ink further contains a sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups.

  According to the present invention, the difference in ozone resistance between the dark ink and the light ink is small, and an image using the dark ink and the light ink that can obtain an image in which the difference in the appearance of the image depending on the type of the recording medium is suppressed is obtained. A recording method can be provided. According to another embodiment of the present invention, an ink set that can be used in the image recording method can be provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments. The image recording method of the present invention is an image recording method comprising a step of recording an image by applying dark ink and a light ink having the same hue as the dark ink to a recording medium, respectively. The ink and the light ink contain a common water-soluble dye, and the light ink further contains a sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups. In the present invention, “dark ink” and “light ink” have the same hue. Furthermore, the content of the water-soluble dye in the light ink is relatively small compared to the content of the water-soluble dye in the dark ink. In the present invention, “having the same hue (dark ink and light ink)” means that, for example, if the dark ink has a black hue, the light ink also has a black hue. Specific examples of hues include yellow, magenta, cyan, black, red, green, and blue.

  The inventors first examined the cause of the “recording medium type-dependent phenomenon” that occurs in the image recording method using dark and light inks. As a result, since the ink absorption characteristics (for example, absorption speed and absorption capacity) differ depending on the type of recording medium, the diffusion behavior and permeation behavior of the dye in the ink applied to the recording medium are the types of recording medium used. It was found that the cause is different depending on the situation. It has been found that the phenomenon in which the diffusion behavior and penetration behavior of the dye changes depending on the type of the recording medium occurs particularly remarkably in the light ink having a low dye concentration. This is considered to be due to the following reason. Since the dark ink has a high dye concentration, there are many dyes present as aggregates when applied to the recording medium, and it is difficult for the recording medium to diffuse and penetrate. In contrast, in light inks with low dye concentration, there are many dyes that do not agglomerate and exist alone, so they easily diffuse and penetrate into the recording medium, and are affected by changes in the ink absorption characteristics depending on the type of recording medium. It becomes easy. As described above, among the images using dark and light inks, the use of the light ink is particularly affected by the type of recording medium, so that the appearance of the entire image is different.

  Accordingly, the present inventors have examined dyes that are difficult to change in diffusion behavior and permeation behavior depending on the type of recording medium, as dyes used in light ink. Specifically, examination was performed using a dye species that hardly diffuses or penetrates, for example, a dye having a large molecule or a dye having high affinity with a recording medium.

  However, dyes whose diffusion behavior and permeation behavior are unlikely to change depending on the type of recording medium are not always dyes with high ozone resistance, and reducing the difference in ozone resistance between dark and light inks and recording images Dyes that can achieve both of the effects of suppressing the medium type dependence phenomenon are limited, and the degree of freedom in selecting the dye is very low. For this reason, in many cases, it is not possible to achieve high image quality, which is the original purpose, using light ink. In other words, an examination focusing solely on the type of dye was not sufficient.

  Therefore, the present inventors further studied a method that can achieve both of the above two effects regardless of the kind of the dye. Specifically, the investigation was conducted paying attention to the behavior of the dye in the recording medium. As a result, in order to achieve both of the above two effects regardless of the type of dye, it was found that “the dye should be aggregated and present near the surface of the recording medium” is important. Details are shown below.

  As described above, the recording medium type-dependent phenomenon occurs due to the fact that the diffusion behavior and permeation behavior of the dye in the recording medium differ depending on the type of the recording medium in the light ink usage region. Therefore, if the dye used for the light ink can always exist in the vicinity of the surface of the recording medium, the phenomenon dependent on the recording medium type can be suppressed. On the other hand, the decrease in ozone resistance of the light ink occurs when the dye is present on the recording medium without agglomeration as described above. Therefore, if the dye can be present in an aggregated state, the molecular structure is not easily destroyed, and ozone resistance can be improved. From the above, it was concluded that the above-mentioned two effects can be achieved regardless of the type of dye used in the light ink by “the dye is present in the vicinity of the surface of the recording medium”.

  From the above viewpoint, various compounds used in the light ink, in particular, water-soluble organic compounds were studied. As a result, when a certain sugar compound was used, good results were obtained. Therefore, when various sugar compounds were further studied, the use of “sugar compounds having 6 or more carbon atoms and 5 or more hydroxyl groups” in the light ink, the above-mentioned “near the surface of the recording medium” In addition, the inventors have found that it is possible to cause the dye to aggregate and exist. The reason will be described in detail below.

  According to the study by the present inventors, “a sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups” (hereinafter referred to as “specific sugar compound”) is caused by hydroxyl groups in the molecule in the ink. Form hydrogen bonds with water molecules. As a result, in the ink, a plurality of molecules of the specific sugar compound are aggregated via water molecules (hereinafter referred to as “molecular aggregate”). Since this molecular aggregate has a certain size, it can be present near the surface of the recording medium when applied to the recording medium. Furthermore, since the mobility in the recording medium is very small compared to the case where the molecule exists alone, it can remain without moving in the recording medium. Moreover, since this molecular aggregate contains water molecules, it has a very high affinity with water-soluble dyes. As a result, water-soluble dyes are likely to be present in the vicinity of the aggregate of molecules, and aggregates of the dyes are formed by aggregating them. With the mechanism described above, the use of the specific sugar compound in the light ink makes it possible to “give the dye to exist in the vicinity of the surface of the recording medium”. As is apparent from the above mechanism, this can be achieved regardless of the type of water-soluble dye.

  In addition, as described above, the present inventors have repeatedly studied various compounds, particularly various sugar compounds, for the number of carbon atoms and the number of hydroxyl groups (the number of carbon atoms is 6 or more and the number of hydroxyl groups is 5 or more) of the specific sugar compound. It was obtained by doing so. That is, when a saccharide compound having 5 or less carbon atoms or a saccharide compound having 4 or less hydroxyl groups is used, the above-mentioned state of “aggregating and existing the dye near the surface of the recording medium” does not occur. The above two effects could not be achieved at the same time. This is because the carbon number contributes to the size of the molecular aggregate, and when the carbon number is 5 or less, the size of the molecular aggregate is sufficient to be present in the vicinity of the surface of the recording medium. It was because it did not become. On the other hand, since the number of hydroxyl groups contributes to hydrogen bonding with water molecules, when the number of hydroxyl groups is 4 or less, the molecular assembly cannot take in water molecules and the size of the molecular assembly is sufficient. This is because there was no affinity to the water-soluble dye. As in the above mechanism, the effects of the present invention can be achieved by the synergistic effects of the components.

[Image recording method]
The image recording method of the present invention includes a step of recording an image by applying dark ink and light ink to a recording medium. Specific examples of the hues of the dark ink and the light ink used in the image recording method of the present invention include yellow, magenta, cyan, black, red, green, and blue. Among these, it is more preferable to apply the configuration of the present invention to an image recording method using a dark ink set with a black hue and a dark ink set with a cyan hue, in which the recording medium type-dependent phenomenon is more easily recognized. Specifically, the dark ink set having a black hue satisfying the configuration of the present invention is a dark black ink and a light black ink (gray ink). Further, if the image recording method uses dark ink and light ink satisfying the configuration of the present invention, the effect of the present invention is exhibited even if the ink recording apparatus further includes other hue inks that do not satisfy the configuration of the present invention.

  In the present invention, an ink jet recording method is preferred in which recording is performed on a recording medium by ejecting ink from an ejection port of a recording head by an ink jet method in accordance with a recording signal. In particular, an ink jet recording method in which ink is ejected from the ejection port of the recording head by applying thermal energy to the ink is more preferable. Hereinafter, each component contained in the dark ink and the light ink used in the image recording method of the present invention will be described.

<Water-soluble dye>
In the present invention, the “water-soluble dye” means a dye that can be dissolved in an aqueous medium. The water-soluble dye used in the present invention may be a known dye or a newly synthesized dye. Specifically, acid dyes, direct dyes, food dyes and the like as shown below can be used.

  Examples of yellow dyes used in yellow ink include C.I. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110, 132, 173, etc .; I. Acid yellow: 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99 and the like.

  Examples of the magenta dye used in the magenta ink include C.I. I. Direct Red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 229, 230, etc .; I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134, 145 158, 198, 249, 265, 289, etc .; I. Food Red: 87, 92, 94, etc .; I. Direct violet: 107 and the like.

  Examples of the cyan dye used in the cyan ink include C.I. I. Direct Blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226, 307, etc .; I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 112, 117, 127, 138, 158 161, 203, 204, 221, 244, and the like. Moreover, the dye shown by the following general formula (1) can also be used.

(In General Formula (1), A, B, C, and D are each independently a six-membered aromatic ring, and at least one of A, B, C, and D is a pyridine ring or a pyrazine ring. M is each independently a hydrogen atom, alkali metal, ammonium, or organic ammonium, [E] is an alkylene group, and [X] is a sulfo-substituted anilino group, a carboxy-substituted anilino group, or a phosphono-substituted anilino group. The substituted anilino group further includes a sulfonic acid group, a carboxyl group, a phosphono group, a sulfamoyl group, a carbamoyl group, a hydroxyl group, an alkoxy group, an amino group, an alkylamino group, a dialkylamino group, an arylamino group, a diarylamino group, Acetylamino group, ureido group, alkyl group, nitro group, cyano group, halogen atom, alkylsulfonyl And 1 to 4 substituents selected from the group consisting of a group and an alkylthio group, [Y] is a hydroxyl group or an amino group, and a, b, and c are 0 ≦ a. ≦ 2.0, 0 ≦ b ≦ 3.0, 0.1 ≦ c ≦ 3.0, and a + b + c = 1.0 to 4.0.)

  In the present invention, among the cyan dyes, it is preferable to use a dye represented by the general formula (1) having a structure having high ozone resistance. Among these, it is preferable to use the following exemplary compound (C1).

(In the formula, each M is independently a hydrogen atom, an alkali metal, ammonium, or organic ammonium. B and c are 0 ≦ b ≦ 2.9 and 0.1 ≦ c ≦ 3.0. And b + c = 1.0 to 3.0.)
Examples of the black dye used in the black ink include C.I. I. Direct Black: 17, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168, 195, etc .; I. Acid Black: 2, 48, 51, 52, 110, 115, 156, etc .; I. Food black: 1, 2, etc. are mentioned. Moreover, the dye shown by the following general formula (2), (3), (4) can also be used.

(In the general formula (2), [A] is an optionally substituted aromatic group or heterocyclic group, and-[B]-is any one of the following general formulas (I) to (V). And each M is independently a hydrogen atom, an alkali metal, ammonium, or organic ammonium.)

(In the general formulas (I) to (V), R _{1 to} R ₉ are each independently a hydrogen atom, halogen atom, aliphatic group, aromatic group, heterocyclic group, carboxyl group, carbamoyl group, alkoxycarbonyl group, Aryloxycarbonyl group, heterocyclic oxycarbonyl group, acyl group, hydroxyl group, alkoxy group, aryloxy group, heterocyclic oxy group, silyloxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, aryloxycarbonyloxy group, Amino group, acylamino group, ureido group, sulfamoylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, alkyl or arylsulfonylamino group, heterocyclic sulfonylamino group, cyano group, nitro group, alkyl or arylthio group, Duplicate One of a ring thio group, an alkyl or arylsulfonyl group, a heterocyclic sulfonyl group, an alkyl or arylsulfinyl group, a heterocyclic sulfinyl group, a sulfamoyl group, and a sulfonic acid group, and each group may be further substituted. )

  In the present invention, it is preferable to use the following exemplary compound (K1) among the dyes represented by the general formula (2).

(In the formula, each M is independently a hydrogen atom, an alkali metal, ammonium, or organic ammonium.)

(In General Formula (3), each M is independently a hydrogen atom, an alkali metal, ammonium, or organic ammonium. [A] is an aliphatic amine residue having a carboxyl group or a sulfonic acid group. is there.)

  In the present invention, among the dyes represented by the general formula (3), it is preferable to use the following exemplary compound (K2).

(In the formula, each M is independently a hydrogen atom, an alkali metal, ammonium, or organic ammonium.)

(In the general formula (4), [A] is a phenyl group having a substituent, and the substituent is a carboxyl group, a sulfonic acid group, a chlorine atom, a cyano group, a nitro group, a sulfamoyl group, a carbon number of 1 to An alkyl group having 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms (which may be substituted with a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a sulfonic acid group, or a carboxyl group), and an alkyl having 1 to 4 carbon atoms Selected from the group consisting of a sulfonyl group (which may be substituted with a hydroxyl group, a sulfonic acid group, or a carboxyl group) [B] and [C] are each independently a paraphenylene group having a substituent; The substituent includes a carboxyl group, a sulfonic acid group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms (a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms). Selected from the group consisting of a sulfonic acid group or a carboxyl group, and an alkylsulfonyl group having 1 to 4 carbon atoms (which may be substituted with a hydroxyl group, a sulfonic acid group, or a carboxyl group). R ₁₁ is any one of an alkyl group having 1 to 4 carbon atoms which may be substituted with a carboxyl group, a phenyl group which may be substituted with a sulfonic acid group, or a carboxyl group, and R ₁₂ is Any one of a cyano group, a carbamoyl group, and a carboxyl group, and R ₁₃ and R ₁₄ are each independently a hydrogen atom, a methyl group, a chlorine atom, or a sulfonic acid group.)

  In the present invention, among the dyes represented by the general formula (4), it is preferable to use the following exemplary compound (K3).

(In the formula, each M is independently a hydrogen atom, an alkali metal, ammonium, or organic ammonium.)

  Examples of red dyes used in red ink include C.I. I. Acid Orange: 7, 10, 33, 56, 67, 74, 88, 94, 116, 142, etc .; I. Acid Red: 111, 114, 266, 374, etc .; I. Direct orange: 26, 29, 34, 39, 57, 102, 118, etc .; I. Food Yellow: 3 etc .; C.I. I. Reactive orange: 1, 4, 5, 7, 12, 13, 14, 15, 16, 20, 29, 30, 84, etc. Alternatively, a material obtained by appropriately mixing the yellow color material and the magenta color material can be used.

  Examples of the green dye used in the green ink include C.I. I. Acid Green: 5, 6, 9, 12, 15, 16, 19, 21, 25, 28, 81, 84, etc .; I. Direct green: 26, 59, 67, etc .; I. Food Green: 3 etc .; I. Reactive green: 5, 6, 12, 19, 21 etc. are mentioned. Alternatively, a material obtained by appropriately mixing the yellow color material and the cyan color material can be used.

  Examples of the blue dye used in the blue ink include C.I. I. Acid Blue: 62, 80, 83, 90, 104, 112, 113, 142, 203, 204, 221, 244, etc .; I. Reactive blue: 49, etc .; I. Pigment Blue: 15: 6, etc .; I. Acid Violet: 19, 48, 49, 54, 129, etc .; I. Direct violet: 9, 35, 47, 51, 66, 93, 95, 99, etc .; I. Reactive violet: 1, 2, 4, 5, 6, 8, 9, 22, 34, 36, and the like. Alternatively, a material obtained by appropriately mixing the magenta color material and the cyan color material can be used.

(Common water-soluble dyes)
The dark ink and the light ink used in the image recording method of the present invention contain a common water-soluble dye. In the present invention, “containing a common water-soluble dye” means containing the same water-soluble dye. For example, dark ink and light ink are both C.I. I. The case of containing direct black 17 is mentioned. At this time, when the water-soluble dye contained in the dark ink and the light ink takes the form of a free acid or salt, if the structure other than the hydrogen atom of the free acid or the cation of the salt is the same, “common” It is assumed that it is a water-soluble dye. For example, when the dark ink includes “Exemplary Compound (K1)” in which M is a hydrogen atom, and the light ink includes “Exemplary Compound (K1) in which M is lithium”, the dark ink and the light ink are common. It is judged that the exemplified compound (K1) is contained as a water-soluble dye. Further, in the case of a structure having a substituent in the phthalocyanine skeleton as in the general formula (1), if the type of the substituent is the same, the position of the phthalocyanine skeleton into which the substituent is introduced may be different. Assume that it is a “common water-soluble dye”. The dark ink and the light ink may further contain other water-soluble dyes in addition to the common water-soluble dye.

(Water-soluble dye content)
In the present invention, the total content (% by mass) of the water-soluble dye in the dark ink is preferably 3.0% by mass or more and 15.0% by mass or less based on the total mass of the dark ink. Furthermore, it is more preferable that it is 3.0 mass% or more and 10.0 mass% or less. In the present invention, the total content (% by mass) of the water-soluble dye in the light ink is preferably 0.1% by mass or more and less than 3.0% by mass based on the total mass of the light ink.

  In the present invention, the ratio of the content of the common water-soluble dye to the total content of the water-soluble dye in the dark ink is preferably 40% by mass or more and 100% by mass or less. Moreover, it is preferable that the ratio of the content of the common water-soluble dye to the total content of the water-soluble dye in the light ink is 40% by mass to 100% by mass. Furthermore, it is more preferable that the content of the common water-soluble dye in the dark ink is larger than the content of the common water-soluble dye in the light ink.

<Sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups>
In the present invention, examples of the “sugar compound” include monosaccharides, dehydration condensates thereof, and sugar alcohols. Here, the “dehydrated condensation product of monosaccharides” means a compound in which two or more molecules of monosaccharides form a glycoside bond by dehydration condensation. The “sugar alcohol” means a compound obtained by reducing the aldehyde group and the ketone group of a monosaccharide or a monosaccharide dehydration condensate. Many sugar compounds have stereoisomers, but in the present invention, they may be D-form or L-form.

  Specific examples of the sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups that can be used in the present invention (hereinafter also simply referred to as “sugar compound”) are as follows. For example, as monosaccharides, allose, altrose, glucose, mannose, gulose, idose, galactose, talose, psicose, fructose, sorbose, tagatose, sedheptulose, coliose, fructofuranose, allopyranose, altropyranose, glucopyranose, man Nopyranose, gropyranose, idopyranose, galactopyranose, taropyranose and the like can be mentioned. Examples of the monosaccharide dehydration condensate include maltose, cellobiose, gentiobiose, melibiose, lactose, tulanose, sophorose, trehalose, isotrehalose, sucrose, and isosaccharose. Examples of the sugar alcohol include sorbitol, mannitol, iditol, galactitol, boremitol, perseitol, maltitol and the like. These sugar compounds can be used alone or in combination of two or more as required. Of these, sorbitol, galactose, and trehalose are preferably used in the present invention.

  The sugar compound used in the present invention preferably has 12 or more carbon atoms. Moreover, it is preferable that the number of hydroxyl groups is 8 or more. According to the study by the present inventors, it was confirmed that when a sugar compound having 12 or more carbon atoms and 8 or more hydroxyl groups was used, the moisture resistance of the image was improved. Therefore, it is more preferable to use trehalose among the sugar compounds exemplified above. The number of carbon atoms is preferably 20 or less and the number of hydroxyl groups is preferably 15 or less.

(Content of sugar compound in light ink)
In the present invention, the content (% by mass) of the sugar compound in the light ink is preferably 1.0% by mass or more and 20.0% by mass or less based on the total mass of the light ink. Furthermore, it is preferable that they are 5.0 mass% or more and 10.0 mass% or less. If the content of the sugar compound in the light ink is less than 1.0% by mass, the effect of using the specific sugar compound may not be obtained. If it is larger than 20.0% by mass, the bronzing phenomenon may occur due to excessive aggregation of the dye. In the present invention, the “bronze phenomenon” means a phenomenon in which a recorded image causes a metallic luster-like glare or the reflected light looks different from the original color of the dye depending on the observation angle of the image. .

  Moreover, it is preferable that content (mass%) of the sugar compound in light ink is 0.2 times or more and 20.0 times or less by mass ratio with respect to content (mass%) of the dye in light ink. More preferably, it is 0.30 times or more and less than 6.00 times. The effect by using the above-mentioned specific sugar compound is further acquired by being in the range of the above-mentioned mass ratio. In the present invention, the content of the component when calculating the mass ratio is based on the total mass of the ink.

(Content of sugar compound in dark ink)
In the present invention, it is preferable that the dark ink does not substantially contain a sugar compound. In the present invention, “substantially not containing” means that the content (% by mass) of the sugar compound is 0% by mass or more and less than 1.0% by mass based on the total mass of the dark ink. If the content of the sugar compound in the dark ink is 1.0% by mass or more, a bronze phenomenon may occur due to dye aggregation. Further, it is more preferably 0% by mass, that is, the dark ink does not contain the sugar compound.

<Aqueous medium>
Each ink used in the present invention can use water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 5.0% by mass or more and 90.0% by mass or less based on the total mass of the ink. Furthermore, it is more preferable that it is 10.0 mass% or more and 50.0 mass% or less. As the water-soluble organic solvent, any of those generally used in the past can be used. Examples thereof include alcohols, glycols, alkylene glycols having 2 to 6 carbon atoms in the alkylene group, polyethylene glycols, nitrogen-containing compounds, and sulfur-containing compounds. These water-soluble organic solvents can be used alone or in combination of two or more as required. It is preferable to use deionized water (ion exchange water) as the water. The content (% by mass) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink.

<Other additives>
In addition to the above components, each ink used in the present invention is water-soluble at room temperature, such as polyhydric alcohols such as trimethylolpropane and trimethylolethane, and urea derivatives such as urea and ethyleneurea, if necessary. An organic compound may be contained. Furthermore, each ink used in the present invention includes a surfactant, a pH adjuster, a rust inhibitor, a preservative, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, a chelating agent, and the like, if necessary. You may contain various additives, such as resin.

[Ink set]
The ink set of the present invention is an ink set having a dark ink and a light ink having the same hue as the dark ink, wherein the dark ink and the light ink contain a common water-soluble dye, The light ink further comprises a sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups, and is a dark ink and a light ink used in the image recording method of the present invention described above. Is to use.

[recoding media]
Examples of the recording medium that can be used in the present invention include a recording medium having an ink receiving layer, a permeable recording medium such as plain paper, and a non-permeable recording medium such as glass, plastic, and film. Among them, those having an ink receiving layer are preferable, and those having a surface having gloss or semi-gloss properties are more preferable. Specifically, at least one surface of the support is mainly composed of a pigment such as silica, alumina or a hydrate thereof, and contains an ink receiving agent such as a binder or a cationic polymer as necessary. It is preferable to use a recording medium having a layer. Such a recording medium is suitable because it absorbs ink through a void having a porous structure composed of pigment particles, and the formed image becomes high quality. The support is preferably one that can form the ink-receiving layer and gives rigidity that can be transported by a transport mechanism of an ink jet recording apparatus. Etc. Further, a recording medium in which a resin layer such as polyolefin is provided on at least one surface of a support and an ink receiving layer is further formed thereon may be used. Further, a recording medium having an ink receiving layer on both sides of the support can be used.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples as long as the gist thereof is not exceeded. In the description of the following examples, “part” is based on mass unless otherwise specified.

<Preparation of dark ink and light ink>
Water-soluble dyes and sugar compounds shown in Tables 1 to 4 were mixed with the following components. The balance of ion-exchanged water is such that the total of all components constituting the ink is 100.0% by mass.
・ Water-soluble dyes See Tables 1 to 4 ・ Sugar compounds See Tables 1 to 4 ・ Glycerin See Tables 1 to 4 ・ Ethylene glycol See Tables 1 to 4 ・ Acetylenol E100 (Surfactant: manufactured by Kawaken Fine Chemicals) 1.0% by mass
-Ion-exchanged water The remainder was sufficiently stirred, and then pressure filtered through a filter having a pore size of 0.20 µm to prepare each ink.

  In addition, the exemplified compound (M1) and the exemplified compound (Y1) in the table are represented by the following formulae. In the exemplary compound (C1), b is 2.4 and c is 0.6.

<Evaluation>
In the present invention, in the evaluation criteria of the following evaluation items, AA to C are preferable levels, and D is an unacceptable level. In addition, each following evaluation was performed using the inkjet recording device PIXUS iP8600 (made by Canon). The recording conditions were temperature: 23 ° C. and relative humidity: 55%. In this embodiment, the recording duty is set under the condition that the ink jet recording apparatus is used to apply eight drops of 2.5 pL of volume to a unit area of 1/600 inch × 1/600 inch with a resolution of 600 dpi × 600 dpi. It is defined as 100%.

(Difference in ozone resistance between dark ink and light ink)
Each of the dark and light inks obtained above was filled in an ink cartridge to form an ink set with the combinations shown in Table 5 and mounted on the ink jet recording apparatus PIXUS iP8600. A solid image using only dark ink (image with 100% dark ink duty) and a solid image using only light ink (recording of light ink) on Canon photographic paper / glossy professional PR-201 (manufactured by Canon) 100% duty image) was recorded. The size of the solid image was 10 cm × 10 cm, respectively. For the two types of images obtained at this time, the brightness (L value) and color tone (a value and b value) in the L ^* a ^* b ^* display system defined by the CIE (International Commission on Illumination) were measured using a spectrophotometer ( (Trade name: Spectrolino; manufactured by Gretag Macbeth) was used under the conditions of light source: D50, field of view: 2 °. This measured value is defined as “Lab value before the ozone resistance test”. Furthermore, the same two types of images were exposed for 24 hours at an ozone gas concentration of 10.0 ppm, a relative humidity of 50%, and a bath temperature of 23 ° C. using an ozone tester (trade name: OMS-H; manufactured by Suga Test Instruments). The ozone resistance test was conducted. Thereafter, the “Lab value after the ozone resistance test” was measured in the same manner as before the ozone resistance test. For the two images, the color difference (ΔE) was calculated from the Lab value before the ozone resistance test and the Lab value after the ozone resistance test based on the following formula (A). At this time, the color difference of the solid image using only the dark ink is ΔE ₁ , the color difference of the solid image using only the light ink is ΔE _2, and the value of ΔE ₂ −ΔE ₁ is calculated. The difference in ozone resistance was evaluated. The evaluation criteria are as follows. The evaluation results are shown in Table 5.

AA: ΔE ₂ −ΔE ₁ was less than 5 A: ΔE ₂ −ΔE ₁ was 5 or more and less than 6 B: ΔE ₂ −ΔE ₁ was 6 or more and less than 8 C: ΔE ₂ −ΔE ₁ Was 8 or more and less than 10. D: ΔE ₂ −ΔE ₁ was 10 or more.

(Phenomenon dependent on recording medium type of image)
Each of the dark and light inks obtained above was filled in an ink cartridge, made into an ink set with the combinations shown in Table 5, and mounted on the ink jet recording apparatus PIXUS iP8600 to perform the following evaluations. At this time, the light ink (black) ink cartridge is at the R position, the dark ink (black) ink cartridge is at the Bk position, the dark ink (cyan) ink cartridge is at the C position, and the light ink (cyan). The ink cartridges were mounted at the PC positions. And for each of Canon Photo Paper / Glossy Professional PR-201 and Canon Photo Paper / Glossy Pro [Platinum Grade] PT-101, the total recording duty of dark ink and light ink is 100%. Images were recorded in which the recording duty was changed stepwise from 0% to 100% in 10% increments. Thereafter, the film was dried at a temperature of 23 ° C. and a relative humidity of 55% for 24 hours. For each of the dark and light ink sets, the recording medium type-dependent phenomenon was evaluated by visually comparing the images recorded on the two types of recording media. The evaluation criteria are as follows. The evaluation results are shown in Table 5.

A: There was no difference in the appearance of the image depending on the type of recording medium. B: A slight difference in the appearance of the image was observed depending on the type of recording medium. Depending on the type of recording medium, there was a clear difference in the appearance of the image.

(Bronze phenomenon in images)
Whether or not bronze phenomenon occurred visually with respect to the images of Canon photographic paper / glossy professional PR-201 obtained in the above (phenomenon dependent on recording medium type of image) was evaluated. The evaluation criteria are as follows. The evaluation results are shown in Table 5.

A: Bronze phenomenon was not seen. Or, although it was slightly observed, it was a level that was hardly noticed. B: Bronze phenomenon was observed, but it was an inconspicuous level. C: Bronze phenomenon was observed.

Claims (7)

An image recording method comprising a step of recording an image by applying a dark ink and a light ink having the same hue as the dark ink to a recording medium,
The dark ink and the light ink contain a common water-soluble dye,
The image recording method, wherein the light ink further contains a sugar compound having 6 or more carbon atoms and 5 or more hydroxyl groups.   The image recording method according to claim 1, wherein the content (% by mass) of the sugar compound in the light ink is 1.0% by mass or more and 20.0% by mass or less based on the total mass of the light ink.   The image recording method according to claim 1, wherein the content (% by mass) of the sugar compound in the light ink is 5.0% by mass or more and 10.0% by mass or less based on the total mass of the light ink.   The ratio of the content of the common water-soluble dye to the total content of the water-soluble dye in the dark ink is 40% by mass or more and 100% by mass or less in terms of mass ratio, and the water-soluble dye in the light ink 4. The image recording according to claim 1, wherein the ratio of the content of the common water-soluble dye to the total content of the functional dye is 40% by mass to 100% by mass in mass ratio. Method.   The content (% by mass) of the sugar compound in the light ink is 0.30 times or more and less than 6.00 times as a mass ratio with respect to the content (% by mass) of the water-soluble dye. 5. The image recording method according to any one of 4 above.   The image recording method according to claim 1, wherein hues of the dark ink and the light ink are black or cyan. An ink set having a dark ink and a light ink having the same hue as the dark ink, wherein the dark ink and the light ink contain a common water-soluble dye, and the light ink further has a carbon number. An ink set comprising: a sugar compound having a hydroxyl group number of 5 or more and 5 or more.