JP2006008908A - Water-based ink, inkset, ink jet recording method, ink cartridge, recording unit, ink jet recording device and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkset exhibiting a high light resistance in imaging with a combination of more than one water-based ink. <P>SOLUTION: At least two kinds of water-based inks composed of at least water, a water-insoluble colorant and a water-soluble organic solvent are used in an inkset. Such inkset includes a combination of water-based inks for imaging by over-printing two or more kinds of water-based inks. In these water-based inks a water-based ink having a comparatively higher light resistance contains at least one kind of water-soluble organic solvent which is a poor solvent for the water-insoluble colorants contained in the ink. The other water-based inks contain comparatively larger amounts of water-soluble organic solvents which are good solvents for the water-insoluble colorants contained in the respective water-based inks. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a set of aqueous ink containing water, a water-soluble organic solvent, and a water-insoluble colorant, an aqueous ink constituting the set, an ink cartridge using the same, a recording unit, an ink jet recording apparatus, and an image forming method.

  Conventionally, in an image formed from a plurality of inks containing a colorant, the light resistance varies depending on the type of the colorant forming the image. It is known that it can change. In recent years, various techniques have been proposed for the purpose of further improving the light resistance of images formed with such inks. For example, there is a proposal to achieve an image with less color balance disruption by using an ink set that makes the fading property uniform. (For example, refer to Patent Document 1).

  In addition, there is a proposal for making it difficult for humans to visually recognize fading by using an ink set in which the magnitude of fading of ink decreases in order from high to low ink. (For example, refer to Patent Document 2).

Thus, in order to improve the light resistance of an ink set (the expression “light resistance of ink” means the light resistance of images and dots formed by the ink; In the past, means such as an ink set with uniform fading or an ink set combining high brightness and fading have been mainly used.
JP 2002-309140 A JP 2000-178491 A

  Regarding the change in the image formed using the above-mentioned plural kinds of colorants, the present inventors generally design appropriate components such as a water-insoluble colorant and a water-soluble organic solvent that form a water-based ink. In addition, by controlling the combination and the like, intensive studies were made on the possibility of an image having light resistance similar to that described above. Based on the study, the components of the ink were functionally separated, and an ink system using the interaction between the water-insoluble colorant and the water-soluble organic solvent was designed and actually prepared. A water-based ink set comprising a combination of a plurality of water-based inks that can be secured in a well-balanced manner can be provided.

Accordingly, an object of the present invention is to provide an ink set capable of having high light resistance when an image is formed by combining a plurality of water-based inks. Another object of the present invention relates to an ink cartridge, a recording unit, an ink jet recording apparatus, an image forming method using the ink set, and an aqueous ink used for the image forming method.

  The above object is achieved by the present invention described below.

The ink set according to the present invention is an ink set having two or more types of water-based inks.
Including water, a first water-insoluble colorant, and a good solvent and a poor solvent for the first water-insoluble colorant, the total amount (% by mass) of the good solvent is A, and the total amount (% by mass) of the poor solvent in the ink Where A: B is in the range of 10: 5 or more and 10:30 or less,
It contains water, a second water-insoluble colorant, a good solvent for the second water-insoluble colorant, and a poor solvent as necessary. The total amount (% by mass) of the good solvent is A, and the poor solvent in the ink A second ink in which A: B is less than 10: 5 (including B = 0) when the total amount (% by mass) is B;
Having at least
The first water-based ink and the second water-based ink are applied in contact with a recording medium,
The ink set is characterized in that the light resistance of the first ink is higher than the light resistance of the second ink.

  One aspect of the ink jet recording method according to the present invention is an ink jet recording method including a step of discharging the ink constituting the ink set by the ink jet method.

  The ink cartridge of the present invention is an ink cartridge characterized by individually containing the ink constituting the ink set.

  The recording unit of the present invention includes an ink storage unit that individually stores the ink that constitutes the ink set, and an ink jet head that discharges the ink that constitutes the ink set. A recording unit.

  The ink jet recording apparatus of the present invention includes an ink containing portion that individually contains the ink constituting the ink set, and an ink jet head for discharging the ink constituting the ink set. This is an ink jet recording apparatus.

According to another aspect of the ink jet recording apparatus of the present invention, recording is performed by relatively scanning a recording head that individually discharges ink constituting an ink set in which water-based inks having different light resistance are combined with respect to a recording medium. An ink jet recording method comprising:
Using the ink set according to any one of claims 1 to 3 as an ink set,
Further, when forming an image formed by each water-based ink having different light resistance, after forming an image by performing scanning that applies an ink containing a water-insoluble colorant having relatively low light resistance, the image is The inkjet recording method is characterized in that scanning is performed to apply ink having relatively high light resistance to the formed region.

One aspect of the water-based ink according to the present invention includes water, a first water-insoluble colorant, and a water-soluble organic solvent, and the poor solvent for the first water-insoluble colorant as the water-soluble organic solvent A first ink containing at least a water, a second water-insoluble colorant, and a water-soluble organic solvent, wherein the water-soluble organic solvent is a poor solvent for the second water-insoluble colorant as necessary. A second ink containing,
The first water-based ink and the second water-based ink are applied in contact with a recording medium, and the light resistance of the first ink is higher than that of the second ink. A water-based ink used as the first water-based ink of the image recording method which is relatively high,
The water-based ink is characterized in that the content ratio of the poor solvent relative to the first water-insoluble colorant is greater than the content ratio of the poor solvent relative to the second water-insoluble colorant.

  A: B is in the range of 10: 5 or more and 10:30 or less, where A is the total amount (% by mass) of the good solvent and B is the total amount (% by mass) of the poor solvent. The water-based ink according to claim 11.

Another aspect of the water-based ink according to the present invention includes water, a first water-insoluble colorant, and a water-soluble organic solvent, and the water-soluble organic solvent is at least for the first water-insoluble colorant. A first ink containing a poor solvent, water, a second water-insoluble colorant, and a water-soluble organic solvent, wherein the water-soluble organic solvent is poor against the second water-insoluble colorant as necessary. A second ink containing a solvent;
The first water-based ink and the second water-based ink are applied in contact with the recording medium, and the light resistance of the first ink is higher than that of the second ink. Is a water-based ink used as the second water-based ink of the image recording method, which is relatively high,
The water-based ink is characterized in that the content ratio of the poor solvent relative to the second water-insoluble colorant is smaller than the content ratio of the poor solvent relative to the first water-insoluble colorant.

Furthermore, another aspect of the ink set according to the present invention is an ink set having two or more types of water-based inks.
Including water, a first water-insoluble colorant, and a good solvent and a poor solvent for the first water-insoluble colorant, the total amount (% by mass) of the good solvent is A, and the total amount (% by mass) of the poor solvent in the ink Where A: B is in the range of 10: 5 or more and 10:30 or less,
Including water, a second water-soluble colorant, and a solvent;
The first water-based ink and the second water-based ink are applied in contact with a recording medium,
An ink set, wherein the light resistance of the first ink is higher than the light resistance of the second ink.

  According to the present invention, there are provided an ink set capable of having high light resistance when an image is formed by combining a plurality of water-based inks, and inks constituting them. In addition, according to the present invention, by using such an ink set, an ink jet recording method capable of forming an image having high light resistance, an ink cartridge, a recording unit, and ink jet recording that can be suitably used in the above recording method. An apparatus and an image forming method can be provided. Furthermore,

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

  The ink set of the present invention has at least two types of water-based inks, and each of these water-based inks contains water, a coloring material, and a water-soluble organic solvent. The ink set includes one or more combinations of a first water-based ink having relatively high light resistance and a second water-based ink having relatively low light resistance. The first water-based ink contains a poor solvent and a good solvent for the first water-insoluble color material, and the second water-based ink contains only the good solvent for the second water-insoluble color material, or both the poor solvent and the good solvent. Including. It is preferable that the poor solvent contained in the first ink is also a poor solvent for the water-insoluble colorant contained in the second ink.

  Further, when the Ka values obtained by the Bristow method of each of the plurality of water-soluble organic solvents contained in the first ink are compared, the water-soluble organic solvent exhibiting the maximum Ka value among them is a poor solvent. It is preferable.

  The content ratio of the poor solvent in the first water-based ink is preferably larger than the content ratio of the second poor solvent. Furthermore, the total amount (% by mass) of the good solvent in the ink is A, and the poor solvent in the ink. When the total amount (mass%) of B is B, it is preferable that A: B is in the range of 10: 5 or more and 10:30 or less. The second water-based ink includes A: B preferably less than 10: 5 (B = 0).

  The first water-based ink can contain a plurality of types of water-insoluble color materials (first water-insoluble color material group). Independently of this, the second water-based ink also contains a plurality of types of water-insoluble color materials. A color material (first water-insoluble color material group) can be included, and even in these cases, the water-insoluble color material is selected so as to satisfy the above-mentioned rules for each water-insoluble color material group as a whole.

  Further, a water-soluble color material may be used as the second color material of the second ink having relatively low light resistance.

  By forming an image as an ink set using the ink having the above-described configuration, there is a remarkable effect that an image formed from a plurality of inks, which has been a problem in the past, can have high light resistance. It has been found out that it can be obtained and has led to the present invention.

  Although the reason why the above-described effects can be obtained by the present invention is not clear, the present inventors presume as follows. In general, when an image is formed with a plurality of water-based inks on a recording medium, a means for suppressing the light resistance of an ink having a relatively low light resistance is required in order to obtain an image having high light resistance. is there. For this purpose, an image having a relatively excellent light resistance is formed in the vicinity of the paper surface of the recording medium, and an image formed from another ink having a relatively low light resistance is the inside of the recording medium, that is, the relative It is an important condition that the ink is formed inside the image formed from the ink having excellent light resistance.

  Therefore, in the present invention, the water-soluble organic solvent that does not stabilize the water-insoluble colorant is a poor solvent for the water-insoluble colorant, the water-soluble organic solvent that stabilizes the water-insoluble colorant is a good solvent, and the poor solvent Water-soluble organic solvent which becomes the poor solvent after the ink containing the water-insoluble colorant has landed by containing more ink than the ink having relatively excellent light resistance than the ink having relatively low light resistance When the ink containing the ink is injected, the water-insoluble colorant aggregates and is formed in the vicinity of the paper surface of the recording medium.On the other hand, the ink having low light resistance has a smaller amount of poor solvent than the ink having excellent light resistance. By including the ink, it is considered that the water-insoluble colorant does not aggregate even after the ink containing the water-insoluble colorant lands, and penetrates into the recording medium.

  When the ink set according to the present invention is printed on a recording medium, it is considered that it is possible to have extremely excellent light resistance for the following reasons. When the ink set of the present invention is printed on the recording medium, the state from when the ink lands on the recording medium until the colored portion by the secondary color is fixed is shown in FIGS. ). First, as shown in (a), the second ink droplet 91 having relatively low light resistance has landed on the recording medium 90, and as shown in (b), the ink dots 92 are located near the recording medium. It diffuses in a shape close to a perfect circle. At that time, the water-insoluble colorant 93 in the second ink is only a good solvent, or the amount of poor solvent is less than that of the good solvent. Since the concentration does not increase, aggregation of the water-insoluble colorant due to the influence of the poor solvent does not occur, and the water-insoluble colorant also enters the recording medium in the same manner as the penetration of water and the water-soluble organic solvent into the recording medium. Diffusion begins. Then, during the diffusion of the second ink droplet to the recording medium, as shown in (c), the next first ink droplet 94 having a relatively high light resistance is landed, and similarly to the second ink, As shown in (d), the second ink dot 95 diffuses in a shape close to a perfect circle in the vicinity of the recording medium, but the first water-insoluble color contained in the first ink in the course of the diffusion. The concentration of 97, which is a poor solvent, for the material 96 suddenly increases. Along with this, the first water-insoluble colorant 96 becomes unstable, and the water-insoluble colorant aggregates or breaks down. As a result, as shown in FIG. Is fixed near the surface of the recording medium. Further, since the water-soluble organic solvent and water in the ink spread radially while further diffusing, the water-soluble organic solvent contained in the first ink that has landed later on the second water-insoluble colorant. In the case where the solvent acts as a poor solvent, the second water-insoluble colorant diffusing inside the recording medium is also destabilized. It takes place and settles where agglomeration or dispersion failure occurs.

  The first water-insoluble colorant in the first ink, which is present near the surface of the recording medium and has relatively high light resistance, is present near the surface, so that it is directly exposed to light. Since it has high light resistance and is in an agglomerated state, fading is unlikely to occur. Therefore, even when the first ink is a single color, it can have the same light resistance as when the amount of the poor solvent is small. On the other hand, since the second water-insoluble colorant in the second ink, which has relatively low light resistance, is present inside the recording medium, the amount of light irradiation is greater than that in the vicinity of the surface. Therefore, the discoloration is suppressed, and further, due to the influence of the poor solvent contained in the first ink having relatively light resistance, it is present in an aggregated state despite being inside the recording medium. Therefore, it becomes possible to have higher light resistance than when the water-insoluble colorant is diffused. As a result, an image using the ink set of the present invention has not only the degree of fading but also the color fading difference between the inks, so that the color balance is good.

  FIG. 8 illustrates the case where two types of water-based inks (first ink and second ink) are overprinted, but the ink set of the present invention also includes the case where three or more types of ink are overprinted. The configuration is available. That is, these three or more types of inks are classified into a first water-based ink having a relatively high light resistance and a second water-based ink having a relatively low light resistance, and their compositions are applied to the present invention. It can be set.

  In addition, as a preferable form of the ink set according to the present invention, as described above, the amount of the poor solvent contained in the first ink having relatively high light resistance is relatively low in light resistance. The total amount (% by mass) of the good solvent contained in the first ink having a relatively higher light resistance than the amount of the poor solvent contained in the ink is A, and the total amount of the poor solvent in the ink. (Mass%), the ratio of A: B is in the range of 10: 5 or more and 10:30 or less, and the amount of the poor solvent contained in the second ink having relatively low light resistance is , A: B ratio is 10: 5 or less.

  Furthermore, as a preferable form of the ink set according to the present invention, the Ka values obtained by the Bristow method of each of the plurality of water-soluble organic solvents contained in the first ink having relatively excellent light resistance were compared. Sometimes, the water-soluble organic solvent having the largest Ka value is a poor solvent. As a result, the dispersion stability of the water-insoluble colorant in the ink becomes excellent, and at the same time, the water-insoluble color contained in the first ink, which is relatively excellent in light resistance when printed on a recording medium. Not only has the effect of keeping the coloring material near the surface of the recording medium efficiently, but also acts as a poor solvent for the second water-insoluble coloring material contained in the second ink having relatively low light resistance. In this case, the second water-insoluble colorant can also be aggregated to have an effect of improving light resistance.

Here, the ka value obtained by the Bristow method will be described. This value is used as a scale representing the penetrability of the ink into the recording medium. The ink liquid will be described as a cited example. When the ink permeability is expressed by the ink amount V per 1 m ² , the ink is applied to the recording medium after a predetermined time t has elapsed since the ink droplet was ejected. The permeation amount V (mL / m ² = μm) is expressed by the Bristow equation shown below.

V = Vr + Ka (t−tw) ^1/2
Here, immediately after the ink droplets adhere to the surface of the recording medium, the ink is mostly absorbed in the uneven portion of the surface of the recording medium (the roughness portion of the surface of the recording medium). It hardly penetrates into the medium. The time between them is the contact time (tw), and the amount of ink absorbed in the concavo-convex portion of the recording medium at the contact time is Vr. Then, when the contact time is exceeded after the ink is deposited, the amount of penetration into the recording medium increases by a time proportional to the time that exceeds the contact time, that is, (t-tw) to the power of 1/2. . Ka is a proportional count of this increase and shows a value according to the penetration rate. The Ka value can be measured using a Bristow method liquid dynamic permeability tester (for example, trade name: Dynamic permeability tester S; Toyo Seiki Seisakusho).

  Furthermore, in the ink image formed by the above-described process using the ink set according to the present invention, the presence of the water-insoluble colorant in the recording medium is determined by the solvent characteristics contained in the aqueous ink. Therefore, it becomes possible to have high light resistance. The present invention is effective for any recording medium. In particular, plain paper, and coated paper having an ink receiving layer on a substrate such as paper or a resin film, in which ink easily penetrates into the recording medium. In particular, the effect can be obtained with fine art paper or the like, which is a coated paper with a small amount of ink receiving layer applied to make use of the color and texture of the recording medium.

  Further, in the ink set of the present invention, when the ink set is composed of three or more types of ink, the ink having the relatively best light resistance is the first ink of the present invention, and the remaining ink is the second ink. By using the same ink configuration, it is possible to have high light resistance even in an image formed from three or more types of ink.

  Further, in the image forming method according to the present invention, since the water-insoluble colorant in the second ink having relatively low light resistance is present in the recording medium, the second ink having relatively low light resistance is used. It is preferable to perform image formation prior to image formation with the first ink having relatively excellent light resistance.

  Furthermore, in the ink set of the present invention, the second color material of the second ink having relatively low light resistance is present in the recording medium, and suppresses the amount of light irradiated to the color material, thereby improving the light resistance. Since it is improved, it is possible to use a water-soluble coloring material.

  The ink set referred to in the present invention is an ink composed of an ink tank integrated with a first ink having a relatively high light resistance and a second ink having a relatively low light resistance, or an ink tank with a head. The use of a set or an individual ink tank so as to be detachable from the recording apparatus is substantially referred to as an “ink set having these inks”. In any case, in the present invention, the characteristics of the ink alone of the present invention are defined relative to other inks used (in the printer or as an ink tank). The present invention is not limited to this, and any form of deformation may be used.

  Each ink constituting the ink set according to the present invention is characterized in that the water-soluble organic solvent in the ink component has the above-described configuration in relation to the water-insoluble colorant to be used. May have the same configuration as that of a conventional water-based ink. Below, each component which comprises this invention, and the confirmation method of an effect are demonstrated.

[Determination method of poor solvent and good solvent]
Next, the definition and selection method of the poor solvent and the good solvent that play an important role in the present invention, which are essential for causing the above-described mechanism, will be described. As a result of various studies on the criteria for determining the poor solvent that brings about the effects of the present invention in relation to the effects of the present invention, the present inventors have found that the following determination methods are effective. That is, a water-insoluble colorant-containing liquid containing 50% by mass of the water-soluble organic solvent to be determined, 45% by mass of water, and 5% by mass of the water-insoluble colorant used in the ink is prepared. When the water-insoluble colorant-containing liquid is stored at room temperature (60 ° C.) for 48 hours, the water-insoluble colorant in the water-insoluble colorant-containing liquid has an average particle diameter of 5% by mass, water What increased compared with the average particle diameter of the aqueous dispersion containing 95% by mass was defined as a poor solvent and those not increased were defined as good solvents.

  More specifically, the following method was used to determine whether or not the water-soluble organic solvent used was a poor solvent for a certain water-insoluble colorant. First, two types of water-insoluble colorant-containing liquid A, which is a water-insoluble colorant, and water-insoluble colorant-containing liquid B, which is a water-insoluble colorant, including the water-soluble organic solvent to be measured are listed below. A water-insoluble colorant-containing liquid is prepared.

  Water-insoluble colorant-containing liquid A: The concentration of the water-soluble organic solvent as the determination target is 50% by mass, and the concentration of the water-insoluble colorant or the total amount of the water-insoluble colorant and substances that contribute to its dispersion is 5% by mass. A water-insoluble colorant-containing liquid having a composition with a water concentration of 45% by mass.

  Water-insoluble colorant-containing liquid B: A water-insoluble colorant or a water-insoluble colorant containing a water-insoluble colorant containing a concentration of 5% by mass and 95% by mass of water. Material-containing liquid.

  Next, the average particle size after the water-insoluble colorant-containing liquid A is stored at 60 ° C. for 48 hours is measured using a concentrated particle size analyzer (trade name: FPAR-1000; manufactured by Otsuka Electronics Co., Ltd.). Measured. Similarly, the average particle size of the water-insoluble colorant-containing liquid B was measured using the concentrated particle size analyzer. When the average particle size of each of the water-insoluble colorant-containing liquid A and the water-insoluble colorant-containing liquid B is defined as a particle size (A) and a particle size (B), the particle size (A) is a particle size. When the diameter was larger than the diameter (B), the water-soluble organic solvent was determined to be a poor solvent, and when the particle diameter (A) was equal to or smaller than the particle diameter (B), it was determined to be a good solvent.

[Method for evaluating light resistance]
The present invention is characterized in that the light resistance of an image formed by at least two kinds of inks is ensured in a balanced manner. Here, the light resistance of the formed image can be expressed using a color space such as CIELAB. In the CIELAB color space, colors are displayed using three terms L *, a *, and b *. L * defines the brightness of the color and is in the range of 0 (black) to 100 (white). a * and b * define the hue and chromaticity characteristics of the color.

ΔE is used as an index representing the degree of fading. ΔE indicates the difference in color between the initial image and the image after fading in the CIELAB color space, and the difference in ΔE represents the difference in fading between the two color images. As the value increases, the difference in fading between the two colors increases. ΔE is expressed by the following equation.
_{ΔE = [(L * 1 -L} * 2) 2 + (a * 1 -a * 2) 2 + (b * 1 -b * 2) 2] 1/2
That is, ΔE = (ΔL * ² + Δa * ² + Δb * ² ) ^1/2
The light resistance of the ink can be known using this ΔE. That is, if ΔE after printing (before the light resistance test) and after light fading (after the light resistance test) is large, the photobleaching is large, and if ΔE is small, the light fading property is small and the light resistance is high.

[Water-soluble organic solvent]
Each water-based ink constituting the ink set according to the present invention includes at least water, a water-insoluble colorant, and a water-soluble organic solvent, but the water is not general water containing various ions but ion exchange. It is preferred to use water (deionized water). Examples of the water-soluble organic solvent used by mixing with water include carbon atoms of 1 such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like. Alkyl alcohols of -4; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol Alkylene glycols having 2 to 6 carbon atoms, such as coal; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of monohydric alcohols; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred. Among these, at least one poor solvent and at least one good solvent can be selected and used.

  In the present invention, the water-insoluble colorant used in the most light-resistant ink contains a water-soluble organic solvent that is a poor solvent, and the other inks are composed of a good solvent for the water-insoluble colorant. It's important to. Furthermore, a water-soluble organic solvent that works as a good solvent for a water-insoluble color material of an ink having low light resistance but works as a poor solvent for a water-insoluble color material in an ink having the most light resistance is particularly preferable. . This is because the water-insoluble colorant in the ink having the lowest light resistance in the recording medium is the water-soluble organic solvent in the ink that has the lowest light resistance when ink droplets are hit on the same location on the recording medium. By acting as a poor solvent, the water-insoluble colorant in the ink having light resistance can be more efficiently kept near the surface of the recording medium.

  The content of the water-soluble organic solvent as described above in each water-based ink constituting the ink set according to the present invention is generally in the range of 3 to 50% by mass, preferably 3 to 40% by mass of the total mass of the ink. The mass is in the range. The water content used is in the range of 10 to 90% by mass, preferably 30 to 80% by mass, based on the total mass of the ink.

[Water-insoluble colorant]
In the present invention, the type of the water-insoluble colorant is not particularly limited, but the effect of the present invention is likely to occur when the ink having the highest light resistance contains a water-insoluble colorant. Furthermore, the water-insoluble colorant of all inks When is a water-insoluble colorant, the effect of the present invention is remarkably exhibited. The content of the color material is 0.1 to 10% by mass, preferably 0.5 to 5% by mass in the ink.

Next, the water-insoluble colorant constituting the water-based ink according to the present invention will be described.
Regardless of the dispersion method, the water-insoluble color material constituting the water-based ink according to the present invention is, for example, a resin dispersion type pigment (resin dispersion type pigment) using a dispersant or an activator or an activator dispersion type. It may be a pigment or a self-dispersing microcapsule-type pigment that has improved the dispersibility of the water-insoluble colorant itself and that can be dispersed without using a dispersant, or a hydrophilic group introduced on the surface of pigment particles A type of pigment (self-dispersing pigment) can be used. Of course, these pigments having different dispersion methods can also be used in combination.

[Pigment]
The pigment that can be used in the aqueous ink according to the present invention is not particularly limited, and any of those listed below can be used. In addition, a plurality of types of pigments can be used in combination in one water-based ink as necessary. The content of the pigment in the aqueous ink is set according to the use of the aqueous ink.

  Carbon black is suitable as the pigment used in the black ink. For example, carbon black such as furnace black, lamp black, acetylene black and channel black can be used. Specifically, for example, Raven 7000, Ray Van 5750, Ray Van 5250, Ray Van 5000 ULTRA, Ray Van 3500, Ray Van 2000, Ray Van 1500, Ray Van 1250, Ray Van 1200, Ray Van 1190 ULTRA-II, Ray Van 1170, Ray Van 1255 (above, Colombia), Black Pearls L, Legal 400R, Legal 330R, Legal 660R, Mogul L, Monarch 700, Monak 800, Monak 880, Monak 900, Monak 1000, Monak 1100, Monak 1300, Monak 1400, Monak 2000, Valcan XC-72R (above, Bot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (above, manufactured by Degussa), No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. Commercial products such as 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical Corporation) can be used. Carbon black newly prepared for the present invention can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used. Further, the material is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used as a black pigment.

  Specific examples of organic pigments include, for example, insoluble azo pigments such as toluidine red, toluidine maroon, Hansa Yellow, Benzidine Yellow, and pyrazolone red, soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B, Derivatives from vat dyes such as alizarin, indanthrone, thioindigo maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, perylene pigments such as perylene red and perylene scarlet, Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange, benzimidazolone yellow, benzimidazolone orange and benzimidazolone red Zyrone pigments, pyranthrone pigments such as pyranthrone red, pyranthrone orange, indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo Examples include yellow, copper azomethine yellow, perinone orange, anthrone orange, dianslaquinonyl red, and dioxazine violet. Of course, it is not limited to these, Other organic pigments may be used.

  The organic pigment that can be used in the present invention is represented by a color index (CI) number. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153, 154, 166, 168, 180, 185, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272, C.I. I. Pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment green 7, 36, C.I. I. Examples thereof include CI Pigment Brown 23, 25, 26, and the like.

[Resin dispersion type pigment]
As described above, as the water-insoluble colorant contained in the water-based ink according to the present invention, resin-dispersed pigments using a dispersant can also be used. A compound for dispersing such a hydrophobic pigment is required. As such a thing, what is called a dispersing agent, surfactant, resin dispersing agent, etc. can be used. The dispersant or surfactant is not particularly limited, but among them, anionic and nonionic ones can be preferably used. For example, anionic compounds include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensates, polyoxyethylene alkyls. Sulfuric acid ester salts and substituted derivatives thereof; nonionic compounds such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxy Examples thereof include ethylene alkylamine, glycerin fatty acid ester, oxyethyleneoxypropylene block polymer, and substituted derivatives thereof. Resin dispersants include styrene and its derivatives, vinyl naphthalene and its derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and its derivatives, maleic acid and its derivatives, itaconic acid and its A block copolymer comprising at least two monomers (of which at least one is a hydrophilic monomer) selected from derivatives, fumaric acid and derivatives thereof, vinyl acetate, vinyl alcohol, vinyl pyrrolidone, acrylamide, and derivatives thereof. Examples thereof include a polymer, a random copolymer, a graft copolymer, and salts thereof. Further, these copolymers may be used together.

[Microcapsule type pigment]
As the water-insoluble colorant contained in the water-based ink according to the present invention, as described above, a microcapsule type pigment formed by coating a water-insoluble colorant with an organic polymer to form a microcapsule is used. You can also Examples of a method for coating a water-insoluble colorant with organic polymers to form microcapsules include a chemical production method, a physical production method, a physicochemical method, and a mechanical production method. Specifically, interfacial polymerization method, in-situ polymerization method, submerged cured coating method, coacervation (phase separation) method, submerged drying method, melt dispersion cooling method, air suspension coating method, spray drying method , Acid precipitation method, phase inversion emulsification method and the like.

  Examples of organic polymers used as the material constituting the wall membrane material of the microcapsule include polyamide, polyurethane, polyester, polyurea, epoxy resin, polycarbonate, urea resin, melamine resin, phenol resin, polysaccharide, gelatin, Gum arabic, dextran, casein, protein, natural rubber, carboxypolymethylene, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, cellulose, ethyl cellulose, methyl cellulose, nitrocellulose, hydroxyethyl cellulose, cellulose acetate, polyethylene , Polystyrene, (meth) acrylic acid polymer or copolymer, (meth) acrylic acid ester polymer or copolymer, (meth) acrylic acid- (meth) acrylic acid Le ester copolymer, styrene - (meth) acrylic acid copolymer, styrene - maleic acid copolymer, sodium alginate, fatty acids, paraffin, beeswax, water wax, hardened beef tallow, carnauba wax, albumin and the like.

  Among these, organic polymers having an anionic group such as a carboxylic acid group or a sulfonic acid group can be used. Examples of the nonionic organic polymer include polyvinyl alcohol, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate or their (co) polymer, and 2-oxazoline cationic ring-opening polymer. Can be mentioned. In particular, a completely saponified product of polyvinyl alcohol is particularly preferable because it has low water solubility and is easily dissolved in hot water but difficult to dissolve in cold water.

  When the phase inversion method or the acid precipitation method is selected as the microencapsulation method, anionic organic polymers are used as the organic polymers constituting the wall membrane material of the microcapsules. The phase inversion method is a composite or composite of an anionic organic polymer having self-dispersing ability or solubility in water and a water-insoluble colorant such as a self-dispersing organic pigment or self-dispersing carbon black, Alternatively, a mixture of a water-insoluble colorant such as a self-dispersing organic pigment or self-dispersing carbon black, a curing agent and an anionic organic polymer is used as an organic solvent phase, and water is added to the organic solvent phase, or In this method, the organic solvent phase is introduced into water and microencapsulated while self-dispersing (phase inversion emulsification). In the above phase inversion method, there is no problem even if the organic solvent phase is produced by mixing a water-soluble organic solvent or additive used in the ink. In particular, it is more preferable to mix an ink liquid medium because a dispersion liquid for ink can be directly produced.

  On the other hand, in the acid precipitation method, a part or all of the anionic groups of the anionic group-containing organic polymers are neutralized with a basic compound, and a water-insoluble colorant such as a self-dispersing organic pigment or self-dispersing carbon black. And a water-containing cake obtained by a production method comprising a step of kneading in an aqueous medium and a step of neutralizing and acidifying the pH with an acidic compound to precipitate an anionic group-containing organic polymer and fixing it to the pigment, This is a method of microencapsulation by neutralizing part or all of an anionic group using a basic compound. By doing in this way, the anionic microencapsulated pigment which is fine and contains many pigments can be manufactured.

  Examples of the solvent used for microencapsulation as described above include alkyl alcohols such as methanol, ethanol, propanol and butanol; aromatic hydrocarbons such as benzol, toluol and xylol; methyl acetate Esters such as ethyl acetate and butyl acetate; Chlorinated hydrocarbons such as chloroform and ethylene dichloride; Ketones such as acetone and methyl isobutyl ketone; Ethers such as tetrahydrofuran and dioxane; Cellosolves such as methyl cellosolve and butyl cellosolve Etc. The microcapsules prepared by the above method are separated once from these solvents by centrifugation or filtration, and this is stirred and redispersed with water and the necessary solvent to obtain the desired microcapsule type pigment and You can also The average particle size of the microencapsulated pigment obtained by the above method is preferably 50 nm to 180 nm.

[Self-dispersing pigment]
As described above, the water-insoluble colorant contained in the water-based ink according to the present invention is a self-dispersible material that has improved dispersibility of the water-insoluble colorant itself and can be dispersed without using a dispersant or the like. It is also possible to use a type of pigment. Examples of the self-dispersing pigment include those in which a hydrophilic group is chemically bonded to the pigment particle surface directly or through another atomic group. For example, the hydrophilic group introduced into the pigment particle surface is —COOM1, —SO ₃ M1 and —PO ₃ H (M1) ₂ (wherein M1 represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. And the like selected from the group consisting of Furthermore, those in which the other atomic group is an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group can be preferably used. In addition, a method of oxidizing carbon black with sodium hypochlorite, a method of oxidizing carbon black by ozone treatment in water, and a method of modifying the carbon black surface by wet oxidation with an oxidizing agent after ozone treatment A self-dispersing pigment of the surface oxidation treatment type obtained by the above method can also be suitably used.
[dye]
In the present invention, when a dye is used as the water-soluble colorant for water-based inks, examples include oil-soluble dyes and water-soluble dyes. Water-soluble dyes are particularly desirable from the viewpoint of storage stability as inks.

[Water-soluble dye]
As the water-soluble dye, any of a direct dye, an acid dye, a reactive dye, and a basic dye can be used. Even those not described in the color index can be used as long as they are water-soluble dyes.

Examples of direct dyes include C.I. I. Direct Black 17, 19, 19, 22, 32, 38, 51, 71, C.I. I. Direct Yellow 4, 12, 24, 26, 44, 50, 86, 87, 98, 100, 130, 132, 142, C.I. I. Direct Red 1, 4, 13, 13, 23, 28, 31, 31, 37, 39, 62, 75, 79, 80, 81, 83, 89, the same 225, 226, 227, 240, 242 and 243, C.I. I. Direct Blue 1, 6, 15, 22, 25, 71, 78, 86, 106, 199 and the like.
Examples of acid dyes include C.I. I. Acid Black 1, 2, 24, 26, 31, 31, 52, 107, 109, 110, 119, 154, C.I. I. Acid Yellow 7, 11, 17, 19, 23, 25, 29, 38, 42, 49, 61, 71, 72, 78, 110, 127, 135, 141, 142, C.I. I. Acid Red 1, 6, 8, 9, 18, 18, 26, 27, 32, 35, 37, 51, 52, 57, 80, 82, the same 85, 87, 92, 94, 111, 115, 129, 131, 138, 186, 249, 254, 265, 276, 289, C.I. I. Acid Violet 15, 17 and C.I. I. Acid Blue 1, 7, 9, 22, 23, 25, 40, 41, 43, 59, 62, 78, 83, 90, 93, 102, 103, 104, 112, 113, 117, 120, 158, C.I. I. Acid Green 3, 9, 16, 25, 27 and the like.
Examples of basic dyes include C.I. I. Basic Black 2, 8 and C.I. I. Basic Yellow 1, 2 and 21, C.I. I. Basic Orange 2, 14, 32, C.I. I. Basic Red 1, 2, 9, 9, 14 C.I. I. Basic Violet 1, 3 and 7, C.I. I. Basic Blanc 12, C.I. I. Acid Blue 3, 26, C.I. I. Examples include Basic Green 49.

[Other ingredients]
The water-based ink according to the present invention may use a moisturizing solid content such as urea, urea derivative, trimethylolpropane, trimethylolethane or the like as an ink component in addition to the above-described components in order to maintain the moisture retention. In general, the content of moisturizing solids such as urea, urea derivatives, and trimethylolpropane in the ink is preferably in the range of 0.1 to 20.0% by mass, more preferably in the range of the ink. It is the range of 3.0-10.0 mass%.

  Furthermore, in addition to the above components, the ink according to the present invention includes a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, and an evaporation accelerator as necessary. Various additives such as chelating agents may be contained.

  It is preferable that the ink used in the present invention composed of the constituents described above has a characteristic that it can be discharged well from an ink jet recording head. For this reason, from the viewpoint of ejectability from the ink jet recording head, the ink characteristics are, for example, a viscosity of 1 to 15 mPa · s, a surface tension of 25 mN / m or more, and a viscosity of 1 to 5 mPa · s. The surface tension is preferably 25 to 50 mN / m.

[Recording method, recording unit, cartridge, and recording apparatus]
Next, an example of the ink jet recording apparatus according to the present invention will be described. The apparatus is characterized in that the ink set according to the present invention described above is accommodated. First, an example of a head configuration which is a main part of an ink jet recording apparatus using thermal energy is shown in FIGS. FIG. 1 is a cross-sectional view of the head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along line AB in FIG. The head 13 is obtained by bonding a heating element substrate 15 to a glass, ceramic, silicon or plastic plate having a flow path (nozzle) 14 through which ink passes.

  The heating element substrate 15 includes a protective layer 16 made of silicon oxide, silicon nitride, silicon carbide, etc., electrodes 17-1 and 17-2 made of aluminum, gold, aluminum-copper alloy, etc., HfB2, TaN, TaAl From a heating resistor layer 18 formed from a high melting point material such as, a heat storage layer 19 formed from thermal silicon oxide, aluminum oxide or the like, and a substrate 20 formed from a material with good heat dissipation such as silicon, aluminum or aluminum nitride. It has become.

  When a pulsed electric signal is applied to the electrodes 17-1 and 17-2 of the head 13, the region indicated by n of the heating element substrate 15 rapidly generates heat, and bubbles are generated in the ink 21 in contact with the surface. The pressure causes the meniscus 23 to protrude, and the ink 21 is ejected through the nozzles 14 of the head to form ink droplets 24 from the ejection orifices 22 and fly toward the recording medium 25. FIG. 3 shows an external view of an example of a multi-head in which a large number of heads shown in FIG. 1 are arranged. This multi-head is made by adhering a glass plate 27 having multi-nozzles 26 and a heating head 28 similar to that described in FIG.

  FIG. 4 shows an example of an ink jet recording apparatus incorporating this head. In FIG. 4, reference numeral 61 denotes a blade as a wiping member, one end of which is held and fixed by a blade holding member, and forms a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head 65, and in the illustrated example, is held in a form protruding in the moving path of the recording head 65.

  Reference numeral 62 denotes a cap on the projection port surface of the recording head 65, which is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, contacts the ink ejection port surface, and performs capping. The structure to perform is provided. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61 and, like the blade 61, is held in a form protruding in the moving path of the recording head 65. The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the ejection port surface.

  Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording medium facing the discharge port surface where the discharge port is arranged. Reference numeral 66 denotes a movement of the recording head 65 by mounting the recording head 65. It is a carriage for performing. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording area and its adjacent area can be moved by the recording head 65.

  51 is a paper feed section for inserting a recording medium, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording medium is fed to a position facing the ejection port surface of the recording head 65, and discharged to a paper discharge unit provided with a paper discharge roller 53 as recording progresses. In the above configuration, when the recording head 65 finishes recording and returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port of the recording head 65 is wiped.

  When the cap 62 is in contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as the above-described wiping position. As a result, the ejection port surface of the recording head 65 is wiped even during this movement. The above-mentioned movement of the recording head to the home position is not only at the end of recording or at the time of ejection recovery, but also to the home position adjacent to the recording area at a predetermined interval while the recording head moves the recording area for recording. Then, the wiping is performed with this movement.

  FIG. 5 is a diagram illustrating an example of an ink cartridge that contains ink supplied to the recording head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink container, for example, an ink bag, in which supply ink is stored, and a rubber plug 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives waste ink. The ink container preferably has a liquid contact surface made of polyolefin, particularly polyethylene.

  The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separated as described above, but is preferably used in an apparatus in which they are integrated as shown in FIG. It is done. In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage portion that stores ink, for example, an ink absorber is stored, and the ink in the ink absorber from the head portion 71 having a plurality of orifices. It is configured to be ejected as ink droplets. It is preferable for the present invention to use polyurethane as the material of the ink absorber. Alternatively, a structure may be used in which the ink container is an ink bag with a spring or the like inside without using an ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere. The recording unit 70 is used in place of the recording head 65 shown in FIG. 4 and is detachable from the carriage 66.

  Next, a preferred example of an ink jet recording apparatus using mechanical energy will be described. As an ink jet recording apparatus using mechanical energy, a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material arranged opposite to the nozzles, and the periphery of the pressure generating element are filled. An on-demand ink jet recording head that includes ink, displaces a pressure generating element by an applied voltage, and discharges a small droplet of ink from a nozzle can be exemplified. An example of the configuration of a recording head which is a main part of the recording apparatus is shown in FIG.

  The head includes an ink flow path 80 communicating with an ink chamber (not shown), an orifice plate 81 for ejecting ink droplets of a desired volume, a vibration plate 82 that directly applies pressure to ink, and the vibration plate 82. And a substrate 84 for indicating and fixing the orifice plate 81, the diaphragm 82 and the like.

  In FIG. 7, an ink flow path 80 is formed of a photosensitive resin or the like, an orifice plate 81 has a discharge port 85 formed by electroforming or punching a metal such as stainless steel or nickel, and the vibration plate 82 is The piezoelectric element 83 is formed of a dielectric material such as barium titanate or PZT. The piezoelectric element 83 is formed of a metal film such as stainless steel, nickel, or titanium and a highly elastic resin film. The recording head configured as described above applies a pulsed voltage to the piezoelectric element 83 to generate a distortion stress, and the energy deforms the vibration plate bonded to the piezoelectric element 83, so that the ink in the ink flow path 80 is obtained. Is pressed vertically and ink droplets (not shown) are ejected from the ejection ports 85 of the orifice plate 81 to perform recording. Such a recording head is used by being incorporated in an ink jet recording apparatus similar to that shown in FIG. The detailed operation of the ink jet recording apparatus can be performed in the same manner as described above.

  Next, an Example and a comparative example are given and this invention is demonstrated concretely. The present invention is not limited by the following examples as long as the gist thereof is not exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified.

(Preparation of black pigment dispersion)
4.0% by mass of sulfanilic acid was mixed with 20% by mass of carbon black. This mixture was placed in a beaker in a 70 ° C. water bath. Next, a solution consisting of 1.68% by weight sodium nitrite dissolved in 74.32% by weight distilled water was added to the beaker with rapid mixing to form a pigmented slurry. Hydrochloric acid was added to this solution and the slurry was adjusted to pH2. The slurry was rapidly mixed at 70 ° C. for 1 hour using a magnetic stirrer and then dried in a 70 ° C. oven. The resulting material was dried and obtained as a surface-modified colored pigment. This 6% by weight sample was then extracted with methanol in a Soxhlet extractor for 10 hours to remove any reaction by-products and re-dried. The obtained pigment was collected, ion-exchanged water was added, and a black pigment dispersion was prepared at a pigment addition level of 10% by mass.

(Preparation of cyan pigment dispersion)
First, using benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer having an acid value of 250 and a number average molecular weight of 2000 is prepared by a conventional method, further neutralized with an aqueous potassium hydroxide solution, diluted with ion-exchanged water, and homogeneous. A 50% by weight polymer aqueous solution was prepared. 120 g of the above polymer solution, C.I. I. 100 g of CI Pigment Cyan 15: 3 and 280 g of ion-exchanged water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing it through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 700 kg / cm @ 2).

Furthermore, the dispersion obtained above was centrifuged (12,000 rpm, 20 minutes) to remove non-dispersed materials containing coarse particles, and a cyan pigment dispersion on the large particle size side was prepared.
Apart from this, the number of times of passage through the chamber of the microfluidizer was set to 10 by the same method as described above, and more fine particles were attempted. The obtained dispersion was centrifuged (12,000 rpm, 20 minutes) to remove non-dispersed materials including coarse particles, and a cyan pigment dispersion on the small particle diameter side was prepared. By mixing these two types of pigment dispersions, cyan pigment dispersions used in the examples were prepared. The finally obtained cyan pigment dispersion had a pigment concentration of 10.0% by mass and a dispersant concentration of 7.0% by mass.

(Preparation of magenta pigment dispersion)
First, using benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer having an acid value of 250 and a number average molecular weight of 2000 is prepared by a conventional method, further neutralized with an aqueous potassium hydroxide solution, diluted with ion-exchanged water, and homogeneous. A 50% by weight polymer aqueous solution was prepared.

  120 g of the above polymer solution, C.I. I. 100 g of Pigment Red 122 and 280 g of ion-exchanged water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing it through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 700 kg / cm @ 2).

Further, the dispersion obtained above was centrifuged (12,000 rpm, 20 minutes) to remove non-dispersed materials containing coarse particles, and a magenta pigment dispersion on the large particle size side was prepared.
Apart from this, the number of times of passage through the chamber of the microfluidizer was set to 10 by the same method as described above, and more fine particles were attempted. The obtained dispersion was centrifuged (12,000 rpm, 20 minutes) to remove non-dispersed materials containing coarse particles, and a magenta pigment dispersion on the small particle size side was prepared. By mixing these two types of pigment dispersion liquids, a magenta pigment dispersion liquid used in the examples was prepared. The magenta pigment dispersion finally obtained had a pigment concentration of 10.0% by mass and a dispersant concentration of 7.0% by mass.

(Preparation of yellow pigment dispersion)
First, using benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer having an acid value of 250 and a number average molecular weight of 2000 is prepared by a conventional method, further neutralized with an aqueous potassium hydroxide solution, diluted with ion-exchanged water, and homogeneous. A 50% by weight polymer aqueous solution was prepared.

  120 g of the above polymer solution, C.I. I. 100 g of Pigment Yellow 74 and 280 g of ion-exchanged water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing it through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 700 kg / cm @ 2).

Further, the dispersion obtained above was centrifuged (12,000 rpm, 20 minutes) to remove non-dispersed materials containing coarse particles, and a yellow pigment dispersion on the large particle size side was prepared.
Apart from this, the number of times of passage through the chamber of the microfluidizer was set to 10 by the same method as described above, and more fine particles were attempted. The obtained dispersion was centrifuged (12,000 rpm, 20 minutes) to remove non-dispersed materials containing coarse particles, and a yellow pigment dispersion on the small particle diameter side was prepared. By mixing these two types of pigment dispersions, yellow pigment dispersions used in the examples were prepared. The finally obtained yellow pigment dispersion had a pigment concentration of 10.0% by mass and a dispersant concentration of 7.0% by mass.

[Method for determining good and poor solvents of water-soluble organic solvents]
The following experiment was conducted to determine the water-soluble organic solvent that acts as a good solvent and a poor solvent for each water-insoluble colorant. First, for each water-insoluble colorant, a dispersion A for determination of a good solvent and a poor solvent and an aqueous dispersion B for determination were prepared at the following blending ratio.

(Compounding ratio of determination dispersion)
(1) Determination dispersion A
・ Water-insoluble colorant: 5% by mass
-Each water-soluble organic solvent described in Table 1: 50% by mass
・ Pure water: 45% by mass
(2) Determination aqueous dispersion B
・ Water-insoluble colorant: 5% by mass
・ Pure water: 95% by mass
(Judgment method)
Next, 10 g of each dispersion for determining good and poor solvents for each water-insoluble colorant prepared as described above was placed in a transparent glass lidded sample bottle, capped, and then sufficiently stirred. This was allowed to stand at room temperature of 60 ° C. for 48 hours. Then, using the dispersion that was allowed to stand as a measurement sample, the average particle size of the water-insoluble colorant in the solution was measured using a concentrated particle size analyzer (trade name: FPAR-1000; manufactured by Otsuka Electronics Co., Ltd.). Measured. When the average particle size of the dispersion after storage at 60 ° C. for 48 hours is equal to or less than that of the determination aqueous dispersion B, the determination dispersion A The water-soluble organic solvent which becomes larger than the determination aqueous dispersion B (stock solution) was defined as a poor solvent. Table 1 shows the results of determining whether each ink is a good solvent or a poor solvent obtained by measuring the average particle diameter as described above. In Table 1, the determination results are shown as ◯ when there is an increase in the stock solution particle size and determined as a poor solvent, and x when there is no increase in the stock solution particle size and is determined as a good solvent. In the case of a water-soluble dye, since the particle size cannot be confirmed with the determination aqueous dispersion B, the particle size confirmed with the determination aqueous dispersion A was determined as x.

[Method of measuring Ka value for each water-soluble organic solvent]
In measuring the Ka value of each water-soluble organic solvent, an aqueous dye solution having the following composition and having a dye concentration of 0.5% was prepared for easy measurement.

Water-soluble dyes C.I. I. Direct Blue 199: 0.5 part Pure: 99.5 part Next, using this 0.5% dye solution, it was colored using each water-soluble organic solvent to be measured at the following blending ratio. A 20% aqueous solution of a water-soluble organic solvent was prepared.

・ 0.5% dye aqueous solution: 80 parts ・ Water-soluble organic solvent listed in Table 2: 20 parts A 20% aqueous solution of each water-soluble organic solvent prepared above was used as a measurement sample. The Ka value of a 20% aqueous solution of a water-soluble organic solvent was determined by a Bristow method using a test penetration device S (trade name), and the measurement results of the Ka value are shown in Table 2.

[Light resistance evaluation of water-insoluble colorant contained in ink]
In order to confirm the superiority or inferiority of the light resistance of each ink constituting the ink set of the present invention, using the colorant of the concentration used in the ink shown in Table 3, for other materials, the following blending ratio, An ink was produced and evaluated for light resistance.

Color material: see Table 3 ・ Glycerin: 7 parts ・ Ethylene glycol: 7 parts ・ Acetylenol E100: 1 part ・ Pure water: remaining part In order to evaluate the light resistance of each ink adjusted as described above, thermal energy according to the recording signal Was printed using an ink jet recording apparatus BJF-900 having an on-demand type multi-recording head that ejects ink by applying to the ink to form a 100% solid image. As the recording medium, PhotoRag (188 g / m ² ), which is a fine art paper having an ink receiving layer manufactured by Hahnemuehle, was used as the recording medium.

  The coated material prepared above was subjected to color measurement before the test was input, the color of the part to be tested was measured again after the optical test, and the degree of fading was confirmed using ΔE.

(Color measurement method)
Colorimetry performed as an index for confirming the degree of fading was performed using Spectrolino manufactured by Gretag Macbeth Co., Ltd., with a light source of D50 and a viewing angle of 2 degrees. In the color measurement, in order to completely dry the coated product, the color was measured after natural drying for 24 hours after coating.

(Light resistance test method)
As a light resistance tester, Xenon Fade Meter Ci4000 manufactured by Atlas Co., Ltd. was used. The test conditions were a black panel temperature of 63 ° C., a relative humidity of 70%, and an irradiation intensity of 340 nm ultraviolet light irradiation of 0.39 W / m ² for 100 hours.

[Light resistance evaluation result of each ink]
Color measurement was performed before and after the light resistance test of the coated material shown above, and ΔE was calculated from the color measurement result using the calculation formula of Formula 1 and evaluated according to the following criteria (Table 3).
○: ΔE value of less than 5 Δ: ΔE value of 5 or more and less than 10 ×: ΔE value of 10 or more

[Create ink]
Each of the pigments prepared above and a water-soluble dye, C.I. I. Acid Red 289 and C.I. Ingredients listed in Tables 4 and 5 were weighed using I Direct Blue 199, sufficiently dissolved and stirred, and pressure-filtered with a microfilter (Fuji Film) having a pore size of 1.2 μm, and inks A to A P was created.

[Storage stability evaluation]
Each of the inks A to P was put in a shot bottle and sealed, put into an oven at 60 ° C., taken out after 2 weeks, and the storage stability was evaluated from the state of the ink at that time according to the following criteria. The obtained evaluation results are shown in Table 6.

  ○: The color material in the ink is stably and uniformly dispersed.

  X: The ink is changed into a gel or the upper part of the ink is transparent. Or it is clearly thickened.

[Examples 1-3 and Comparative Examples 1-3]
The inks prepared above were combined as shown in Table 4-3, and ink sets of Examples 1 to 3 and Comparative Examples 1 to 3 were obtained. Then, an image was formed using these ink sets, a light resistance test was performed, and light resistance was evaluated. Evaluation is performed by forming an image in which at least two types of inks are mixed using an inkjet recording apparatus BJF-900 having an on-demand type multi-recording head that discharges ink by applying thermal energy to the ink in accordance with a recording signal. did. As a recording medium, PhotoRag (188 g / m ² ), which is fine art paper having an ink receiving layer manufactured by Hahnemuehle, was used.

[Evaluation]
<Light resistance evaluation>
After printing on the recording medium so that each ink of at least two types of ink sets becomes 100%, and naturally drying for 24 hours, using Spectrolino manufactured by Gretag Macbeth, the light source is D50, and the viewing angle is Color measurement was performed under two conditions. After colorimetry, a light resistance test was performed using a Xenon Fade Meter Ci4000 manufactured by Atlas. The test conditions were a black panel temperature of 63 ° C., a relative humidity of 70%, and an irradiation intensity of 340 nm ultraviolet light irradiation of 0.39 W / m ² for 100 hours. After the test, the color was measured again, and the ΔE value shown in Equation 1 was calculated.

Using the printing density obtained by measurement as described above, the light resistance was evaluated according to the following criteria, and the results obtained are shown in Table 7.
○: ΔE value of less than 5 Δ: ΔE value of 5 or more and less than 10 ×: ΔE value of 10 or more <Storage stability evaluation>
Each of the inks of Examples 1 to 3 and Comparative Examples 1 to 3 was put into a shot bottle and sealed, put into a 60 ° C. oven, taken out after 2 weeks, and the storage stability from the ink state at that time was as follows. Evaluated by criteria. The evaluation results obtained are shown in Table 7.

[Verification method of ink whose sample is unknown]
Using the determination method described above, it is also possible to identify whether or not the ink [verification target ink] constituting the ink set whose composition is unknown is the target of the present invention.

  Specifically, first, the path of the type and amount of the water-soluble organic solvent contained in [Verification target ink] is performed. For example, by analyzing [Inspection target ink] diluted to a predetermined concentration with methanol using GC / MS (trade name: TRACE DSQ; manufactured by ThermoQuest), the [Verification target ink] The type and amount of the water-soluble organic solvent contained can be specified.

  Subsequently, a water-insoluble color material component is collected from [Verification target ink]. At this time, it is preferable to remove components other than the water-insoluble colorant, for example, a solvent, a surfactant, and an additive contained in the ink as much as possible. An example of means for separating the water-insoluble colorant and the components other than the water-insoluble colorant is as follows. First, the [verification ink] is diluted about 10 times with pure water, and an ultrafiltration device (trade name: Centramate Low Volume). Using a filter with a molecular weight cut off of 300,000) and ultrafiltration until the liquid volume reaches the original volume, separating water-soluble components other than water-insoluble colorants together with the filtrate. To do. By repeating this process several times, a liquid mainly composed of a water-insoluble colorant and pure water can be obtained. In addition, as a standard of the number of repetitions of the above-mentioned process, until the water-soluble component other than the water-insoluble coloring material, for example, the solvent, the surfactant, the additive, etc. contained in the ink are hardly contained in the filtrate. preferable.

  Next, the water-insoluble colorant and the liquid containing water as a main component are dried (for example, in an environment at 60 ° C.) to remove moisture, and then pulverized into a powder form in a mortar or the like. To make a powder. If necessary, this powder can be dried (for example, for 24 hours) under reduced pressure and high temperature (for example, 100 ° C.) to remove components other than the water-insoluble colorant remaining in a minute amount. Through the above series of operations, a water-insoluble colorant extracted from [verification target ink] can be obtained.

Then, using the water-insoluble colorant extracted from the [verification target ink] and the water-soluble organic solvent contained in the identified [verification target ink], a test according to the above-described determination method is performed, It is determined whether or not the ink with unknown [ink for verification] is the object of the present invention.
As a result of performing the above operations and determinations on the inks constituting the ink sets of the examples and comparative examples described above, the validity of the determination results is obtained, and thus the ink whose characteristics are unknown It was confirmed that the above operation and determination method are effective for identifying whether or not [verification target ink] is the target of the present invention.

FIG. 3 is a longitudinal sectional view of an ink jet recording apparatus head. FIG. 3 is a vertical and horizontal view of an ink jet recording apparatus head. FIG. 2 is an external perspective view of a head in which the head shown in FIG. 1 is a perspective view illustrating an example of an ink jet recording apparatus. FIG. 3 is a longitudinal sectional view of an ink cartridge. The perspective view which shows an example of a recording unit. FIG. 3 illustrates an example of a configuration of a recording head. The figure for demonstrating typically a mode that the ink droplet of this invention landed in the recording medium, and observed from the cross section when a dot was formed.

Explanation of symbols

13: head 14: ink nozzle 15: heating element substrate 16: protective layer 17-1, 17-2: electrode 18: heating resistor layer 19: heat storage layer 20: substrate 21: ink 22: discharge orifice (micropore)
23: Meniscus 24: Ink droplet 25: Recording medium 26: Multi-nozzle 27: Glass plate 28: Heat generating head 40: Ink bag 42: Plug 44: Ink absorber 45: Ink cartridge 51: Paper feed unit 52: Paper feed roller 53 : Discharge roller 61: blade 62: cap 63: ink absorber 64: ejection recovery unit 65: recording head 66: carriage 67: guide shaft 68: motor 69: belt 70: recording unit 71: head unit 72: air communication port 80: Ink channel 81: Orifice plate 82: Vibration plate 83: Piezoelectric element 84: Substrate 85: Ejection port 90: Recording medium 91: Ink droplet 92 of the second ink having relatively low light resistance 92: Relative Ink dots 93 of the second ink having low light resistance: the water-insoluble colorant 94 contained in the second ink having relatively low light resistance: relatively Ink droplet 95 of the first ink having low light resistance: Ink dot 96 of the first ink having relatively low light resistance: Water-insoluble color material 97 contained in the first ink having relatively low light resistance 97: Poor solvent

Claims (15)

In an ink set having two or more types of water-based inks,
Including water, a first water-insoluble colorant, and a good solvent and a poor solvent for the first water-insoluble colorant, the total amount (% by mass) of the good solvent is A, and the total amount (% by mass) of the poor solvent in the ink Where A: B is in the range of 10: 5 or more and 10:30 or less,
It contains water, a second water-insoluble colorant, a good solvent for the second water-insoluble colorant, and a poor solvent as necessary. The total amount (% by mass) of the good solvent is A, and the poor solvent in the ink A second ink in which A: B is less than 10: 5 (including B = 0) when the total amount (% by mass) is B;
Having at least
The first water-based ink and the second water-based ink are applied in contact with a recording medium,
An ink set, wherein the light resistance of the first ink is higher than the light resistance of the second ink.   When comparing the Ka values obtained by the Bristow method for each of the plurality of water-soluble organic solvents contained in the first ink, the water-soluble organic solvent exhibiting the maximum Ka value among them is a poor solvent. The ink set according to claim 1.   The ink set according to claim 1 or 2, wherein the poor solvent contained in the first ink is also a poor solvent for the water-insoluble colorant contained in the second ink.   An ink jet recording method comprising a step of ejecting the ink constituting the ink set according to claim 1 by an ink jet method.   The ink jet recording method according to claim 4, wherein the ink jet method includes a step of ejecting ink using a film boiling pressure generated by thermal energy applied to the ink.   The ink jet recording method according to claim 4, wherein the ink jet method includes a step of ejecting ink by applying mechanical energy to the ink.   An ink cartridge that individually contains the ink constituting the ink set according to any one of claims 1 to 3.   An ink storage unit that individually stores the ink that constitutes the ink set according to any one of claims 1 to 3, and an inkjet head that discharges the ink that constitutes the ink set. A recording unit characterized by that.   An ink storage unit that individually stores the ink that constitutes the ink set according to any one of claims 1 to 3, and an inkjet head that discharges the ink that constitutes the ink set. An ink jet recording apparatus characterized by comprising: An ink jet recording method for performing recording by scanning a recording head that individually discharges ink constituting an ink set in which water-based inks having different light resistance are combined, relative to a recording medium,
Using the ink set according to any one of claims 1 to 3 as an ink set,
Further, when forming an image formed by each water-based ink having different light resistance, after forming an image by performing scanning that applies ink having relatively low light resistance, the image is formed relative to the area where the image is formed. And an ink jet recording method characterized by performing scanning to apply ink having relatively high light resistance. A first ink comprising water, a first water-insoluble colorant, and a water-soluble organic solvent, and at least a poor solvent for the first water-insoluble colorant as the water-soluble organic solvent;
A second ink containing water, a second water-insoluble colorant, and a water-soluble organic solvent, wherein the water-soluble organic solvent optionally contains a poor solvent for the second water-insoluble colorant;
Use at least
The first water-based ink and the second water-based ink are applied in contact with a recording medium,
A water-based ink used as the first water-based ink of the image recording method, wherein the light resistance of the first ink is relatively higher than that of the second ink,
The water-based ink, wherein the content ratio of the poor solvent relative to the first water-insoluble colorant is greater than the content ratio of the poor solvent relative to the second water-insoluble colorant.   The first ink according to claim 11, wherein the first ink includes a poor solvent and a good solvent, the total amount (% by mass) of the good solvent is A, and the total amount (% by mass) of the poor solvent is B. In this case, the water-based ink according to claim 11, wherein A: B is in a range of 10: 5 or more and 10:30 or less. A first ink comprising water, a first water-insoluble colorant, and a water-soluble organic solvent, wherein the water-soluble organic solvent comprises at least a poor solvent for the first water-insoluble colorant;
A second ink containing water, a second water-insoluble colorant, and a water-soluble organic solvent, wherein the water-soluble organic solvent optionally contains a poor solvent for the second water-insoluble colorant;
Use at least
The first water-based ink and the second water-based ink are applied in contact with a recording medium,
A water-based ink used as the second water-based ink in the image recording method, wherein the light resistance of the first ink is relatively higher than that of the second ink,
A water-based ink, wherein the content ratio of the poor solvent relative to the second water-insoluble colorant is less than the content ratio of the poor solvent relative to the first water-insoluble colorant.   The second ink according to claim 13, wherein the second ink contains a poor solvent and a good solvent, the total amount (% by mass) of the good solvent is A, and the total amount (% by mass) of the poor solvent is B. In some cases, A: B is less than 10: 5 (including B = 0). In an ink set having two or more types of water-based inks,
Including water, a first water-insoluble colorant, and a good solvent and a poor solvent for the first water-insoluble colorant, the total amount (% by mass) of the good solvent is A, and the total amount (% by mass) of the poor solvent in the ink Where A: B is in the range of 10: 5 or more and 10:30 or less,
Including water, a second water-soluble colorant, and a solvent;
The first water-based ink and the second water-based ink are applied in contact with a recording medium,
An ink set, wherein the light resistance of the first ink is higher than the light resistance of the second ink.

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