JP2011224779A - Clear ink, inkjet recording method, ink set, and ink cartridge - Google Patents

Abstract

An object of the present invention is to provide a clear ink capable of recording an image having excellent color developability and improved gloss change when used in ink jet recording, more specifically, improved gloss change, In addition, a clear ink that can obtain a smooth surface image with a small amount of regular reflection light is provided.
SOLUTION: At least polymer fine particles and 1,2-alkanediol are contained, the polymer fine particles are a modified polyethylene emulsion, and the density thereof is 940 kg / m ³ or more and 960 kg / m ³ or less. Clear ink characterized by being.
[Selection figure] None

Description

  The present invention relates to a clear ink, an ink jet recording method using the ink, an ink set, and an ink cartridge.

  In recent years, with the advancement of ink jet recording technology, it is possible to record high-definition and high-coloring images, such as those realized by silver salt photography and offset printing, relatively easily and inexpensively even in general households. It is becoming possible.

  In order to achieve high color developability, when a dye ink containing a dye is used as a coloring material, a good image can be obtained without graininess. On the other hand, the image has light resistance, water resistance, and gas resistance. There is a problem that it is inferior in robustness such as property. For this reason, in recent years, pigment ink containing a pigment as a coloring material has been used. The pigment ink contains a so-called resin-dispersed pigment in which the pigment is dispersed with a water-soluble polymer for the purpose of improving the fastness of the pigment to the recording medium and the fastness such as image scratch resistance. Pigment inks are widely used.

  In such a pigment ink, the dispersion state of the pigment is stabilized as water or a volatile water-soluble organic solvent evaporates in the process of drying the ink after the ink adheres to a recording medium such as paper. There is a problem that the property is lost and the pigment is easily aggregated. When the aggregated pigment is deposited on the surface of the recording medium, the smoothness of the image surface is lowered, and the image becomes dull due to an increase in the amount of scattered light. In addition, when the refractive index of the image layer is high, the amount of specular reflection on the image surface is large, and the diffused light amount, which is the original color component of the pigment, is relatively reduced, resulting in excellent color development and high quality. There arises a problem that an image cannot be obtained. Also, images recorded with such pigment inks are difficult to scrape against strong rubbing due to fingernails or the like, that is, the scratch resistance is improved. There is a problem with the gloss change phenomenon in which the gloss changes due to the deformation of the image surface.

  Attempts have been made to solve these problems of improving color developability and improving gloss change in pigment ink images. For example, there is a proposal that the gloss change can be reduced by including polymer fine particles in the pigment ink (see Patent Document 1). And it is described that a polyester emulsion is used as the polymer fine particles.

  In addition, in order to improve the scratch resistance of an image, there has been a proposal regarding an ink containing at least two types of waxes having different average particle diameters, and it is described that the color developability of an image recorded with the ink is also improved ( Patent Document 2). Furthermore, there is a proposal regarding an ink containing a pigment and a polyolefin wax such as a polyethylene wax (see Patent Document 3).

JP 2005-162981 A JP 2007-277290 A JP 2005-048108 A

  However, as a result of investigations by the present inventors, it has been found that the conventional techniques as described above have the following problems. First, the polyester emulsion which is a polymer fine particle described in Patent Document 1 has a relatively high refractive index among polymer materials. Therefore, the amount of specular reflection on the surface of the image is large, and the amount of diffuse light, which is the original color component of the color material, is relatively reduced. Therefore, it has been found that the color development of the image is not sufficiently satisfactory. .

  In addition, the present inventors conducted a detailed study on images recorded using an ink set of clear ink and pigment ink containing polymer fine particles as described in Examples of Patent Documents 2 and 3. went. The polymer fine particles used at this time are polyethylene waxes described in these documents (Chemipearl W4005; manufactured by Mitsui Chemicals and Nopcoat PEM17; manufactured by San Nopco). As a result, although the scratch resistance of the image is improved, the density of the polymer fine particles is low, so when the image is lightly rubbed with a fingernail or the like, the gloss of the rubbed portion changes. Then, it turned out that the gross change phenomenon is not improved.

  Accordingly, an object of the present invention is to provide a clear ink capable of recording an image having excellent color developability and improved gloss change when used in, for example, ink jet recording. More specifically, it is an object of the present invention to provide a clear ink which can improve gloss change and can obtain a smooth surface image with a small amount of specular reflection. Another object of the present invention is to provide an ink jet recording method and an ink set that enable image recording with improved color development and improved gloss change by using the clear ink.

The above object is achieved by the present invention described below. That is, the present invention contains at least polymer fine particles and 1,2-alkanediol, the polymer fine particles are a modified polyethylene emulsion, and the density thereof is 940 kg / m ³ or more and 960 kg / m ^3. The present invention provides a clear ink characterized by the following, an ink jet recording method using the ink, an ink set, and the like.

  According to the present invention, there is provided a clear ink capable of recording an image having excellent color developability and improved gloss change, particularly when used for ink jet recording. More specifically, there is provided a clear ink which can improve the gloss change and can record an image of a smooth surface with a small amount of specular reflection. In addition, according to the present invention, there are provided an ink jet recording method, an ink set, and an ink cartridge capable of recording an image that achieves improved color developability and improved gloss change by using the clear ink.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention. In the following description, the modified polyethylene emulsion constituting the clear ink of the present invention may be simply referred to as “polymer fine particles”. The “recording duty” in the present invention is defined as 100% when the amount of ink applied to the recording medium is 15.64 g / m ² . For example, when 8 dots of ink droplets having a mass of 3.5 ng (nanogram) are applied to a unit area (vertical resolution 600 dpi × horizontal resolution 600 dpi), the recording duty is 100%. .

<Clear ink>
Hereinafter, each component constituting the clear ink of the present invention will be described. The clear ink of the present invention is preferably colorless, milky white, or white. In particular, the absorption spectrum of clear ink diluted 50 times (mass times) with pure water has no peak in the range of 400 nm to 800 nm, and the abs value in the range of 400 nm to 800 nm is 1.0 or less. Preferably there is. The clear ink of the present invention is preferably capable of forming a colorless and transparent film when the clear ink is applied to a recording medium. Such a clear ink preferably does not contain a coloring material such as a dye or a pigment.

(Modified polyethylene emulsion)
The fine polymer particles that characterize the clear ink of the present invention are modified polyethylene emulsions having a density of 940 kg / m ³ or more and 960 kg / m ³ or less. In the clear ink, the polymer fine particles exist as a so-called emulsion dispersed in an aqueous medium. Examples of the modified polyethylene emulsion showing a specific density range used in the present invention include the following. For example, an acid-modified polyethylene emulsion graft-modified with an unsaturated carboxylic acid or a derivative thereof, an oxidatively-modified polyethylene emulsion into which a polar group has been introduced by oxidative modification, and the like can be mentioned, and any of them can be preferably used in the present invention. That is, by modifying in this way, the dispersion stability of the polymer fine particles in the clear ink is increased. Then, the rapid aggregation of the polymer fine particles after the clear ink is applied to the recording medium is suppressed, thereby making it possible to obtain a smooth surface image. Furthermore, the modified polyethylene emulsion showing the specific density range belongs to a class having a low polarity among the polymer materials and has an advantage that a polymer film having a relatively low refractive index can be produced because the electron density is low.

As described above, by using the clear ink of the present invention, the gloss change is improved, and a smooth surface image with a small amount of specular reflection can be recorded. And in order to acquire this effect, it is necessary to contain the polymer fine particle which has a specific density range, The reason is explained in full detail. The clear ink of the present invention needs to contain a modified polyethylene emulsion (polymer fine particles) having a density of 940 kg / m ³ or more and 960 kg / m ³ or less. The reason for this is as follows. I am thinking. First, when the density of the polymer fine particles is less than 940 kg / m ³ , the intermolecular force or affinity between molecules is weak, and even if this is used, sufficient rigidity as a polymer film cannot be obtained. Therefore, a gloss change occurs when the image is lightly rubbed with a fingernail or the like. On the other hand, if the density of the polymer fine particles exceeds 960 kg / m ³ , even if this is used, the color developability of the image recorded with the pigment ink is not sufficiently satisfactory. The reason why these occur is considered as follows. The apparent color developability of the image depends on the ratio of the diffused light amount, which is the original color component of the pigment, and the ratio of the regular reflection light amount and scattered light amount on the image surface, which is a reduction factor of the color developability. When the density of the polymer fine particles is high, the electron density is also increased, and the refractive index as the polymer film is improved. Reduce relatively. Further, when the density exceeds 960 kg / m ³ , it is considered that the amount of diffused light is significantly reduced, and as a result, the color developability is lowered.

  The composition and density of the fine polymer particles whose composition is unknown in the clear ink can be obtained, for example, by separating the polymer in the clear ink by the following method and measuring the density by the gas displacement method. . First, with respect to the clear ink containing polymer fine particles, water-soluble components are removed using a dialysis membrane, and the polymer fine particles are taken out from the clear ink. Then, after the obtained polymer fine particles are redispersed in water, an acid is dropped into the aqueous dispersion to destabilize the dispersion state of the polymer fine particles. Next, the polymer component is separated by centrifuging the liquid at a rotational speed of 80,000 rpm for 15 hours. Next, the separated polymer component is washed several times with water and then dried under reduced pressure to obtain a solid polymer. Finally, the monomer composition constituting the polymer of the polymer thus obtained is determined by pyrolysis GC / MS and NMR. Further, the density of the polymer can be determined by a gas displacement method or the like, but in Examples described later, it was determined using a dry automatic densitometer Accupic 1330-03 (manufactured by Micromeritics).

[Volume average particle diameter of polymer fine particles]
The polymer fine particles used in the clear ink of the present invention preferably have a volume average particle size of 30 nm to 200 nm. When a clear ink containing polymer fine particles having a volume average particle diameter of less than 30 nm is applied to the recording medium, the ratio of the polymer fine particles penetrating into the recording medium increases, and conversely, it remains on the surface of the recording medium. This is not preferable because the proportion of polymer fine particles to be reduced decreases. For these reasons, if the volume average particle size of the polymer fine particles is less than 30 nm, the gloss change of the image may not be sufficiently improved or the color developability of the image may not be sufficiently improved. On the other hand, if the volume average particle diameter of the polymer fine particles exceeds 200 nm, the smoothness of the image surface is lowered, and the color developability of the image may not be sufficiently improved.

  In addition, the volume average particle diameter in this invention is what was measured on condition of the following. That is, for polymer fine particles diluted 50 times (volume basis) with pure water, using UPA-EX150 (manufactured by Nikkiso), SetZero: 30 s, number of measurements: 3 times, measurement time: 180 seconds, refractive index: 1 It is a volume average particle diameter measured under the measurement condition of .5. Of course, the apparatus and conditions for measuring the volume average particle diameter of the polymer fine particles used in the present invention are not limited to the above.

[Content of polymer fine particles in clear ink]
The content (% by mass) of the polymer fine particles in the clear ink is preferably 1.0% by mass or more and 5.0% by mass or less based on the total mass of the clear ink. When the content is less than 1.0% by mass, a sufficient amount of polymer fine particles cannot remain on the surface of the recording medium, and the gloss change of the image cannot be sufficiently improved, or the color developability of the image is reduced. Since it may not be able to improve sufficiently, it is not preferable. On the other hand, if the content exceeds 5.0% by mass, the content of the solid content in the clear ink becomes too high. Therefore, when clear ink is applied to the recording medium, the dots formed on the surface of the recording medium are increased, the smoothness of the image surface is lowered, and the color developability of the image may not be sufficiently improved. Absent.

(1,2-alkanediol)
The clear ink of the present invention needs to contain 1,2-alkanediol together with the polymer fine particles described above. The reason why the color change of the image is improved and the gloss change is improved by adding 1,2-alkanediol as an essential component in addition to the polymer fine particles to the clear ink of the present invention. The inventors consider as follows. First, the decrease in color developability is considered to be caused by the increase in scattered light caused by the smoothness of the surface of an image recorded with a recording medium or pigment ink, which may be lowered by application of clear ink. The smoothness of the surface of the recording medium or image decreases because the surface tension of the clear ink dots is high, and the contact angle between the surface of the recording medium or image and the clear ink droplet is high. This is thought to be caused by the fact that the plurality of dots that were formed did not wet each other and spread. On the other hand, if 1,2-alkanediol is added to the clear ink containing polymer fine particles, the surface tension of the clear ink attached to the recording medium can be reduced. For this reason, in the clear ink of the present invention having such a configuration, it is considered that the dots attached to the recording medium come into contact with adjacent dots and spread each other, resulting in an increase in the smoothness of the image surface. Furthermore, 1,2-alkanediol is a class having a relatively high hydrophobicity among water-soluble organic solvents, and this is also considered to contribute to the manifestation of the effects of the present invention. That is, in the case of the ink of the present invention having a modified polyethylene emulsion having a specific density as polymer fine particles, 1,2-alkanediol softens the emulsion or dissolves part of it during the drying and fixing process of the clear ink. And this improves the adhesion between emulsions, and further increases the strength of the image surface, which is considered to effectively prevent the occurrence of a gloss change due to deformation when the image is lightly rubbed with a nail. ing.

  The 1,2-alkanediol used in the clear ink of the present invention is preferably a linear or branched alkanediol having 3 to 8 carbon atoms. Among these, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol are particularly preferable. The content (% by mass) of 1,2-alkanediol in the clear ink is 1.0% by mass to 10.0% by mass, and further, 3.0% by mass to 10.0% by mass. Is preferred. When the content is less than 1.0% by mass, it becomes difficult to suppress rapid aggregation of the polymer fine particles after the ink is applied to the recording medium. May not be sufficient. On the other hand, if the content exceeds 10.0% by mass, the viscosity of the ink is excessively increased, and the discharge stability required when the clear ink is used for inkjet may not be obtained sufficiently. . Further, when the viscosity of the ink increases, it may be difficult to apply a sufficient amount of clear ink, and the gloss change of the image cannot be sufficiently improved, and the color development of the image cannot be sufficiently improved. There is also concern that there may be cases.

  In the clear ink of the present invention containing the 1,2-alkanediol and the polymer fine particles described above, the content of the polymer fine particles in the clear ink is the same as the amount of 1,2-alkanediol added. It is preferable to determine the relationship. That is, the content (mass%) of the polymer fine particles is 0.20 times or more and 1.25 times or less, more preferably 0.40 as a mass ratio with respect to the content (mass%) of 1,2-alkanediol. It is preferable to be in the range of doubling or more and 1.00 or less. When the mass ratio is less than 0.20, the content of 1,2-alkanediol becomes excessive with respect to the content of the polymer fine particles, and the softening and dissolution of the polymer fine particles is promoted more than necessary. Therefore, the dispersion stability of the polymer fine particles and the increase in the viscosity of the ink are not preferable because the discharge stability required when the clear ink is used for inkjet may not be sufficiently obtained. Further, when the viscosity of the ink increases, it may be difficult to apply a sufficient amount of clear ink, and the gloss change of the image cannot be sufficiently improved, and the color development of the image cannot be sufficiently improved. There are also concerns. On the other hand, if it exceeds 1.25 times, the content of 1,2-alkanediol is insufficient with respect to the content of the polymer fine particles, so that the softening and dissolution of the polymer fine particles in the drying and fixing process of the clear ink becomes insufficient. . Therefore, sufficient adhesion between the polymer fine particles is not obtained, and there are cases where it is impossible to effectively prevent the occurrence of a gloss change due to deformation when the image is lightly rubbed with a nail.

(Polyoxyethylene alkyl ether)
In addition to the above components, the clear ink of the present invention preferably further contains a polyoxyethylene alkyl ether having an alkyl group having 8 to 20 carbon atoms, which functions as a surfactant. In this case, when the number of carbon atoms of the alkyl group is less than 8, the affinity with the polymer fine particles is lowered, and it is difficult to suppress rapid aggregation of the polymer fine particles after the clear ink is applied to the recording medium. On the other hand, when the number of carbon atoms in the alkyl group of the component exceeds 20, the solubility in the aqueous medium constituting the clear ink is low, so that the surfactant is separated and cleared when stored under high temperature conditions. Since the performance as an ink may deteriorate, it is not preferable. The alkyl group in the polyoxyethylene alkyl ether used in the present invention is particularly preferably a lauryl group, a cetyl group, or an oleyl group. The content (% by mass) of the polyoxyethylene alkyl ether in the clear ink is preferably 0.1% by mass or more and 5.0% by mass or less based on the total mass of the clear ink. By including such a component that functions as a surfactant, it is possible to avoid or suppress abrupt aggregation of the polymer fine particles in the clear ink after ink landing on the recording medium. As a result, the polymer fine particles in the image layer are densely packed, and the smoothness of the image surface is further improved, so that the gloss change and the color development can be improved.

(Aqueous medium)
For the clear ink, water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used. The content (% by mass) of the water-soluble organic solvent in the clear ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the clear ink. The content of the water-soluble organic solvent includes the above-described content of 1,2-alkanediol essential as a component of the clear ink of the present invention. The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and any water-soluble organic solvent known in the art for ink jet ink can be used. The water is preferably deionized water (ion exchange water). The water content (% by mass) in the clear ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the clear ink.

(Other ingredients)
The clear ink of the present invention can contain a dispersant in order to further stabilize the dispersion state of the polymer fine particles in the aqueous medium. Examples of the dispersant include a surfactant and a water-soluble resin. In the present invention, as the water-soluble resin for dispersing the polymer fine particles, it is particularly preferable to use a (meth) acrylic acid polymer or the like that is generally used for dispersing pigments in ink jet ink. In addition to the above components, the clear ink may contain a water-soluble organic compound that is solid at room temperature, such as urea, urea derivatives, trimethylolpropane, and trimethylolethane. The content (% by mass) of such a water-soluble organic compound in the clear ink is 0.1% by mass or more and 20.0% by mass or less, and further 1.0% by mass or more based on the total mass of the clear ink. It is preferable that it is 15.0 mass% or less. Furthermore, in order to obtain a clear ink having desired physical properties as required, surfactants other than those described above, water-soluble polymers, pH adjusters, rust preventives, antiseptics, antifungal agents, You may contain various additives, such as antioxidant and a reduction | restoration agent.

<Pigment ink>
The clear ink of the present invention can also be used as an ink set with a clear ink in combination with a pigment ink. Hereafter, each component which comprises the pigment ink which can be used with the clear ink of this invention is demonstrated.

(Pigment)
Examples of the color material used for the pigment ink include inorganic pigments such as carbon black and organic pigments known in the art. As a pigment dispersion method, a known dispersion method such as a self-dispersion pigment in which a hydrophilic group or a polymer is bonded to the surface of pigment particles, a resin dispersion pigment using a polymer dispersant (polymer), or a microcapsule pigment is used. Can be used. The pigment content (% by mass) in the pigment ink is 0.1% by mass or more and 15.0% by mass or less, more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the pigment ink. Preferably there is.

(Polymer component)
In addition to the polymer used as a dispersant, when the resin dispersed pigment described above is used, another polymer can be added to the pigment ink. Also, when the self-dispersed pigment or microcapsule pigment is used. In addition, a polymer can be further added. Such polymers may be used to more stably disperse the pigment in the aqueous medium, or may be added to the ink for other purposes.

  The polymer that can be added to the pigment ink may be any polymer, but the following can be used. For example, as described above, polymer fine particles constituting the clear ink of the present invention, polymer fine particles different from the fine particles, and (meth) acrylic acid-based polymers generally used for ink-jet inks, etc. Is mentioned. Examples of the polymer form that can be added to the pigment ink include a block copolymer, a random copolymer, a graft copolymer, or a salt thereof. These polymers are preferably alkali-soluble polymers that are soluble in an aqueous solution in which a base is dissolved. Among the above-mentioned polymers, it is particularly preferable that the pigment ink contains the same polymer fine particles contained in the clear ink from the viewpoint of the compatibility between the pigment ink and the clear ink on the recording medium.

(Aqueous medium and other components)
For the pigment ink, water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used. The content (% by mass) of the water-soluble organic solvent in the pigment ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the pigment ink. As the water-soluble organic solvent, those similar to the water-soluble organic solvents listed as usable for clear ink can be used. It is preferable to use deionized water (ion exchange water) as the water. The water content (% by mass) in the pigment ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the pigment ink. In addition, as the pigment ink, the same components as those described above that can be used for the clear ink can be used.

<Recording medium>
The recording medium to which each ink constituting the clear ink of the present invention or an ink set in combination with the clear ink is applied may be any type. Preferably, a recording medium that can cause the pigment in the pigment ink or the polymer fine particles in the clear ink to exist on the surface of the recording medium is used. Examples of such a recording medium include swelling type and absorption type recording media. In order to obtain the remarkable effects of the present invention described above, it is preferable to use a recording medium in which the ink receiving layer has gloss, and further, the recording medium in which the ink receiving layer includes a layer having gloss. It is more preferable. Specifically, it is preferable to use a recording medium having a 20 ° gloss value of 10 or more on the surface of the recording medium. In addition, the value of 20 degree gloss can be measured using a micro haze meter (product made from BYK Gartner), for example.

  Examples of the recording medium having such characteristics include the following. Canon Photo Paper / Glossy Gold GL-101, Canon Photo Paper / Glossy Professional PR-201 (above, manufactured by Canon). Photographic paper Krispia High gloss, photo paper gloss (above Epson). Painting Photo Finishing Pro, Painting Photo Finishing Hi (Fujifilm). Of course, the recording medium to which the clear ink of the present invention can be applied is not limited to this.

<Inkjet recording method>
The clear ink of the present invention is used in the ink jet recording method of the present invention in which clear ink is ejected by an ink jet method and applied to a recording medium. In particular, in the present invention, an ink jet recording method using thermal energy can be preferably used. The ink jet recording method of the present invention is preferably carried out using an ink jet recording apparatus comprising a container for housing the clear ink of the present invention and a recording head for discharging the clear ink. However, the configuration of the apparatus is not particularly limited, and any known inkjet recording apparatus can be used.

  Further, another ink jet recording method of the present invention is an ink jet recording method using the clear ink and the pigment ink of the present invention, and includes the following steps. That is, it has the process (I) which records on a recording medium using a pigment ink, and the process (II) which discharges clear ink by an inkjet system and provides to a recording medium. In these steps (I) and (II), for example, when step (II) is performed after step (I), when step (I) is performed after step (II), or when these are combined, etc. Can be considered and may be performed in any order. However, in the present invention, since the image is protected with a polymer film by applying the clear ink of the present invention on the image recorded with the pigment ink, the process (I) is performed in at least a partial region of the recording medium. It is particularly preferable to perform the step (II) after performing the above. Further, it is particularly preferable that the region where the clear ink is applied to the recording medium by the step (I) and the region where the pigment ink is applied to the recording medium by the step (II) are at least partially overlapped. preferable.

  In the ink jet recording method of the present invention, it is necessary to apply at least the clear ink of the present invention to the recording medium by the ink jet method, but the method of applying the pigment ink to the recording medium is not particularly limited. However, in the ink jet recording method of the present invention, it is preferable to perform recording on a recording medium by ejecting not only clear ink but also pigment ink by an ink jet method. In the ink jet recording method having such a configuration, clear ink can be accurately applied to an intended area such as an area including at least an image recorded with pigment ink, and the amount of clear ink applied can be appropriately adjusted. Because you can. The amount of pigment ink and clear ink applied by the ink jet method can be adjusted by appropriately determining the recording duty.

<Ink set>
The clear ink of the present invention can be combined with at least one pigment ink to form the ink set for inkjet of the present invention. The hue of the pigment ink can be selected from one or more of cyan, magenta, yellow, black, red, green, and blue inks. In addition, as the pigment ink constituting the ink set, a plurality of inks having the same hue as the above-described ink and having different pigment contents may be used. Examples of the combination of the plurality of inks include inks having a black hue such as black, light black, gray, and light gray. Further, an ink having a cyan hue such as dark cyan, medium cyan, and light cyan, and an ink having a magenta hue such as dark magenta, medium magenta, and light magenta can be given. Of course, the present invention is not limited to inks of these hues, and the names of inks such as dark, medium, and light are not limited thereto.

<Ink cartridge>
As an ink cartridge suitable for performing recording using the clear ink of the present invention, the ink cartridge of the present invention provided with a storage portion for storing the clear ink can be mentioned. The configuration of the ink cartridge of the present invention is not particularly limited except that the clear ink of the present invention is accommodated in the accommodating portion, and any known ink cartridge can be used.

  Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited by the following Example, unless the summary is exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified.

<Synthesis of polymer particles>
(Synthesis of high density polyethylene)
High density polyethylene was synthesized with reference to the slurry multistage polymerization method using low pressure described in Japanese Patent No. 4072980. At this time, by controlling the polymerization pressure in the polymerization step of high molecular weight polyethylene (high density polyethylene) as shown in Table 1 below, high density polyethylenes E1 to 6 having different densities were respectively synthesized. The density of the synthesized high-density polyethylene was measured by a gas displacement method using a dry automatic densimeter Accupic 1330-03 (manufactured by Micromeritics).

(Synthesis of modified high-density polyethylene emulsion)
In a stainless steel autoclave equipped with a stirring blade having a helical double helical ribbon, 100 parts of the particulate high-density polyethylene obtained above was charged, and the inside of the reaction system was purged with nitrogen. Then, 1.00 parts of maleic anhydride, 0.40 parts of benzoyl peroxide, 0.06 parts of tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane A liquid containing 5.0 parts of toluene was prepared. Then, the liquid was dropped into the reaction system over 10 minutes at room temperature with stirring, and then further stirred at room temperature for 30 minutes. Thereafter, the temperature of the reaction system was set to 100 ° C. and reacted for 4 hours to obtain a maleic acid-modified high-density polyethylene emulsion. 20 parts of the polyethylene emulsion thus obtained, 50 parts of an aqueous solution of a dispersant, and 30 parts of water are placed in a bead mill (LMZ2; manufactured by Ashizawa Finetech Co., Ltd.) having a filling rate of zirconia beads having a diameter of 0.3 mm of 80%. And dispersed for 5 hours at a rotation speed of 1,800 rpm. As an aqueous solution of the dispersant, an aqueous solution having a solid content of 15.0% obtained by neutralizing Joncryl 683 (manufactured by BASF) with potassium hydroxide equivalent to its acid value was used. Thereafter, the aggregated components are removed by centrifuging at a rotational speed of 5,000 rpm for 30 minutes and further diluted with ion-exchanged water, so that the polymer fine particle content of 25.0% is dispersed in water. A liquid P1 was obtained. Further, by changing the rotation speed and dispersion time in the bead mill, the polymer fine particles P2 having a polymer fine particle content of 25.0% including the polymer fine particles having a volume average particle diameter shown in Table 2 below. An aqueous dispersion of P10 was obtained.

(Main characteristics of polymer fine particles)
The main characteristics of the polymer fine particles of P1 to P10 obtained above are shown in Table 2 below.

<Preparation of clear ink>
After mixing each component shown in Table 3 below, each clear ink of Examples and Comparative Examples was prepared by pressure filtration with a membrane filter (HDCII filter; manufactured by Pall) having a pore size of 1.2 μm. Each of the clear inks of Examples thus obtained is colorless, milky white, or white and does not contain a color material. In addition, each clear ink of the example has no peak in the range of 400 nm to 800 nm and has a peak of 400 nm to 800 nm when the absorbance of the clear ink diluted 50 times (mass times) with pure water is measured. The abs value in the range was 1.0 or less.

<Preparation of pigment ink>
First, 20 parts of a pigment, 50 parts of an aqueous solution of a dispersant, and 30 parts of water were placed in a bead mill (LMZ2; manufactured by Ashizawa Finetech Co., Ltd.) with a filling rate of zirconia beads having a diameter of 0.3 mm of 80%. Dispersion was carried out at 800 rpm for 5 hours. Examples of the pigment include C.I. I. Pigment Red 122 (trade name: Toner Magenta E02; manufactured by Clariant) was used. Further, as an aqueous solution of the dispersant, an aqueous solution having a solid content of 15.0% obtained by neutralizing Joncryl 678 (manufactured by BASF) with potassium hydroxide equivalent to its acid value was used. Thereafter, the aggregated components were removed by centrifuging at a rotational speed of 5,000 rpm for 30 minutes, and further diluted with ion-exchanged water to obtain a pigment dispersion having a pigment content of 15.0%.

Next, after mixing the pigment dispersion obtained above and the following components, the pigment ink is filtered under pressure with a membrane filter (HDCII filter; manufactured by Pall) having a pore size of 1.2 μm. 1 was prepared.
・ Pigment dispersion 16.7%
・ Glycerin 10.0%
・ Polyethylene glycol (average molecular weight: 1,000) 5.0%
・ Trimethylolpropane 5.0%
・ Acetylenol E100 (surfactant: manufactured by Kawaken Fine Chemicals) 0.5%
・ Ion exchange water 62.8%

In addition, the following components were mixed using the pigment dispersion obtained above and the aqueous dispersion of polymer fine particles P1 previously synthesized, and then a membrane filter (HDCII filter; manufactured by Pall) having a pore size of 1.2 μm. The pigment ink 2 was prepared by filtration under pressure.
・ Pigment dispersion 16.7%
-Aqueous dispersion of polymer fine particles P1 (solid content 25.0%) 2.0%
・ Glycerin 10.0%
・ Polyethylene glycol (average molecular weight: 1,000) 5.0%
・ Trimethylolpropane 5.0%
・ Acetylenol E100 (surfactant: manufactured by Kawaken Fine Chemicals) 0.5%
・ Ion exchange water 60.8%

<Evaluation>
The ink cartridge filled with each clear ink and each pigment ink obtained above was mounted on an ink jet recording apparatus (trade name: PIXUS Pro 9500; manufactured by Canon) that discharges by the action of thermal energy. This ink jet recording apparatus sets a recording duty of 100% when 8 dots of ink droplets having a mass per droplet of 3.5 ng (nanogram) are applied to a region having a vertical resolution of 600 dpi × horizontal resolution of 600 dpi. . In addition, as a result of giving each clear ink of an Example to a recording medium, all of these clear ink can form a colorless and transparent film | membrane.

(Evaluation of gross change)
The pigment ink and each clear ink were combined as shown in Table 4 below to form an ink set. A pattern including a solid image of 5 cm × 5 cm was recorded on a recording medium (trade name: Canon Photographic Paper / Glossy Gold GL-101; manufactured by Canon) with the above-described inkjet recording apparatus. At this time, the order in which the pigment ink and the clear ink were applied to the recording medium was such that the clear ink was applied after the pigment ink was applied, and an image in which the pigment ink and the clear ink were superimposed was recorded. After the image obtained above was stored at room temperature for 24 hours, the image was lightly rubbed with the back of the nail, and the gloss change state was evaluated by visually confirming the change in gloss of the image. The evaluation criteria for gross change are as follows. The evaluation results are shown in Table 4. In the present invention, a gloss change level that allows an A or more according to the following evaluation criteria.
AA: The gloss change did not occur and the image was not damaged.
A: The gloss change did not occur, but the image was scratched.
B: A gross change occurred.

(Evaluation of color development)
The same image used for the evaluation of the gloss change was stored at room temperature for 24 hours, and then the image was visually confirmed to evaluate the color development. The evaluation criteria of color developability are as follows. The evaluation results are shown in Table 4. In the present invention, the level of color developability that is acceptable is A or more according to the following evaluation criteria.
AA: The color developability was vivid.
A: Although it was inferior to AA, it was sufficient color development.
B: Color developability was low.

  The gloss change and color developability of Examples 12 and 17 and the color developability of Example 19 were slightly inferior to those of other AA ranks.

Claims (11)

It contains at least polymer fine particles and 1,2-alkanediol, and the polymer fine particles are a modified polyethylene emulsion, and the density thereof is 940 kg / m ³ or more and 960 kg / m ³ or less. And clear ink.   Furthermore, the clear ink of Claim 1 formed by containing the polyoxyethylene alkyl ether whose carbon atom number of an alkyl group is 8-20.   The clear ink according to claim 1 or 2, wherein the polymer fine particles have a volume average particle diameter of 30 nm or more and 200 nm or less.   The clear ink according to any one of claims 1 to 3, wherein a content (% by mass) of the polymer fine particles is 1.0% by mass or more and 5.0% by mass or less based on the total mass of the clear ink.   The content (% by mass) of the 1,2-alkanediol is 1.0% by mass or more and 10.0% by mass or less based on the total mass of the clear ink. Clear ink.   The content (mass%) of the polymer fine particles is 0.20 times or more and 1.25 times or less as a mass ratio with respect to the content (mass%) of the 1,2-alkanediol. Or the clear ink according to item 1.   An inkjet recording method for ejecting clear ink by an inkjet method and applying the clear ink to a recording medium, wherein the clear ink is the clear ink according to any one of claims 1 to 6. Method. An inkjet recording method using a clear ink and at least one pigment ink,
A step (I) of recording on a recording medium using a pigment ink, and a step (II) of applying a clear ink to the recording medium by ejecting it with an inkjet method, and
An inkjet recording method, wherein the clear ink is the clear ink according to any one of claims 1 to 6.   The ink jet recording method according to claim 8, wherein the step (II) is performed after the step (I) is performed in at least a partial region of the recording medium.   An ink set for ink jetting comprising a combination of a clear ink and a pigment ink, wherein the clear ink is the clear ink according to any one of claims 1 to 6.   An ink cartridge comprising an accommodating portion for accommodating clear ink, wherein the clear ink is the clear ink according to any one of claims 1 to 6.