JP4681844B2 - Ink jet ink, ink tank, recording unit, ink jet recording apparatus, and ink jet recording method - Google Patents

Description

  The present invention relates to an inkjet ink, an ink tank, a recording unit, an inkjet recording apparatus, and an inkjet recording method used in an inkjet recording method in which an image is recorded by discharging ink.

  The ink jet method is a method for recording images, characters, etc. by ejecting micro droplets of ink by various operating principles and attaching them to a recording medium (paper, etc.). It has features such as easy, high flexibility of recording patterns, no need for development and fixing operations, and is rapidly spreading in various applications. Furthermore, in recent years, full-color multi-color inkjet recording technology has been developed, and it is also possible to form multi-color images that are comparable to multi-color printing by plate-making method and printing by color photographic method. When the amount of ink is small, a printed matter can be obtained at a lower cost than ordinary multicolor printing or printing, so that it is widely applied to the field of full-color image recording. Under such circumstances, ink jet recording apparatuses and recording methods have been improved in accordance with demands for improving recording characteristics such as higher recording speed, higher definition, and full color. Since an image forming apparatus such as a printer using an ink jet recording system is used in various usage environments, recording stability is also important, and improvement in durability is also required as an ink characteristic.

  Various recording media such as plain paper, coated paper, glossy paper, OHP sheet, and back print film are commercially available for recording by the ink jet recording method, but it is low for business use in general offices. Often the price is plain paper. In addition to satisfying the above-described characteristics, the characteristics required at this time include reducing or suppressing the curl (paper warping or curling) phenomenon that easily occurs when a large amount of ink is applied to the paper. It is done. Here, not only the occurrence of curling during recording but also the relaxation and suppression of the occurrence of post-recording curl that occurs when moisture dries and evaporates after recording (hereinafter, both are included in the case of simply curling). .

  There are various uses of ink-jet-recorded paper, but when curling occurs, the paper cannot be kept flat, such as being stacked or curled when filing, causing various problems. In addition, for example, when trial printing of an OHP presentation manuscript, if a figure, a photograph, or even a background or the like is printed in a secondary color such as blue, the paper is often warped and it is difficult to handle.

  Here, the phenomenon of curling is largely caused by the application of moisture to the recording medium. That is, it has been found that curling occurs remarkably when the printing area is large and further when the amount of ink applied during printing is large.

  Conventionally, several methods have been proposed as a method for reducing or suppressing the occurrence of curling. For example, there is a proposal for an ink-jet ink that contains a solid substance that has four or more hydroxyl groups in the molecular structure and is soluble in water or a water-soluble organic solvent (see Patent Document 1). There is also a proposal for an ink containing an anti-curl agent such as sugar (see Patent Document 2). There are also proposals for inks containing sugars and sugar alcohols (see Patent Documents 3 and 4). There is also a proposal for an ink containing a specific amide compound (see Patent Document 5). There is also a proposal for an ink containing a combination of a specific polyhydric alcohol and glycerin (see Patent Document 6). There is also a proposal for an ink containing a solvent, a polymer binder, a mordant, a water-soluble anti-curl compound, a water-soluble paste removing compound, a light-resistant compound, an antifoaming agent, and the like (see Patent Document 7).

  However, although these methods can suppress the occurrence of curl to some extent, there is room for improvement in image characteristics and stability in printing, such as a reduction in image quality of the obtained image, kogation, and nozzle clogging.

  In addition, it has been proposed that the reaction liquid and the ink are separately printed and each contains a compound that prevents curling (see Patent Document 8). At this time, a certain kind of polyol is put in the ink in an amount larger than the amount of the polyvalent metal in the reaction solution, but even with this method, curling is still insufficiently suppressed.

  Furthermore, in ink jet recording, the speed has been further increased in recent years, and the importance of ejection stability and reliability at the time of high-speed printing is also increasing. For this reason, it has become very important to alleviate and suppress the occurrence of curl while satisfying various properties such as stability, permeability and viscosity with respect to the ink jet recording characteristics of the ink itself.

JP-A-4-332775 JP-A-6-157955 JP-A-6-240189 JP-A-9-16539 JP 9-176538 A JP-A-10-130550 JP 2000-19826 A JP-A-9-207424

  Accordingly, the object of the present invention is to reduce the curl of the above-described problems of the prior art, that is, the printed matter formed, particularly the printed matter printed on plain paper, and the long-term stability and recording of ink in inkjet recording. An object of the present invention is to provide an ink jet ink, an ink tank, a recording unit, an ink jet recording apparatus, and an ink jet recording method that can obtain stability at the same time, and in particular, can obtain stable recording characteristics in high-speed printing.

The above object is achieved by the present invention described below. That is, the present invention is a water-based ink for recording on paper containing at least water, a water-soluble organic solvent, and a colorant, and the water-soluble organic solvent includes bishydroxyethyl sulfone, 1,5- At least one of a diol having 5 or more carbon atoms and a triol having 5 or more carbon atoms selected from the group consisting of pentanediol, 1,6-hexanediol, 1,7-heptanediol and 1,2,6-hexanetriol ; contains, and the amount of the bis-hydroxyethyl sulfone, the ratio between the content of the 5 or more diols carbon and 5 or more triols carbon, by weight, 1: 2-10: Ru 1 der Ink-jet ink characterized by the above.

According to another aspect of the invention, there is provided an ink tank having an ink storage portion for storing the ink.
According to another aspect of the present invention, there is provided a recording unit comprising an ink jet recording head for discharging the ink.
The present invention also provides an ink jet recording apparatus comprising an ink jet recording head for discharging the ink.
The present invention also provides an ink jet recording method comprising a step of discharging the above ink onto a recording medium by an ink jet method.

  According to the present invention, curling can be sufficiently suppressed particularly in ink jet recording on plain paper, and the printed matter does not cause curling even when recorded on plain paper, and can be handled easily. In addition, long-term stability and recording stability of the ink can be obtained at the same time, and particularly stable recording characteristics can be obtained in high-speed printing by inkjet recording. Furthermore, if the ink is used, an ink jet recorded image that is favorable in terms of image characteristics can be obtained.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments. When forming an image by an inkjet recording method using a water-based ink containing a colorant, the present inventors have used bishydroxyethyl sulfone as a component of the water-based ink (hereinafter referred to as ink) and a carbon number of 5 or more. When the diol or triol is contained in the ink, curling after printing when an image is formed on a recording medium, particularly plain paper, can be sufficiently suppressed. The inventors have obtained knowledge that sufficient performance can be obtained with respect to ejection stability, and have reached the present invention.

  The fact that bishydroxyethyl sulfone is suitable as an ink-jet ink solvent is disclosed, for example, in JP-A-7-278476. However, in this conventional example, no study is made on the technical problem of suppressing the occurrence of curling after printing.

  According to the study of the present inventors, when an image is formed with the ink added with bishydroxyethyl sulfone, a minute curl is generated within a few hours after printing. The knowledge that curl does not advance was obtained. Furthermore, the present inventors have obtained the knowledge that, when a diol or triol having 5 or more carbon atoms is used in combination with an ink to which bishydroxyethyl sulfone has been added, the curling that occurs within a few hours after printing can be reduced.

(Water-soluble liquid medium)
Preferred examples of the diol or triol having 5 or more carbon atoms used in the present invention include 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,2,6-hexanetriol. Etc.

  The content of bishydroxyethyl sulfone in the ink according to the present invention is preferably 1% by mass or more and 40% by mass or less, and more preferably 3% by mass or more and 30% by mass or less. Further, the content of the diol or triol having 5 or more carbon atoms in the ink according to the present invention in the ink is preferably such that the total amount is from 1% by mass to 30% by mass with respect to the total mass of the ink. Further, it is more preferably 3% by mass or more and 20% by mass or less.

Further, the content of bishydroxyethyl sulfone (abbreviated as BHES) in the ink according to the present invention and the content of diol or triol having 5 or more carbon atoms (abbreviated as C5) to be used in combination with the above content respectively. It is preferable that the amount is within a range and the ratio (BHES: C5) is contained within the following range. That is, the effect of the present invention can be obtained more significantly when the ink is contained in a ratio of BHES: C5 = 1: 10 to 100: 1, more preferably BHES: C5 = 1: 2 to 10: 1. It is done.
The ink according to the present invention contains at least one of bishydroxyethyl sulfone, a diol having 5 or more carbon atoms, and triol, and further contains water. Besides these, a water-soluble organic solvent that can be used by mixing with water is used. It can mix | blend suitably.

  Examples of the water-soluble organic solvent include alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; 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 ethylene glycol, propylene glycol, butylene glycol, and triethylene glycol , Thiodiglycol, hexylene glycol, diethylene glycol, etc., alkylene glycols containing 2 to 6 carbon atoms; glycerin; Lower alkyl ethers of polyhydric alcohols such as coal monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1, Examples include 3-dimethyl-2-imidazolidinone. Among these many water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, glycerin, and lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred, and diethylene glycol and glycerin are particularly preferred.

  The content of the water-soluble organic solvent other than the diol or triol having 5 or more carbon atoms as described above is preferably 10% by mass or less based on the total mass of the ink. If it is further contained in the ink, the curl prevention effect, which is the object of the present invention, is inhibited and may not be fully expressed.

  In particular, in order to obtain an ink that suppresses curling for a longer period, attention should be paid to the amounts of ethylene glycol and glycerin among the above compounds. Specifically, the ratio X of the total amount of bishydroxyethyl sulfone and diol having 5 or more carbon atoms or triol having 5 or more carbon atoms to the total mass of the ink is 15% by mass to 30% by mass, and the ratio of the total amount It is preferable that the ratio Y (mass%) of X and the amount of ethylene glycol and glycerin relative to the total mass of the ink satisfies 0 <Y / X ≦ 0.9.

  In addition, as the water used in the ink of the present invention, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions. The water content is preferably 10 to 90% by mass, and particularly preferably 30 to 80% by mass, based on the total mass of the ink.

[Colorant: Dye, Pigment]
Next, the colorant used in the ink according to the present invention will be described. Generally, colorants that record black, cyan, magenta and yellow colors are used. As the colorant, water-soluble dyes, water-dispersible pigments, and combinations thereof can be used. Specific examples include the following.

(dye)
Examples of the dye used in the ink according to the present invention include an anionic water-soluble dye. The water-soluble dye having an anionic group that can be used in the present invention is not particularly limited as long as it is a water-soluble acidic dye, a direct dye, or a reactive dye described in the color index (COOLUR INDEX). Moreover, even if it is a dye which is not described in a color index, if it has an anionic group, for example, a sulfone group, it will not restrict | limit in particular. These dyes are used in the ink in an amount of 1 to 10% by mass, preferably 1 to 5% by mass.

Specific examples of the dye include the following. Of course, it is not limited to these.
C. I. Direct yellow 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 98, 100, 110
C. I. Direct Red 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226, 227, 228, 230
C. I. Direct Blue 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226
C. I. Acid Yellow 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99
C. I. Acid Red 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 94, 106, 114, 115, 133, 134, 145, 158, 198, 249, 265, 289
C. I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 117, 127, 138, 158, 161
C. I. Direct black 17, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168
C. I. Acid Black 2, 48, 51, 52, 110, 115, 156
C. I. Reactive Black 1, 8, 12, 13
C. I. Food black 1, 2

  In addition, examples of the ink coloring material that can be used in the present invention include dyes having a carboxyl group as a solubilizing group other than those described above. Furthermore, the dye which shows the dependence of solubility with respect to pH is mentioned. These dyes are used in the ink in an amount of 1 to 10% by mass, preferably 1 to 5% by mass.

  The preferable range of physical properties of the ink according to the present invention is around 25 ° C., pH is 3 to 12, preferably 7 to 10, surface tension is 10 to 60 dyn / cm (mN / m), preferably 10 to 40 dyn /. cm (mN / m) and a viscosity of 1 to 30 cps (mPa · s), preferably 1 to 5 cps (mPa · s).

  Furthermore, the ink according to the present invention may contain other components, for example, a viscosity adjuster, a pH adjuster, an antifungal agent, a surfactant, an antioxidant and the like, if necessary.

(Recording device)
As a recording apparatus suitable for recording using the ink of the present invention, thermal or mechanical energy corresponding to a recording signal is applied to ink in a recording head having an ink storage portion for storing ink. And an apparatus for generating ink droplets by the energy.

  FIG. 1 shows an example of an ink jet recording apparatus incorporating this head. In FIG. 1, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end and form a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head, and in the case of the example shown in FIG. 1, it is held in a form protruding in the moving path of the recording head. Reference numeral 62 denotes a cap, which is disposed at a home position adjacent to the blade 61 and moves in a direction perpendicular to the moving direction of the recording head so as to come into contact with the ejection surface and perform capping. Further, reference numeral 63 in FIG. 1 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.

  The blade 61, the cap 62, and the absorber 63 constitute a discharge recovery portion 64, and the blade 61 and the absorber 63 remove moisture, dust, dust, and the like from the ink discharge port surface. Reference numeral 65 denotes a recording head that has discharge energy generation means and performs recording by discharging ink onto a recording medium facing the discharge port surface on which the discharge ports are arranged. Reference numeral 66 denotes a recording head 65 on which the recording head 65 is mounted. It is a carriage for performing the movement. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 driven by a motor 68. Accordingly, the carriage 66 can move along the guide shaft 67, and the recording area by the recording head 65 and its adjacent area can be moved.

  Reference numeral 51 denotes a paper feed unit for inserting a recording medium, and 52 denotes 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, and is discharged to a paper discharge portion provided with a paper discharge roller 53 as recording progresses.

  In the above configuration, when the recording head 65 returns to the home position due to the end of recording or the like, 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 surface 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 that at the time of wiping described above. As a result, even in this movement, the ejection port surface of the recording head 65 is wiped. The above-mentioned movement of the recording head to the home position is performed not only at the end of recording or at the time of recovery of ejection, 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. In accordance with this movement, the wiping is performed.

  FIG. 2 is a cross-sectional view showing an example of an ink cartridge 45 that contains ink supplied to the 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 jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge as described above are separated, and an apparatus in which they are integrated as shown in FIG. 3 is also preferably used. In FIG. 3, 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 has a plurality of orifices. 71 is ejected as ink droplets. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head 65 shown in FIG. 1, and is detachable from the carriage 66.

  FIG. 4 shows an example of an ink jet cartridge that can be mounted on the above-described ink jet recording apparatus. The cartridge 1012 in this example is of a serial type, and a main part is composed of an ink jet recording head (hereinafter also referred to as a liquid discharge head) 100 and a liquid tank 1001 for containing a liquid such as ink. . The inkjet recording head 100 is formed with a number of ejection ports 832 for ejecting liquid, and liquid such as ink is supplied from the liquid tank 1001 to a common liquid chamber of the liquid ejection head 100 via a liquid supply passage (not shown). It has come to be guided. A cartridge 1012 shown in FIG. 4 is formed by integrally forming an ink jet recording head 100 and a liquid tank 1001 so that liquid can be supplied into the liquid tank 1001 as necessary. A structure in which a liquid tank 1001 is connected to 100 in a replaceable manner may be adopted.

  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 unless it exceeds the gist. In the text, “part” or “%” is based on mass unless otherwise specified.

  The materials listed in Table 1 were mixed, and further filtered under pressure with a membrane filter having a pore size of 0.2 microns to obtain Inks 1 to 7 of Examples and Ink 1 of Comparative Example. The composition of each component constituting each ink was adjusted with water so that the total amount would be 100 parts.

  Using the inks of the Examples and Comparative Examples obtained above, images were formed as follows, and the obtained printed matter was evaluated for curl as follows. As the ink jet recording apparatus, the same recording apparatus as shown in FIG. 1 was used. The recording head used had a recording density of 4800 × 1200 dpi, and the driving condition was a driving frequency of 10 kHz. The discharge amount per dot was 2.8 pL. These recording conditions are the same throughout the examples and comparative examples. Using this recording head, a color image having a 100% duty was formed in the range of A4 full solid (20 × 25 cm). The recording paper used for the evaluation is A4 size PPC paper (manufactured by Canon). The printing was performed by two-pass printing in which the printing area was scanned twice. The curl amount of the printed matter printed under the above conditions was evaluated as follows.

[Evaluation]
(Initial curl amount)
The printed matter was allowed to stand at room temperature / normal humidity for 10 hours, and then the curl amount was measured. Since the curl of any printed matter lifted the edge of the printed matter, the printed matter was placed on a horizontal surface, and the distance from the tip of the curled paper to the ground contact surface of the paper was measured with a ruler. And it determined by the following reference | standard using the obtained measured value, and evaluated. The evaluation results are shown in Table 1.
○: Less than 15 mm ×: 15 mm or more

(Curl amount after 3 days)
The printed matter was allowed to stand at room temperature / humidity for 3 days, and the curl amount was measured in the same manner as described above. And it determined by the following reference | standard using the obtained measured value, and evaluated. The evaluation results are shown in Table 1.
○: Less than 25 mm Δ: 25 mm or more and less than 40 mm ×: 40 mm or more

It is a perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view of an ink cartridge. It is a perspective view of a recording unit. It is a schematic perspective view showing an example of an ink jet cartridge provided with a liquid discharge head.

Explanation of symbols

40: ink container 42: plug 45: ink cartridge 44: ink absorber 51: paper feed unit 52: paper feed roller 53: paper discharge roller 61: blade 62: cap 63: ink absorber 64: discharge recovery unit 65: Recording head 66: Carriage 67: Guide shaft 68: Motor 69: Belt 70: Recording unit 71: Head unit 72: Atmospheric communication port 100: Inkjet recording head 832: Discharge port 1001: Liquid tank 1012: Cartridge

Claims (7)

A water-based ink for recording on paper containing at least water, a water-soluble organic solvent, and a colorant, wherein the water-soluble organic solvent includes bishydroxyethyl sulfone, 1,5-pentanediol, 1,6 -Containing at least one of a diol having 5 or more carbon atoms and a triol having 5 or more carbon atoms selected from the group consisting of hexanediol, 1,7-heptanediol and 1,2,6-hexanetriol , and the content of hydroxyethyl sulfone, the ratio between the content of the diol having 5 or more carbon and 5 or more triols carbon, by weight, 1: 2 to 10: inkjet characterized by 1 der Rukoto For ink. The content of the bishydroxyethyl sulfone in the ink is 1 mass% or more and 40 mass% or less, and the total content of the diol having 5 or more carbon atoms and the triol having 5 or more carbon atoms is 1 mass in the ink. The ink-jet ink according to claim 1, wherein the amount is from 30% to 30% by mass.   The ink further contains at least one of ethylene glycol and glycerin, and the ratio X of the total amount of bishydroxyethyl sulfone, diol having 5 or more carbon atoms and triol having 5 or more carbon atoms to the total mass of the ink is 15% by mass or more. 3. The ratio X of the total amount and the ratio Y (mass%) of the amount of ethylene glycol and glycerin to the total mass of the ink satisfy 0 <Y / X ≦ 0.9. The ink for inkjet described in 2. An ink tank, characterized by having an ink storage portion for housing the ink according to any one of claims 1-3. A recording unit comprising an ink jet recording head for discharging the ink according to any one of claims 1 to 3 . An ink jet recording apparatus characterized by having an ink jet recording head for ejecting the ink according to any one of claims 1-3. An ink jet recording method comprising a step of discharging the ink according to any one of claims 1 to 3 onto a recording medium by an ink jet method.

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