JP2006144013A - Ink, ink cartridge receiving the ink and recorder using the ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink which is suitable as an ink jet ink and maintains dispersion stability and storage stability, to provide an ink jet cartridge receiving the ink, and to provide a recorder using the ink. <P>SOLUTION: This water-based dispersion system ink comprising at least water, a water-soluble organic solvent and a coloring material is characterized in that a Ko/Kt ratio R (=Kt/Ko) is ≤5, wherein Ko (=Dm/Do) is the ratio of the maximum particle diameter Dm to the average particle diameter Do of dispersed particles contained in the ink, measured by a method for converting particle diameters by rear scattered light detection based on a dynamic light scattering method as a measurement principle; Kt (=Tm/To) is the ratio of the maximum particle diameter Tm to the average particle diameter To of the dispersed particles contained in the ink, measured by the above-mentioned principle and the above-mentioned detection method, after the ink is stored in a 50°C thermostatic chamber for six months. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to ink (ink), and more particularly to printing ink used in a recording apparatus such as a printer. The ink of the present invention is suitable for ink applied to a piezo-type ink jet head or a film boiling type (or bubble type) ink jet head that uses a piezoelectric element as a print head. In addition to a single recording device (ink jet printer), The present invention can be widely applied to a copying machine, a facsimile, a computer system, a word processor, or a complex machine having a printing function.

  Currently, demand for inkjet recording apparatuses is increasing due to advantages such as quietness and easy full colorization. In particular, drop-on-demand ink jet heads that eject small droplets from ink jet nozzles only when necessary during printer operation have become widely used.

  Among ink jet heads, those using piezoelectric elements (piezo type) have been attracting more and more attention in recent years because of their excellent energy efficiency. This type of inkjet head typically includes a piezoelectric element, a common ink chamber that is supplied with ink from the outside and stores the ink, a plurality of pressure chambers connected to the piezoelectric element, and a nozzle in each pressure chamber. And a nozzle plate connected to the pressure chamber. Each pressure chamber is connected to a common ink chamber by an ink supply path, receives ink from the common ink chamber, increases the internal pressure by utilizing deformation of the piezoelectric element, and ejects ink from the nozzle.

  As ink jet head inks other than the piezo type, for example, there are known ink droplets ejected by an ejection means called a bubble type (film boiling type).

  Conventionally, inks used in this type of ink jet recording apparatus are basically composed of a dye and a water-soluble organic solvent, but the dye has a problem in that the water resistance and light resistance of the recorded matter are poor. is there. Therefore, in order to solve such problems, an aqueous dispersion ink (pigment ink) using a pigment instead of a dye has been developed. Compared to dye inks, aqueous dispersion inks (pigment inks) using pigments have advantages such as higher water resistance and light resistance of recorded matter, higher recording density of recorded matter, and less occurrence of bleeding. Have

  However, since the pigment ink itself is insoluble in a solvent such as water, it is difficult to keep the pigment particles stable, and there is a problem that clogging easily occurs in the recording nozzle. Therefore, ensuring the dispersion stability of the ink has been the biggest problem with pigment inks. Various proposals for solving this problem have been made, but the proposals of the prior art are still insufficient.

For example, Patent Document 1 discloses acrylic acid that shares a hydrophilic part and a lipophilic part as a dispersant in order to increase dispersion stability and storage stability in an ink for a writing instrument such as a sign pen made of a pigment, a dispersant, and an aqueous medium. Alternatively, it has been proposed to use a polymer containing an alkyl ester of methacrylic acid as a main component and an aqueous medium containing a nonvolatile hydrophilic organic solvent such as ethylene glycol as the aqueous medium.
JP 55-35434 A

  However, ink for writing instruments is originally unsuitable as ink for an ink jet recording apparatus (hereinafter referred to as “ink jet ink”) that ejects droplets from micro nozzles, and when stored for a long period of time, the viscosity of the ink increases due to evaporation of water, and particles Therefore, it cannot be said that the dispersion stability and the storage stability are ensured as the ink jet ink, which is not satisfactory.

  Accordingly, it is a general object of the present invention to provide a new and useful ink for solving such a conventional problem, an ink cartridge for storing the ink, and a recording apparatus using the ink.

  More specifically, it is another object of the present invention to provide an ink that maintains dispersion stability and storage stability suitable for inkjet ink, an ink cartridge that stores the ink, and a recording apparatus that uses the ink. For illustrative purposes.

  As a result of intensive studies to achieve the above object, the inventors of the present invention newly formed a dispersion ink composed of a specific pigment and a dispersant and / or an additive, and measured by a specific principle and detection method. It has been found that the conventional problem can be solved when the average particle size of the dispersed particles is within a specific range.

  The ink according to claim 1 is an aqueous dispersion ink containing at least water, a water-soluble organic solvent, and a coloring material, and is converted into a particle size by detecting backscattered light using a dynamic light scattering method as a measurement principle. The ratio between the average particle diameter Do and the maximum particle diameter Dm of the dispersed particles contained in the ink measured by the method is determined as Ko (= Dm / Do), and the ink is stored for 6 months in a constant temperature of 50 ° C. When the ratio of the average particle diameter To and the maximum particle diameter Tm of the dispersed particles contained in the ink measured by the detection method is Kt (= Tm / To), the ratio R of Ko and Kt (= Kt / Ko) R ≦ 5. When R is 5 or more, the ratio (size) between the average particle size and the maximum particle size is 5 times or more than the initial value, and the dispersed particles (especially the maximum particles) in the ink are growing rapidly. Means. Since such ink has a tendency to disperse dispersed particles over time over a long period of time, the possibility of precipitation increases. Such an ink is likely to have an unstable dispersion system and poor storage stability.

  The ink according to claim 2, which is dependent on claim 1, has an average particle size To of the dispersed particles contained in the ink measured by the principle and the detection method after being stored for 6 months in a constant temperature of 50 ° C., and 10 nm ≦ To ≦ 1000 nm and Do ≦ To are satisfied. Ink satisfying 10 nm ≦ To ≦ 1000 nm and Do ≦ To has a more stable dispersion system than the ink of claim 1. This is because when To becomes 1000 nm or more, nozzle clogging of the ink jet recording apparatus occurs, and the reliability is remarkably impaired. In addition, it is practically impossible to stably produce particles of 10 nm or less. To is the average particle diameter after aging from the initial stage, and generally becomes larger than the initial Do.

  The ink according to claim 3, which is dependent on claim 1, has a maximum particle size Tm of the dispersed particles contained in the ink of 10 nm ≦ Tm measured by the principle and the detection method after being stored for 6 months at a constant temperature of 50 ° C. ≦ 10000 nm and Dm ≦ Tm are satisfied. An ink satisfying 10 nm ≦ Tm ≦ 10000 nm and Dm ≦ Tm has a more stable dispersion system than the ink of claim 1. This is because when the Tm is 10000 nm or more, nozzle clogging of the ink jet recording apparatus occurs, and the reliability is significantly impaired. In addition, it is practically impossible to stably produce particles of 10 nm or less. Further, Tm is the maximum particle size after aging from the initial stage, and is generally larger than the initial Dm.

  The ink according to claim 4, which is dependent on claim 1, filters the ink, and the pore diameter Df of the filter medium used for the filtration satisfies 1 <Df / Dm ≦ 4. Df has a minimum pore diameter of Df through which the entire amount is filtered (100% passage). Ink that has passed a specific range of filter pore sizes, considering that filtering may not be possible if the filter pore size is selected based on the measured values (average and maximum diameter, etc.) with a particle size distribution meter. It is said.

  In the ink according to claim 5, which is dependent on claim 4, the material of the filter used for the filtration is any of cellulose acetate, cellulose nitrate, regenerated cellulose, polysulfone, polypropylene, polyamide, or a combination thereof. . In order to facilitate the filtration of ink, a hydrophilic material is used as the filter material.

  The ink according to claim 6, which is dependent on claim 1, further includes a dispersant. The dispersion stability of the ink is increased by the dispersant.

  In an ink according to claim 7, which is dependent on claim 6, the dispersant is a polymer having a lipophilic component, a cationic component, and a hydrophilic component. Such an ink is more stable than the ink according to the sixth aspect. This is because carbon black has a negative charge in an aqueous medium, and when the dispersant is used, the dispersant is not only adsorbed by the lipophilic component but also by the electric attractive force of the cationic component. This is because the hydrophilic part is considered to be dissolved in the aqueous medium. The pigment particles are believed to be stably retained in the aqueous medium by the action of these three parts of the dispersant.

  The ink according to claim 8, which is dependent on claim 1, has a viscosity η at 20 ° C. of 1 cp ≦ η ≦ 100 cp. The inventors have discovered that such inks are excellent in stability.

  A ninth aspect to a tenth aspect are an ink cartridge and a recording apparatus that use the ink described above. Since an ink having excellent dispersion stability and storage stability is used, it is possible to provide a stable recording operation and high printing quality without clogging.

  The ink according to claim 11 is an aqueous dispersion ink containing at least water, a water-soluble organic solvent, and a coloring material, and the particle size change due to the measurement is measured by directly measuring the ink without diluting the ink. The ratio of the average particle diameter Do and the maximum particle diameter Dm of the dispersed particles contained in the ink measured without causing it to be set to Ko (= Dm / Do), and the ink was stored for 6 months in a constant temperature at 50 ° C. When the ratio of the average particle diameter To and the maximum particle diameter Tm of the dispersed particles contained in the ink measured by the detection method is Kt (= Tm / To), the ratio R of Ko and Kt (= Kt / Ko) R ≦ 5.

  Other objects and further features of the present invention will become apparent from the embodiments described below with reference to the accompanying drawings.

  According to the present invention, it is possible to provide an ink excellent in dispersion stability, storage stability, and ejection stability from a recording apparatus. Therefore, the ink cartridge of the present invention can store ink for a longer period than before. In addition, the recording apparatus using the ink of the present invention can realize a stable operation with high print quality and less clogging.

  The ink according to the first aspect of the present invention uses a dynamic light scattering method (hereinafter, abbreviated as “DLS method”) as a measurement principle for dispersed particles in an aqueous dispersion ink, and converts the particle size by detecting backscattered light. The ratio of the maximum particle size and the average particle size measured by the principle and the detection method is 5 or less after the maximum particle size and the average particle size measured by the method used, and after the ink was stored for 6 months in a constant temperature of 50 ° C. By doing so, dispersion stability and storage stability can be improved. The “dispersed particles” in the present invention means a state of particles in which a coloring material or a dispersing agent is independent or combined.

  Generally, when measuring the particle size of particles dispersed in a solvent, an optical or electrochemical measurement method is known. Among these, particle size distribution analyzers (for example, those based on the photon correlation method) that measure and detect optical scattering (static / dynamic light scattering, etc.) have been used frequently. However, it could not be measured unless the sample was diluted greatly. For this reason, the particle size measurement of the conventional measurement principle and detection method cannot measure the dispersion state of the stock solution. On the other hand, when diluted, the dispersion / aggregation state of the stock solution may change. There was a risk of mistakes.

  In contrast, in recent years, laser light is irradiated to particles dispersed in a solvent, and frequency analysis is performed by detecting the speed of Doppler-shifted light scattered by moving particles. A particle size distribution meter appeared (for example, a MICROTRAC particle size distribution meter). The feature of this apparatus is that particle size conversion is performed by irradiating dispersed particles in a sample with laser light and measuring backscattered light that is reflected by the laser. This principle and the characteristics of the detection method enable measurement of a high-concentration sample, which could not be measured conventionally, and does not require a large dilution of the sample.

  On the other hand, a drawback of this principle and detection method is that it is greatly affected by the viscosity of the sample. This is because the speed of the Doppler shift light by the dispersed particles is also a function of temperature and viscosity, and thus is significantly influenced by the viscosity of the sample. For this reason, the credibility of the measurement value is suspected in principle when the viscosity of the sample gradually changes or for a high viscosity sample. However, the ink referred to in the present invention is a low viscosity sample of 100 cP or less, more desirably 30 cP or less, and there is no problem in measurement.

  As described above, on the premise that the dispersion and aggregation state of aqueous dispersion ink that could not be measured conventionally can be approximated by detecting the backscattered light by the DLS method and performing particle size conversion. The ink of the present invention was newly constructed.

  That is, the present invention relates to an aqueous dispersion ink composed of at least water, a water-soluble organic solvent, and a color material, and uses ink as a measurement principle based on a dynamic light scattering method and by converting a particle size by detecting backscattered light. The ratio of the average particle diameter Do (nm) and the maximum particle diameter Dm (nm) of the dispersed particles contained therein is set to Ko (= Dm / Do), and the ink is stored in a constant temperature at 50 ° C. for 6 months. / When the ratio of the average particle diameter To (nm) and the maximum particle diameter Tm (nm) of the dispersed particles contained in the ink measured by the detection method is Kt (= Tm / To), the ratio R of Ko and Kt ( = Kt / Ko) is provided, wherein R ≦ 5.

  When R is 5 or more, the ratio (size) between the average particle diameter and the maximum particle diameter is 5 times or more of the initial particle size, and the dispersed particles (especially the maximum particles) in the ink grow rapidly. Means that. Since such ink has a tendency to disperse dispersed particles over time over a long period of time, the possibility of precipitation increases. Such an ink is likely to have an unstable dispersion system and poor storage stability.

  Preferably, after the ink is stored for 6 months at a constant temperature of 50 ° C., the average particle diameter To of the dispersed particles contained in the ink measured by the principle / detection method is 10 nm ≦ To ≦ in relation to the Do. It is 1000 nm and is in the range of Do ≦ To. Thereby, an ink with a more stable dispersion system can be provided.

  This is because when To becomes 1000 nm or more, nozzle clogging of the ink jet recording apparatus occurs, and reliability is significantly impaired. In addition, it is practically impossible to stably produce particles of 10 nm or less. Further, To is an average particle diameter after a change with time from the initial stage, and is generally larger than the initial Do.

  Preferably, after the ink is stored for 6 months at a constant temperature of 50 ° C., the maximum particle diameter Tm of the dispersed particles contained in the ink measured by the principle / detection method is 10 nm ≦ Tm ≦ in relation to the Dm. It is 10,000 nm and is in the range of Dm ≦ Tm. Thereby, an ink with a more stable dispersion system can be provided.

  This is because when the Tm is 10000 nm or more, nozzle clogging of the ink jet recording apparatus occurs, and the reliability is significantly impaired. In addition, it is practically impossible to stably produce particles of 10 nm or less. Further, Tm is the maximum particle size after aging from the initial stage, and is generally larger than the initial Dm.

  Preferably, when the ink is filtered, when the pore diameter (= pore size) of the filter medium (= filter) used for the filtration is Df (nm), the ratio to Dm is 1 <Df / Dm It is in the range of ≦ 4. Thereby, an ink with a more stable dispersion system can be provided.

  Conventionally or even now, if the pore size of the filter is selected based on the measured value (average / maximum diameter, etc.) with a particle size distribution meter, filtration may not be possible. Probably, the actual dispersed particles are not a simple sphere, but may be caused by influences such as a chain-like shape or a branched shape inside the particle. For this reason, since the particle size (average or maximum) estimated from the particle size conversion and the pore size of the actual filter are greatly different from each other, in the present invention, the ink has passed the filter / pore size in a specific range. There are features.

  In the present invention, the “pore size (= pore size)” is based on the bubble point method (a kind of pore size measuring method) widely used for measuring the maximum pore size of the filter medium (= filter) shown in JIS K3832. Or, it is managed by measuring the retention property of the filter medium by the method using indicator bacteria (method of actually filtering the indicator bacteria (microorganisms) determined for each filter pore size and managing the pore size from its trapping ability) Means a numerical value.

  Here, when Df is 4 times or more of Dm, the pore size of filtration is too large with respect to the size of the dispersed particles, and coarse particles pass through, so there is no point in performing filtration. Further, filtration is not possible unless Df is greater than Dm.

  More preferably, when the ink is filtered, the material of the filter used for the filtration is composed of cellulose acetate, cellulose nitrate, regenerated cellulose, polysulfone, polypropylene, polyamide, or a combination thereof. Has been. Thereby, a more stable dispersion ink can be obtained.

  In the case of filtering the ink, not only the filter and pore size but also the filter material may not be used for filtration. Probably, it is considered that the filter material is caused by the influence of the dispersion ink (or a specific chemical substance in the composition) and the property of being difficult to wet. For this reason, since the possibility of filtration may be determined depending on what kind of filter is selected, the present invention is characterized in that the ink has passed through a filter of a specific material.

Preferably, the dispersed particles in the ink are composed of a color material containing at least carbon black, and the characteristics thereof are a primary particle size of 30 nm or less, a BET specific surface area of 200 m ² / g or less, a DBP oil absorption of 80 cc / 100 g or less, and a volatile content of 20 % Or more and pH 7 or less. Thereby, a stable dispersion ink can be provided.

This is because when the primary particle diameter of the dispersed particles is 30 nm or more, the BET specific surface area is 200 m ² / g or more, the DBP oil absorption is 80 cc / 100 g or more, the volatile content is 2, 0% or less, and the pH is 7 or more. This is because agglomeration tends to occur and dispersion becomes unstable.

  In addition to carbon black, such dispersed particles include insoluble azo, isoindolinone, benzimidazolone, and condensed azo yellow pigments, insoluble azo, quinacridone, perylene, and dioxazine. And red pigments such as fusocyanin and induslen are also usable.

  Furthermore, if the ink contains a dispersant composed of an acrylic polymer having a weight average molecular weight of 80,000 or less, the ink is further excellent in stability.

  This is because when the weight average molecular weight of the polymer copolymer is 80000 or more and the addition amount is 100% or more with respect to the pigment, the solubility in water becomes low and the viscosity of the ink becomes high. If it is ejected with, printing failure tends to occur. On the other hand, when the addition amount of the polymer copolymer to the pigment is 10% or less, the dispersion of the pigment becomes unstable.

  As a result, the weight average molecular weight of the polymer copolymer in the dispersant is preferably 80,000 or less, more preferably 3000 to 60000. The added amount is 10 to 100%, preferably 10 to 30% with respect to the pigment.

  For the acrylic polymer dispersant satisfying the above conditions, an alkali-soluble water-soluble resin is preferred. For example, styrene-acrylic acid copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-α-methylstyrene-acrylic. Acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer and salts thereof, polyacrylate polymer methacrylate, vinylnaphthalene-acrylic acid copolymer salt, styrene Mention may be made of maleic acid copolymers, maleic acid-maleic anhydride copolymer bases, vinylnaphthalene-maleic acid copolymer salts, and the like. These may be added singly or in combination.

  Further, when the dispersant is a polymer having a lipophilic component, a cationic component, and a hydrophilic component, the dispersion stability of the ink is excellent. This is because the above-mentioned pigment (for example, carbon black) has a negative charge in an aqueous medium, and when the dispersant is used, in addition to adsorption by the lipophilic component, electrical attraction by a cationic component. It is considered that the dispersant is fixed to the pigment surface by force, and the hydrophilic portion is dissolved in the aqueous medium. The pigment particles are believed to be stably retained in the aqueous medium by the action of these three parts of the dispersant.

  In such dispersants, the lipophilic component is an alkyl ester, cycloalkyl ester, aryl ester and arylalkyl ester of α, β ethylenically unsaturated carboxylic acid including acrylic acid, methacrylic acid, itaconic acid, fumaric acid, styrene , Α-methylstyrene or a polymer composed of a mixture thereof, and a polymer whose cationic component is a primary, secondary, tertiary amino group, quaternary ammonium group, pyridinium group or a mixture thereof. The hydrophilic part is (a) a salt of an anionic group such as a carboxyl group, a sulfonic acid group, a sulfate ester group or a phosphate ester group, (b) a salt of a cationic group of a cationic component, (c) a hydroxyl group, ethylene Oxide adducts, nonionic groups such as carpamide groups or polymers composed of mixtures of these That.

  In order to solubilize the dispersant, an organic or inorganic base such as monoethanolamine, diethanolamine, triethanolamine, aminomethylpropanol, or ammonia can be added.

  Water-soluble organic solvents used in the ink include monohydric alcohols such as methanol, ethanol, (normal) propyl alcohol, isopropyl alcohol, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol. Dihydric alcohols such as diethylene glycol and triethylene glycol, trihydric alcohols such as glycerin, trimethylolpropane, 1,2,3-trimethylolpropane, tetrahydric alcohols such as pentaerythritol, polyethylene glycol -Low polyhydric alcohols such as polyalkylene glycol such as polybutylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether And alkyl ethers can be used. Of these, polyhydric alcohols such as diethylene glycol are preferred. These water-soluble organic solvents can be used as a mixture, and the weight ratio in the ink is preferably 1 to 20%.

  The ink of the present invention may be added with a surfactant, a pH adjuster (or a buffer), a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an evaporation accelerator, a penetrating agent, a chelating agent, etc., as necessary. Thing can be contained.

  As a method for dispersing the pigment, various methods used for ordinary pigment dispersion can be used. For example, the ink of the present invention can be obtained by performing dispersion with various commercially available dispersers such as a ball mill, a sand mill, an attritor, a roll mill, a bead mill, a colloid mill, an ultrasonic homogenizer, and a high-pressure homogenizer.

  Preferably, the ink has a viscosity η (cP) at 20 ° C. in a range of 1 ≦ η ≦ 100. Thereby, an ink with a more stable dispersion system can be provided. This is because when η is 100 or more, a large amount of energy is required for ink ejection of the ink jet recording apparatus, and nozzle clogging occurs and the reliability is remarkably impaired. If η is desirably 30 or less, more desirably η is 10 or less, the effect is high in terms of ejection energy and reliability. On the other hand, it is practically impossible to stably produce an aqueous ink having η of 1 or less.

  Hereinafter, an inkjet printer 1 to which the ink of the present invention is applied will be described with reference to FIGS. 1 to 3. In addition, in each figure, the member which attached | subjected the same reference number represents the same member, and duplication description is abbreviate | omitted. Further, members having the same reference numbers with alphabets are the same type of members, but are distinguished by alphabets, and are simply summarized with reference numbers.

  FIG. 1 schematically shows an embodiment of a color inkjet printer (recording apparatus) 1 to which the ink of the present invention, which will be described in detail later, is applied. A platen 12 is rotatably provided in the housing 10 of the recording apparatus 1.

  During the recording operation, the platen 12 is intermittently rotated by the drive motor 14, whereby the recording paper P is intermittently fed in the arrow W direction at a predetermined feed pitch. Further, a guide rod 16 is provided in the housing 10 of the recording apparatus parallel to the platen 12 and on the upper side thereof, and a carriage 18 is slidably mounted on the guide rod 16.

  The carriage 18 is attached to an endless drive belt 20, and the endless drive belt 20 is driven by a drive motor 22, whereby the carriage 18 is reciprocated (scanned) along the platen 12.

  A black recording head 24 and a color recording head 26 are mounted on the carriage 18. The color recording head 26 can be composed of three parts. A black ink cartridge 28 is detachably attached to the black recording head 24, and color ink cartridges 30, 32, and 34 are detachably attached to the color recording head 26.

  The black ink cartridge 28 contains black ink of the ink of the present invention, and the color ink cartridges 30, 32 and 34 respectively contain yellow ink, cyan ink and magenta ink of the ink of the present invention. Since the black ink is used more frequently than the other color inks, the capacity of the black ink cartridge 28 is larger than the capacity of the other ink cartridges.

  FIG. 2 is a schematic enlarged perspective view of each ink cartridge shown in FIG. 1, and FIG. 3 is a schematic enlarged perspective view of the ink cartridge 30. The ink cartridge 30 includes an engaging portion 52 that engages with the claw portion 41 of the lever 40 and a hole 53 that engages with the protruding portion 43 of the lever 40. The cartridge has a hole (ink supply portion) (not shown) connected to the corresponding head on the bottom surface, and the cartridge soaked with a sponge soaked with ink or an aluminum pack filled with ink.

  While the carriage 18 is reciprocated along the platen 12, the black recording head 24 and the color recording head 26 are driven based on image data obtained from a word processor, personal computer, etc. Predetermined characters, images, etc. are recorded on the. When the recording operation is stopped, the carriage 18 is returned to the home position, and a nozzle maintenance mechanism (backup unit) 36 is provided at the home position.

  The nozzle maintenance mechanism 36 is provided with a movable suction cap (not shown) and a suction pump (not shown) connected to the movable suction cap. When the recording heads 24 and 26 are positioned at the home position, the suction cap is attracted to the nozzle plate of each recording head, and the nozzles of the nozzle plate are sucked by driving the suction pump. In this way, clogging of the nozzle is prevented in advance.

  Hereinafter, the present invention will be specifically described with reference to examples and comparative examples of the present invention.

Example 1
(A) Preparation of concentrated pigment dispersion Acrylic polymer copolymer: 8.3 parts by weight (styrene-maleic acid system, weight average molecular weight 20000, nonvolatile content 30%)
Ion-exchanged water: 80.5 parts by weight The above components were mixed and stirred, and this aqueous solution was mixed with carbon black (primary particle size 24 nm, BET specific surface area l38 m ² / g, DBP oil absorption 60 cc / 100 g, volatile content 4 0.5%, pH 2.5) 10 parts by weight, defoaming agent: 1.2 parts by weight is added, dispersed for 1 hour in a bead mill disperser, and concentrated by removing coarse particles through a high-speed centrifuge. A pigment dispersion was obtained.

  (B) Preparation of aqueous recording liquid Concentrated pigment dispersion: 18 parts by weight Diethylene glycol: 2.2 parts by weight Ion exchange water: 9.8 parts by weight After mixing and stirring the above components, cellulose acetate material having a pore size of 0.8 μm The target aqueous recording liquid was obtained by filtration using a filter.

(Example 2)
In the preparation of the concentrated pigment dispersion (a) in Example 1 above, acrylic polymer copolymer: 9.0 parts by weight (styrene-maleic acid system, weight average molecular weight 20000, nonvolatile content 30%)
Ion exchange water: 76.7 parts by weight Carbon black Addition amount: 13 parts by weight Antifoaming agent: 1 part by weight The same dispersion treatment and centrifugal separation treatment as in Example 1 were performed to obtain a concentrated pigment dispersion. Next, concentrated pigment dispersion: 90 parts by weight pentaerythritol: ll parts by weight ion-exchanged water: 48.7 parts by weight The above components were mixed and stirred, and then filtered through a polyamide material filter having a pore size of 1 μm to obtain the desired aqueous recording. A liquid was obtained.

(Example 3)
In the preparation of the concentrated pigment dispersion of (a) in Example 1 above, acrylic polymer copolymer: 10 parts by weight Ion-exchanged water: 76.5 parts by weight Carbon black Addition amount: 12 parts by weight Antifoaming agent 1 0.5 parts by weight, and the same dispersion treatment and centrifugal separation treatment as in Example 1 were performed to obtain a concentrated pigment dispersion.

  Next, concentrated pigment dispersion: 90 parts by weight Trimethylolpropane: ll parts by weight Ion exchange water: 48.7 parts by weight The above components were mixed and stirred, and then filtered through a cellulose nitrate material filter having a pore size of 0.8 μm. The intended aqueous recording liquid was obtained.

Example 4
In the preparation of the concentrated pigment dispersion (a) in Example 1 above, acrylic polymer copolymer: 5.4 parts by weight Ion-exchanged water: 87.3 parts by weight Carbon black added amount: 6.5 parts by weight Agent: 0.8 parts by weight The same dispersion treatment and centrifugal separation treatment as in Example 1 were performed to obtain a dark pigment dispersion night.

  Next, concentrated pigment dispersion: 90 parts by weight glycerin: 1 part by weight ion-exchanged water: 48.7 parts by weight The above components were mixed and stirred, and then filtered through a regenerated cellulose material filter having a pore size of 0.8 μm to obtain the desired aqueous system A recording liquid was obtained.

(Example 5)
In the preparation of the concentrated pigment dispersion of (a) in Example 1 above, acrylic polymer: 9.0 parts by weight ion-exchanged water: 76.7 parts by weight Carbon black addition amount: 13 parts by weight antifoaming agent: 1 part by weight, and the same dispersion treatment and centrifugal separation treatment as in Example 1 were performed to obtain a concentrated pigment dispersion night.

  Next, concentrated pigment dispersion: 90 parts by weight glycerin: 11 parts by weight ion-exchanged water: 48.7 parts by weight The above components were mixed and stirred, and then filtered through a polysulfone material filter having a pore size of 3 μm to obtain the desired aqueous recording liquid. Obtained.

(Example 6)
In preparation of (a) concentrated pigment dispersion night in Example 1 above, acrylic polymer copolymer: 9.0 parts by weight ion exchange water: 76.7 parts by weight Carbon black addition amount: 13 parts by weight defoaming agent: 1 part by weight, and the same dispersion treatment and centrifugal separation treatment as in Example 1 were performed to obtain a concentrated pigment dispersion.

  Next, concentrated pigment dispersion: 90 parts by weight propylene glycol: 11 parts by weight ion-exchanged water: 48.7 parts by weight After mixing and stirring the above components, the mixture was filtered with a polypropylene filter having a pore size of 5 μm to obtain the desired aqueous recording. A liquid was obtained.

(Comparative Example 1)
In place of the acrylic polymer copolymer of Example 1, Sunspar PDNl73 (manufactured by Sanyo Kasei Co., Ltd., polycarboxylic acid special polymer copolymer) was used. The ink was filtered through a polytetrafluoroethylene material filter having a pore diameter of 5 μm.

(Comparative Example 2)
Nonionic NS-210 (made by NOF Corporation, nonionic) was used in place of the acrylic polymer copolymer of Example 1, and the other composition and production method were the same as in Example 1 to obtain an ink. It was.

(Comparative Example 3)
In place of the acrylic polymer copolymer of Example 1, Sunsizer SA501-20 (manufactured by Sanyo Chemical Co., Ltd., acrylic polymer copolymer, weight average molecular weight 100,000, nonvolatile content 20%) was used. The composition and production method were the same as in Example 1, and an ink was obtained.

  About the above-mentioned aqueous recording liquid, the dynamic light scattering method is used as a measurement principle, and the particle size is converted by detecting the backscattered light using a particle size analyzer MICROTRAC-UPA (trade name, manufactured by Nikkiso Co., Ltd.). Average particle diameter Do (nm) and maximum particle diameter Dm (nm) of dispersed particles, average of dispersed particles contained in ink measured by the principle / detection method after storing the ink at 50 ° C. for 6 months The particle size To (nm) and the maximum particle size Tm (nm) were measured, and Ko (= Dm / Do), Kt (= Tm / To), and R (= Kt / Ko) were calculated.

  Table 1 shows the results of evaluating the R, the dispersibility before and after storage of the aqueous recording liquid, the ejection stability, and the printing characteristics.

  The ink recording characteristics and dispersion stability were measured using an on-demand ink jet recording apparatus (nozzle diameter φ40 μm, number of nozzles 24). For the recording medium at this time, XER0X4024 paper was used as plain paper. Each test was performed on the recorded image obtained with this ink. The results are shown in Table 1.

ここで、分散安定性は、インクを常温で２年保存したときの、保存前と保存後の粒度分布を測定比較し、平均粒径の増加が３０％以下の場合を○、５０％以下の場合を△、５０％以上の場合を×と評価した。

Here, the dispersion stability is measured by comparing the particle size distribution before and after storage when the ink is stored at room temperature for 2 years. The case where the increase in average particle size is 30% or less is ○, 50% or less. The case was evaluated as Δ, and the case of 50% or more was evaluated as ×.

  In addition, the ejection stability is compared with the number of prints with no missing dots when ink is continuously printed with an ink jet recording apparatus. The number of continuous prints is 10 or more; Less than was evaluated as x.

  Further, the printing characteristics are determined by the density of the recorded image, and the density of the recorded image is determined by the value evaluated by the optical reflection density OD measured by a spectrocolorimeter (for example, manufactured by X RITE). However, the case where it is 1.0 or more was evaluated as ◯, the stand of 1.0-0.5 was evaluated as Δ, and less than 0.5 was evaluated as ×.

  As a result, the inks shown in Examples 1 to 6 were able to obtain good aqueous dispersion inks excellent in dispersion stability, ejection stability, and printing characteristics.

  Although the preferred embodiments of the present invention have been described above, the present invention can be variously modified and changed within the scope of the gist thereof.

1 is a schematic perspective view of an ink jet printer to which the ink of the present invention can be applied. FIG. 2 is a schematic enlarged perspective view of an ink cartridge portion applicable to the ink jet printer shown in FIG. 1. FIG. 3 is a schematic enlarged perspective view of the ink cartridge shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inkjet head, 28 ... Ink cartridge, 30 ... Ink cartridge, 32 ... Ink cartridge, 34 ... Ink cartridge

Claims (11)

  An aqueous dispersion ink containing at least water, a water-soluble organic solvent, and a color material, the ink measured by a method of converting the particle size by detecting backscattered light using a dynamic light scattering method as a measurement principle The ratio of the average particle diameter Do and the maximum particle diameter Dm of the dispersed particles contained in the ink was set to Ko (= Dm / Do), and the ink was measured by the principle and the detection method after being stored at 50 ° C. for 6 months. The ratio of Ko to Kt R (= Kt / Ko) is R ≦ 5, where Kt (= Tm / To) is the ratio of the average particle size To and the maximum particle size Tm of the dispersed particles contained in the ink.   The average particle diameter To of the dispersed particles contained in the ink measured by the principle and detection method after being stored for 6 months in a constant temperature at 50 ° C satisfies 10 nm ≤ To ≤ 1000 nm and Do ≤ To. The ink described.   The maximum particle diameter Tm of the dispersed particles contained in the ink measured by the principle and the detection method after being stored for 6 months in a constant temperature at 50 ° C satisfies 10 nm ≤ Tm ≤ 10000 nm and Dm ≤ Tm. The ink described.   The ink according to claim 1, wherein the ink is filtered and a pore diameter Df of a filter medium used for the filtration satisfies 1 <Df / Dm ≦ 4.   The ink according to claim 4, wherein a material of the filter used for the filtration is any one of cellulose acetate, cellulose nitrate, regenerated cellulose, polysulfone, polypropylene, polyamide, or a combination thereof.   The ink of claim 1, further comprising a dispersant.   The ink according to claim 6, wherein the dispersant is a polymer having a lipophilic component, a cationic component, and a hydrophilic component.   The ink according to claim 1, wherein the viscosity η at 20 ° C. satisfies 1 cp ≦ η ≦ 100 cp.   An aqueous dispersion ink containing at least water, a water-soluble organic solvent, and a color material, the ink measured by a method of converting the particle size by detecting backscattered light using a dynamic light scattering method as a measurement principle The ratio of the average particle diameter Do and the maximum particle diameter Dm of the dispersed particles contained in the ink was set to Ko (= Dm / Do), and the ink was measured by the principle and the detection method after being stored at 50 ° C. for 6 months. An ink in which the ratio R (= Kt / Ko) of Ko to Kt is R ≦ 5, where Kt (= Tm / To) is the ratio of the average particle size To and the maximum particle size Tm of the dispersed particles contained in Contains ink cartridge.   A recording apparatus having a head and an ink cartridge for supplying ink to the head, wherein the ink is an aqueous dispersion ink containing at least water, a water-soluble organic solvent, and a coloring material, The ratio of the average particle diameter Do to the maximum particle diameter Dm of the dispersed particles contained in the ink measured by a method of converting the particle diameter by detecting the backscattered light based on the light scattering method is Ko (= Dm / Do). And the ratio of the average particle diameter To and the maximum particle diameter Tm of the dispersed particles contained in the ink measured by the principle and the detection method after storing the ink at a constant temperature of 50 ° C. for 6 months is Kt (= Tm / To ), The ratio R (= Kt / Ko) of Ko and Kt is R ≦ 5.   A water-soluble dispersion-based ink containing at least water, a water-soluble organic solvent, and a colorant, wherein the particle diameter of the dispersed particles contained in the ink is directly measured, and the average particle diameter Do and the maximum of the measured particle diameters are measured. The ratio of the particle diameter Dm is set to Ko (= Dm / Do), and after storing the ink in a constant temperature of 50 ° C. for 6 months, the particle diameter of the dispersed particles contained in the ink is directly measured. An ink in which the ratio R (= Kt / Ko) of Ko to Kt is R ≦ 5, where the ratio of the average particle diameter To and the maximum particle diameter Tm is Kt (= Tm / To).

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