JP6158000B2 - Ink, ink set, ink jet recording method, ink jet recording head, and ink jet recording apparatus - Google Patents

Description

The present invention relates to an ink, an ink set, an ink jet recording method, an ink jet recording head, and an ink jet recording apparatus.

The ink jet recording method is a recording method in which images, characters, and the like are recorded by causing ink droplets to fly according to various operating principles and adhere to a recording medium such as paper.
The ink jet recording system is characterized in that it is excellent in high-speed printing properties, low noise properties, and flexibility in recording patterns, can easily perform multi-coloring, and does not require development and image fixing. In particular, in a multi-color inkjet recording method using multiple colors, the obtained image is comparable to a multi-color printed image formed by a plate-making method or a print formed by a color photographic method, and the number of copies produced If there is a small amount, there is an advantage that the printing cost is lower than that of the normal printing technique or photographic technique. Therefore, an ink jet recording apparatus (hereinafter also referred to as “recording apparatus”) that employs an ink jet recording method is rapidly spreading.

  Conventionally, dyes have been used as color materials contained in water-based inks for inkjet recording apparatuses. However, the water-based ink using the dye is excellent in the accuracy of landing on the recording medium and the sharpness of the obtained image, but has problems in the light resistance and water resistance of the obtained image. Therefore, in recent years, in order to solve the problems of light resistance and water resistance of the obtained image, it has been actively studied to convert the color material contained in the water-based ink from a dye to a pigment.

  However, in the thermal method in which ink droplets fly by heating the ink with a heater, the ink undergoes a temperature change of 300 ° C. or more due to heating, and the gas-liquid phase change occurs in the foamed portion. Therefore, it is extremely difficult to keep the dispersibility of the pigment dispersed by the pigment dispersant in the ink stable. Therefore, when the dispersibility of the pigment becomes unstable, the pigment dispersant is separated from the pigment, and when the pigment that has lost the dispersibility comes into contact with the heater surface portion, it leads to a phenomenon of kogation in which the pigment is kogated at the heater portion. Due to this phenomenon, there is a problem that the landing accuracy of ink droplets ejected from an ink jet recording head (hereinafter also referred to as “recording head”) is lowered, and the quality of a printed image obtained is lowered.

  In particular, in an ink using a phthalocyanine compound as a pigment, the surface of the phthalocyanine compound may be high in hydrophilicity when compared with other pigment types, and the adsorptive power with the pigment dispersant is weak and heated. Thus, the pigment dispersant adsorbed on the phthalocyanine compound is easily separated. Therefore, the phthalocyanine compound is more likely to cause kogation than other pigment types, and the landing accuracy is likely to be lowered. Therefore, in an ink set including a plurality of types of ink, there has been a problem that the landing position on the recording medium is shifted by an ink using a phthalocyanine compound as a pigment.

  Therefore, an ink and a recording method that include an acrylic polymer having a glass transition temperature (Tg) of less than 100 ° C., minimize the kogation of the heater, and have good landing accuracy have been proposed (for example, see Patent Document 1). ). As a method for improving the landing accuracy, a method of using an aldonic acid additive (for example, gluconic acid) in an ink jet ink has been proposed (for example, see Patent Document 2).

Special table 2013-518739 gazette US Patent Application Publication No. 2002/113842

  However, it has been found that the above-described method is not always sufficient to solve the above problem. In other words, the above-described method has an effect of suppressing kogation of the phthalocyanine compound, and the ink ejection speed is improved. However, the ink ejection speed is uniformly improved for all inks in the ink set. Therefore, when there is a difference in the discharge speed between the inks, it is difficult to control the discharge speed to be the same.

Therefore, the present invention has been made in view of the above problems. That is, the object of the present invention is to maintain the dispersibility of the pigment in the water-based ink stably by, for example, preventing the kogation of the pigment in the heater portion of the inkjet recording head when used in the thermal method. An object of the present invention is to provide an ink, an ink set including a plurality of types of water-based inks, an ink jet recording method, an ink jet recording head, and an ink jet recording apparatus capable of realizing excellent landing accuracy.

  As a result of intensive studies to achieve the above object, the present inventors can achieve the above object by controlling the acid value of the dispersant used in the aqueous ink containing the phthalocyanine compound. The present inventors have found that an ink set can be realized and completed the present invention.

That is, according to the present invention, the following ink, ink set, inkjet recording method, inkjet recording head, and inkjet recording apparatus are provided.
[1] An ink set comprising a water-based ink containing a pigment and a (meth) acrylic acid ester-based random copolymer in which the pigment is dispersed as a set of a plurality of types of the water-based ink, The (meth) acrylic acid ester-based random copolymer contained in each has an acid value of 100 to 160 mgKOH / g, and one of the plurality of water-based inks includes a phthalocyanine compound as the pigment. The cyan ink contains the (meth) acrylic acid ester contained in the water-based ink other than the cyan ink in which the (meth) acrylic acid ester-based random copolymer contained therein is contained. An ink set having an acid value of 0.70 to 0.95 times that of a random copolymer .

[2] Among the plurality of types of water-based inks, the water-based ink other than the cyan ink includes a black ink containing carbon black as the pigment and a magenta ink containing a quinacridone compound as the pigment. The ink set described.

[3] The (meth) acrylic acid ester random copolymer contained in a plurality of types of the water-based inks is composed of a common monomer species, and changes the mixing ratio of the monomer species. The ink set according to [1] or [2], wherein the acid value is adjusted by this.

[4] The plurality of types of the water-based inks each have a viscosity of 1.5 to 5.0 mPa · s, and the difference in viscosity between them is 0.5 mPa · s or less. The ink set according to any one of [3].

[5] The water-based inks according to [1] to [4], wherein each of the plurality of water-based inks has a surface tension of 25 to 45 mN / m, and a difference in surface tension between them is 5 mN / m or less. The ink set according to any one of the above.

[6] The ink set according to any one of [1] to [5], which is used in an ink jet recording method that is ejected from a recording head by a thermal method.

[7] An ink jet recording method in which a plurality of types of water-based inks are ejected by a thermal method from a recording head having a plurality of nozzle rows in which a plurality of nozzles are arranged, each of the nozzles having an opening area of 100 to 350 μm ² And the plurality of types of water-based inks are water-based inks constituting the ink set according to any one of [1] to [6].

[8] The inkjet recording method according to [7], wherein the nozzle row includes 1200 or more nozzles per row and has a length of 2 inches or more.

[9] An inkjet recording head comprising a plurality of nozzle rows in which a plurality of nozzles are arranged, and ejecting a plurality of water-based inks from the nozzle rows by a thermal method, each of the nozzles having an opening of 100 to 350 μm ² The nozzle row has 1200 or more nozzles per row, has a length of 2 inches or more, and the water-based ink is any one of [1] to [6]. An ink jet recording head, which is a water-based ink constituting the ink set.

[10] An inkjet recording head that includes a plurality of nozzle rows in which a plurality of nozzles are arranged and discharges a plurality of water-based inks from the nozzle rows by a thermal method, and a plurality of nozzle flow paths communicate as the nozzle rows. A common liquid chamber, an opening communicating with the common liquid chamber, a main liquid supply chamber communicating with the opening, a liquid supply path communicating with the main liquid supply chamber, and a liquid communicating with the liquid supply path A supply filter disposed so as to separate the supply chamber, the liquid supply chamber into a first liquid supply chamber and a second liquid supply chamber from the upstream side along a flow in supplying the liquid, and the main A gas-liquid separator provided in a part of the liquid supply chamber; and an air chamber communicating with the gas-liquid separator; the nozzle flow path, the common liquid chamber, the opening, and the main A liquid supply chamber and the liquid The supply path, the liquid supply chamber, the supply filter, the gas-liquid separator, and the air chamber are parallel to a plane including the arrangement direction of the nozzle flow paths and the liquid discharge direction. [9] in which the main liquid supply chamber, the liquid supply path, the supply filter, the gas-liquid separator, and the air chamber are arranged without being stacked, respectively. The ink-jet recording head described.

[11] An inkjet recording apparatus including a plurality of aqueous ink storage portions that respectively store a plurality of types of water-based inks, and an inkjet recording head that discharges the water-based ink. A water-based ink constituting the ink set according to any one of [6] to [6], wherein the inkjet recording head is the inkjet recording head according to [9] or [10].
[12] A cyan ink for use in combination in an ink set containing at least an aqueous ink other than cyan ink,
The cyan ink and the water-based ink other than the cyan ink each contain a (meth) acrylic acid ester random copolymer having an acid value of 100 to 160 mgKOH / g as a dispersant for dispersing the pigment,
The cyan ink contains a phthalocyanine compound as a pigment, and
The (meth) acrylic acid ester random copolymer contained in the cyan ink is 0.70 to 0 relative to the (meth) acrylic acid ester random copolymer contained in the aqueous ink other than the cyan ink. Cyan ink having an acid value of .95 times.
[13] The cyan ink according to [12], wherein the water-based ink other than the cyan ink contains carbon black or a quinacridone compound as a pigment.
[14] The (meth) acrylic acid ester-based random copolymer is composed of a common monomer species, and the acid value is adjusted by changing the blending ratio of the monomer species. The cyan ink according to [12] or [13].
[15] The ink set further includes an aqueous ink other than cyan ink, and each of the inks has a viscosity of 1.5 to 5.0 mPa · s, and a difference in viscosity between the inks. The cyan ink according to any one of [12] to [14], having a viscosity of 0.5 mPa · s or less.
[16] The ink set further includes an aqueous ink other than cyan ink, and each of the inks has a surface tension of 25 to 45 mN / m, and a difference in surface tension between the inks is 5 mN. The cyan ink according to any one of [12] to [15], which is / m or less.
[17] A water-based ink other than cyan ink for use in combination in an ink set containing at least cyan ink,
The cyan ink and the water-based ink other than the cyan ink each contain a (meth) acrylic acid ester random copolymer having an acid value of 100 to 160 mgKOH / g as a dispersant for dispersing the pigment,
Aqueous ink other than the cyan ink contains carbon black or a quinacridone compound as a pigment,
The cyan ink contains a phthalocyanine compound as a pigment, and
The (meth) acrylic acid ester random copolymer contained in the cyan ink is 0.70 to 0 relative to the (meth) acrylic acid ester random copolymer contained in the aqueous ink other than the cyan ink. A water-based ink other than cyan ink, having an acid value of .95 times.
[18] The (meth) acrylic ester random copolymer is composed of a common monomer species, and the acid value is adjusted by changing the blending ratio of the monomer species. A water-based ink other than the cyan ink according to [17].
[19] The ink set further includes another water-based ink other than the cyan ink, and each of the water-based inks has a viscosity of 1.5 to 5.0 mPa · s and has a viscosity between the inks. The water-based ink other than the cyan ink according to [17] or [18], wherein the difference is 0.5 mPa · s or less.
[20] The ink set further includes an aqueous ink other than the cyan ink, the aqueous ink has a surface tension of 25 to 45 mN / m, and a difference in surface tension between the inks is present. The water-based ink other than the cyan ink according to any one of [17] to [19], which is 5 mN / m or less.
[21] The water-based ink according to any one of [12] to [20], which is used in an ink jet recording method ejected from a recording head by a thermal method .

According to the present invention, for example, when used in a thermal system, by preventing pigment kogation in the heater portion of the inkjet recording head, the dispersibility of the pigment in the water-based ink is stably maintained, and excellent Provided are an ink, an ink set including a plurality of types of water-based inks, an ink jet recording method, an ink jet recording head, and an ink jet recording apparatus capable of realizing landing accuracy.

FIG. 3 is a top view schematically showing an internal structure of a nozzle of a recording head. It is a side view which shows typically the internal structure of the nozzle shown to FIG. 1A. It is a front view which shows typically the ink discharge port of the nozzle shown to FIG. 1A. FIG. 3 is a front view schematically showing the recording head of the present invention. It is AA sectional drawing of the recording head shown to FIG. 2A. It is a BB sectional view of the recording head shown in FIG. 2A. It is an expanded sectional view of an ink tank. FIG. 3 is an enlarged cross-sectional view of a recording head. FIG. 5 is an enlarged perspective view of the ink holding member shown in FIG. 4. It is Vb-Vb sectional drawing of the ink holding member shown to FIG. 5A. 1 is a schematic configuration diagram schematically illustrating an overall configuration of an ink jet recording apparatus. It is a block block diagram of the control system of the recording apparatus shown in FIG. 6 is a flowchart showing a recording head recovery sequence process.

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

I. Ink set The ink set of the present embodiment is an ink set including a water-based ink containing a pigment and a (meth) acrylic acid ester-based random copolymer in which the pigment is dispersed as a set of a plurality of types of water-based inks. Each of the (meth) acrylate random copolymers contained in the water-based ink has an acid value of 100 to 160 mgKOH / g, and one of the plurality of water-based inks is phthalocyanine as a pigment. The cyan ink contains a compound, and the cyan ink contains a (meth) acrylic acid ester random copolymer contained in an aqueous ink other than the cyan ink. It has an acid value 0.70 to 0.95 times that of the polymer.

  Here, the ink set is integrally configured by combining a state of an ink cartridge that independently stores a plurality of types of ink and a plurality of ink storage portions that respectively store a plurality of types of ink. The state of the ink cartridge. A recording head may be formed integrally with the ink cartridge. The ink set of the present invention is not limited to these forms. Hereinafter, each component will be described.

1. Configuration of water-based ink The water-based ink used in the present embodiment contains a pigment and a (meth) acrylic acid ester-based random copolymer in which the pigment is dispersed, and is used as a set of a plurality of types of water-based inks. Further, one of the plural types of water-based inks is a cyan ink containing a phthalocyanine compound as a pigment, and preferably includes a black ink containing carbon black as a pigment and a magenta ink containing a quinacridone compound as a pigment. .

(1) Pigment Examples of the pigment used in the water-based ink used in the present embodiment include carbon black and organic pigments. Moreover, various pigments can be used individually by 1 type or in combination of 2 or more types. The content of the pigment in the water-based ink is preferably 0.5 to 10.0% by mass, more preferably 1.0 to 8.0% by mass, and 1.5 to 6.0% by mass. Most preferably. If the amount is less than 0.5% by mass, a printed matter having a desired image density may not be formed. If the amount exceeds 10.0% by mass, the viscosity of the aqueous pigment ink may increase, making it difficult to discharge. . Hereinafter, the pigment of the water-based ink used in the present embodiment will be broadly described when used for cyan ink and water-based ink other than cyan ink.

(1-1) Cyan Ink The cyan ink used in the present embodiment contains a pigment and a (meth) acrylic ester random copolymer that disperses the pigment. Moreover, a phthalocyanine compound is contained as a pigment.

  Examples of the phthalocyanine compound include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15: 6, 16, 22 and the like.

(1-2) Aqueous ink other than cyan ink As described above, the aqueous ink other than cyan ink preferably includes black ink containing carbon black as a pigment and magenta ink containing a quinacridone compound as a pigment.

(1-2-1) Black Ink The black ink used in the present embodiment contains carbon black as a pigment. Specific examples of carbon black are carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. For example, as a trade name, Ray Van (manufactured by Longbia); Black Pearls L, Legal, Mogul L, Monarch, Valcan (made by Cabot); Color Black, Printex, Special Black (made by Degussa); Mitsubishi -What has a title, such as Bon Black (made by Mitsubishi Chemical Corporation), can be used. Of course, it is not limited to these, and conventionally known carbon black can also be used. Physically, the carbon black used in the present invention has a primary particle size of 10 to 40 nm, a specific surface area by the BET method of 50 to 400 m ² / g, an oil supply amount of 40 to 200 ml / 100 g, and a volatile content of 0.5. The effect of the present invention is effective when the carbon black is 10 to 10% and the pH is 2 to 9. The DBP absorption is measured by the JIS K6221 A method.

(1-2-2) Magenta Ink The magenta ink used in the present embodiment contains a quinacridone compound as a pigment. A quinacridone compound is a pigment having a quinacridone structure, and is known as a red pigment excellent in light resistance and heat resistance. Examples of quinacridone compounds include C.I. I. Pigment Red 122, 202, 206, 207, 209; I. Pigment Violet 19, 42 and the like.

(1-2-3) Other water-based inks Examples of other water-based inks include yellow ink, orange ink, red ink, violet ink, blue ink, green ink, and brown ink. The organic pigments that can be used in the above-mentioned water-based inks can be illustrated by the following color index (CI) numbers. Of course, conventionally known organic pigments can be used other than the following.

  Examples of pigments used in other water-based inks include C.I. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 151, 153, 154, 166 168; I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61 etc .; C.I. I. Pigment Red: 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227 228, 238, 240, etc .; I. Pigment violet: 19, 23, 29, 30, 37, 40, 50, etc .; C.I. I. Pigment Blue: 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, etc .; I. Pigment Green: 7, 36; C.I. I. Pigment brown: 23, 25, 26, and the like.

(2) (Meth) acrylic acid ester random copolymer As the monomer species constituting the (meth) acrylic acid ester random copolymer used in the present embodiment, (meth) acrylic acid; (meth) acrylic Examples include acid esters; monoethylenically unsaturated monomers capable of random copolymerization with acrylic acid or (meth) acrylic acid esters; styrenic monomers, and the like. The (meth) acrylic acid ester random copolymer can be obtained by random copolymerization of the above monomer species. Other than the random copolymer, for example, a block copolymer or the like is not preferable because many of the pigments have high hydrophilicity and many of the printed images have poor water resistance.

  The content of the (meth) acrylate random copolymer is preferably 20 to 100 parts by mass, and more preferably 20 to 60 parts by mass with respect to 100 parts by mass of the pigment. If the amount is less than 20 parts by mass, the dispersion stability of the pigment may be low. If the amount exceeds 100 parts by mass, the viscosity of the water-based ink may increase due to the large amount of free polymer, which may reduce the ejection stability. is there.

  The monomer species is preferably (meth) acrylic acid in consideration of the wide control of the coexistence range between the electrically neutral state and the anion state, availability, and price. In addition, (meth) acryl means methacryl and acryl.

  (Meth) acrylic acid ester includes methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, dodecyl (meth) acrylate, Alkyl (meth) acrylates such as octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meta ) Hydroxyalkyl (meth) acrylates such as 3-hydroxypropyl acrylate; diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate Dipropylene glycol mono (meth) acrylate, tripropylene glycol mono (meth) acrylate, tetramethylene ether glycol mono (meth) acrylate, polyethylene oxide-polypropylene oxide random copolymer glycol or block polymer glycol mono ( Alkylene glycol mono (meth) acrylates such as (meth) acrylate, polyethylene oxide-polytetramethylene ether random copolymer glycol or mono (meth) acrylate of the same block polymer glycol, glycidyl (meth) acrylate, (meth) acrylic acid Benzyl etc. can be mentioned.

  Monoethylenically saturated monomers capable of random copolymerization include unsaturated fatty acid esters such as dimethyl maleate, dimethyl fumarate, 2-aminoethyl (meth) acrylate; (meth) acrylamide, N-methyl ( Unsaturated amides such as (meth) acrylamide; unsaturated nitriles such as (meth) acrylonitrile; unsaturated ethers such as vinyl acetate and vinyl propionate; ethylene, propylene, 1-butene, 1-octene, vinylcyclohexane, Unsaturated hydrocarbons such as 4-vinylcyclohexene; Unsaturated halogenated hydrocarbons such as vinyl chloride, vinylidene chloride, tetrafluoroethylene, 3-chloropropylene; 4-vinylpyridine, N-vinylcarbazole, N-vinylpyrrolidone Vinyl-substituted heterocyclic compounds such as Reaction products of monomers containing substituents containing active hydrogen such as carboxyl group, hydroxyl group, amino group and epoxides such as ethylene oxide, propylene oxide, cyclohexene oxide; hydroxyl group, amino group in the aforementioned monomer And a reaction product of a monomer containing a substituent containing a carboxylic acid such as acetic acid, propionic acid, butanoic acid, hexanoic acid, decanoic acid, and dodecanoic acid.

  Examples of the styrene monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 4-methoxystyrene, 4-chlorostyrene, and the like. Can do.

  In order to stably disperse the (meth) acrylic ester random copolymer in an aqueous medium, the (meth) acrylic ester random copolymer has an anionic group (for example, carboxyl group, A sulfonic acid group, a phosphoric acid group, a thiocarboxyl group and the like. The (meth) acrylic acid ester random copolymer preferably contains a carboxyl group or a sulfonic acid group in consideration of the availability of raw material monomers, price, etc., and coexistence of an electrically neutral state and an anionic state It is more preferable to contain a carboxyl group in that the range can be controlled widely, and the anionic group contains both a carboxyl group and a salt of the carboxyl group (a form in which at least a part of the carboxyl group is ionized by a basic substance) It is most preferable (at least a part of the carboxyl group is in a form ionized by a basic substance).

  The (meth) acrylic acid ester random copolymer has an acid value of 100 to 160 mgKOH / g, preferably 104 to 155 mgKOH / g. When the acid value is less than 100 mgKOH / g, the acid value is too low and the dispersion stability of the pigment is lowered. On the other hand, when the acid value exceeds 160 mgKOH / g, the adsorptivity between the pigment surface and the (meth) acrylic acid ester random copolymer is lowered, and the discharge stability cannot be satisfied. Here, the acid value means the number of mg of potassium hydroxide necessary to neutralize 1 g of the (meth) acrylic acid ester random copolymer.

  The (meth) acrylic acid ester random copolymer contained in the cyan ink is 0.7 to 0. 0 relative to the (meth) acrylic acid ester random copolymer contained in the aqueous ink other than the cyan ink. The acid value is 95 times. When the acid value is less than 0.7 times, the acid value is too low and the dispersion stability of the pigment is lowered. Moreover, when it exceeds 0.95 times, the adsorptive power between the phthalocyanine compound and the (meth) acrylate random copolymer becomes weak, and the (meth) acrylate random copolymer becomes a phthalocyanine compound when heated. , And kogation occurs in the heater, resulting in unstable foaming and reduced discharge speed.

  The (meth) acrylic acid ester random copolymer is preferably composed of a common monomer species. Moreover, it is preferable that the acid value is adjusted by changing the blending ratio of the monomer species. Further, from the viewpoint of common discharge characteristics, it is preferable to use the same (meth) acrylic acid ester random copolymer contained in the water-based ink other than the cyan ink.

  The weight average molecular weight of the (meth) acrylic acid ester random copolymer is preferably in the range of 6,000 to 12,000 in terms of weight average molecular weight (Mw) in terms of styrene, and is preferably 7,000 to 9,000. More preferably, it is in the range. When the weight average molecular weight is less than 6,000, the dispersion stability of the (meth) acrylate random copolymer itself tends to be lowered. When the weight average molecular weight exceeds 12,000, not only the viscosity of the water-based ink increases, but also the dispersibility of the pigment tends to decrease. Further, the kogation in the heater portion of the pigment becomes severe, which may cause non-ejection of ink droplets from the nozzle tip of the thermal ink jet recording head.

As a method of coating the pigment with a (meth) acrylic acid ester random copolymer, it is preferable to incorporate an acid precipitation step.
The acid precipitation step is (meta) by adding an acidic substance to a liquid medium containing a pigment and a (meth) acrylic acid ester random copolymer dissolved in an aqueous solution of a basic substance, and acidifying it. This means that the anionic group in the acrylate ester random copolymer is returned to the functional group before being neutralized to precipitate the (meth) acrylate random copolymer.

  Such an acid precipitation step is to acidify by adding an acid such as hydrochloric acid, sulfuric acid or acetic acid to an aqueous dispersion obtained through a dispersion step and a distillation step carried out as necessary to form a base and a salt. This means a step of precipitating the (meth) acrylic acid ester random copolymer in a dissolved state on the surface of the pigment particles. By carrying out this step, the interaction between the pigment and the (meth) acrylate random copolymer can be further enhanced. As a result, the resin-dispersed composite particles can take a form dispersed in an aqueous medium, and as an aqueous resin-dispersed pigment, physical properties such as a dispersion reaching level, dispersion required time and dispersion stability, and solvent resistance In terms of suitability for use and the like, a more excellent effect can be fully exhibited.

  A filtration step is carried out for separating the precipitate obtained by enhancing the interaction in this manner, and more preferably, a washing step for washing the precipitate after completion of the filtration step is carried out again in the aqueous medium together with the basic substance. By carrying out the redispersion step of dispersing in water, an aqueous resin-dispersed pigment having better dispersion stability can be obtained.

(3) Other components Hereinafter, in addition to the pigment and the (meth) acrylic acid ester-based random copolymer, components that can be contained in common in each aqueous ink constituting the ink set of the present invention will be described. .

(3-1) Water-soluble compound The water-based ink used in the present embodiment is preferably one in which a pigment dispersion is dispersed in at least a water-soluble compound. The type of the water-soluble compound is not particularly limited, but the water-soluble compound is preferably at least one selected from the group of water-soluble organic solvents and water-soluble compounds that are solid at 25 ° C.

  The “water-soluble compound” as used herein means a compound that is freely miscible with water or has a solubility in water (25 ° C.) of 20 g / 100 g or more. By containing a water-soluble compound, it is possible to prevent water from evaporating and prevent ink sticking due to drying.

  Examples of water-soluble compounds include various water-soluble organic solvents such as alcohols, polyhydric alcohols, glycol ethers, carboxylic acid amides, heterocycles, ketones, and alkanolamines as listed below. Can do. A water-soluble compound that is solid at 25 ° C., such as urea, ethylene urea, trimethylol propane, or the like can also be used.

(3-1-1) Alcohols:
Chain alcohols having 1 to 5 carbon atoms such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, n-pentyl alcohol;

(3-1-2) Polyhydric alcohols:
Ethylene glycol (ethanediol), propanediol (1,2-, 1,3-), butanediol (1,2-, 1,3-, 1,4-), 1,5-pentanediol, 1,2 -Alkanediols such as hexanediol;
Condensates of alkanediols such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol;
Polyhydric alcohols other than alkanediols such as glycerin, trimethylolpropane, 1,2,6-hexanetriol, thiodiglycol;

(3-1-3) Glycol ethers:
Monomethyl ether of ethylene glycol;
Monomethyl ether, monoethyl ether of diethylene glycol;
Monomethyl ether, monoethyl ether, monobutyl ether, dimethyl ether, diethyl ether of triethylene glycol;
Tetraethylene glycol dimethyl ether, diethyl ether;

(3-1-4) Carboxylic acid amides:
N, N-dimethylformamide, N, N-dimethylacetamide;

(3-1-5) Heterocycles:
Cyclic ethers such as tetrahydrofuran and dioxane;
Nitrogen-containing heterocycles such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-methylmorpholine;
Sulfur-containing heterocycles such as sulfolane;

(3-1-6) Ureas:
Ureas such as urea, ethylene urea, 1,3-dimethyl-2-imidazolidinone (N, N′-dimethylethyleneurea);

(3-1-7) Ketones:
Ketones such as acetone and methyl ethyl ketone;
Keto alcohols such as 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol);

(3-1-8) Alkanolamines:
Monoethanolamine, diethanolamine, triethanolamine;

(3-1-9) Other:
Sulfur-containing compounds such as dimethyl sulfoxide and bishydroxyethyl sulfone;

  Among the water-soluble organic solvents, polyhydric alcohols are preferable, and glycerin is more preferable. Glycerin is preferable in that it hardly evaporates and is excellent in the effect of preventing ink sticking. Moreover, the said water-soluble organic solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it. For example, it is also preferable to use glycerin together with polyhydric alcohols other than glycerin and nitrogen-containing heterocycles. At this time, triethylene glycol or the like can be used as the polyhydric alcohol other than glycerin, and 2-pyrrolidone or the like can be used as the nitrogen-containing heterocyclic ring. Such a mixed solvent is preferable in that the effect of preventing the viscosity increase of the ink is high.

  The content rate of the water-soluble compound is not particularly limited. However, in order to prevent the aqueous medium from evaporating and to prevent the ink from sticking due to drying, the content is preferably 10% by mass or more, more preferably 15% by mass or more based on the total mass of the ink. . On the other hand, from the viewpoint of being able to cope with a high driving frequency and preventing the occurrence of mold, it is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the ink.

  As the water-soluble compound that is solid at 25 ° C., urea, ethylene urea, or the like is preferably used, and ethylene urea is more preferably used. The content of the water-soluble compound that is solid at 25 ° C. is not particularly limited. However, in order to prevent the aqueous medium from evaporating and to prevent the ink from sticking due to drying, the content is preferably 5% by mass or more, more preferably 9% by mass or more based on the total mass of the ink. . On the other hand, in order to prevent problems due to excessive addition, it is preferably 30% by mass or less, more preferably 15% by mass or less, based on the total mass of the ink.

(3-2) Surfactant In the present invention, the surface tension of aqueous ink described later is controlled to arbitrarily control the degree of bleeding and penetrability of the aqueous ink in the recording medium and the wettability of the aqueous ink in the head. If necessary, the above-mentioned water-based ink may contain a surfactant for the purpose of improving the viscosity, preventing kogation of the pigment on the heater surface, and improving ejection. Such a surfactant is not particularly limited, and can be exemplified as follows.
In addition, the said surfactant may be used individually or may be used in combination of multiple.

  (3-2-1) Nonionic surfactant Polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene / polyoxypropylene block copolymer, and the like. Fatty acid diethanolamide, acetylene glycol ethylene oxide adduct, acetylene glycol surfactant, and the like.

(3-2-2) Anionic surfactant Polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether sulfonate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfonate, etc. . Alpha sulfo fatty acid ester salts, alkylbenzene sulfonates, alkylphenol sulfonates, alkylnaphthalene sulfonates, alkyltetralin sulfonates, dialkylsulfosuccinates and the like.

  (3-2-3) Cationic surfactant Alkyltrimethylammonium salt, dialkyldimethylammonium chloride and the like.

(3-2-4) Amphoteric surfactants such as alkylcarboxybetaines.
Among them, acetylene glycol surfactants and polyoxyethylene alkyl ethers are particularly preferably used because they can improve the ejection stability of the ink.

  As an acetylene glycol surfactant, the compound (1) represented by the following general formula (1) (2,4,7,9-tetramethyl-5-decyne-4,7-diol, or an ethylene oxide adduct thereof) Is used.

（一般式（１）中、Ｕ＋Ｖは０乃至２０の整数である）

(In General Formula (1), U + V is an integer of 0 to 20)

(3-3) Water It is preferable to use deionized water (ion exchange water) as water. The water content is not particularly limited. However, it is preferably 10 to 90% by mass, more preferably 40 to 85% by mass, and most preferably 50 to 80% by mass with respect to the total mass of the ink. By setting it as 10 mass% or more, a pigment and a water-soluble compound can be hydrated, and aggregation of a pigment or a water-soluble compound can be prevented. On the other hand, by setting the amount to 90% by mass or less, even when the amount of the water-soluble organic compound is relatively increased and the volatile component (water or the like) in the aqueous medium is volatilized, the pigment dispersion state is maintained. And the precipitation and solidification of the pigment can be prevented.

(3-4) Other additives The water-based ink may contain an additive other than the surfactant depending on the purpose. Examples of such additives include pH adjusters, rust inhibitors, antiseptics, antifungal agents, antioxidants, reduction inhibitors, salts, and the like.

2. Physical Properties of Aqueous Ink The aqueous ink constituting the ink set of the present embodiment preferably has a viscosity at 25 ° C. in the range of 1.5 to 5.0 mPa · s, and more preferably 1.6 to 3. The range is preferably 5 mPa · s, and most preferably 1.7 to 3.0 mPa · s. By setting the viscosity to 1.5 mPa · s or more, good ink droplets can be formed. On the other hand, by setting the pressure to 5.0 mPa · s or less, the fluidity of the ink is improved, and the ink supply property to the nozzle, and thus the ejection stability of the ink is improved. Furthermore, it is preferable that the difference in viscosity between water-based inks in the ink set is 0.5 mPa · s or less. If the difference in viscosity between the water-based inks exceeds 0.5 mPa · s, there may be a difference in the discharge speed of the recording ink.

  The viscosity of the water-based ink is measured using an E-type viscometer (for example, product name: “RE-80L viscometer” manufactured by Toki Sangyo Co., Ltd.) under a temperature of 25 ° C. in accordance with JIS Z 8803. can do.

  The water-based ink constituting the ink set of the present embodiment preferably has a surface tension at 25 ° C. of 25 to 45 mN / m. When the surface tension is 25 to 45 mN / m, it can be applied to high-speed recording. Further, the difference in surface tension between the water-based inks in the ink set is preferably 5 mN / m or less. If the difference in surface tension between the water-based inks exceeds 0.5 mN / m, the dot diameter at the time of landing differs, so that the image quality may be lowered.

  The surface tension of the water-based ink can be measured using a surface tension meter (for example, trade name: “CBVP-Z” manufactured by Kyowa Interface Science Co., Ltd.) under the condition of a temperature of 25 ° C.

  The pH of the water-based ink constituting the ink set of the present embodiment is preferably 7.5 to 10.0, and more preferably 8.5 to 9.5. When the pH is less than 7.5, the dispersion stability of the pigment particles is deteriorated, and the aggregation of the pigment particles may easily occur. On the other hand, if the pH exceeds 10.0, the pH of the ink is too high, and depending on the member of the device used, a chemical attack may be caused by contact with the ink, thereby causing organic and inorganic substances to elute into the ink. As a result, ejection failure may occur.

  The pH of the water-based ink can be measured using a pH meter (for example, product name: “D-51” manufactured by HORIBA) under the condition of a temperature of 25 ° C.

II. Inkjet recording method In the inkjet recording method of the present embodiment, a plurality of water-based inks are ejected by a thermal method from an inkjet recording head having a plurality of nozzle rows in which a plurality of nozzles are arranged. Each of the nozzles has an opening area of 100 to 350 μm ² , and the plurality of types of water-based inks are water-based inks constituting the ink set described above. The nozzle row preferably has 1200 or more nozzles per row and has a length of 2 inches or more.

  The recording method of the present invention uses an inkjet recording head, discharges aqueous ink from the inkjet recording head, applies aqueous ink to the recording medium conveyed under the inkjet recording head, and performs recording. It is.

III. Inkjet recording head:
Hereinafter, an embodiment of a recording head according to the present embodiment will be described with reference to the drawings. However, the recording head of the present invention is not limited to the configuration described below.

(1) Nozzle part structure:
First, the structure of the nozzle portion will be described with reference to FIGS. 1A to 1C. FIG. 1A is a top view schematically showing the internal structure of the nozzles of the recording head. FIG. 1B is a side view schematically showing the internal structure of the nozzle shown in FIG. 1A. FIG. 1C is a front view schematically showing an ink discharge port of the nozzle shown in FIG. 1A.

  As shown in the figure, the thermal recording head has a nozzle row composed of a plurality of nozzle flow paths 159 partitioned by a nozzle wall 153, and a plurality of ink discharge ports 151 communicating with the nozzle flow paths 159. An ink discharge heater 152 is disposed inside the nozzle flow path 159. The head having such a structure can cause ink droplets to fly from the ink discharge ports 151 by heating the ink filled in the nozzle flow path 159 with the heater 152 and causing the ink to foam.

  In the illustrated form, a nozzle filter 155 is provided between the nozzle channel 159 and the common liquid chamber 112 for trapping foreign matter floating in the ink channel in the head. The top plate member 113 to which the nozzle top plate 162 is attached has an ink supply opening (not shown) formed by anisotropic etching or the like, and introduces ink from the outside from the common liquid chamber 112 to the nozzle channel 159. It is configured to be possible.

  In addition to the right and left side surfaces of the nozzle channel 159 being partitioned by the nozzle wall 153, the upper surface side is partitioned by the nozzle top plate 162 and the bottom surface side is partitioned by the nozzle bottom plate 164. That is, the nozzle flow path 159 is a substantially rectangular columnar internal space partitioned from the surrounding space by using the nozzle wall 153, the nozzle top plate 162, and the nozzle bottom plate 164 as partitions. The nozzle top plate 162 is attached to a top plate member 113 made of Si or the like, and the nozzle bottom plate 164 is attached to the heater substrate 111.

The ink discharge port 151 is an opening that discharges ink formed at one end of the nozzle flow path 159 and communicates with the common liquid chamber 112 via the nozzle flow path 159. The ink discharge port 151 is formed on the face surface. In the illustrated example, the face surface is formed integrally with the nozzle wall 153, but a face plate may be separately provided to form the face surface. The opening area of the ink ejection port 151 is configured to be 100 μm ² or more and 350 μm ² or less. By setting the opening area to 100 μm ² or more, it is possible to prevent the occurrence of an undischarge nozzle. On the other hand, by setting it to 350 μm ² or less, it is possible to form minute droplets in which the amount of one ink droplet is 10 pL or less, and the resolution can be 600 dpi or more. The opening area is represented by the product of the discharge port width 171 and the discharge port height 172.

  The recording head is a line type head in which nozzle rows are formed by a plurality of nozzle flow paths. The number of nozzle flow paths forming the nozzle row is not particularly limited. However, in order to achieve the effect of the present invention, the total number of nozzles in the nozzle row needs to be 1200 or more, preferably 1200 or more and 9600 or less, and more preferably 1200 or more and 4800 or less. . The length of the nozzle row needs to be 2 inches or more, and preferably 2 inches or more and 4 inches or less.

  The heater 152 is a heating unit for heating and foaming the ink filled in the nozzle channel 159. The heater 152 is installed on the heater substrate 111. As the heater 152, a resistor (for example, a resistor made of tantalum nitride) can be used. An electrode (not shown) made of aluminum or the like for energization is connected to the heater 152, and a switching transistor (not shown) for controlling energization to the heater 152 is connected to one of the heaters 152. . The drive of the switch transistor is controlled by an IC including a circuit such as a control gate element, and the switch transistor is driven in a predetermined pattern by a signal from the outside of the head.

  The recording head can be driven at a driving frequency of 1 kHz to 10 kHz. By driving at a driving frequency of 1 kHz or more, even when the amount of ink per droplet is very small, the amount of ink applied per unit time can be increased, and the amount of image data and the number of recording dots can be increased. That is, a high-quality image can be printed at high speed. By driving at a driving frequency of 10 kHz or less, such a problem that the ink supply amount to the nozzle is insufficient with respect to the ink discharge amount at the time of high-speed printing as described above and the ejection stability is reduced is suppressed. In order to obtain the effect more reliably, it is preferable that the driving can be performed at a driving frequency of 3 kHz or more and 8 kHz or less. The recording head of the present invention can be driven at a driving frequency of 6 kHz or more and 10 kHz or less because the ejection stability is unlikely to deteriorate even under a high driving frequency and nozzle non-discharge is difficult to occur. preferable.

  The overall length of the nozzle is preferably 200 μm or more and 300 μm or less. In this case, the “total length of the nozzle” means the length of the nozzle flow path 159, specifically, the common liquid chamber 112 from the end of the nozzle wall 153 constituting the nozzle flow path 159 on the ink discharge port 151 side. It means the length to the end of the side.

  The nozzle flow path 159 includes a nozzle front portion 181 that is a portion from the heater center 157 to the end portion on the ink discharge port 151 side, and a nozzle rear portion 182 that is a portion from the heater center 157 to the end portion on the common liquid chamber 112 side. It is divided into. From the viewpoint of the discharge speed, the flow resistance (front resistance) of the nozzle front part 181 and the flow resistance (rear resistance) of the nozzle rear part 182 have a front resistance / rear resistance value of 0.3 to 0.8. It is preferable. The flow resistance can be calculated by the Hagen-Poiseuille law from values such as the cross-sectional area of the flow path, the flow path length, and the viscosity of the ejected ink. That is, if the ink to be used (and its viscosity) is determined, the value of the front resistance / rear resistance can be adjusted by the flow path cross-sectional area of the nozzle, the flow path length, and the like.

(2) Nozzle material:
The nozzle wall 153, the nozzle top plate 162, and the nozzle bottom plate 164 that partition the nozzle flow path 159 can be formed of, for example, a photosensitive resin. As the photosensitive resin, a negative photoresist or the like can be used. Specific commercial products include, for example, “SU-8 series”, “KMPR-1000” (above, manufactured by Kayaku Microchem Corp.), “TMMR”, “TMMR S2000”, “TMMF S2000” (above, Tokyo Ohka). (Manufactured by Kogyo Co., Ltd.). Among these, it is preferable to use an epoxy photosensitive resin excellent in solvent resistance and strength as a nozzle wall. As a specific commercial product, “TMMR S2000” manufactured by Tokyo Ohka Kogyo Co., Ltd. is particularly preferable.

(3) Hydrophilic region, water-repellent region:
The recording head of the present invention preferably has a hydrophilic region or a water-repellent region formed at the periphery of the ink discharge port. Which of the hydrophilic region and the water repellent region is formed may be determined in consideration of the type of the color material of the ink to be used and the surface tension.

  For example, when the color material is a pigment or when an ink having a surface tension of 34 mN / m or less is used, a recording head (hydrophilic head) in which a hydrophilic region is formed at the periphery of the ink discharge port is preferable. Further, it is preferable that a hydrophilic region having a contact angle of 60 ° or less with the ink to be used is formed at the periphery of the ink discharge port. The hydrophilic region having the contact angle of 0 ° (that is, forming no contact angle). It is more preferable that a sex region is formed. Note that the contact angle of the hydrophilic region or the water repellent region is measured by the ATAN1 / 2θ method using a contact angle meter (for example, trade name “SIMage-mini”, manufactured by Excimer Co., Ltd.) in accordance with JIS R 3257. be able to. Also in the examples described later, the contact angle is measured by the above method.

  The hydrophilic region includes a method in which a member (face material) in which ink discharge ports are formed is made of a hydrophilic material, a method in which a surface of the face material (face surface) is subjected to a hydrophilic treatment, and a hydrophilic film on the face surface. It can form by the method of providing.

  As the face material, for example, a resin such as an epoxy resin, particularly an epoxy-based photosensitive resin can be used.

Examples of the method for hydrophilic treatment of the face surface include a method of roughening the face surface. Examples of the roughening method include laser irradiation treatment, UV / O ₃ treatment, plasma treatment, heat treatment, oxidation treatment, and embossing treatment. Lasers such as excimer laser, YAG laser, and CO ₂ laser can be used for the laser irradiation treatment. Alternatively, the peripheral portion of the ink discharge port may be treated by a method of immersing in a highly hydrophilic liquid for a long time. Examples of the “hydrophilic liquid” include pigment inks. For example, what is necessary is just to immerse in the pigment ink which uses a face material for 10 minutes or more.

  Examples of a method for providing a hydrophilic film on the face surface include a method of forming a metal film or a hydrophilic resin film on the face surface. The hydrophilic film is preferably formed of a material having good adhesion to the face material as well as hydrophilicity. Examples of such a material include a composition containing a water-soluble resin and a water-insoluble low molecular weight compound. For example, a water-soluble resin (such as hydroxypropylcellulose) and a water-insoluble low molecular weight compound (such as bisphenol A) are dissolved in a suitable solvent (such as dimethylformamide), and the solution is applied to the face and dried. Accordingly, a hydrophilic film can be formed by treatment with alcohol or the like.

The formation of the hydrophilic region may be appropriately selected from the above methods according to the material constituting the face material. In addition, the hydrophilic region may be formed by combining two or more of the above methods. Among the above methods, a method in which the peripheral portion of the nozzle is made of an epoxy-based photosensitive resin, and the peripheral portion of the nozzle is subjected to a UV / O ₃ treatment and further immersed in pigment ink to perform a hydrophilic treatment.

  For example, when the color material is a dye and an ink having a surface tension of more than 34 mN / m is used, a recording head (water-repellent head) in which a water-repellent region is formed at the periphery of the ink discharge port is preferable. . Further, it is more preferable that a water-repellent region having a contact angle of 90 ° or more with the ink to be used is formed at the periphery of the ink discharge port, and a water-repellent region having a contact angle with the ink to be used of 100 ° or more. It is particularly preferred that it is formed.

  The water repellent region can be formed by a method of providing a water repellent film on the surface (face surface) of the member (face material) on which the ink discharge ports are formed.

  Examples of the method for providing the water repellent film on the face surface include a method of forming a super water repellent resin film on the face surface. The super water-repellent resin film can be formed by a conventionally known method. For example, a method of forming a resin film by applying a fluororesin, a silicone resin or the like on the face surface, a method of forming a fluororesin film by plasma polymerizing a fluorine-based monomer on the face surface, and the like can be given. Further, a method of forming a water- and oil-repellent resin film on the face surface may be employed. Examples thereof include a method of forming a film made of a fluororesin obtained by polymerizing a fluorocarbon compound. Among them, fluorine-containing silicones are used in fluorine-based solvents (“CXT-809A” manufactured by Asahi Glass, “<Novec> HFE-7100”, “<Novec> HFE-7200”, “<Novec> HFE-71IPA”, etc., manufactured by Sumitomo 3M Ltd.). A method of forming a water-repellent film by preparing a solution in which a coupling agent (for example, “KP-801M” manufactured by Shin-Etsu Chemical Co., Ltd.) is dissolved and vapor-depositing this solution on the face surface is preferable.

(4) Overall structure of recording head:
Next, the overall structure of the recording head will be described with reference to FIGS. 2A to 2C. A recording head having a structure as shown in FIGS. 2A to 2C is disclosed in Japanese Patent Laid-Open No. 2013-014111. Therefore, in the present specification, the contents of the above publication are cited, and only an outline thereof is described. 2A is a front view schematically showing the recording head of the present invention, FIG. 2B is a cross-sectional view taken along line AA in FIG. 2A, and FIG. 2C is a cross-sectional view taken along line BB in FIG. 2A. . For convenience of explanation, the liquid supply case cover is omitted from the front view.

  As shown in the drawing, the recording head of the present invention includes a common liquid chamber 112 that communicates with a plurality of nozzle channels forming a nozzle row, a liquid supply port 127 that communicates with the common liquid chamber 112, and a liquid type head. A main liquid supply chamber 126 that communicates with the supply port 127, a liquid supply path 137 that communicates with the main liquid supply chamber 126, and a liquid supply chamber that communicates with the liquid supply path 137 (the first liquid supply chamber 134 and the second liquid supply chamber). 135), a supply filter 118 disposed so as to separate the liquid supply chamber into the first liquid supply chamber 134 and the second liquid supply chamber 135 from the upstream side along the flow in supplying the liquid, and the main liquid It is preferable that a gas-liquid separator 120 provided in a part of the supply chamber 126 and an air chamber 141 communicating with the gas-liquid separator 120 are provided.

  The nozzle channel, the common liquid chamber 112, the liquid supply port 127, the main liquid supply chamber 126, the liquid supply path 137, and the liquid supply chamber (the first liquid supply chamber 134 and the second liquid supply chamber 135) The supply filter 118, the gas-liquid separator 120, and the air chamber 141 are arranged on a plane parallel to the plane including the nozzle channel arrangement direction and the liquid discharge direction, and the main liquid supply chamber 126. The liquid supply path 137, the supply filter 118, the gas-liquid separation unit 120, and the air chamber 141 are preferably arranged without being stacked.

  The recording head having the structure shown in FIGS. 2A to 2C is referred to as a gas-liquid separation type recording head. Since the gas-liquid separation type recording head fills the nozzles with ink by utilizing its own weight, it is extremely difficult to ensure the ejection stability as compared with the recording head having a conventional structure. Therefore, it can be said that the gas-liquid separation type recording head is one of the forms in which the effects of the present invention can be most enjoyed.

  A ceramic base plate 110 supports a heater substrate 111 formed of silicon. The heater substrate 111 has a plurality of electrothermal transducers (heaters or energy generators) as liquid discharge energy generating elements and a plurality of flow path walls for constituting nozzles corresponding to these electrothermal transducers. Is formed. The heater substrate 111 is also formed with a liquid chamber frame surrounding the common liquid chamber 112 communicating with each nozzle. A top plate member 113 that forms the common liquid chamber 112 is joined on the side wall of the nozzle and the liquid chamber frame formed in this manner. Therefore, the heater substrate 111 and the top plate member 113 are laminated and bonded to the base plate 110 in an integrated state. Such lamination adhesion is performed with an adhesive having good thermal conductivity such as silver paste. A mounted electrical wiring board (PCB 114) is supported by a double-sided tape (not shown) behind the heater board 111 in the base plate 110. Each ejection energy generating element on the heater substrate 111 and the PCB 114 are electrically connected by wire bonding corresponding to each wiring.

  A liquid supply member 115 is joined to the top surface of the top plate member 113. The liquid supply member 115 includes a liquid supply case 116 and a liquid supply case cover 117. When the liquid supply case cover 117 closes the upper surface of the liquid supply case 116, a liquid chamber and a liquid supply path to be described later are formed. . The liquid supply case 116 and the liquid supply case cover 117 are joined by, for example, a thermosetting adhesive. The liquid supply case 116 is provided with a supply filter 118 and a discharge filter 119. The supply filter 118 is intended to remove foreign matters in the liquid supplied to the liquid supply member 115, and the discharge filter 119 is intended to prevent foreign matters from entering from the outside of the recording head. Each filter is fixed to the liquid supply case 116 by heat welding. Furthermore, a gas-liquid separation unit 120 is formed in a part of the liquid supply case 116, and a liquid level detection sensor 121 is mounted from the outside so as to protrude from the gas-liquid separation unit 120. Control the amount.

  Here, the configuration of the liquid chamber, the liquid supply path, and the like formed by fitting the two parts of the liquid supply case and the 116 liquid supply case cover 117 will be described. A liquid supply port 127 that is a rectangular opening is formed on the joint surface of the liquid supply case 116 with the top plate member 113 and is substantially parallel to the nozzle arrangement direction and across the width of the nozzle row. A storage liquid main liquid supply chamber 126 is formed on the extension of the mouth 127. That is, the main liquid supply chamber 126 is formed substantially parallel to the nozzle row and across the width of the nozzle row. Further, the top surface on the side opposite to the liquid supply port 127 constitutes an inclination (main liquid supply chamber inclination 129) with the gas-liquid separation part 120 as the uppermost portion over almost the entire area. Two openings are formed in the main liquid supply chamber inclination 129, one being the liquid communication part 131 and the other being the gas-liquid separation part 120.

  The gas-liquid separator 120 is formed as a part of the main liquid supply chamber 126 and has a depth larger than that of the other parts of the main liquid supply chamber 126. This is to enhance the effect of breaking bubbles that are mixed in the liquid in the liquid chamber, as will be described later. In the illustrated form, three stainless steel electrodes are mounted inside the gas-liquid separator 120, and are an upper limit detection electrode 123, a ground electrode 124, and a lower limit detection electrode 125 from the left side in the figure. The liquid level in the main liquid supply chamber 126 is maintained between the upper limit and the lower limit by energization between the ground electrode 124 and the upper limit detection electrode 123 and energization between the ground electrode 124 and the lower limit detection electrode 125. In the inkjet head of the illustrated form, the detection reliability can be improved by detecting the liquid level of the liquid that has undergone gas-liquid separation.

  On the extension of the gas-liquid separation unit 120, there is an air communication unit 130, and the tip is an air chamber 141 that functions as an air flow path. Further, the above-described discharge filter 119 is disposed and communicates with the discharge joint 133. The discharge filter 119 is made of a material having water repellency. If a liquid flows into the air flow path (air chamber 141) and the ink adheres to the discharge filter 119, an ink meniscus is formed inside the filter. However, the capillary force of the filter portion can be reduced by the water repellency, and the ink can be easily removed.

  On the other hand, a liquid supply path 137 is provided via a liquid communication portion 131 provided in the main liquid supply chamber inclination 129. The liquid supply path 137 has a tubular shape from the liquid communication portion 131 to the vicinity of the supply filter 118 and is formed on substantially the same plane as the main liquid supply chamber 126. The supply filter 118 is also disposed on substantially the same plane as the main liquid supply chamber 126. The supply filter 118 is disposed so as to separate the liquid supply chamber into two chambers. The chamber on the side communicating with the supply joint 132, that is, the upstream chamber along the flow of liquid supply in the recording head is the first liquid supply. The chamber 134 and the downstream chamber are the second liquid supply chamber 135. Since the supply filter 118 is disposed on substantially the same plane as the main liquid supply chamber 126, the first liquid supply chamber 134 and the second liquid supply chamber 135 adjacent to both surfaces of the supply filter 118 are also the main liquid supply chamber. 126 and the ink discharge port array surface 139 are arranged on a plane substantially parallel to the surface.

  The second liquid supply chamber 135 has an opening above the supply filter 118 (hereinafter referred to as a second liquid supply chamber opening 136), and communicates with the liquid supply path 137 through the opening. In addition, the top surface of the second liquid supply chamber 135 is formed with an inclination (hereinafter referred to as a second liquid supply chamber inclination 138) with this opening as the uppermost portion.

  As described above, the main liquid supply chamber 126, the gas-liquid separator 120, the liquid supply path 137, the supply filter 118, the first liquid supply chamber 134, and the second liquid supply chamber 135 are each substantially the same as the ink discharge port arrangement surface 139. Set on a parallel plane. On the other hand, as shown in the AA cross section, it is important to arrange the main liquid supply chamber 126, the liquid supply path 137, the supply filter 118, and the gas-liquid separator 120 so as not to overlap each other in the vertical direction of the plane.

The supply filter 118 is preferably a stainless steel mesh having a filter pore diameter of 1 μm to 10 μm and a filter area of 10 mm ^{2 to} 500 mm ² . By setting the filter hole diameter to 1 μm or more and the filter area to 10 mm ² or more, the flow path resistance (pressure loss) can be reduced, and the bubbles in the recording head can be easily moved. In order to obtain the above effect more reliably, the filter area is more preferably 200 mm ² or more. On the other hand, when the filter hole diameter is 10 μm or less, dust can be reliably prevented from flowing into the nozzle, and when the filter area is 500 mm ² or less, the recording head can be downsized. In order to obtain the effect more reliably, it is more preferable that the filter pore diameter is 3 μm or more and 8 μm or less.

(5) Ink filling:
In the recording head of the present invention, the ink for ink jet recording is filled in the internal space communicating with the ink discharge port of the line type head. The ink is preferably filled in at least a portion from the ink discharge port to the common liquid chamber (that is, the nozzle flow path and the common liquid chamber) in the internal space.

IV. Inkjet recording device:
The ink jet recording apparatus of the present invention is an ink jet recording apparatus provided with a recording head for ink jet recording and an ink containing portion for containing ink to be supplied to the recording head. The recording head is a recording head according to the present invention. The form of the ink container is not particularly limited. For example, an ink tank as shown in FIG.

(1) Ink tank:
FIG. 3 is an enlarged sectional view of the ink tank. The ink tank 230 is a liquid storage container, and a liquid chamber (ink chamber 231) for storing ink is formed therein. The ink chamber 231 is a closed space in which only the joint portion 232 can communicate with the outside. The ink tank 230 is configured to be detachable from the recording head. The ink tank 230 is provided in the upper part of the recording head. The ink chamber 231 is formed of a flexible member, and a negative pressure generating spring 233-1 and a pressure plate 233-2 connected to the spring 233-1 are incorporated therein. The spring 233-1 urges the ink chamber 231 from the inside to the outside via the pressure plate 233-2, and expands the internal space of the ink chamber 231. That is, the spring 233-1 generates a predetermined negative pressure inside the ink chamber 231, and the spring 233-1, the pressure plate 233-2, and the ink chamber 231 together constitute a negative pressure generating unit 233. ing. The joint portion 232 is provided with a non-woven filter 234.

  FIG. 4 is an enlarged cross-sectional view of the recording head. The recording head 220 includes an energy generation element (not shown) such as an electrothermal conversion element (ink ejection heater). By this energy generating element, the ink I in the ink chamber 221 (liquid in the liquid chamber) is discharged from the discharge port 220A. In the ink chamber 221, air (gas) is present together with the ink I. Therefore, in the ink chamber 221, an ink storage part (liquid storage part) in which the ink I is stored and an air storage part (gas storage part) in which air (gas) is stored are formed. .

  An ink supply unit 222 for connecting the ink chamber 221 and the ink chamber of the ink tank is provided above the ink chamber 221. The average width of the ink supply unit 222 is about 10 mm. A filter member 223 is provided at the opening of the ink supply unit 222. The illustrated filter member 223 is formed of a SUS mesh. The mesh has a structure in which metal fibers are woven. Since the filter member 223 has fine eyes, it is difficult for dust to enter the recording head from the outside.

  The lower surface of the filter member 223 is pressed against an ink holding member 224 that can hold ink. 5A is an enlarged perspective view of the ink holding member shown in FIG. 4, and FIG. 5B is a Vb-Vb sectional view of the ink holding member shown in FIG. 5A. As shown in FIGS. 5A and 5B, the ink holding member 224 has a plurality of channels 224A having a circular cross section. The diameter of each flow path 224A is about 1.0 mm.

  As shown in FIG. 4, an opening 225 is provided in the upper part of the ink chamber 221. The opening 225 is provided with a filter 226. The opening 225 is configured to be connectable to a transfer unit (not shown) that is an external flow path. This transfer part is a flow path capable of transferring liquid and / or gas. The opening 225 allows the ink I and / or gas in the ink chamber 221 to flow out, or allows liquid (such as ink) and / or gas outside the recording head 220 to flow into the ink chamber 221. It is configured. That is, the opening 225 is formed so that not only the liquid can flow out and flow in alone, but also the gas can flow out and flow in with the liquid.

  The ink tank 230 shown in FIG. 3 and the recording head 220 shown in FIG. 4 are directly connected by connecting the joint part 232 of the ink tank 230 shown in FIG. 3 and the ink supply part 222 of the recording head 220 shown in FIG. Connected. At this time, the filter 234 of the ink tank 230 shown in FIG. 3 and the filter member 223 of the recording head 220 shown in FIG. 4 are in pressure contact with each other from above and below. The connecting portion between the ink tank and the recording head formed in this manner is surrounded by a rubber elastic cap member to maintain hermeticity. The structure in which the recording head and the ink tank are directly connected as described above is preferable in that the ink supply path (liquid supply path) between them can be extremely shortened.

(2) Overall configuration of recording apparatus:
Other structures of the ink jet recording apparatus are not particularly limited. For example, a recording apparatus 300 as shown in FIG. 6 can be suitably used.

  FIG. 6 is a schematic configuration diagram schematically showing the overall configuration of the ink jet recording apparatus. An external host device (computer device 308) is connected to the recording device 300. The recording apparatus 300 is configured to record an image by ejecting ink from the recording head 305 based on the recording data input from the computer apparatus 308.

  In the recording apparatus 300, a label sheet temporarily attached with a plurality of labels is used as the recording medium 301. The recording medium 301 is set in a state wound in a roll shape. However, in the ink jet recording apparatus of the present invention, any material can be used as long as it can accept not only paper, but also ink such as cloth, plastic film, metal plate, glass, ceramics, wood, and leather. Can be used.

  The recording apparatus 300 includes a conveyance motor 303, a conveyance roller 302, a rotary encoder 310, and a roll motor 311 as conveyance means for conveying the recording medium 301. By driving the conveyance roller 302 by the conveyance motor 303, the recording medium 301 can be conveyed at a constant speed in the direction of arrow A. The rotary encoder 310 can detect the conveyance speed and conveyance amount of the recording medium 301. The roll motor 311 can rewind the recording medium 301 in the direction opposite to the arrow A direction. The paper detection sensor 304 is a sensor that detects a specific portion of the recording medium 301. In the illustrated example, the tip of each label temporarily attached to the label sheet is detected. The recording timing of the image can be determined based on the detection.

  The recording apparatus 300 includes four recording heads 305 and ink tanks 306 corresponding to the four recording heads 305 at the top thereof. The four recording heads are recording heads for ejecting black, cyan, magenta, and yellow ink, respectively.

  The recording head 305 is a so-called line-type head configured to be wider than the maximum width recording width of the recording medium 301 and includes a plurality of nozzles that can eject ink. The ink discharge port of the nozzle is opened on the lower surface side of the recording head 305. The recording head 305 is disposed so that its longitudinal direction intersects with the conveyance direction of the recording medium 301 (direction orthogonal to the arrow A in the figure), and a plurality of nozzles are arranged along the longitudinal direction. As a result, a nozzle row is formed.

  In the recording apparatus 300, the conveyance roller 302 is driven by the conveyance motor 303, and the recording medium 301 is conveyed at a constant speed in the direction of arrow A by the conveyance roller 302. When a specific portion of the recording medium 301 is detected by the paper detection sensor 304, ink is sequentially discharged from the ink discharge ports of the four recording heads 305 based on the detection position. At this time, ink is supplied from the ink tank 306 to the recording head 305. Thus, when the recording medium 301 passes under the recording head 305, ink is ejected from the plurality of nozzles of the recording head 305, and an image is recorded on the recording medium 301. Note that since the recording head 305 is a line-type head, ink is ejected while being fixed at a fixed position. That is, ink is not ejected while reciprocating left and right like a serial head.

  The recording apparatus 300 includes a capping mechanism 307, a blade 309, and the like as a recovery mechanism for performing a recovery operation of the recording head 305.

  The recovery operation is an operation for recovering the recording head 305 so as to exhibit an appropriate ejection performance similar to the initial state. For example, operations such as suction recovery, pressure recovery, preliminary discharge, and wipe recovery can be given. The suction recovery is an operation of sucking and removing the thickened ink in the nozzles of the recording head 305 to the capping mechanism 307, and the pressure recovery is pressurizing the thickened ink in the nozzles of the recording head 305 to the capping mechanism 307. Preliminary ejection is an operation that discharges the thickened ink in the nozzles to the capping mechanism 307 by ejection, and stabilizes the ink meniscus. Wipe recovery means that the face surface of the recording head is wiped by the blade 309. In this operation, dust and ink attached to the face surface are removed. These recovery operations can also be implemented in combination.

  The capping mechanism 307 is a mechanism for capping the ink discharge port of each recording head 305 and is disposed below the recording head 305. The recording head 305 and the capping mechanism 307 are configured to be relatively movable in the left-right direction in FIG. On the other hand, the blade 309 is a member that wipes the face surface of each recording head 305, and is disposed below the recording head 305.

  When performing suction recovery, the inside of the buffer tank (not shown) of the capping mechanism 307 is decompressed by a tube pump (not shown) while the recording head 305 is capped by the capping mechanism 307. As a result, the thickened ink in the nozzles of the recording head 305 is removed by suction to the capping mechanism 307, and the nozzles are refreshed.

  When pressure recovery is performed, the inside of the nozzles of the recording head 305 is pressurized while the recording head 305 is capped by the capping mechanism 307. As a result, the thickened ink in the nozzle is pressurized and discharged into the cap of the capping mechanism 307, and the inside of the nozzle is refreshed.

  When performing wipe recovery, the blade 309 is driven by a blade motor (not shown), the face of the nozzle of the recording head 305 is wiped, and pressure recovery (preliminary ejection) is performed. Thereby, the face surface of the nozzle is cleaned, and the meniscus at the ink discharge port is adjusted.

  The ink accumulated in the capping mechanism 307 by these recovery operations is sucked by a tube pump (not shown) and discarded in a waste ink tank (not shown) when it is accumulated to a predetermined amount.

(3) Control system:
Next, control of the ink jet recording apparatus will be described. FIG. 7 is a block diagram of the control system of the recording apparatus shown in FIG. In addition to a recording mechanism including a recording head, the recording apparatus includes a control system component such as a CPU (Central Processing Unit), a USB interface unit, and a ROM. The CPU 401 executes a program stored in the program ROM 402 and controls each unit of the recording apparatus. A program ROM 402 stores programs and data for controlling the recording apparatus. The processing of the recording apparatus is realized by the CPU 401 reading and executing a program in the program ROM 402.

  The recording data output from the computer device 308 is input to the interface controller 403 of the recording device. Commands that specify the number, type, size, and the like of the recording medium (label) are also input to the interface controller 403 and analyzed. In addition to analyzing these commands, the CPU 401 executes arithmetic processing for controlling the entire recording apparatus, such as recording data input, recording operation, and recording medium handling. The arithmetic processing is executed based on a processing program stored in the program ROM 402. The program includes a program corresponding to the procedure of the flowchart shown in FIG. A work RAM 404 is used as a working memory for the CPU 401. The EEPROM 405 is a rewritable nonvolatile memory. This EEPROM 405 is specific to the recording apparatus, such as the time when the previous recovery operation was performed, the mutual distance of a plurality of recording heads, and the correction value for finely adjusting the recording position in the transport direction (vertical registration). Parameters are stored.

  More specifically, after analyzing the input command, the CPU 401 develops the image data of each color component of the recording data in the image memory 406 as a bitmap. Drawing is performed based on this data. Further, the CPU 401 controls the transport motor 303, the roll motor 311, the capping motor 409, the head motor 410, and the pump motor 418 via the input / output circuit 407 and the motor driving unit 408. The capping motor 409 is a motor for driving the capping mechanism 307, the head motor 410 is a motor for moving the recording heads 305K, 305Y, 305M, and 305C, and the pump motor 418 is a motor for driving the tube pump. It is. The recording heads 305K, 305Y, 305M, and 305C are moved between the capping position, the recording position, and the recovery position. The capping position is a position capped by the capping mechanism 307, the recording position is a position for recording an image, and the recovery position is a position for performing a recovery operation.

  When an image is recorded by the recording apparatus, the conveyance roller 302 is driven by the conveyance motor 303 as shown in FIG. 6 to convey the recording medium 301 (label paper in the illustrated example) at a constant speed. The rotary encoder 310 detects the conveyance speed and conveyance amount of the recording medium 301. In the control system shown in FIG. 7, the leading edge of the label is detected by the paper detection sensor 304 in order to determine the recording timing of the image on the recording medium conveyed at this constant speed. A detection signal from the paper detection sensor 304 is input to the CPU 401 via the input / output circuit 411. When the recording medium is conveyed by the conveyance motor, the CPU 401 sequentially reads out image data for each color from the image memory 406 in synchronization with a signal from a rotary encoder (not shown). The image data is transferred to one of the corresponding recording heads 305K, 305Y, 305M, and 305C via the recording head control circuit 412. Accordingly, the recording heads 305K, 305Y, 305M, and 305C eject ink based on the image data.

  The driving of the pump motor 413 for driving the pump is controlled via the input / output circuit 407 and the motor driving unit 408. The operation panel 414 is connected to the CPU 401 via the input / output circuit 415. Further, the environmental temperature and environmental humidity of the recording apparatus are detected by a temperature / humidity sensor 416 and input to the CPU 401 via the A / D converter 417.

(4) Recovery sequence:
When the environmental temperature is 40 ° C. or higher and the water evaporates, the ink sticks easily to the recording head. Accordingly, it is preferable to insert a recovery sequence for recovering the face surface of the recording head when the head cap is removed from the recording head and the moisture evaporates.

  FIG. 8 is a flowchart showing the steps of the printhead recovery sequence. The recovery sequence shown in FIG. 8 is activated when a cap opening condition (condition 501) in which the recording head is released from the cap is satisfied. When the recovery sequence is activated, the environmental temperature and the environmental humidity of the recording apparatus are acquired (detected) by the temperature / humidity sensor (step 502). As a result of the detection, when the environmental temperature is 40 ° C. or more, the environmental humidity is 70% or less (condition 503), and the cumulative time from the previous suction recovery is one hour or more (condition 504), the inside of the nozzle Pressure recovery (preliminary ejection) for refreshing the ink and wipe recovery for wiping and cleaning the face surface are performed (step 505). The condition 504 is reset when suction recovery is performed.

  Next, although an Example demonstrates this invention more concretely, this invention does not receive any restriction | limiting by an Example. In the text, “parts” and “%” are based on mass unless otherwise specified.

(Synthesis example)
(Synthesis of (meth) acrylic ester random copolymer)
1000 parts of methyl ethyl ketone was charged into a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introducing device at the top, and the inside of the reaction vessel was purged with nitrogen while stirring. After raising the temperature in the reaction vessel to 80 ° C. while maintaining a nitrogen atmosphere, 63 parts 2-hydroxyethyl methacrylate, 158 parts methacrylic acid, 417 parts styrene, 171 parts benzyl methacrylate, 25 parts glycidyl methacrylate from the dropping device. , 33 parts of a polymerization degree adjusting agent (Nippon Yushi Co., Ltd., trade name: “Blemmer TGL”) and active ingredient t-butyl peroxy-2-ethylhexanoate (Nippon Yushi Co., Ltd., trade name: “Perbutyl (registered trademark) O ”) 67 parts were mixed to obtain a mixed solution, and the obtained mixed solution was added dropwise over 4 hours. After completion of the dropping, the reaction was further continued at the same temperature for 10 hours to obtain a dispersion resin solution of a styrene-methacrylate random copolymer having an acid value of 124 mgKOH / g.

(Synthesis example of (meth) acrylic acid ester random copolymer having different acid values) In the above synthesis, the acid value is changed from 80 mgKOH / g to 170 mgKOH / g by changing the blending ratio of methacrylic acid and benzyl methacrylate. Various styrene-methacrylic acid ester random copolymer dispersion resin solutions were obtained.

(Preparation example of aqueous resin dispersed pigment)
A dispersion tank solution of a styrene-methacrylate random copolymer obtained in a mixing tank having a cooling function, 25% aqueous potassium hydroxide solution, water, and 1,000 parts of various pigments are charged, stirred, mixed and mixed. A liquid was obtained. In addition, the (meth) acrylic acid ester random copolymer synthesized above was used in such an amount that the nonvolatile content was 40% with respect to the pigment. The 25% aqueous potassium hydroxide solution was used in such an amount that the (meth) acrylic acid ester random copolymer was neutralized 100%. Furthermore, the water used the quantity which makes the non volatile matter of the obtained liquid mixture 27%. The obtained mixed liquid was passed through a dispersing apparatus filled with zirconia beads having a diameter of 0.3 mm, and dispersed for 4 hours by a circulation method to obtain a dispersion. The temperature of the dispersion was kept at 40 ° C. or lower.

  After the dispersion liquid was extracted from the mixing tank, the mixing tank and the flow path of the dispersion apparatus were washed with 10,000 parts of water, and the cleaning liquid and the dispersion liquid were mixed to obtain a diluted dispersion liquid. The obtained diluted dispersion was put into a distillation apparatus, and the whole amount of methyl ethyl ketone and a part of water were distilled off to obtain a concentrated dispersion. The concentrated dispersion which had been allowed to cool to room temperature was added dropwise with 2% hydrochloric acid while stirring to adjust the pH to 4.5, and then filtered and washed with water using a Nutsche filter device to obtain a solid (cake). The obtained solid (cake) was put in a container, water was added, and then redispersed using a dispersion stirrer and adjusted to pH 9.5 with 25% aqueous potassium hydroxide solution. Thereafter, using a centrifuge, coarse particles were removed at 6000 G for 30 minutes, and then the non-volatile content was adjusted to obtain an aqueous resin dispersed pigment (pigment content: 14%).

Example 1
(Preparation of ink set)
The aqueous ink solvent obtained while stirring the various aqueous resin-dispersed pigments obtained in the synthesis examples and adjustment examples so as to have the following blending ratio was gradually added dropwise and stirred at room temperature for 20 minutes (total of 100 %). Thereafter, the mixture was filtered through a 5 μm membrane filter to obtain a water-based ink to obtain an ink set. “NIKKOL BC-20” of the following blending component is a trade name of a surfactant manufactured by Nikko Chemicals. “Acetylenol E100” is a trade name of a surfactant manufactured by Kawaken Fine Chemical Co., Ltd.

(Black ink composition)
・ Carbon black (Mitsubishi Chemical Corporation, trade name: “MA-7”) 3%
(Dispersion resin: styrene-methacrylate random copolymer (acid value: 155))
・ Glycerin 7%
・ Triethylene glycol 3%
・ Ethyleneurea 10%
・ NIKKOL BC-20 1%
・ Acetylenol E100 0.1%
・ Ion exchange water remaining

(Composition of cyan ink)
・ C. I. Pigment Blue 15: 3 3%
(Dispersion resin: styrene-methacrylate random copolymer (acid value: 124))
・ Glycerin 7%
・ Triethylene glycol 3%
・ Ethyleneurea 10%
・ NIKKOL BC-20 1%
・ Acetylenol E100 0.1%
・ Ion exchange water remaining

(Magenta ink composition)
・ C. I. Pigment Red 122 3%
(Dispersion resin: styrene-methacrylate random copolymer (acid value: 155))
・ Glycerin 7%
・ Triethylene glycol 3%
・ Ethyleneurea 10%
・ NIKKOL BC-20 1%
・ Acetylenol E100 0.1%
・ Ion exchange water remaining

(Examples 2 to 4)
The ink sets of Examples 2 to 4 were obtained by changing the pigment and the styrene-methacrylic acid ester random copolymer to those having the acid values of the combinations of Examples in Table 1.

(Comparative Examples 1-4)
Ink sets of Comparative Examples 1 to 4 were obtained by changing the pigment and the styrene-methacrylic acid ester random copolymer to those having the acid values of the combinations of Comparative Examples in Table 1.

  The viscosity and surface tension of each water-based ink constituting the obtained ink set were measured, and the results are shown in Table 2. The viscosity of the water-based ink was measured using an E-type viscometer (trade name: “RE-80L viscometer” manufactured by Toki Sangyo Co., Ltd.) under a temperature of 25 ° C. in accordance with JIS Z 8803. Further, the surface tension was measured using a fully automatic surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., trade name: “CBVP-Z”) at a temperature of 25 ° C.

(Evaluation)
With respect to the ink sets of Examples and Comparative Examples, the ejection stability (landing accuracy) of the water-based ink was evaluated by the following method.

  Each water-based ink obtained above is filled in an ink tank of an ink jet recording head, and the ink jet recording head is placed in an ink jet recording apparatus having a structure shown in FIG. 6 (trade name: “LXP5500” manufactured by Canon Finetech Co., Ltd.). It was installed. Under an environment of a temperature of 15 ° C. and a relative humidity of 10%, a 10-point character “Electric surprise” was recorded on the recording medium. The recording conditions were a conveyance speed of 150 mm / sec and a resolution of 1200 dpi × 1200 dpi.

  As the ink jet recording head, one having the structure shown in FIGS. 1A to 1C and 2A to 2C was used. This ink jet recording head is a head for the above ink jet recording apparatus.

  As a recording medium, a 100 mm × 100 mm mat label (manufactured by Canon Inc., trade name: “matt label 100 × 100 mm”) was used.

The landing accuracy of the water-based ink constituting each ink set was evaluated according to the following criteria. The results are shown in Table 3.
A: There is no deviation in all the water-based inks at the landed dot positions.
B: The landing dot position is not noticeable although there is a shift between the water-based inks.
C: The landing dot position is noticeable with a shift between water-based inks.

110: base plate, 111: heater substrate, 112: common liquid chamber, 113: top plate member, 115: liquid supply member, 116: liquid supply case, 117: liquid supply case cover, 118: supply filter, 119: discharge filter, 120: Gas-liquid separator, 121: Liquid level detection sensor, 123: Upper limit detection electrode, 124: Ground electrode, 125: Lower limit detection electrode, 126: Main liquid supply chamber, 127: Liquid supply port, 129: Main liquid supply chamber Inclination, 130: air communication part, 131: liquid communication part, 132: supply joint, 133: discharge joint, 134: first liquid supply chamber, 135: second liquid supply chamber, 136: second liquid supply chamber opening, 137 : Liquid supply path, 138: second liquid supply chamber inclination, 139: ink discharge port arrangement surface, 141: air chamber, 151: ink discharge 152: heater, 153: nozzle wall, 155: nozzle filter, 157: heater center, 159: nozzle flow path, 162: nozzle top plate, 164: nozzle bottom plate, 171: discharge port width, 172: discharge port height, 181: nozzle front part, 182: nozzle rear part, 220: recording head, 220A: ejection port, 221: ink chamber, 222: ink supply part, 223: filter member, 224: ink holding member, 224A: flow path, 225 : Opening, 226: Filter, 230: Ink tank, 231: Ink chamber, 232: Joint part, 233: Negative pressure generating part, 2333-1: Spring, 233-2: Pressure plate, 234: Filter, 300: Recording Device 301: recording medium 302: transport roller 303: transport motor 304: paper detection sensor 305 305K 05Y, 305M, 305C: recording head, 306: ink tank, 307: capping mechanism, 308: computer device, 309: blade, 310: rotary encoder, 311: roll motor, 401: CPU, 402: program ROM, 403: interface Controller, 404: Work RAM, 405: EEPROM, 406: Image memory, 407: Input / output circuit, 408: Motor drive unit, 409: Capping motor, 410: Head motor, 411: Input / output circuit, 412: Print head control Circuit, 413: Pump motor, 414: Operation panel, 415: Input / output circuit, 416: Temperature / humidity sensor, 417: A / D converter, 418: Pump motor, 501: Condition, 502: Process, 503: Condition, 504: Condition 5 05: Process, I: Ink.

Claims (21)

An ink set comprising a water-based ink containing a pigment and a (meth) acrylic acid ester-based random copolymer in which the pigment is dispersed, as a set of a plurality of water-based inks,
The (meth) acrylic acid ester-based random copolymer contained in the water-based ink has an acid value of 100 to 160 mgKOH / g,
One of the plurality of water-based inks is a cyan ink containing a phthalocyanine compound as the pigment, and the cyan ink contains the (meth) acrylic acid ester-based random copolymer contained therein. An ink having an acid value of 0.70 to 0.95 times that of the (meth) acrylic acid ester random copolymer contained in the water-based ink other than the cyan ink. set.   2. The ink set according to claim 1, wherein the water-based ink other than the cyan ink includes a black ink containing carbon black as the pigment and a magenta ink containing a quinacridone compound as the pigment. .   The (meth) acrylic acid ester-based random copolymer contained in a plurality of types of water-based inks is composed of a common monomer species, and an acid is changed by changing the blending ratio of the monomer species. The ink set according to claim 1 or 2, wherein the value is adjusted.   The plurality of types of water-based inks each have a viscosity of 1.5 to 5.0 mPa · s, and a difference in viscosity between them is 0.5 mPa · s or less. The ink set according to item 1.   5. The plurality of types of water-based inks each have a surface tension of 25 to 45 mN / m, and a difference in surface tension between them is 5 mN / m or less. Ink set.   The ink set according to claim 1, wherein the ink set is used in an ink jet recording method in which a thermal head discharges a recording head. An ink jet recording method for discharging a plurality of types of water-based inks by a thermal method from a recording head having a plurality of nozzle rows in which a plurality of nozzles are arranged,
The inkjet recording method, wherein each of the nozzles has an opening area of 100 to 350 μm ² , and the plurality of types of water-based inks are water-based inks constituting the ink set according to claim 1. .   The inkjet recording method according to claim 7, wherein the nozzle row has 1200 or more nozzles per row and has a length of 2 inches or more. An inkjet recording head comprising a plurality of nozzle rows in which a plurality of nozzles are arranged, and ejecting a plurality of water-based inks from the nozzle rows by a thermal method,
Each of the nozzles has an opening area of 100 to 350 μm ² , the nozzle row has 1200 or more nozzles per row, has a length of 2 inches or more, and the water-based ink includes: An ink jet recording head, which is a water-based ink constituting the ink set according to claim 1. An inkjet recording head comprising a plurality of nozzle rows in which a plurality of nozzles are arranged, and ejecting a plurality of water-based inks from the nozzle rows by a thermal method,
A common liquid chamber in which a plurality of nozzle channels communicate as the nozzle row, an opening in communication with the common liquid chamber, a main liquid supply chamber in communication with the opening, and a liquid supply in communication with the main liquid supply chamber And a liquid supply chamber communicating with the liquid supply passage, and the liquid supply chamber is separated from the upstream side into a first liquid supply chamber and a second liquid supply chamber along a flow during liquid supply. A supply filter disposed on the main liquid supply chamber, a gas-liquid separator provided in a part of the main liquid supply chamber, and an air chamber communicating with the gas-liquid separator.
The nozzle flow path, the common liquid chamber, the opening, the main liquid supply chamber, the liquid supply path, the liquid supply chamber, the supply filter, the gas-liquid separator, and the air Chambers are arranged on a plane parallel to a plane including the arrangement direction of the nozzle channels and the liquid discharge direction, the main liquid supply chamber, the liquid supply path, the supply filter, The inkjet recording head according to claim 9, wherein the gas-liquid separation unit and the air chamber are arranged without being laminated. An inkjet recording apparatus comprising: a plurality of water-based ink storage portions that respectively store a plurality of types of water-based ink; and an inkjet recording head that discharges the water-based ink,
The aqueous ink is an aqueous ink constituting the ink set according to any one of claims 1 to 6, and the inkjet recording head is an inkjet recording head according to claim 9 or 10. Recording device. A cyan ink for use in combination in an ink set containing at least an aqueous ink other than cyan ink,
The cyan ink and the water-based ink other than the cyan ink each contain a (meth) acrylic acid ester random copolymer having an acid value of 100 to 160 mgKOH / g as a dispersant for dispersing the pigment,
The cyan ink contains a phthalocyanine compound as a pigment, and
The (meth) acrylic acid ester random copolymer contained in the cyan ink is 0.70 to 0 relative to the (meth) acrylic acid ester random copolymer contained in the aqueous ink other than the cyan ink. Cyan ink having an acid value of .95 times. The cyan ink according to claim 12, wherein the water-based ink other than the cyan ink contains carbon black or a quinacridone compound as a pigment. The (meth) acrylic acid ester-based random copolymer is composed of a common monomer species, and the acid value is adjusted by changing the blending ratio of the monomer species. The cyan ink according to 12 or 13. The ink set further includes an aqueous ink other than the cyan ink, and each of the inks has a viscosity of 1.5 to 5.0 mPa · s, and a difference in viscosity between the inks is 0.1. The cyan ink according to claim 12, which is 5 mPa · s or less. The ink set further includes another water-based ink other than cyan ink, and each of the inks has a surface tension of 25 to 45 mN / m, and a difference in surface tension between the inks is 5 mN / m or less. The cyan ink according to any one of claims 12 to 15. A water-based ink other than cyan ink for use in combination in an ink set containing at least cyan ink,
The cyan ink and the water-based ink other than the cyan ink each contain a (meth) acrylic acid ester random copolymer having an acid value of 100 to 160 mgKOH / g as a dispersant for dispersing the pigment,
Aqueous ink other than the cyan ink contains carbon black or a quinacridone compound as a pigment,
The cyan ink contains a phthalocyanine compound as a pigment, and
The (meth) acrylic acid ester random copolymer contained in the cyan ink is 0.70 to 0 relative to the (meth) acrylic acid ester random copolymer contained in the aqueous ink other than the cyan ink. A water-based ink other than cyan ink, having an acid value of .95 times. The (meth) acrylic acid ester-based random copolymer is composed of a common monomer species, and the acid value is adjusted by changing the blending ratio of the monomer species. An aqueous ink other than the cyan ink described in Item 17. The ink set further includes an aqueous ink other than the cyan ink, and each of the aqueous inks has a viscosity of 1.5 to 5.0 mPa · s, and a difference in viscosity between the inks is 0. The water-based ink other than cyan ink according to claim 17 or 18, wherein the water-based ink is not more than 0.5 mPa · s. The ink set further includes an aqueous ink other than the cyan ink, and the aqueous ink has a surface tension of 25 to 45 mN / m, and a difference in surface tension between the inks is 5 mN / m. The water-based ink other than the cyan ink according to any one of claims 17 to 19, which is: The water-based ink according to any one of claims 12 to 20, which is used for an ink jet recording method ejected from a recording head by a thermal method .

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