JP2006218661A - Double-side recording system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high-speed double-side recording by using a special ink composed of a high-viscosity ink prepared in consideration of a permeation/drying process of plain paper, in a double-side inkjet recording method and a double-side inkjet recording apparatus, which eliminate waiting time for drying and prevent a deterioration in image quality. <P>SOLUTION: The inkjet recording apparatus performs recording by an ink droplet jetted for performing color printing. The ink, which contains at least a coloring agent, a wetting agent, ≥8C polyol or glycol ether, an anionic or nonionic surface active agent, a water-soluble organic solvent and water, has the characteristics of a 5 wt% or more coloring agent concentration and a 6 cps (25°C) or more ink viscosity. The inkjet recording apparatus, which is equipped with the ink as at least one of special color inks of red, green and blue, added to four basic colors, that is, cyan, magenta, yellow and black, performs the double-side recording by using a paper carrying mechanism corresponding to automatic double-side printing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing method and a recording system equipped with the image processing. In particular, in addition to basic inks of cyan, magenta, yellow, and black, red ( This is a technology related to an ink jet recording apparatus that employs so-called special color inks such as Red, Green, and Blue, and that employs high-viscosity inks for all used inks including special color inks. .

  Inkjet recording devices have rapidly become popular for personal use because of their low price and high-quality characteristics when special paper is used. Recently, even in offices where electrophotographic laser printers have been the mainstream, they are steadily building their ground as recording devices capable of color output at low cost.

Here, there are the following two problems that must be cleared when the inkjet recording apparatus is widely used for office use.
First, there is a problem related to cost, and it is possible to deal with plain paper (paper generally used as copy paper). When special paper is used, inkjet recording images can reproduce images with extremely high quality, and with recent inkjet recording apparatuses for personal use, it has become possible to obtain image quality that is mistaken for photographs. Yes.

However, these special papers are generally expensive and difficult to introduce when strict cost control is required in companies, etc., and so-called business documents are mainly used for output in offices, and output of photographic images is required. Because it is rare, the high image quality with special paper has not been a merit.
Therefore, in order to deal with the above-mentioned plain paper, manufacturers have tried to improve the ink composition, for example, development of low-penetration dye ink, use of fixing aids, development of pigment-based ink, etc. It was. With the latest models, even plain paper that is commonly used in the office has become capable of clear image recording without taking the mark of a laser printer.

  Another problem is the recording speed. Except for special industrial types, in a general ink jet recording apparatus, recording is performed by a recording head that is much smaller than the recording paper repeatedly scanning the paper and spraying ink. This is a so-called “line” recording method, which is inferior in terms of recording speed as compared to an electrophotographic recording in paper (page) units, that is, “surface”.

  In order to eliminate this disadvantage of speed, it is necessary to improve the scanning speed by increasing the ink ejection period, to reduce the number of scans by increasing the size of the recording head and bidirectional recording, and to the part where image data is recorded Increasing the efficiency of the scanning sequence, such as the shortest control for scanning only, has come to be adopted. As a result, some of the latest models have realized recording speeds higher than electrophotography, which takes time to warm up, rather than printing small to medium copies.

A function often used in offices is a duplex printing function. In order to eliminate paper waste as part of environmental measures, double-sided printing is actively recommended in offices, and the double-sided printing function is becoming an essential function as an office printer. Medium-sized and larger laser printers and FAX multifunction printers have a built-in or optional paper transport mechanism for duplex printing, and can realize double-sided printing without stress, but an inkjet recording device that was mainly used for personal use Then, at first, the printed paper had to be replaced manually.
However, with regard to this double-sided printing, in recent years, an ink jet recording apparatus that has a double-sided conveyance function as a standard or option and can perform double-sided recording without replacing paper has gradually come to the market.

  As described above, the ink jet recording apparatus has become a very attractive product even in the office by improving the image quality and the recording speed and mounting the double-sided printing function. In particular, since it has a high cost advantage compared to a laser printer and can be easily reduced in size, it is also being used on a desktop in addition to being used as a centralized output terminal.

  However, unlike a laser printer having a mechanism for thermally fixing a colorant to the surface of a paper, an ink jet recording apparatus that performs fixing by using the penetration of the colorant liquid (ink) into the paper and evaporation of water accompanies this permeation process. There will always be problems and limitations.

As an example, there is a problem of cockling in which the paper is swollen by moisture contained in the ink, and the deformed paper comes into contact with the print head and soils the recording surface. In order to increase the ink droplet ejection position accuracy, it is necessary to reduce the gap between the head and the paper as much as possible, but unlike the inkjet dedicated paper, the plain paper used in the office has no measures against swelling, so If the gap is set too small, contact between the swollen paper and the head may occur, leading to defective image output.
In addition, while the ink ejected on the paper surface is undried, it rubs against a member of the transport mechanism, the ink adhering to the member stains the surface of the paper, or the undried ink on the discharged paper surface In some cases, the backside of the discharged paper may become dirty.

  Conventionally, in order to solve these problems, the gap (distance) between the head and the paper is widened to reduce the physical contact surface, the printing sequence is optimized, the drying time is secured, or the drying is forcibly performed. Means such as providing a heater were taken.

  However, the method of increasing the gap causes a decrease in dot position accuracy, and the method of ensuring the drying time leads to a decrease in throughput. In addition to increasing the cost, it was necessary to pay attention to safety when installing the heater. In some cases, the heated paper could curl.

  In recent years, countermeasures have advanced from the aspect of ink formulation, and it has become possible to perform recording on plain paper without degrading print quality without using special means such as those described above. For example, by increasing the permeability to the paper, the ink can be quickly penetrated without remaining on the surface of the paper, so that it is possible to prevent secondary transfer due to contact with parts or paper. Due to such improvements, the ink jet recording apparatus has been able to realize a recording speed comparable to that of a laser printer in “single-sided recording”.

  Here, the reason for limiting to “single-sided recording” is that it is still necessary to secure the drying time in double-sided recording, and this waiting time takes much longer recording time than “during single-sided recording”. The reason for ensuring the drying time is to prevent secondary transfer in reloading (resetting) of the paper. In general, in a paper transport mechanism, there are roller-shaped parts such as a pressure roller and a pressure roller that send a paper under pressure for the purpose of preventing the paper from floating or misaligned. When the undried recording surface passes under the pressure roller, the undried ink is transferred to the surface of the pressure roller as if by offset printing, and the ink is retransferred to the surface of the paper by the rotation of the roller. Become. At the contact level, ink that has penetrated into the paper will not be retransferred to these parts, but under pressure rollers, the ink in the paper will be forcibly squeezed out. This is because transfer tends to occur.

In order to reduce this waiting time, a method for suppressing the amount of ink used during double-sided printing has been conventionally proposed. For example, Japanese Patent No. 2879872 of Patent Document 1 proposes the suppression of ink consumption by thinning out and the like in addition to adjusting the waiting time for drying according to the type of recording paper. This is performed for the purpose of preventing secondary transfer and show-through, that is, preventing ink recorded on the front side from penetrating to the back side due to permeation and degrading the image quality of double-sided recording.
Such a countermeasure method not only leads to a decrease in printing speed as described above, but also causes a decrease in image quality such that the recorded image becomes light.

Japanese Patent No. 2879872

  Accordingly, an object of the present invention is to focus on this point and propose a double-sided recording method that eliminates the waiting time for drying and does not deteriorate the image quality. Specifically, by using a special color ink with a high viscosity ink adjusted in consideration of the permeation / drying process in plain paper, and adjusting the blend with the reference four color inks with the high viscosity ink at the time of duplex printing, the ink An object of the present invention is to realize high-speed double-sided recording that suppresses adhesion amount and image quality deterioration at the same time and has no waiting time.

That is, the said subject is solved by (1)-(10) of this invention.
(1) In an ink jet recording apparatus equipped with a head unit provided with a nozzle for ejecting each color ink necessary for color printing onto the surface of a paper and performing recording with ink droplets ejected from the head unit,
It contains at least a colorant, a wetting agent, a polyol or glycol ether having 8 or more carbon atoms, an anionic or nonionic surfactant, a water-soluble organic solvent, water, a colorant concentration of 5% by weight or more, and an ink viscosity of 6 cps ( In addition to the basic four colors of cyan, magenta, yellow, and black, at least one special color ink of red, green, and blue is mounted on the ink with the characteristics of 25 ° C or higher, and automatic double-sided Inkjet recording apparatus characterized in that double-sided recording is performed using a paper transport mechanism compatible with printing ";
(2) “Inkjet recording apparatus according to item (1), wherein the colorant is water-insoluble or hardly soluble”;
(3) The item (1) or (2), wherein the at least one kind of ink contains the colorant in the form of colored polymer fine particles colored with the colorant. Inkjet recording apparatus ";
(4) “The carbon number 8 or more polyol or glycol ether is composed of 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol. The inkjet recording apparatus according to any one of Items (1) to (3);
(5) “The anionic surfactant is selected from surfactants represented by formulas (I), (II), (III), (IV), (V), (VI) and (VII) described later. The inkjet recording apparatus according to any one of (1) to (4), wherein the inkjet recording apparatus includes at least one kind.

（Ｒ_１：炭素数６〜１４の分岐してもよいアルキル基、ｍ＝３〜１２、Ｍ：アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、アルカノールアミン）

(R ₁ : alkyl group having 6 to 14 carbon atoms which may be branched, m = 3 to 12, M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

（Ｒ_２：炭素数５〜１６の分岐したアルキル基、Ｍ：アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、アルカノールアミン）

(R ₂ : branched alkyl group having 5 to 16 carbon atoms, M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

（Ｒは分岐してもよい炭素数６〜１４の炭化水素基、ｋ＝５〜２０）

(R is a C 6-14 hydrocarbon group which may be branched, k = 5-20)

（Ｒは分岐してもよい炭素数６〜１４の炭化水素基、ｎ＝５〜２０）

(R is a hydrocarbon group having 6 to 14 carbon atoms which may be branched, n = 5 to 20)

（Ｒ’は炭素数６〜１４の炭化水素基、ｍ≦２０、ｎ≦２０）

(R ′ is a hydrocarbon group having 6 to 14 carbon atoms, m ≦ 20, n ≦ 20)

（Ｒ’は炭素数６〜１４の炭化水素基、ｍ≦２０、ｎ≦２０）

(R ′ is a hydrocarbon group having 6 to 14 carbon atoms, m ≦ 20, n ≦ 20)

（ｐ、ｑ＝０〜４０）」；
（６）「前記湿潤剤が、前記インクに１０〜５０重量％含まれることを特徴とした前記第（１）項乃至第（５）項のいずれかに記載のインクジェット記録装置」；
（７）「前記湿潤剤が、次の一般式で表わされるものであることを特徴とした前記第（１）項乃至第（６）項のいずれかに記載のインクジェット記録装置。

(P, q = 0-40) ";
(6) “The inkjet recording apparatus according to any one of (1) to (5), wherein the wetting agent is included in the ink in an amount of 10 to 50% by weight”;
(7) The inkjet recording apparatus according to any one of (1) to (6), wherein the wetting agent is represented by the following general formula.

（但し、上記式中ｎは５〜８の整数を表わす。）」；
（８）「前記特色インクは、その着色剤が、前述した４色の基本インクに使用される基本着色剤の混合着色剤であり、該混合着色剤の色相特性が、混合されるそれぞれ基本着色剤固有の基本色の中間であることを特徴とした前記第（１）項乃至第（７）項のいずれかに記載のインクジェット記録装置」；
（９）「インク噴射エンジンとして、ヒータによる膜沸騰を利用した体積変動をインク噴射に使用する記録ヘッドを搭載することを特徴とした前記第（１）項乃至第（８）項のいずれかに記載のインクジェット記録装置」；
（１０）「インク噴射エンジンとして、圧電素子による体積変動をインク噴射に使用する記録ヘッドを搭載することを特徴とした前記第（１）項乃至第（８）項のいずれかに記載のインクジェット記録装置」。

(Where n represents an integer of 5 to 8) ";
(8) “In the special color ink, the colorant is a mixed colorant of the basic colorant used in the basic inks of the four colors described above, and the hue characteristics of the mixed colorant are mixed with each of the basic colors. The inkjet recording apparatus according to any one of Items (1) to (7), wherein the inkjet recording apparatus is in the middle of a basic color unique to the agent;
(9) In any one of the above paragraphs (1) to (8), a recording head that uses volume fluctuation using film boiling by a heater for ink ejection is mounted as an ink ejection engine. The inkjet recording apparatus according to the description;
(10) The inkjet recording according to any one of (1) to (8) above, wherein a recording head that uses volume fluctuation caused by a piezoelectric element for ink ejection is mounted as an ink ejection engine. apparatus".

  As will be understood from the following detailed and specific explanation, according to the present invention, by adding a high viscosity property to the ink used, thickening and fixing are performed promptly after landing on the paper, and double-sided printing can be performed. Therefore, even if the paper is reloaded without taking a dry waiting time, it is possible to prevent the secondary transfer by the paper conveying member, and the ink that can be used for double-sided recording by using the special color ink at the same time It is possible to reproduce the saturation and density that is not inferior during single-sided recording, and to use the colorant used in the basic four-color ink to prepare the colorant for the special color ink used. Thus, it becomes possible to add intermediate hue characteristics of the four basic colors, and it is possible to minimize the ink adhesion amount in the intermediate hue expression. By minimizing the ink adhesion amount, secondary transfer can be achieved. Extremely excellent effect that it is possible to further enhance the effect of preventing is exhibited.

  An ink jet recording apparatus as an image recording apparatus according to the present invention will be described with reference to FIGS. 2 is a schematic configuration diagram of the entire mechanism unit of the recording apparatus, and FIG. 3 is a schematic cross-sectional explanatory view of a conveyance belt of the recording apparatus.

This ink jet recording apparatus has an image forming unit (2) and the like inside the apparatus main body (1), and a large number of recording media (3) [hereinafter referred to as "paper"] on the lower side of the apparatus main body (1). ], A sheet feeding tray (4) that can be loaded, a sheet (3) fed from the sheet feeding tray (4) is taken in, and the sheet (3) is conveyed by the conveying mechanism (5) while the image forming unit After recording a required image in (2), the sheet (3) is discharged to a discharge tray (6) mounted on the side of the apparatus main body (1).
In addition, the ink jet recording apparatus includes a duplex unit (7) that can be attached to and detached from the apparatus main body (1). When performing duplex printing, after the printing on one side (front side) is completed, a sheet (3 ) Is fed into the duplex unit (7) while being transported in the reverse direction, reversed and sent to the transport mechanism (5) as the other side (back side) as a printable side, and after the other side (back side) is printed, the paper discharge tray The sheet (3) is discharged to (6).

  Here, the image forming unit (2) slidably holds the carriage (13) on the guide shafts (11, 12), and the main scanning motor (not shown) moves the carriage (13) in the conveyance direction of the sheet (3). Move (main scan) in the orthogonal direction. The sheet conveyance direction and carriage movement are shown in FIG.

  The carriage (13) is equipped with a recording head (14) [details are shown in FIG. 5] composed of a droplet discharge head in which nozzle holes as a plurality of discharge ports for discharging droplets are arranged. An ink cartridge (15) for supplying liquid to the head (14) is detachably mounted. It is also possible to install a sub tank in place of the ink cartridge (15) and supply ink from the main tank to the sub tank.

  Here, as the recording head (14), for example, in addition to the basic four colors of black (K), cyan (C), magenta (M), and yellow (Y), red (R), green (G), An inkjet head for each color that ejects ink droplets of a special color such as blue (B), or a single inkjet head having a plurality of nozzle rows that eject ink droplets of these colors can be used. The number of colors and the order of arrangement are not limited to this.

As an ink jet head constituting the recording head (14), a piezoelectric actuator such as a piezoelectric element, a thermal actuator utilizing phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, a metal phase caused by temperature change, and the like. It is possible to use a shape memory alloy actuator using change, an electrostatic actuator using electrostatic force, or the like as a means for discharging ink.
The paper (3) in the paper feed tray (4) is separated one by one by a paper feed roller (half-moon roller) (21) and a separation pad (not shown), and is fed into the apparatus main body (1) to be transported (5) Is sent to.
The transport mechanism (5) guides the fed paper (3) upward along the guide surface (23a), and feeds the paper (3) fed from the duplex unit (7) along the guide surface (23b). A conveyance guide section (23) for guiding the sheet (3), a conveyance roller (24) for conveying the sheet (3), a pressure roller (25) for pressing the sheet (3) against the conveyance roller (24), and a sheet ( 3) from a guide member (26) for guiding the transport roller (24) to the side, a guide member (27) for guiding the sheet (3) returned during duplex printing to the duplex unit (7), and the transport roller (24). And a pressing roller (28) for pressing the paper (3) to be sent out.

  Further, the transport mechanism (5) is transported between the driving roller (31) and the driven roller (32) in order to transport the recording head (14) while maintaining the flatness of the paper (3). A belt (33), a charging roller (34) for charging the conveying belt (33), a guide roller (35) facing the charging roller (34), and a conveying belt (33) (not shown). Cleaning composed of a guide member (plastic template) guided at a portion facing the image forming section (2) and a porous body as a cleaning means for removing the recording liquid (ink) adhering to the conveying belt (33). It has a roller.

Here, the conveying belt (33) is an endless belt, and is stretched between the driving roller (31) and the driven roller (tension roller) (32) to move forward (in the direction indicated by an arrow in FIG. 2). It is configured so that it can circulate in the paper conveyance direction) and also in the reverse direction.
The conveyor belt (33) has a single-layer configuration, or a two-layer configuration of a first layer (outermost layer) (33a) and a second layer (back layer) (33b) as shown in FIG. It can be. For example, this transport belt (33) is made of a resin layer having a pure thickness of about 40 μm that is not subjected to resistance control, for example, a surface layer that becomes a sheet adsorbing surface formed of ETFE pure material, and a resistance material made of carbon that is the same material as the surface layer. It consists of a controlled back layer (medium resistance layer, earth layer).

The charging roller (34) is disposed so as to come into contact with the surface layer of the conveyor belt (33) and rotate following the rotation of the conveyor belt (33). A high voltage is applied to the charging roller (34) in a predetermined pattern from a high voltage circuit (high voltage power source) (not shown).
Further, on the downstream side from the transport mechanism (5), a paper discharge roller (38) for sending the paper (3) on which the image is recorded to the paper discharge tray (6) is provided.
In the image recording apparatus configured as described above, the transport belt (33) is rotated in the direction of the arrow and is positively charged by coming into contact with the charging roller (34) to which a high applied voltage is applied. In this case, the charging roller (34) is charged at a predetermined charging pitch by switching the polarity at predetermined time intervals.

  Here, when the sheet (3) is fed onto the conveying belt (33) charged to this high potential, the inside of the sheet (3) becomes polarized, and has a polarity opposite to that of the charge on the conveying belt (33). The electric charge is dielectrically formed on the surface of the paper (3) in contact with the belt (33), and the electric charge on the belt (33) and the electric charge which is dielectrically conveyed on the conveyed paper (3) are electrostatically pulled from each other. The sheet (3) is electrostatically attracted to the conveyor belt (33). In this way, the sheet (3) strongly adsorbed to the transport belt (33) is calibrated for warpage and unevenness, and a highly flat surface is formed.

Accordingly, the recording head (14) is driven in accordance with the image signal while the paper (3) is moved around the conveyor belt (33), so that ink droplets that are liquid droplets are placed on the stopped paper (3). Is ejected to record one line, and after a predetermined amount of paper (3) is conveyed, the next line is recorded. When the recording end signal or the signal that the rear end of the paper (3) reaches the recording area is received, the recording operation is ended. When a double-sided printing command is input, the sheet trailing edge detection means monitors the passage of the sheet trailing edge through the recording area and feeds back a monitor signal to the driving power control circuit for the driving roller (31). Reverse transfer at high speed in the direction of the duplex unit (7).
In this way, the sheet (3) on which the image is recorded is discharged to the discharge tray (6) by the discharge roller (38).

Next, the ink to be used will be described.
In order to form an image having high quality and excellent fastness, which is the object of the present invention, it is necessary to satisfy ink jet suitability such as ink absorptivity, image density, beading, and fixability (abrasion resistance). For this purpose, an ink composed of a specific wetting agent, a penetrating agent, and a water-soluble organic solvent using an emulsion in which a colorant (colorant) is contained in polymer fine particles has a higher viscosity than conventional inks. However, the present inventors have found that an image with low surface tension, high saturation, high color density, and little show-through can be obtained in high-speed printing on plain paper.

  In addition, when the color ink having the above-described configuration containing colored fine polymer particles and the black ink having high viscosity and low surface tension similar to the color pigment ink using self-dispersing carbon black as a coloring material (coloring agent) are combined, It has been found that in high-speed printing on plain paper, the black image density is high and the color boundary between black and color is extremely small, the color development of the color is excellent, and the printed image with excellent double-sided printability with little show-through can be obtained. .

  In the present invention, the print quality is remarkably improved by using a high viscosity ink of preferably 5 cp or more, more preferably 6 cp (25 ° C.) or more. In the low viscosity ink of about 3 cp (25 ° C.) used in the conventional ink jet printer, the water content in the ink is about 70% by weight, but in the high viscosity ink of about 6 cp (25 ° C.), it is about 50% by weight or less. Thus, the water evaporation rate when ink droplets land on the paper surface is increased by 2 to 3 times. For this reason, the speed at which high-concentration pigments agglomerate on the paper surface is increased, and bleeding is almost eliminated. FIG. 6 is a comparison diagram with an ink generally used in an ink jet recording apparatus. Although a general dye ink penetrates rapidly, it easily spreads, and in some cases, the dye component reaches the back side. There is. In addition, with low viscosity pigment ink, moisture does not evaporate easily and undried ink remains on the surface of the paper, so there is a risk that the ink may be transferred due to rubbing or contact.

A preferred ink composition in the present invention comprises a coloring agent for printing and water for dispersing the same as essential components, and a wetting agent, a water-soluble organic solvent, an anion or nonionic surfactant added as necessary. It is composed of an agent, an emulsion, a preservative, and a pH adjuster as follows.
[1] Colorant [2] Wetting agent 1 (glycerin)
[3] Wetting agent 2 (selected from 1,3-butanediol, triethylene glycol, 1,6-hexanediol, propylene glycol, 1,5-pentanediol, diethylene glycol, dipropylene glycol, trimethylolpropane, trimethylolethane At least one type)
[4] Water-soluble organic solvent [5] Anion or nonionic surfactant [6] C8-C11 polyol or glycol ether [7] Preservative [8] pH adjuster [9] Pure water The mixing of 1 and 2 is to take advantage of the characteristics of each wetting agent and to adjust the viscosity, but it is not always necessary to use them together. Further, by setting the ink surface tension to 40 mN / m or less, the ink is better wetted to the head member, and the frequency response is improved even with high viscosity ink of 6 cp (25 ° C.) or more, and the ejection stability is remarkably improved. To improve. This low surface tension ink can be achieved by using a polyol or glycol ether having 8 to 11 carbon atoms and an anionic or nonionic surfactant.

Hereinafter, components of each ink used in the present invention will be described.
As a black ink coloring material (coloring agent), for example, carbon black is used. Carbon black produced by a furnace method, a channel method, or the like has a primary particle diameter of 15 to 40 nm, and a specific surface area of 50 to 50 nm by a BET adsorption method. Those having 300 m ² / g and pH ² to 9 are preferably used, and acidic carbon black having a pH of 6 or less is particularly preferred at a high concentration. Further, carbon black treated with hypochlorous acid, carbon black treated with a sulfonating agent, carbon black treated with a diazonium compound and introduced with an anionic dissociating group such as sulfonic acid or carboxylic acid, so-called self-dispersing carbon black is preferred.
Black ink using self-dispersing carbon black is excellent in ejection stability and has excellent image density and character quality when recorded on plain paper, but recording with an ink absorption layer on a substrate such as glossy paper When recording on a medium, the scratch resistance may be insufficient. For the purpose of supplementing the scratch resistance, a resin emulsion may be added to self-dispersing carbon black.

  The resin emulsion means an emulsion in which the continuous phase is water and the dispersed phase is the following resin component. Examples of the resin component in the dispersed phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, and styrene resins.

  According to a preferred embodiment of the present invention, the resin is preferably a polymer having both a hydrophilic part and a hydrophobic part. The particle size of these resin components is not particularly limited as long as an emulsion is formed, but is preferably about 150 nm or less, more preferably about 5 to 100 nm.

These resin emulsions can be obtained by mixing resin particles in water, optionally with a surfactant. For example, an acrylic resin or a styrene-acrylic resin emulsion can be obtained by mixing these resins and a surfactant in water.
The mixing ratio (weight ratio) of the resin component and the surfactant is usually preferably about 10: 1 to 5: 1. When the amount of the surfactant used is less than the above range, it is difficult to form an emulsion, and when it exceeds the above range, the water resistance of the ink composition tends to decrease or the permeability tends to deteriorate, such being undesirable.
In addition, the ratio of the resin and water as the dispersed phase component of the emulsion is suitably in the range of 60 to 400 parts by weight, preferably 100 to 200 parts by weight with respect to 100 parts by weight of the resin.

  Commercially available resin emulsions include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), Boncoat 5454 ( Styrene-acrylic resin emulsion, manufactured by Dainippon Ink Chemical Co., Ltd.), SAE-1014 (styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (acrylic resin emulsion, manufactured by Seiden Chemical Co., Ltd.), etc. can give.

In the present invention, when the resin emulsion is added, the resin component is preferably contained in an amount of 0.1 to 40% by weight, more preferably 1 to 25% by weight of the ink composition.
The resin emulsion has the property of thickening and aggregating, and has the effect of suppressing the penetration of the coloring component into the recording material and further promoting the fixing to the recording material. In addition, depending on the type of resin emulsion, a film is formed on the recording material, which has the effect of improving the scratch resistance of the printed matter.

  The color material for color ink (color material other than black, colorant) is composed of a polymer emulsion in which a water-insoluble or hardly soluble color material is contained in polymer fine particles. In the present invention, “containing a color material” means either or both of a state in which a color material is enclosed in polymer fine particles and a state in which the color material is adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all of the color material blended in the ink of the present invention to be enclosed or adsorbed in the polymer fine particles, and the color material is dispersed in the emulsion as long as the effects of the present invention are not impaired. Also good. The color material is not particularly limited as long as it is water-insoluble or hardly water-soluble and can be adsorbed by the polymer.

In the present invention, water-insoluble or poorly water-soluble means that the coloring material does not dissolve 10 parts by weight or more with respect to 100 parts by weight of water at 20 ° C. This means that no separation or sedimentation is observed. Examples of the coloring material include dyes such as oil-soluble dyes and disperse dyes, pigments, and the like. Oil-soluble dyes and disperse dyes are preferable from the viewpoint of good adsorption and encapsulation, but pigments are preferably used from the light resistance of the obtained image.
Each dye used in the present invention is preferably dissolved in an organic solvent, for example, a ketone solvent in an amount of 2 g / liter or more, preferably 20 to 600 g / liter, from the viewpoint of efficiently impregnating the polymer fine particles. Is more preferable.

  The pigment for color ink is for yellow ink and C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 74, 81, 83 (Disazo Yellow HR), 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153 and the like can be used.

  For magenta and C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48 : 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G Lake), 83, 88, 92, 101 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Dimethylquinacridone), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 2 It can be used 9 like.

For cyan, C.I. I. Pigment Blue 1, 2, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63, etc. can be used.
In addition, the following pigments can be used alone or as a mixture for red, green, and blue as intermediate colors. The following pigments can also be used for the above-mentioned magenta and cyan toning.
C. I. Pigment red 177, 194, 224, C.I. I. Pigment orange 43, C.I. I. Pigment violet 3, 19, 23, 37, C.I. I. Pigment Green 7, 36.
Examples of other suitable colored pigments are described in The Color Index, 3rd edition (The Society of Dyers and Colorist, 1982).
In addition, when using a pigment as a coloring agent, the said dye can also be used together for a complementary color, toning, etc.

The blending amount of the coloring material is preferably about 10 to 200% by weight, particularly preferably about 25 to 150% by weight with respect to the weight of the polymer in relation to the blending amount of the polymer.
As the polymer that forms the polymer emulsion, for example, vinyl polymers, polyester polymers, polyurethane polymers, and the like can be used. Particularly preferred polymers are vinyl polymers and polyester polymers, and polymers disclosed in JP-A Nos. 2000-53897, 2000-53898, and 2001-139849 are exemplified.

According to a preferred embodiment of the present invention, the average particle size of the polymer fine particles containing these coloring materials is most preferably 0.16 μm or less in the ink.
The content of the polymer fine particles in the ink is preferably about 8 to 20% by weight, more preferably about 8 to 12% by weight in terms of solid content.
Regarding the wetting agent and the water-soluble organic solvent, the ink of the present invention uses water as a liquid medium. In order to make the ink have desired physical properties, to prevent the ink from drying, and to improve the dispersion stability. For the purpose of improving, for example, the following water-soluble organic solvents are used. A plurality of these water-soluble organic solvents may be used in combination.

Specific examples of the wetting agent and the water-soluble organic solvent include the following.
Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerol, Polyhydric alcohols such as 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether , Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether Polyhydric alcohol alkyl ethers such as propylene glycol monoethyl ether; Polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl Nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; amides such as formamide, N-methylformamide, N, N-dimethylformamide; monoethanol Amines such as amine, diethanolamine, triethanolamine, monoethylamine, diethylamine and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol; propylene carbonate Over bets is ethylene carbonate.

  Among these organic solvents, diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1,5-pentane Diol, 2-pyrrolidone and N-methyl-2-pyrrolidone are preferred. These are excellent in solubility and prevention of poor jetting characteristics due to water evaporation.

  The other wetting agent preferably contains sugar. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, Examples include lactose, sucrose, trehalose, and maltotriose. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature such as α-cyclodextrin and cellulose.

Moreover, as derivatives of these saccharides, reducing sugars of the saccharides described above (for example, sugar alcohols (represented by the general formula HOCH ₂ (CHOH) _n CH ₂ OH (where n = 2 to 5 represents an integer)) , Oxidized sugars (for example, aldonic acid, uronic acid, etc.), amino acids, thioic acids, etc. Particularly preferred are sugar alcohols, and specific examples thereof include maltitol, sorbit and the like.
The content of these saccharides is suitably 0.1 to 40% by weight, preferably 0.5 to 30% by weight of the ink composition.

The ratio of pigment to wetting agent has a great influence on the stability of ink ejection from the head. If the pigment solid content is high but the amount of the wetting agent is small, water evaporation near the ink meniscus of the nozzle advances and discharge failure occurs.
The blending amount of the wetting agent is preferably 10 to 50% by weight. On the other hand, the polymer fine particles containing the coloring material are preferably 8% by weight or more, more preferably 8 to 20% by weight. The ratio of both solid contents is preferably 0.5 to 6.25, more preferably 2.0 to 6.0, and most preferably 3.0 to 5.0. Ink within this range has very good drying, storage and reliability tests.

  As the surfactant, an anionic surfactant or a nonionic surfactant is used. A surfactant that does not impair the dispersion stability is selected depending on the combination of the type of colorant, the wetting agent, and the water-soluble organic solvent.

  Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate, and the like.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl amines, polyoxyethylene alkyl amides, and the like. Can be mentioned.

Acetylene glycol surfactants are 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl. An acetylene glycol type such as -1-hexyn-3-ol (for example, Surfynol 104, 82, 465, 485 or TG manufactured by Air Products (USA)) can be used, and particularly Surfinol 465, 104 and TG. Indicates good print quality.
The surfactants can be used alone or in combination of two or more.

  In the present invention, wettability to recording paper can be improved by using a surfactant. Preferred surfactants include polyoxyethylene alkyl ether acetates, dialkyl sulfosuccinates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polyoxypropylene block copolymers, and acetylene glycol surfactants. Is mentioned. More specifically, as the anionic surfactant, polyoxyethylene alkyl ether acetate represented by the general formula (I) and / or branched alkyl chain having 5 to 16 carbon chains represented by the general formula (II) The dialkylsulfosuccinic acid having the above formula is used, and by using these, the properties of plain paper are improved, and further, the dissolution / dispersion stability of the colorant is obtained.

（Ｒ_１：炭素数６〜１４の分岐してもよいアルキル基、ｍ＝３〜１２、Ｍ：アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、アルカノールアミン）

(R ₁ : alkyl group having 6 to 14 carbon atoms which may be branched, m = 3 to 12, M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

（Ｒ_２：炭素数５〜１６の分岐したアルキル基、Ｍ：アルカリ金属イオン、第４級アンモニウム、第４級ホスホニウム、アルカノールアミン）

(R ₂ : branched alkyl group having 5 to 16 carbon atoms, M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

  Table 1 specifically shows the surfactants (I) and (II) used in the present invention in free acid form.

  Furthermore, by using lithium ions, quaternary ammonium ions and quaternary phosphonium ions represented by the formula (II ′) as counter ions of the surfactant of the present invention, the surfactant has excellent dissolution stability. Show.

（式中、Ｚは窒素またはリンを表わし、Ｒ_３〜Ｒ_６は独立に水素、炭素数１〜４のアルキル基、またはハロゲン化アルキル基を表わす）

(In the formula, Z represents nitrogen or phosphorus, and R _{3 to} R ₆ independently represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group)

  Preferred nonionic surfactants include polyoxyethylene alkylphenyl ethers represented by general formula (III), orioxyethylene alkyl ethers represented by general formula (IV), and general formulas (V) and (VI). And polyoxyethylene polyoxypropylene alkyl ethers and acetylene glycol surfactants represented by the general formula (VII). By using these together, penetrability can be mentioned as a further synergistic effect, and this reduces ink bleeding at the color boundary, and ink with less character bleeding can be obtained.

（Ｒは分岐してもよい炭素数６〜１４の炭化水素基、ｋ＝５〜２０）

(R is a C 6-14 hydrocarbon group which may be branched, k = 5-20)

（Ｒは分岐してもよい炭素数６〜１４の炭化水素基、ｎ＝５〜２０）

(R is a hydrocarbon group having 6 to 14 carbon atoms which may be branched, n = 5 to 20)

（Ｒ’は炭素数６〜１４の炭化水素基、ｍ≦２０、ｎ≦２０）

(R ′ is a hydrocarbon group having 6 to 14 carbon atoms, m ≦ 20, n ≦ 20)

（Ｒ’は炭素数６〜１４の炭化水素基、ｍ≦２０、ｎ≦２０）

(R ′ is a hydrocarbon group having 6 to 14 carbon atoms, m ≦ 20, n ≦ 20)

（ｐ、ｑ＝０〜４０）

(P, q = 0-40)

The storage stability of the ink can be obtained by setting the pH of the ink to 6 or more, and many copy papers and sticky notes used in the office have a pH of 5 to 6, and these recording papers are used. The ink is discharged from a fine discharge port of 9 to 60 μm and is ejected as a droplet having a weight of 3 to 50 ng at 5 to 20 m / s, and the amount of adhesion in a single color is changed from 1.5 g / m ² to 30 g / m ^2. By recording on a so-called plain paper having a Steecht sizing degree of 3 seconds or more according to the JIS P-8122 test method, it is possible to provide a recording method for forming a high-quality and high-resolution recorded image. However, when the surfactant represented by the general formula (II) is used, it is preferable to adjust the pH to 6 to 9 because if the pH is 9 or more, physical properties change due to decomposition during storage is likely to occur.

  The amount of the surfactant represented by the general formulas (I), (II), (III), (IV), (V), (VI), (VII) that can be used in the present invention is 0.05. It is possible to provide the desired penetrability for the ink properties required by the printer system between -10% by weight. Here, if it is less than 0.05% by weight, bleeding occurs at the boundary between the two-color overlapping portions in any case, and if it is added more than 10% by weight, the compound itself may be easily precipitated at a low temperature, resulting in poor reliability. Become.

  The surface tension in the present invention is an index indicating the permeability to paper. In particular, the surface tension indicates the dynamic surface tension in a short time of 1 second or less after the surface is formed, and is different from the static surface tension measured by the saturation time. . As a measuring method, any method can be used as long as it can measure a dynamic surface tension of 1 second or less by a conventionally known method described in JP-A-63-131237. In the present invention, a Wilhelmy type suspension plate type surface is used. Measurement was performed using a tensiometer. When the value of the surface tension is preferably 40 mN / m or less, more preferably 35 mN / m or less, excellent fixing properties and drying properties can be obtained.

The polyol or glycol ether having 8 to 11 carbon atoms used in the present invention is a partially water-soluble polyol and / or glycol having a solubility of preferably less than 0.1 to 4.5% by weight in water at 25 ° C. By adding 0.1 to 10.0% by weight, preferably 0.1 to 10.0% by weight based on the total weight of the recording ink, the wettability of the ink to the thermal element is improved. Frequency stability is obtained.
The following are mentioned as these preferable examples.

[1] Solubility of 2-ethyl-1,3-hexanediol: 4.2% by weight (20 ° C.)
[2] Solubility of 2,2,4-trimethyl-1,3-pentanediol: 2.0% by weight (25 ° C.)
A penetrant composed of a polyol or glycol ether having a solubility of less than 0.1 to 4.5% by weight in water at 25 ° C. has an advantage that the permeability is very high instead of low solubility. Therefore, a highly penetrating ink can be obtained by combining a penetrant having a solubility of less than 0.1 to 4.5% by weight in water at 25 ° C. with another solvent or another surfactant. It becomes possible to create.

Conventionally known additives can be added to the ink of the present invention in addition to the colorant, solvent, surfactant and the like.
For example, as a preservative and antifungal agent, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol and the like can be used.

As the pH adjuster, any substance can be used as long as the pH can be adjusted to 7 or more without adversely affecting the ink to be prepared.
Examples thereof include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium. Examples thereof include carbonates of alkali metals such as hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate.

  Furthermore, as a chelating reagent, for example, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate and the like can be used.

Furthermore, as a rust preventive agent, for example, acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite and the like can be used.
Depending on the purpose, a water-soluble ultraviolet absorber, a water-soluble infrared absorber, or the like can be added.

Examples and Comparative Examples of the present invention are shown below, but the present invention is not limited to these.
<Create ink>
Colorant Example 1
Preparation of phthalocyanine pigment-containing polymer fine particle dispersion Preparation Example 3 of JP-A No. 2001-139849 was additionally tested, and specifically, the following operation was performed.
(1) Preparation of polymer solution After thoroughly substituting nitrogen gas into a 1 L volume flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel, 11.2 g of styrene, acrylic acid 2 0.8 g, 12.0 g of lauryl methacrylate, 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer (manufactured by Toa Gosei Co., Ltd., trade name: AS-6) and 0.4 g of mercaptoethanol are charged to 65 ° C. did.
Next, styrene 100.8 g, acrylic acid 25.2 g, lauryl methacrylate 108.0 g, polyethylene glycol methacrylate 36.0 g, hydroxyethyl methacrylate 60.0 g, styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6) ) A mixed solution of 36.0 g, mercaptoethanol 3.6 g, azobisdimethylpareronitrile 2.4 g and methyl ethyl ketone 18 g was dropped into the flask over 2.5 hours.

After completion of dropping, a mixed solution of 0.8 g of azobisdimethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 g of azobisdimethylvaleronitrile was added, and further aging was performed for 1 hour.
After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution having a concentration of 50% by weight.

(2) Preparation of aqueous dispersion of polymer fine particles 28 g of polymer solution obtained in (1) above, phthalocyanine pigment (manufactured by Dainippon Ink & Chemicals, Inc., trade name: TGR-SD) 26 g, 1 mol / L of water After sufficiently stirring 13.6 g of an aqueous potassium oxide solution, 20 g of methyl ethyl ketone and 30 g of ion-exchanged water, the mixture was kneaded 20 times using a three-roll mill. The obtained paste was put into 200 g of ion-exchanged water and sufficiently stirred, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a blue polymer fine particle dispersion.
The average particle diameter (D50%) of the polymer fine particles measured by Microtrac UPA was 93 nm.

Colorant Example 2
Preparation of dimethylquinacridone pigment-containing polymer fine particle dispersion A red-purple polymer fine particle dispersion was obtained in the same manner as in Colorant Example 1 except that the phthalocyanine pigment of Colorant Example 1 was changed to Pigment Red 122. The average particle diameter (D50%) of the polymer fine particles measured by Microtrac UPA was 127 nm.

Colorant Example 3
Preparation of Monoazo Yellow Pigment-Containing Polymer Fine Particle Dispersion A yellow polymer fine particle dispersion was obtained in the same manner as Colorant Example 1 except that the phthalocyanine pigment of Colorant Example 1 was changed to Pigment Yellow 74. The average particle diameter (D50%) of the polymer fine particles measured by Microtrac UPA was 76 nm.

Colorant Example 4
Carbon black dispersion treated with diazo compound (self-dispersion type)
100 g of carbon black having a surface area of 230 m ² / g and a DBP oil absorption of 70 ml / 100 g and 34 g of p-amino-N-benzoic acid are mixed and dispersed in 750 g of water, and 16 g of nitric acid is added dropwise thereto and stirred at 70 ° C. did. After 5 minutes, a solution of 11 g of sodium nitrite dissolved in 50 g of water was added, and the mixture was further stirred for 1 hour. The resulting slurry was diluted 10 times and centrifuged to remove coarse particles, the pH was adjusted with diethanolamine to pH 8-9, desalted and concentrated with an ultrafiltration membrane, and a carbon black dispersion having a pigment concentration of 15% by weight. It was. This was made into carbon black dispersion 1 with a polypropylene 0.5 μm filter. The average particle size (D50%) measured by Microtrac UPA was 99 nm.

Colorant Example 5
Carbon black dispersion treated with hypochlorous acid (self-dispersion type)
After mixing 300 g of commercially available acidic carbon black having a pH of 2.5 (trade name Monarch 1300, manufactured by Cabot Corporation) with 1000 ml of water, 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise, and 100 to 105 ° C. For 8 hours. To this solution, 100 g of sodium hypochlorite (effective chlorine concentration 12%) was further added and dispersed for 3 hours with a horizontal disperser. The resulting slurry was diluted 10 times with water, pH was adjusted with lithium hydroxide, desalted and concentrated with an ultrafiltration membrane to a conductivity of 0.2 mS / cm, and a carbon black dispersion having a pigment concentration of 15% It was. Coarse particles were removed by centrifugation, and further filtered through a 1 μm nylon filter to obtain a carbon black dispersion 2. The total content of Fe, Ca and Si was 100 ppm or less as measured by ICP. The chlorine ion concentration was also set to 10 ppm or less. The average particle size (D50%) measured by Microtrac UPA was 95 nm.

Ink a
An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 9. Then, it filtered with the membrane filter with an average hole diameter of 0.8 micrometer, and obtained the ink composition.
Colorant Example 4 Carbon black dispersion 1 treated with diazo compound 1 8.0% by weight
(As solids)
1,4-butanediol 22.5% by weight
Glycerin 7.5% by weight
N-methyl-2-pyrrolidone 2.0% by weight
Surfactant of specific example (II-2) 2.0% by weight
2,2,4-Trimethyl-1,3-pentanediol 2.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink b
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Colorant Example 1 Phthalocyanine pigment-containing polymer fine particle dispersion 15.0% by weight
(As solids)
1,5-pentanediol 15.0% by weight
Glycerin 15.0% by weight
N-hydroxyethyl-2-pyrrolidone 2.0% by weight
Surfactant of specific example (II-3) 2.0% by weight
2-ethyl-1,3-hexanediol 2.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink c
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Colorant Example 2 Dimethylquinacridone pigment-containing polymer fine particle dispersion 15.0% by weight
(As solids)
1,6-hexanediol 22.5% by weight
Glycerin 7.5% by weight
2-pyrrolidone 3.0% by weight
Surfactant of specific example (II-4) 2.0% by weight
2,2,4-Trimethyl-1,3-pentanediol 2.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink d
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with sodium hydroxide.
Colorant Example 3 Monoazo yellow pigment-containing polymer fine particle dispersion 15.0% by weight
(As solids)
2-methyl-2,4-pentanediol 22.5% by weight
Glycerin 7.5% by weight
N-methyl-2-pyrrolidone 5.0% by weight
Surfactant represented by formula (III) (R = n-hexyl group, k = 5) 2.0% by weight
2-ethyl-1,3-hexanediol 2.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink e
An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 9. Then, it filtered with the membrane filter with an average hole diameter of 0.8 micrometer, and obtained the ink composition.
Colorant Example 1 Phthalocyanine pigment-containing polymer fine particle dispersion 5.0% by weight
(As solids)
Ethylene glycol 15.0% by weight
Glycerin 5.0% by weight
2-pyrrolidone 2.0% by weight
ECTD-3NEX (anionic surfactant manufactured by Nikko Chemicals) 1.0% by weight
2-ethyl-1,3-hexanediol 2.0% by weight
Acrylic resin emulsion 3.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink f
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Colorant Example 2 Polymer fine particle dispersion containing dimethylquinacridone pigment 6.0% by weight
(As solids)
Diethylene glycol 15.0% by weight
Glycerol 5.0% by weight
N-methyl-2-pyrrolidone 2.0% by weight
ECTD-6NEX (anionic surfactant manufactured by Nikko Chemicals) 1.0% by weight
2,2,4-Trimethyl-1,3-pentanediol 2.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink g
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Colorant Example 3 Monoazo yellow pigment-containing polymer fine particle dispersion 5.0% by weight
(As solids)
Triethylene glycol 15.0% by weight
Glycerin 5.0% by weight
N-hydroxyethyl-2-pyrrolidone 2.0% by weight
Surfactant represented by general formula (IV) (R = C13H27, n = 8) 1.0% by weight
2-ethyl-1,3-hexanediol 2.0% by weight
Acrylic resin emulsion 3.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink h
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Colorant Example 4 Carbon black dispersion 1 treated with diazo compound 1 4.0% by weight
(As solids)
Ethylene glycol 15.0% by weight
Glycerin 5.0% by weight
2-pyrrolidone 2.0% by weight
ECTD-6NEX (anionic surfactant manufactured by Nikko Chemicals) 1.0% by weight
2,2,4-Trimethyl-1,3-pentanediol 2.0% by weight
Proxel LV (preservative) 0.2% by weight
Remaining amount of ion-exchanged water

Ink i
An ink composition was prepared in the same manner as ink a except that the following composition was used, and the pH was adjusted to 9 with lithium hydroxide.
Colorant Example 5 Carbon black dispersion 2 treated with hypochlorous acid 8.0% by weight
(As solids)
Acrylic resin emulsion 3.0% by weight
(As solids)
Triethylene glycol 15.0% by weight
Glycerol 10.0% by weight
N-hydroxyethylpyrrolidone 5.0% by weight
1.0% by weight of surfactant of specific example (I-2)
2-ethyl-1,3-hexanediol 1.0% by weight
Sodium dehydroacetate 0.2% by weight
Residual amount of ion-exchanged water In addition, the concentration of the color material solids (pigment and emulsion) of the ink composition of inks a to i and the wetting agent

  Table 2 shows the density and ink viscosity.

  The high-viscosity ink prepared in this way rapidly increases in viscosity after drying on the paper → drying → fixing, so even if you reload the paper immediately after printing on the surface, Transfer to a contact roller or the like is less likely to occur. As a result of performing double-sided recording with the prototype high-viscosity ink and the recording apparatus shown in FIG. 2, in the applicant's environment, the pressing roller (28) in FIG. Double-sided recording without secondary transfer could be performed up to the ink adhesion amount.

  An adhesion amount of 1.2 times that of a solid monochrome image can be said to ensure an adhesion amount almost sufficient for color image expression. However, compared with an image of single-sided recording that does not require secondary transfer, the secondary color The secondary colors and tertiary colors here are four colors including the basic colors of printing, cyan, magenta, yellow, and black. Individual basic colors can be reproduced to a solid color, but the secondary colors of red, green, blue, and the dark colors mixed with intermediate and black colors should be divided by the number of colors with 120% ink adhesion. Therefore, the reproduced image has low saturation and density.

  Therefore, in the present invention, double-sided image quality not inferior to single-sided recording is realized without reducing the recording speed by using special color ink having high viscosity characteristics together with double-sided recording. For example, when red is expressed with a basic four-color recording device, it is necessary to mix magenta and yellow ink and reproduce the red on the paper. To obtain a satisfactory red, it is about 150 to 200% * Of ink is required (* depends on paper type). This is the amount of adhesion at which secondary transfer can occur sufficiently during double-sided recording, but by mounting red ink in advance, recording can be performed with a single color, that is, 100% ink adhesion. High-speed double-sided recording can be realized.

In addition, as the colorant of the special color ink, the special color may be reproduced by mixing the colorants for the four basic colors mentioned above, or a colorant capable of expressing the special color alone may be used. Good. However, since each color ink does not necessarily realize the desired color tone, it is preferable to prepare the special color ink by mixing the colorants used for the four basic colors. When the colorants used for the basic color are mixed with each other, the intermediate color characteristic of the basic color is obtained as shown in FIG. 7 (Red <1> in which yellow and magenta are on the a * and b * axes). When reproducing colors between basic colors and spot colors, it is possible to make adjustments with a minimum adhesion amount that equalizes the adhesion amount in either hue direction (special color inks that are biased in either basic color direction). Same as the secondary color expression when used (Red <2>, where magenta deviates significantly from the b * axis than yellow in the figure), the one with the larger hue difference to express the desired saturation and density This is because it is necessary to increase the amount of adhering).

  The above is the contents of the present invention. However, high-speed high-quality double-sided recording, which is the aim of the present invention, cannot be realized by using only special color inks or high-viscosity inks. By combining the two elements, the target effect can be realized for the first time. The present invention can be realized in any of so-called piezo-type ink jet recording apparatuses that change volume fluctuations due to piezoelectric elements into ink jetting energy and so-called thermal type ink jet recording apparatuses that change volume fluctuations using film boiling by a heater into ink jetting energy. It is a possible technology.

FIG. 6 is a diagram illustrating secondary transfer at the time of paper reloading in the present invention. 1 is a schematic configuration diagram of a mechanism unit of an ink jet recording apparatus as an embodiment of an image recording apparatus according to the present invention. FIG. 2 is a plan view of a principal part of a mechanism part of an ink jet recording apparatus as an embodiment of an image recording apparatus according to the present invention. FIG. 6 is a diagram illustrating the relationship between the operation of the recording head unit and the main and sub scanning directions in the present invention. 1 is a schematic diagram showing a head configuration of an ink jet recording apparatus according to the present invention. It is the figure which showed the mode of penetration by the kind of ink in this invention. It is a figure explaining the ratio of the ink adhesion amount by the composition of the special color in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus body 2 Image formation part 3 Recording medium (paper)
4 Feeding tray 5 Conveying mechanism 6 Discharging tray 7 Duplex unit 11 Guide shaft 12 Guide shaft 13 Carriage 14 Recording head 15 Ink cartridge 21 Paper feeding roller (half-moon roller)
23 conveyance guide portion 23a guide surface 23b guide surface 24 conveyance roller 25 pressure roller 26 guide member 27 guide member 28 pressing roller 31 driving roller 32 driven roller 33 conveyance belt 33a first layer (outermost layer)
33b Second layer (back layer)
34 Charging roller 35 Guide roller 38 Paper discharge roller

Claims (10)

In an ink jet recording apparatus equipped with a head unit provided with a nozzle for ejecting each color ink necessary for color printing onto the surface of the paper, and performing recording with ink droplets ejected from the head unit,
It contains at least a colorant, a wetting agent, a polyol or glycol ether having 8 or more carbon atoms, an anionic or nonionic surfactant, a water-soluble organic solvent, water, a colorant concentration of 5% by weight or more, and an ink viscosity of 6 cps ( In addition to the basic four colors of cyan, magenta, yellow, and black, at least one special color ink of red, green, and blue is mounted on the ink with the characteristics of 25 ° C or higher, and automatic double-sided An ink jet recording apparatus that performs double-sided recording using a paper conveyance mechanism that supports printing.   2. The ink jet recording apparatus according to claim 1, wherein the colorant is water-insoluble or hardly soluble.   The ink jet recording apparatus according to claim 1, wherein the at least one kind of ink contains the colorant in the form of colored polymer fine particles colored with the colorant.   The polyol or glycol ether having 8 or more carbon atoms comprises 2-ethyl-1,3-hexanediol or 2,2,4-trimethyl-1,3-pentanediol. 4. The ink jet recording apparatus according to any one of 3 above. The anionic surfactant is at least one selected from surfactants represented by the following general formulas (I), (II), (III), (IV), (V), (VI) and (VII) The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is provided.

(R ₁ : alkyl group having 6 to 14 carbon atoms which may be branched, m = 3 to 12, M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

(R ₂ : branched alkyl group having 5 to 16 carbon atoms, M: alkali metal ion, quaternary ammonium, quaternary phosphonium, alkanolamine)

(R is a C 6-14 hydrocarbon group which may be branched, k = 5-20)

(R is a hydrocarbon group having 6 to 14 carbon atoms which may be branched, n = 5 to 20)

(R ′ is a hydrocarbon group having 6 to 14 carbon atoms, m ≦ 20, n ≦ 20)

(R ′ is a hydrocarbon group having 6 to 14 carbon atoms, m ≦ 20, n ≦ 20)

(P, q = 0-40)   6. The ink jet recording apparatus according to claim 1, wherein the wetting agent is contained in the ink in an amount of 10 to 50% by weight. The inkjet recording apparatus according to claim 1, wherein the wetting agent is represented by the following general formula.

(In the above formula, n represents an integer of 5 to 8.)   In the special color ink, the colorant is a mixed colorant of the basic colorant used in the above-described four-color basic inks, and the hue characteristics of the mixed colorant are fundamental to each of the basic colorants to be mixed. 8. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is in the middle of a color.   The ink jet recording apparatus according to any one of claims 1 to 8, wherein a recording head that uses volume fluctuation utilizing film boiling by a heater for ink ejection is mounted as the ink ejection engine. The ink jet recording apparatus according to any one of claims 1 to 8, wherein a recording head that uses volume fluctuation caused by a piezoelectric element for ink ejection is mounted as an ink ejection engine.

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