JP2009035629A - Ink-jet ink, ink-jet recording method, ink cartridge, recording unit and ink-jet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet ink which suppresses deposition of a pigment and a dispersant in the ink on a face with a discharge outlet by paying attention to state variation of ink sticking to the face with the discharge hole, and which suppresses faulty discharge by suppression of change in the surface characteristics of the face with the discharge hole. <P>SOLUTION: The ink-jet ink comprises water, a color material, a water-soluble organic solvent and a surfactant, and is characterized in that, when a rate (%) of evaporation of the ink defined by the following expression (1) is in a range of 10-40%, a content of the surfactant in the ink is always not less than the critical micelle concentration of the surfactant; (1) (rate (%) of evaporation of ink)=[((initial mass of ink)-(mass of ink after evaporation))/(initial mass of ink)×100]. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet ink, an inkjet recording method, an ink cartridge, a recording unit, and an inkjet recording apparatus.

  In recent years, images formed using inkjet inks are required to have the same level of fastness (light resistance and gas resistance) as silver salt photographs. Under such circumstances, it is known that an image having excellent fastness can be obtained by using an ink containing a pigment (pigment ink) as a coloring material. However, when ink containing a pigment as a coloring material is ejected by an ink jet recording apparatus, the following problems may occur. Specifically, the surface characteristics of the face surface change due to the pigment or dispersant in the ink adhering to the surface (hereinafter referred to as the “face surface”) having an ejection port for ejecting ink in the recording head. As a result, a discharge failure may occur easily. In addition, when ejection failure occurs, landing deviation or the like that occurs at a position different from the position where the ink is intended may occur, and image quality may deteriorate.

For such a problem, the surface tension of the ink is regulated, and the contact angle between the evaporated ink obtained by evaporating 20% or more of the volatile component and the face surface is controlled to make the face surface wet. It has been proposed to improve ejection defects (see Patent Document 1).
JP 2004-269800 A

  However, according to the study by the present inventors, it has been found that there is a case where the conventional method cannot sufficiently solve the ejection failure caused by the change in the surface characteristics of the face surface. The present inventors presume this reason as follows. Specifically, since ink or the like is evaporated from the ink attached to the face surface as time passes, the ink characteristics are constantly changing. However, this is because the conventional method does not take into consideration that the characteristics of the ink adhering to the face surface change with time.

  Accordingly, an object of the present invention is to suppress the adhesion of the pigment or the dispersant in the ink to the face surface by focusing on the change in the state of the ink attached to the face surface, and to suppress the change in the surface characteristics of the face surface. An object of the present invention is to provide an inkjet ink that suppresses the occurrence of ejection failure. Another object of the present invention is to provide an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using the ink jet ink.

  The above object is achieved by the present invention described below. That is, the ink-jet ink according to the present invention is an ink-jet ink containing at least water, a colorant, a water-soluble organic solvent, and a surfactant, and has an ink evaporation rate of 10% to In the range of 40%, the content of the surfactant in the ink always reaches or exceeds the critical micelle concentration of the surfactant.

  An ink jet recording method according to another embodiment of the present invention is an ink jet recording method in which ink is ejected by an ink jet method to perform recording on a recording medium, wherein the ink is the ink jet ink described above. To do.

  An ink cartridge according to another embodiment of the present invention is an ink cartridge provided with an ink storage portion for storing ink, wherein the ink is the ink jet ink described above.

  According to another embodiment of the present invention, there is provided a recording unit comprising an ink storage portion for storing ink and a recording head for discharging ink, wherein the ink is the ink jet ink described above. It is characterized by being.

  An ink jet recording apparatus according to another embodiment of the present invention is an ink jet recording apparatus having an ink containing portion for containing ink and a recording head for ejecting ink. It is characterized by being ink.

  By using the ink-jet ink of the present invention, it is possible to suppress sticking of a pigment or a dispersant to the face surface as compared with a conventional pigment ink. As a result, it is possible to suppress ejection failure caused by a change in the surface characteristics of the face surface, and to suppress landing deviation. According to another embodiment of the present invention, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using the ink jet ink can be provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention. In the following description, “ink-jet ink” may be simply referred to as “ink”.

  There are various possible causes of ink landing deviation due to changes in the surface characteristics of the face surface (hereinafter referred to as face wetting). For example, the following phenomenon can be considered. After the mist generated when ejecting ink (fine ink droplets accompanying the main ink droplets) adheres to the face surface, the components in the mist evaporate, causing the pigment and dispersant to dry out. As a result, it is considered that the water repellency of the face surface is lowered. When ink is continuously ejected from the recording head at a high speed while the water repellency of the face surface of the recording head is lowered, the residue of the ink droplets ejected first is ejected before the ejection of the next ink droplet ejected. Difficult to return inside. As a result, the adhering matter in the vicinity of the discharge port is connected to the ink that is about to return to the nozzle. In other words, a phenomenon occurs in which these deposits pull ink droplets and the ink ejection direction is distorted, that is, the straightness of the ink droplets is hindered.

  In order to suppress the above phenomenon, the present inventors have prepared and studied inks in which the physical properties of the ink, the types of water-soluble organic solvents and resins used in the ink, and the characteristics thereof are variously changed. It was. As a result, it was found that the face wetting of the recording head tends to be suppressed as the content of the surfactant in the ink increases.

Therefore, the present inventors prepared several types of inks classified into the following three types as shown below, and conducted further detailed studies.
1. 1. Ink in which the surfactant content in the ink does not reach the critical micelle concentration at all. 2. Ink in which the surfactant content in the ink is in the vicinity of the critical micelle concentration Ink whose surfactant content in the ink far exceeds the critical micelle concentration As a result of these studies, a surfactant with a content far exceeding the critical micelle concentration was obtained. It has been found that even when the ink is contained, the landing of the ink due to the wet face may occur. On the other hand, it was also found that even when the surfactant content does not reach the critical micelle concentration at all, the ink landing due to the wetting of the face may not occur. From these facts, it was found that increasing the content of the surfactant in the ink does not necessarily have a positive effect on the problem of face wetting.

  The present inventors conducted a study again based on the above results. As a result, it has been concluded that there is a main cause of the above phenomenon in the process of evaporating the components constituting the ink.

Therefore, the present inventors do not consider the state of the surfactant in the ink that is filled in the ink cartridge, that is, the component in which the ink is hardly evaporated, but the interface in the ink that adheres to the face surface as a mist. Further investigation was conducted focusing on the state of the activator. Specifically, several types of ink classified into the following two types were prepared and examined.
4). 4. Ink in which the surfactant content in the ink reaches a critical micelle concentration in the process of evaporating the components constituting the ink. Ink in which the content of the surfactant in the ink does not reach the critical micelle concentration in the process of evaporating the components constituting the ink As a result of the above examination, the following was found. In the process in which the evaporation of the ink further proceeds from the time when the evaporation rate of the ink adhering to the face surface reaches 10%, the content of the surfactant in the ink is always above the critical micelle concentration. It was found that the landing of ink due to wet face was suppressed.

  The ink evaporation rate in the present invention is obtained by the following equation.

  The reason why the above effect is obtained is not clear, but the present inventors presume as follows. As a result of the examination by the present inventors, the mist immediately after adhering to the face surface has components constituting the ink in consideration of the size of the droplet and the time from ink ejection from the nozzle until adhering to the face surface. It was found that about 10% had evaporated. For this reason, in order to suppress the aggregation of the pigment on the face surface and the fixation due to the drying of the dispersing agent, the ink is evaporated in the process in which the ink evaporation proceeds after the ink evaporation rate reaches about 10%. It is necessary to continuously suppress aggregation and drying of the dispersant.

  In the ink droplets where an excessive amount of surfactant is always present, the adsorption reaction of the surfactant to the pigment frequently occurs. As a result, the solubility of the pigment and the dispersant can be improved in a pseudo manner, and aggregation can be suppressed. The frequency at which this adsorption reaction occurs can be achieved by always setting the content of the surfactant in the ink to a critical micelle concentration or more. For this reason, it is presumed that the content of the surfactant must always be equal to or higher than the critical micelle concentration from the time when the ink evaporation rate reaches 10% while the ink evaporation proceeds thereafter. .

  In addition, the present inventors have a characteristic that, in the process of evaporating the components constituting the ink, the surfactant content in the ink becomes equal to or higher than the critical micelle concentration after being reduced below the critical micelle concentration. An ink was prepared and the obtained ink was examined. As a result, it has been found that even when ink having the above characteristics is used, the state of ink landing caused by face wetting occurs at the same level as conventional ink. The present inventors presume the cause of such a phenomenon as follows.

  When the content of the surfactant in the ink becomes equal to or lower than the critical micelle concentration, the dispersion destruction of the pigment proceeds rapidly, and the aggregation of the pigment occurs. Even when the surfactant content in the ink reaches the critical micelle concentration again, the effect of dispersing the pigment again is manifested. This is considered to be because the state is returned to the dispersed state.

  This fact also demonstrates the importance of the surfactant content always reaching the critical micelle concentration from the point when the ink evaporation rate reaches 10% or more and then the ink evaporation proceeds. It can be said that it shows.

  From the above, in the present invention, the state in the process of evaporating the components constituting the ink is important, not the ink filled in the ink cartridge. As described above, from the point when the evaporation rate of the ink reaches 10%, it is necessary that the content of the surfactant thereafter is always the critical micelle concentration.

  As a result of further studies by the present inventors, the surfactant content in the ink is always greater than or equal to the critical micelle concentration while the ink evaporation rate is in the range of 40% from the ink in the initial state. As a result, it was found that ink landing due to face wetting was substantially suppressed. Therefore, when the ink evaporation rate is in the range of 10% to 40%, the surfactant content in the ink is always higher than the critical micelle concentration, so that the landing of the ink due to face wetting is substantially suppressed. can do.

  The critical micelle concentration in the present invention is the content of the surfactant when the surface tension of the liquid does not change when the content of the surfactant in the liquid is increased. Whether the content of the surfactant in the ink is equal to or higher than the critical micelle concentration can be verified by checking that the surface tension of the ink containing the surfactant is equal to or lower than the critical micelle concentration of the surfactant.

  As a result of further investigation by the present inventors, it was found that the ink landing dripping due to wetness of the face can be remarkably suppressed when the ink contains a water-soluble organic solvent having low solubility of the surfactant. The present inventors presume the reason why such an effect is obtained as follows.

  As described above, the surfactant whose content reaches the critical micelle concentration or more acts on the pigment to be aggregated and has an effect of suppressing the aggregation. At this time, since the ink contains a water-soluble organic solvent having low solubility of the surfactant, the orientation speed and orientation frequency of the surfactant to the pigment can be increased. When the water-soluble organic solvent in the ink contains only the water-soluble organic solvent that can easily dissolve the surfactant, the surfactant is dissolved in the water-soluble organic solvent. In such a case, the effect that should be obtained when the surfactant content reaches the critical micelle concentration also affects the dissolution of the surfactant in the water-soluble organic solvent, thereby obtaining the effect of the present invention. It may not be possible. However, in the case of containing a water-soluble organic solvent having low solubility of the surfactant, the surfactant is hardly adsorbed on the pigment because the surfactant is hardly dissolved in the water-soluble organic solvent. It is considered that the effect of can be obtained more remarkably.

  In the present invention, specific examples of the water-soluble organic solvent that can be used as the water-soluble organic solvent having low surfactant solubility include ethylene glycol, diethylene glycol, 1,5-pentanediol, and 1,2,6- Examples include hexanetriol.

<Ink>
(Surfactant)
The ink of the present invention needs to contain a surfactant. The type of surfactant is not particularly limited, and anionic surfactants, nonionic surfactants, and the like, and polymerization surfactants having both anionic and nonionic properties may also be used. it can.

  However, it is more preferable to use a nonionic surfactant from the viewpoint of the effect of the present invention. Specifically, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenols, acetylene glycol compounds, acetylene glycol ethylene oxide adducts, and the like are preferably used as the nonionic surfactant. The surfactants listed above are more preferably those that are in a liquid state in the environment where the ink is used.

(Aqueous medium)
An aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used for the ink. It is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions. The water content (% by mass) in the ink is 10.0% by mass or more and 90.0% by mass or less, and further 30.0% by mass or more and 80.0% by mass or less based on the total mass of the ink. Is preferred.

  The content (% by mass) of the water-soluble organic solvent in the ink is 3.0% by mass or more and 50.0% by mass or less, and further 3.0% by mass or more and 40.0% by mass or less based on the total mass of the ink. It is preferable that As the water-soluble organic solvent, for example, the following can be used.

  Alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane. Polyalkylene glycols such as polyethylene glycol and polypropylene glycol. Alkylene glycols having 2 to 6 carbon atoms in the alkylene group, such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, and diethylene glycol; Glycerin. Alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether. N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Of these, polyhydric alcohols such as diethylene glycol and alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether are preferred.

(Color material)
Any colorant can be used as long as it is used for conventional inks. In the present invention, it is preferable to use a pigment as the coloring material. For the pigment, use a resin dispersion type pigment (resin dispersion type pigment) that disperses the pigment using a dispersant, or a self dispersion type pigment (self dispersion type pigment) in which a hydrophilic group is introduced on the surface of the pigment particles. Can do. Also, pigments (resin-bonded self-dispersing pigments) in which organic groups containing a polymer are chemically bonded to the surface of pigment particles, microcapsule types that enhance the dispersibility of pigments and can be dispersed without using dispersants, etc. Pigments and the like can also be used.

  As the pigment, carbon black or an organic pigment is preferably used. The pigment content (% by mass) in the ink is 0.1% by mass or more and 10.0% by mass or less, more preferably 0.1% by mass or more and 6.0% by mass or less, based on the total mass of the ink. preferable.

  For black ink, it is preferable to use carbon black such as furnace black, lamp black, acetylene black and channel black as a pigment. Specifically, for example, the following commercially available products can be used. Ray Van: 7000, 5750, 5250, 5000ULTRA, 3500, 2000, 1500, 1250, 1200, 1190ULTRA-II, 1170, 1255 (above, Colombia). Black Pearls: L, Legal: 400R, 330R, 660R, Moguls: L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, 2000, Vulcan: XC-72R (above, manufactured by Cabot). Color Black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 6, 5, 4A, 4 (above, manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical) and the like. Carbon black newly prepared for the present invention can also be used. Of course, the present invention is not limited to these, and any conventional carbon black can be used. Further, the material is not limited to carbon black, and magnetic fine particles such as magnetite and ferrite, titanium black, and the like may be used as a pigment.

  Specifically, for example, the following can be used as the organic pigment. Water-insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow and pyrazolone red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon. Phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green. Quinacridone pigments such as quinacridone red and quinacridone magenta. Perylene pigments such as perylene red and perylene scarlet. Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Indigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments. Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, etc.

  Moreover, when an organic pigment is shown by a color index (CI) number, the following can be used, for example. C. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 97, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 150, 151, 153 154, 166, 168, 180, 185, etc. C. I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61, 71, etc. C. I. Pigment Red: 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168 and the like. 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272, etc. C. I. Pigment violet: 19, 23, 29, 30, 37, 40, 50, and the like. C. I. Pigment Blue: 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, and the like. C. I. Pigment Green: 7, 36 etc. C. I. Pigment Brown: 23, 25, 26, etc.

(Resin dispersion type pigment)
In the present invention, in order to disperse the hydrophobic pigment as mentioned above in an aqueous medium, a resin-dispersed pigment using a so-called dispersant such as a surfactant or a resin can be used.

  As the surfactant, an anionic surfactant or a nonionic surfactant can be used. As the anionic surfactant, for example, the following can be used. Fatty acid salt, alkyl sulfate ester salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene sulfonate formalin condensate, polyoxyethylene alkyl sulfate ester salt and the like. Or these substituted derivatives. As the nonionic surfactant, for example, the following can be used. Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, etc. Polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, oxyethyleneoxypropylene block polymer and the like. Or these substituted derivatives.

  As the resin, for example, a polymer composed of the following monomers can be used. Styrene, vinyl naphthalene, aliphatic alcohol ester of α, β-ethylenically unsaturated carboxylic acid, acrylic acid, maleic acid, itaconic acid, fumaric acid, vinyl acetate, vinyl alcohol, vinyl pyrrolidone, acrylamide, or derivatives thereof. In addition, it is preferable that at least one monomer constituting the polymer is a hydrophilic monomer, and a block copolymer, a random copolymer, a graft copolymer, or a salt thereof may be used. good.

(Self-dispersing pigment)
In the present invention, it is possible to use a self-dispersing pigment that has improved dispersibility of the pigment itself and is dispersible without using a dispersant or the like. Self-dispersing pigments include those in which a hydrophilic group is chemically bonded to the surface of pigment particles directly or through other atomic groups. For example, the hydrophilic group introduced on the surface of the pigment particle includes —COOM, —SO ₃ M, and —PO ₃ HM ₂ (wherein M represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium). And the like selected from the group consisting of: Examples of the other atomic group include an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group.

  In addition, a self-dispersing pigment of the surface oxidation treatment type can also be used. Examples of such self-dispersing pigments include the following. Obtained by a method of oxidizing carbon black with sodium hypochlorite, a method of oxidizing carbon black by ozone treatment in water, a method of wet oxidation with an oxidizing agent after ozone treatment and modifying the surface of carbon black, etc. Is mentioned.

[Microcapsule type pigment]
In the present invention, a microcapsule type pigment in which a pigment is coated with an organic polymer and encapsulated can be used. Examples of the method for microencapsulating the pigment include a chemical production method, a physical production method, a physicochemical method, and a mechanical production method. Specifically, interfacial polymerization method, in-situ polymerization method, submerged cured coating method, coacervation (phase separation) method, submerged drying method, melt dispersion cooling method, air suspension coating method, spray drying method , Acid precipitation method, phase inversion emulsification method and the like.

(Other ingredients)
In addition to the above components, the ink according to the present invention may contain a moisturizing solid content such as urea, urea derivatives, trimethylolpropane, trimethylolethane and the like in order to maintain the moisturizing property. The content (% by mass) of the moisturizing solid content in the ink is 0.1% by mass or more and 20.0% by mass or less, and further 3.0% by mass or more and 10.0% by mass or less based on the total mass of the ink. It is preferable that

  In addition to the above components, the ink according to the present invention includes a pH adjuster, a rust inhibitor, a preservative, an antifungal agent, an antioxidant, a reduction inhibitor, an evaporation accelerator, a chelating agent, and the like as necessary. Various additives may be contained.

(Ink physical properties)
It is preferable that the ink according to the present invention has a characteristic that can be favorably ejected from the recording head. Therefore, the viscosity of the ink is 1 mPa · s to 15 mPa · s, further 1 mPa · s to 5 mPa · s, and the surface tension of the ink is 25 mN / m or more, further 25 mN / m to 50 mN / m. It is preferable.

<Inkjet recording method>
The ink of the present invention is particularly preferably used in an ink jet recording method in which the ink is ejected by an ink jet method. Ink jet recording methods include a recording method in which ink is ejected by applying mechanical energy to the ink, and a recording method in which ink is ejected by applying thermal energy to the ink. In particular, in the present invention, an ink jet recording method using thermal energy can be preferably used.

<Ink cartridge>
As an ink cartridge suitable for recording using the ink of the present invention, an ink cartridge provided with an ink containing portion for containing such ink can be mentioned.

<Recording unit>
A recording unit suitable for performing recording using the ink of the present invention includes a recording unit including an ink storage portion for storing the ink and a recording head for discharging the ink. In particular, a recording unit in which the recording head ejects ink by applying thermal energy corresponding to the recording signal to the ink can be preferably used. In particular, in the present invention, it is preferable to use a recording head having a heat generating part wetted surface containing a metal and / or a metal oxide. Specific examples of the metal and / or metal oxide constituting the heat generating part wetted surface include, for example, metals such as Ta, Zr, Ti, Ni, and Al, and oxides of these metals. .

<Inkjet recording apparatus>
An ink jet recording apparatus suitable for performing recording using the ink of the present invention includes an ink jet recording apparatus provided with an ink containing portion for containing the ink and a recording head for discharging the ink. In particular, there is an ink jet recording apparatus that ejects ink by applying thermal energy corresponding to a recording signal to ink inside a recording head having an ink storage portion that stores the ink.

  Below, the schematic structure of the mechanism part of an inkjet recording device is demonstrated. The ink jet recording apparatus includes a sheet feeding unit, a conveyance unit, a carriage unit, a sheet discharging unit, a cleaning unit, and an exterior unit that protects these parts and provides design properties, based on the role of each mechanism.

  FIG. 1 is a perspective view of the ink jet recording apparatus. 2 and 3 are views for explaining the internal mechanism of the ink jet recording apparatus. FIG. 2 is a perspective view from the upper right part, and FIG. 3 is a side sectional view of the ink jet recording apparatus.

  When paper is fed, only a predetermined number of recording media are fed to a nip portion composed of a paper feed roller M2080 and a separation roller M2041 in a paper feed unit including a paper feed tray M2060. The recording medium is separated at the nip portion, and only the uppermost recording medium is conveyed. The recording medium conveyed to the conveyance unit is guided by the pinch roller holder M3000 and the paper guide flapper M3030, and conveyed to the roller pair of the conveyance roller M3060 and the pinch roller M3070. The roller pair of the conveyance roller M3060 and the pinch roller M3070 is rotated by driving of the LF motor E0002, and the recording medium is conveyed on the platen M3040 by this rotation.

  When forming an image on a recording medium, the carriage unit arranges a recording head H1001 (FIG. 4; a detailed configuration will be described later) at a position where a target image is formed, and follows a signal from the electric board E0014. Ink is ejected onto the recording medium. An image is formed on the recording medium by alternately repeating main scanning in which the carriage M4000 scans in the column direction while recording is performed by the recording head H1001 and sub-scanning in which the recording medium is conveyed in the row direction by the conveyance roller M3060. The recording medium on which the image is formed is conveyed in a state sandwiched between the nips of the first paper discharge roller M3110 and the spur M3120 at the paper discharge unit, and is discharged to the paper discharge tray M3160.

  The cleaning unit cleans the recording head H1001 before and after forming an image. When the pump M5000 is operated with the cap M5010 capping the ejection port of the recording head H1001, unnecessary ink or the like is sucked from the ejection port of the recording head H1001. In addition, by sucking ink remaining in the cap M5010 with the cap M5010 open, the remaining ink is prevented from sticking and other problems.

(Configuration of recording head)
The configuration of the head cartridge H1000 will be described. The head cartridge H1000 has a recording head H1001, means for mounting the ink cartridge H1900, and means for supplying ink from the ink cartridge H1900 to the recording head, and is detachably mounted on the carriage M4000.

  FIG. 4 is a diagram showing how the ink cartridge H1900 is mounted on the head cartridge H1000. The ink jet recording apparatus forms an image with yellow, magenta, cyan, black, light magenta, light cyan, and green inks. Therefore, the ink cartridge H1900 is also prepared for seven colors independently. In the above, the ink of the present invention is used as at least one ink. As shown in FIG. 4, each ink cartridge is detachable from the head cartridge H1000. The ink cartridge H1900 can be attached and detached even when the head cartridge H1000 is mounted on the carriage M4000.

  FIG. 5 is an exploded perspective view of the head cartridge H1000. The head cartridge H1000 includes a recording element substrate, a plate, an electric wiring substrate H1300, a cartridge holder H1500, a flow path forming member H1600, a filter H1700, a seal rubber H1800, and the like. The recording element substrate is composed of a first recording element substrate H1100 and a second recording element substrate H1101, and the plate is composed of a first plate H1200 and a second plate H1400.

  The first recording element substrate H1100 and the second recording element substrate H1101 are Si substrates, and a plurality of recording elements (nozzles) for ejecting ink are formed on one side thereof by a photolithography technique. Electric wiring such as Al for supplying electric power to each recording element is formed by a film forming technique, and a plurality of ink flow paths corresponding to individual recording elements are formed by a photolithography technique. Further, an ink supply port for supplying ink to the plurality of ink flow paths is formed to open on the back surface.

  FIG. 6 is an enlarged front view illustrating the configuration of the first recording element substrate H1100 and the second recording element substrate H1101. H2000 to H2600 are arrays of printing elements corresponding to different ink colors (hereinafter also referred to as nozzle arrays). On the first recording element substrate H1100, nozzle rows for three colors, a nozzle row H2000 for yellow ink, a nozzle row H2100 for magenta ink, and a nozzle row H2200 for cyan ink, are formed. On the second recording element substrate H1101, nozzle rows for four colors, a light cyan ink nozzle row H2300, a black ink nozzle row H2400, a green ink nozzle row H2500, and a light magenta ink nozzle row H2600, are formed. ing.

Each nozzle row is composed of 768 nozzles arranged at an interval of 1200 dpi (dot / inch; reference value) in the conveyance direction (sub-scanning direction) of the recording medium, and ejects about 2 picoliters of ink. The opening area at each discharge port is set to approximately 100 μm ² .

  Hereinafter, a description will be given with reference to FIGS. The first recording element substrate H1100 and the second recording element substrate H1101 are bonded and fixed to the first plate H1200. Here, an ink supply port H1201 for supplying ink to the first recording element substrate H1100 and the second recording element substrate H1101 is formed. Further, a second plate H1400 having an opening is bonded and fixed to the first plate H1200. The second plate H1400 holds the electrical wiring substrate H1300 so that the electrical wiring substrate H1300 is electrically connected to the first recording element substrate H1100 and the second recording element substrate H1101.

  The electrical wiring substrate H1300 applies an electrical signal for ejecting ink from each nozzle formed on the first recording element substrate H1100 and the second recording element substrate H1101. The electric wiring board H1300 is arranged on the electric wiring corresponding to the first recording element substrate H1100 and the second recording element substrate H1101, and an external part for receiving an electric signal from the ink jet recording apparatus. And a signal input terminal H1301. The external signal input terminal H1301 is positioned and fixed on the back side of the cartridge holder H1500.

  A flow path forming member H1600 is fixed to the cartridge holder H1500 that holds the ink cartridge H1900, for example, by ultrasonic welding, and forms an ink flow path H1501 that communicates from the ink cartridge H1900 to the first plate H1200. A filter H1700 is provided at the ink cartridge side end of the ink flow path H1501 that engages with the ink cartridge H1900, and can prevent dust from entering from the outside. Further, a seal rubber H1800 is attached to the engaging portion with the ink cartridge H1900 so that ink can be prevented from evaporating from the engaging portion.

  Further, as described above, the head cartridge H1000 is configured by bonding the cartridge holder portion and the recording head portion H1001 by bonding or the like. The cartridge holder portion includes a cartridge holder H1500, a flow path forming member H1600, a filter H1700, and a seal rubber H1800. The recording head portion H1001 includes a first recording element substrate H1100, a second recording element substrate H1101, a first plate H1200, an electric wiring substrate H1300, and a second plate H1400.

  Here, as an embodiment of the recording head, a thermal ink jet recording head that performs recording using an electrothermal transducer (recording element) that generates thermal energy for causing ink to cause film boiling in accordance with an electrical signal. Said. About this typical structure and principle, for example, what is performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is preferable. . This method can be applied to both a so-called on-demand type and a continuous type.

  The thermal ink jet method is particularly effective when applied to an on-demand type. In the case of the on-demand type, at least one drive that applies a rapid temperature rise exceeding nucleate boiling corresponding to the recording information to the electrothermal transducer disposed corresponding to the liquid flow path holding the ink Apply a signal. As a result, thermal energy is generated in the electrothermal transducer, and film boiling occurs in the ink. As a result, bubbles in the ink corresponding to the drive signal on a one-to-one basis can be formed. At least one droplet is formed by ejecting ink through the ejection port by the growth and contraction of the bubbles. It is more preferable that the driving signal has a pulse shape, since the bubble grows and contracts immediately and appropriately, so that ink discharge with particularly excellent response can be achieved.

  The ink of the present invention is not limited to the thermal ink jet method, and can be preferably used in an ink jet recording apparatus using mechanical energy as described below. An ink jet recording apparatus having such a configuration includes a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed to face the nozzles, and ink filling the periphery of the pressure generating element. Become. Then, the pressure generating element is displaced by the applied voltage, and ink is ejected from the nozzle.

  As described above, the ink jet recording apparatus is not limited to one in which the recording head and the ink cartridge are separated from each other. Further, the ink cartridge is integrated with the recording head so as to be separable or non-separable and is mounted on the carriage, or is provided at a fixed portion of the ink jet recording apparatus via an ink supply member such as a tube. An ink may be supplied to the recording head. Further, when the ink cartridge is provided with a configuration for applying a preferable negative pressure to the recording head, the following configuration can be adopted. That is, a mode in which an absorber is disposed in the ink storage portion of the ink cartridge, or a mode in which a flexible ink storage bag and a spring portion that exerts a biasing force in the direction of expanding the inner volume of the flexible ink storage bag are provided. It can be. The ink jet recording apparatus may take the form of a line printer in which recording elements are aligned over a range corresponding to the entire width of the recording medium, in addition to the serial type recording method described above.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not limited at all by the following Example, unless the summary is exceeded. “Part” or “%” is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Preparation of pigment dispersion 1)
10 parts of carbon black, 20 parts of a styrene-acrylic acid copolymer having an acid value of 150 mgKOH / g, and 70 parts of pure water were mixed and dispersed using a batch type vertical sand mill (made by Imex) filled with zirconia beads. . Carbon black having a specific surface area of 200 m ² / g and a DBP oil absorption of 100 mL / 100 g was used. Thereafter, coarse particles were removed by centrifugation. Furthermore, pressure filtration was performed with a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm, and Pigment Dispersion 1 having a pigment concentration of 10% was obtained.

(Preparation of pigment dispersion 2)
Batch type vertical sand mill in which 10 parts of carbon black used in preparation of pigment dispersion 1, 20 parts of styrene-acrylic acid copolymer having an acid value of 270 mg KOH / g, 70 parts of pure water are mixed and filled with zirconia beads (Imex) was used for dispersion. Thereafter, coarse particles were removed by centrifugation. Furthermore, pressure filtration was performed with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm to obtain Pigment Dispersion 2 having a pigment concentration of 10%.

(Preparation of pigment dispersion 3)
10 parts of carbon black, 20 parts of a styrene-acrylic acid copolymer having an acid value of 270 mg KOH / g, and 70 parts of pure water were mixed and dispersed using a batch type vertical sand mill (made by Imex) filled with zirconia beads. . Carbon black having a specific surface area of 150 m ² / g and a DBP oil absorption of 100 mL / 100 g was used. Thereafter, coarse particles were removed by centrifugation. Furthermore, the mixture was filtered under pressure with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm to obtain pigment dispersion 3 having a pigment concentration of 10%.

<Preparation of ink>
Ingredients shown in Table 1 below were mixed and sufficiently stirred, and then pressure filtration was performed with a microfilter having a pore size of 3.0 μm (manufactured by Fuji Film) to prepare inks 1 to 6.

<Relationship between ink evaporation rate and surfactant content>
10 g of each ink prepared above was collected in a petri dish and left at room temperature. Thereafter, the surface tension of the ink was measured every time the ink evaporation rate obtained by the following formula increased by 2%.

  The relationship between the evaporation rate and the surface tension of the ink thus obtained is shown in the graph of FIG. The measurement was performed 21 times from the state where the ink evaporation rate was 0% (initial state) until the ink evaporation rate reached 40%. The surface tension was measured using a surface tension meter CBVP-A3 (manufactured by Kyowa Interface Science), and the measurement conditions were a measurement temperature of 25.0 ± 0.5 ° C., a 10 mm × 24 mm platinum plate 10 mm × 24 mm. It was measured.

  As can be seen from FIG. 7, the surface tension of the inks 1 to 3 continues while the ink evaporation rate is in the range of 10 to 40%, and an aqueous solution containing acetylenol EH (surfactant) at a critical micelle concentration. The surface tension was 28 mN / m or less. Accordingly, the contents of the surfactant in the ink were always higher than the critical micelle concentration while the ink evaporation rates of the inks 1 to 3 were in the range of 10% to 40%.

<Judgment result>
Table 2 shows the solubility relationship between the water-soluble organic solvent and the surfactant in each of the inks 1 to 6. In Table 2, those having high solubility of the surfactant are represented by +, and those having low solubility are represented by-.

<Evaluation>
The ink obtained above was mounted on an ink jet recording apparatus PIXUS850i (manufactured by Canon) having an on-demand type multi-recording head that discharges ink by applying thermal energy to the ink according to a recording signal. Then, after recording two 18 cm × 24 cm images with a recording duty of 50% on the recording medium, the process of leaving them for 30 minutes and recording two similar images again was defined as one cycle. After repeating this cycle 10 times, one nozzle check pattern of PIXUS850i was recorded, and the landing deviation state in the obtained nozzle check pattern was visually confirmed to evaluate the landing deviation. Further, the recording head was removed from the ink jet recording apparatus, and the face wetness was evaluated by observing the face surface with a microscope. The evaluation criteria are as follows. The results are shown in Table 3.

(Evaluation criteria for face wetting)
A: Face face wetness hardly occurred.
B: Some face wetting occurred, but it was at a level that did not affect the surface characteristics of the face after the initial and after 10 cycles.
C: Wetting of the face surface occurred, and the surface characteristics of the face surface changed greatly after the initial and 10 cycles.

(Evaluation criteria for impact landing)
A: The nozzle check pattern is not disturbed and can be recorded normally.
B: There is a slight disturbance in the nozzle check pattern, but there is no non-ejection.
C: No ejection or disturbance is clearly confirmed in the nozzle check pattern, and normal recording cannot be performed.

It is a perspective view of an inkjet recording device. It is a perspective view of the mechanism part of an inkjet recording device. It is sectional drawing of an inkjet recording device. FIG. 6 is a perspective view illustrating a state where an ink cartridge is mounted on the head cartridge. It is a disassembled perspective view of a head cartridge. FIG. 6 is a front view showing a recording element substrate in the head cartridge. It is a graph which shows the relationship between the evaporation rate and the surface tension in the inks 1-6.

Explanation of symbols

M2041 Separation roller M2060 Paper feed tray M2080 Paper feed roller M3000 Pinch roller holder M3030 Paper guide flapper M3040 Platen M3060 Transport roller M3070 Pinch roller M3110 Paper discharge roller M3120 Spur M3160 Paper discharge tray M4000F Carriage M5000 Pump M500P Head cartridge H1001 Recording head H1100 First recording element substrate H1101 Second recording element substrate H1200 First plate H1201 Ink supply port H1300 Electrical wiring substrate H1301 External signal input terminal H1400 Second plate H1500 Tank holder H1501 Ink channel H1600 Flow path forming member H1700 Luther H1800 seal rubber H1900 ink cartridge H2000 yellow nozzle row H2100 magenta nozzle row H2200 cyan nozzle row H2300 light cyan nozzle row H2400 black nozzle row H2500 green nozzle row H2600 light magenta nozzle row

Claims (6)

An ink-jet ink containing at least water, a coloring material, a water-soluble organic solvent, and a surfactant,
The content of the surfactant in the ink always reaches or exceeds the critical micelle concentration of the surfactant when the evaporation rate of the ink determined by the following formula is in the range of 10% to 40%. Ink for inkjet.

  The inkjet ink according to claim 1, wherein the water-soluble organic solvent contains a water-soluble organic solvent having low solubility of the surfactant.   3. An ink jet recording method in which ink is ejected by an ink jet method to perform recording on a recording medium, wherein the ink is the ink jet ink according to claim 1 or 2.   An ink cartridge comprising an ink containing portion for containing ink, wherein the ink is an ink jet ink according to claim 1 or 2.   3. A recording unit comprising an ink containing portion for containing ink and a recording head for ejecting ink, wherein the ink is the ink jet ink according to claim 1 or 2.   3. An ink jet recording apparatus comprising an ink containing portion for containing ink and a recording head for ejecting ink, wherein the ink is the ink jet ink according to claim 1 or 2. apparatus.

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