JP7062375B2 - Liquid ejection method and inkjet recording device - Google Patents

Description

The present invention relates to a liquid ejection method and an inkjet recording device used thereof.

In recent years, inkjet recording devices have been increasingly used in offices and the like, taking advantage of their advantages of low power consumption, low cost, and space saving. As a scanning method of a recording head adopted in an inkjet recording device, a serial method can be mentioned. In the serial method, an image is recorded by repeatedly moving the recording head in a direction (sub-scanning direction) orthogonal to the paper feed direction (main scanning direction). Since the serial recording head is relatively small, the recording device main body can be miniaturized.

In recent years, in order to further improve the recording speed (throughput), a recording head that extends the arrangement width of the ejection port to the maximum width of the recording medium, that is, a recording device that employs a line head has been developed (Patent Document 1). .. Unlike the serial method, the line head method does not move the recording head, but only conveys the paper, which is advantageous for improving the recording speed.

However, since the line head has a large number of nozzles, the amount of ink ejected from each nozzle tends to vary. Therefore, in order to reduce the viscosity of the ink by heating and suppress the variation in the ejection amount for each nozzle, it is also considered to heat the ink by a heating mechanism provided in the line head.

On the other hand, in a recording device equipped with a line head, in order to give priority to high-speed recording, it is required to simplify the recovery operation and reduce the number of recovery operations. However, if the recovery operation is simplified, air bubbles generated in the ink flow path of the line head grow, which causes another problem that ink non-ejection is likely to occur.

Under such circumstances, a method of covering a part of the wall surface of the ink flow path in the recording head with an inorganic insulating layer has been proposed in order to eject ink stably for a long period of time (Patent Documents 2 and 3). ).

Japanese Unexamined Patent Publication No. 2010-143147 Japanese Unexamined Patent Publication No. 2008-179045 Japanese Unexamined Patent Publication No. 2008-23188

However, as a result of the studies by the present inventors, in any of the methods proposed in Patent Documents 2 and 3, when a line head provided with a heating mechanism is used, the ink ejection stability is maintained in the long term. It turned out to be difficult to maintain. For example, in the ink flow path, there is a hydrophilic portion which is an inorganic insulating layer and a hydrophobic portion which is a layer other than the inorganic insulating layer. Even when the methods proposed in Patent Documents 2 and 3 are adopted, it is difficult to avoid non-ejection of ink when bubbles adsorbed on the hydrophobic portion grow. Further, the portion of the ink flow path that is not covered with the inorganic insulating layer is easily eroded by the heated ink, and if the recording element or the like is damaged, ink non-ejection occurs. This erosion is caused by the action of the hydroxy groups of the components in the water-based ink.

Therefore, an object of the present invention is to provide a liquid discharge method in which the liquid discharge stability is maintained for a long period of time when a recording device provided with a line head having a heating mechanism is used. Another object of the present invention is to provide an inkjet recording apparatus used in the above liquid ejection method.

The above object is achieved by the following invention. That is, according to the present invention, the liquid is discharged to a recording medium by using an inkjet recording device including a liquid, a line head for discharging the liquid, and a heating mechanism for heating the liquid in the line head. The liquid is an aqueous liquid containing a component having an anionic group, and a liquid flow path having a discharge port for discharging the liquid inside the line head. And a liquid supply port communicating with the liquid flow path are formed, and the inner wall surface of at least one of the liquid flow path and the liquid supply port is a protective film formed of titanium oxide which is a hydrophilic material. The method of discharging the liquid from the discharge port is a method of using a liquid discharge heater , wherein the component having an anionic group has a charge amount of 0.005 mmol / g or more. The liquid in the line head is heated to 40 ° C. or higher and 70 ° C. or lower by repeatedly energizing the liquid discharge heater with a current that does not discharge the liquid or by a heater arranged so as to contact the line head. A liquid discharge method is provided.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a liquid discharge method in which a liquid discharge stability is maintained for a long period of time when a recording device provided with a line head having a heating mechanism is used. Further, according to the present invention, it is possible to provide an inkjet recording device used for the above liquid ejection method.

It is an image diagram which records an image by a line head. It is a schematic diagram which shows an example of an inkjet recording apparatus. It is a figure which shows an example of a line head schematically, (a) is a perspective view, (b) is an exploded perspective view. It is a figure which shows an example of the recovery mechanism, (a) is a perspective view, (b) is a schematic view. It is a schematic diagram which shows an example of the supply mechanism which supplies a liquid to a line head. It is a partial perspective view which shows an example of the structure of a line head. It is a figure which shows an example of the structure of a line head schematically, (a) is a front view, (b) is a sectional view taken along the line AA of (a). It is a schematic diagram which shows an example of the manufacturing method of a line head.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. Hereinafter, ink may be taken as an example as a specific example of the liquid, but the liquid of the present invention is not limited to this. The liquid may be an ink containing a coloring material; a reaction liquid used in combination with the ink; an ink used in combination with the ink, which does not substantially contain the coloring material (clear ink). In the present invention, when the compound is a salt, the salt is dissociated into ions and exists in the ink, but for convenience, it is expressed as "containing a salt". Further, the water-based ink for inkjet may be simply referred to as "ink". The physical characteristic values are values at room temperature (25 ° C.) unless otherwise specified. Further, since the liquid used in the present invention is aqueous, the unit of "mmol / g" in the present invention is calculated assuming that the specific gravity of the liquid is "1 g / mL".

<Liquid discharge method>
The liquid ejection method of the present invention uses an inkjet recording apparatus provided with a liquid, a line head for ejecting the liquid, and a heating mechanism for heating the liquid in the line head, and ejects the liquid to a recording medium. It is a liquid discharge method to be applied. The discharged liquid is an aqueous liquid containing a component having an anionic group. Inside the line head, a liquid flow path having a discharge port for discharging the liquid and a liquid supply port communicating with the liquid flow path are formed. The inner wall surface of at least one of the liquid flow path and the liquid supply port is covered with a protective film containing a hydrophilic material.

As mentioned above, in order to expand the use of inkjet recording devices in offices and the like, it is strongly required to improve the recording speed (throughput) that can compete with electrophotographic recording devices. In order to increase the recording speed when using the serial type recording head, it is necessary to increase the moving speed of the recording head in the sub-scanning direction and increase the number of ejections per nozzle (that is, increase the ejection frequency). There is. However, in order to increase the discharge frequency, various restrictions such as mechanical restrictions and the inability to supply (refill) the liquid from the liquid storage portion to the discharge port occur. Therefore, there is a limit to improving the recording speed of an inkjet recording device equipped with a serial recording head.

In view of this situation, in recent years, a line-type recording head (hereinafter, also referred to as a "line head") in which a discharge port (nozzle) for discharging a liquid is arranged over the entire width of the recording medium in the transport direction (maximum paper width). A recording device that employs (described) has been developed. Since the line head has a number of ejection ports corresponding to the maximum paper width of the recording medium, there is no need to move the recording head, and there is an advantage that high-speed recording is possible. That is, in the case of a recording device that employs a line head, it is not necessary to move the recording head in a direction (main scanning direction) orthogonal to the conveying direction (secondary scanning direction) of the recording medium. Therefore, the unit area of the recording medium passes directly under the recording head only once, that is, the image can be recorded in "1 pass", and the time required for recording can be shortened.

The present inventors have studied a further high-speed recording by combining an inkjet recording device that employs a line head with a conventional liquid for inkjet ejection. As a result, it has been found that when the heated liquid is discharged from the line head for a long period of time, there arises a problem that the discharge stability of the liquid is lowered. The present inventors presume that such a decrease in the discharge stability of the liquid is caused by the following reasons.

Since the line head has a large number of discharge ports, it takes time for each recovery operation, but in order to improve the recording speed, it is required to simplify the recovery operation and reduce the number of recovery operations. Further, in the case of a line head, the ink may be heated from the viewpoints of liquid ejection stability and uniform ejection properties from a large number of ejection ports. Further, it is required that sufficient ejection stability can be maintained even if the heated ink is used.

When heated ink is ejected from a recording head in which a part of the wall surface of the ink flow path is covered with an inorganic insulating layer, which employs the methods proposed in Patent Documents 2 and 3, high-speed recording is performed for a long period of time. It is considered that the above phenomenon is occurring. When the ink is heated, the solubility of the gas decreases, so that the gas dissolved in the ink becomes bubbles. Since the generated bubbles are hydrophobic, they are adsorbed on the hydrophobic part in the flow path by the hydrophobic interaction. If there are small bubbles as a single unit or as a group of several small bubbles, the ink ejection is not affected. However, if the bubbles grow to a size that blocks the flow path, ink non-ejection will occur. Further, the heated ink easily erodes the inner wall surface of the ink flow path and the ink supply port. For this reason, in the inner wall surface of the ink flow path and the ink supply port, where the ink flow path and the inner wall surface of the ink supply port are not covered with the inorganic insulating layer, dissolution is likely to proceed, and the recording element or the like is likely to be damaged.

In order to solve the above problems, the present inventors use a protective film containing a hydrophilic material to cover at least one of the inner wall surface of the liquid flow path and the liquid supply port inside the line head provided with the heating mechanism. Covered. As a result, it has been found that the adsorption of bubbles can be suppressed, the non-discharge of the liquid due to the growth of bubbles can be avoided, and the dissolution of the inner wall surface can be suppressed. Further, when a liquid containing a component having an anionic group is used, a pinhole-like defect occurs in the protective film containing the hydrophilic material covering the inner wall surface of the liquid flow path and the liquid supply port. Also found that further dissolution of the inner wall surface could be suppressed. The present inventors speculate the reason why such an effect is obtained as follows.

The surface of the protective film containing the hydrophilic material is negatively charged. However, the surface state of the pinhole portion formed by missing a part of the protective film changes and is positively charged. Therefore, the component having an anionic group is adsorbed on the inner wall surface of the pinhole and closes the pinhole. As a result, it is considered that the attack of the hydroxy group that promotes the dissolution of the inner wall surface of the liquid flow path and the liquid supply port is suppressed.

(Inkjet recording device)
The inkjet recording apparatus used in the liquid ejection method of the present invention includes a liquid, a line head filled with the liquid, and a heating mechanism for heating the liquid in the line head. The liquid is an aqueous liquid containing a component having an anionic group, and a liquid flow path having a discharge port for discharging the liquid and a liquid supply port communicating with the liquid flow path are formed inside the line head. ing. The inner wall surface of at least one of the liquid flow path and the liquid supply port is covered with a protective film containing a hydrophilic material. Hereinafter, the details of the inkjet recording apparatus of the present invention will be described with reference to the drawings, taking as an example a case where ink is used as a liquid as needed.

FIG. 1 is an image diagram in which an image is recorded by a line head. Further, FIG. 2 is a schematic diagram showing an example of an inkjet recording device. In the recording device M4000 shown in FIG. 2, a line head (recording head H1000) is fixed to the recording device main body, and a method is adopted in which the recording medium 47 is conveyed in the direction of the arrow 45 for recording. The recording device M4000 includes, for example, a recording head H1000Y for yellow ink, a recording head H1000M for magenta ink, a recording head H1000C for cyan ink, and a recording head H1000Bk for black ink (FIG. 1).

The recording heads H1000Y to H1000R shown in FIG. 2 are fixed by a recording head holder 42 mounted on the recording device M4000. FIGS. 1 and 2 show configurations in which yellow, magenta, cyan, and black colors, as well as reaction solutions, are discharged from separate recording heads. Of course, an image may be recorded by discharging a plurality of liquids and further a reaction liquid from each of a plurality of discharge port rows provided on one recording element substrate.

The inkjet recording apparatus may be provided with a means for applying a reaction liquid containing a component that agglomerates the coloring material in the ink to the recording medium. Examples of the means for applying the reaction solution to the recording medium include a means for applying the reaction solution to the recording medium by a coating method, a means for applying the reaction solution to the recording medium by a discharge method, and the like. In the means for applying the reaction solution to the recording medium by the coating method, for example, the reaction solution is applied to the recording medium using a coating member such as a conventionally known roller. Further, in the means for applying the reaction liquid to the recording medium by the discharge method, for example, the reaction liquid is applied to the recording medium by using a discharge device such as a line head for the reaction liquid (recording head H1000R) as shown in FIG. do. As shown in FIG. 1, when four recording heads are provided corresponding to four colors of ink, a means for applying the reaction solution to the recording medium can be separately provided. In the present invention, it is preferable to apply the reaction liquid to the recording medium by a method such as coating, and then eject the ink from the recording head to apply the ink to the recording medium.

The paper cassette 46 contains a recording medium 47 such as plain paper, and is detachably attached to the main body of the apparatus. The pickup roller 48 is a member that sends out one of the uppermost surfaces of the recording media 47 housed in the paper feed cassette 46. The transport roller 49 is a member that transports the recording medium 47 sent out from the pickup roller 48 to the transport path 50. Further, the transport roller 51 arranged on the outlet side of the transport path 50 is a member that transports the recording medium 47 toward the recording head H1000 while being mounted on the transport belt 44.

3A and 3B are views schematically showing an example of a line head, where FIG. 3A is a perspective view and FIG. 3B is an exploded perspective view. As shown in FIG. 3, the line head (recording head H1000) includes a recording element unit H1400 and a liquid supply unit H1500 which is a liquid supply unit for supplying a liquid to the recording element unit H1400. The liquid supply unit H1500 includes a connection portion H1700 in which a connection port H1710 for connecting to the outside for supplying liquid from the outside such as a recording device is formed in the liquid chamber (not shown). Further, the recording element unit H1400 is composed of a recording element substrate H1100, a support substrate H1200, and a wiring member H1300.

The support substrate H1200 is a member that holds and fixes the recording element substrate H1100 and the wiring member H1300, and has a liquid supply hole H1210 for supplying the liquid supplied from the liquid supply unit H1500 to the recording element substrate H1100. The plurality of recording element substrates H1100 are arranged and fixed on the main surface of the support substrate H1200 with predetermined position accuracy. Further, the plurality of recording element substrates H1100 are arranged in a staggered manner on the support substrate H1200 so that the ejection ports are continuously arranged between the adjacent recording element substrates H1100 along the direction of the ejection port row. .. In this way, by arranging the recording element board H1100 so as to overlap the discharge ports at the joints of the adjacent recording element boards H1100, it is possible to correct the influence on the image due to the misalignment of the recording element board, and the recording width is long. A full-line type recording head is realized.

The wiring member H1300 transmits an electric signal or electric power for driving a recording element provided on the recording element substrate H1100 from the outside (recording device) of the recording head H1000 to the recording element substrate H1100, so that the recording element substrate H1100 Is electrically connected to. As the wiring member H1300, a flexible printed wiring board such as a flexible wiring board is used. The flexible wiring member H1300 is bent so that the recording element substrate H1100 and the recording device can be easily electrically connected, and is fixed to the liquid supply unit H1500.

The inkjet recording apparatus used in the liquid ejection method of the present invention includes a heating mechanism for heating the liquid in the line head. Specifically, by heating the line head, the liquid in the line head can be heated and the temperature of the liquid can be adjusted. Examples of the heating method include a temperature control heater arranged so as to be in contact with the recording head, a liquid discharge heater, and the like. In order to heat or heat the line head by the heater for discharging the liquid, for example, a current that does not discharge the liquid may be repeatedly applied. The temperature of the line head and the liquid in the line head can be read by, for example, a temperature sensor provided in the line head. The temperature of the line head and the liquid is preferably adjusted to 40 to 70 ° C.

The inkjet recording apparatus used in the inkjet recording method of the present invention may further include a recovery mechanism for recovering the sticking of the liquid at the discharge port of the line head and the state of the wet state of the discharge port surface. 4A and 4B are views showing an example of a recovery mechanism, where FIG. 4A is a perspective view and FIG. 4B is a schematic view. As shown in FIG. 4, the wiper W1001 is held by the clip member W1002, and the clip member W1002 is held by the connecting member W1003. Further, the clip member W1002 is attached to the wipe base W1011 on which the slide rail W1006 can be moved. The wipe base W1011 can move on the slide rail W1006 by driving the timing belt W1007 through the connecting member W1003. The timing belt W1007 is supported by a driven pulley W1004 and a drive pulley W1005, and a shaft of a drive motor W1010 for driving the timing belt W1007 is connected to the drive pulley W1005. Further, in order to control the position of the wiper W1001 during the recovery operation, photosensors W1008 and W1009 are provided at both ends of the slide rail W1006. During the recovery operation by wiping, the wiper W1001 slides and moves by the slide rail W1006, so that the wiper W1001 bends and wipes the discharge port surface H1001 of the recording head H1000.

The inkjet recording device used in the liquid ejection method of the present invention may further include a supply mechanism for supplying the liquid to the line head. FIG. 5 is a schematic diagram showing an example of a supply mechanism for supplying a liquid to a line head. As shown in FIG. 5, the pump P1 supplies the liquid from the sub tank T2 to the line head H1000. The liquid overflowing from the line head H1000 is returned to the sub tank T2. The valve V1 is provided for switching to pressurize or release the pressure in the liquid chamber inside the line head during the recovery operation. When the pressure is restored, the valve V1 is closed and the pump P1 pressurizes to remove a part of the bubbles in the liquid supply path and the liquid flow path. The liquid level in the sub tank T2 is configured to maintain the head difference from the discharge port surface of the line head H1000 within a certain range, and maintains the negative pressure of the discharge port surface of the line head H1000 within an appropriate range. do. When the liquid in the sub tank T2 is insufficient, the liquid is sent from the main tank T1 to the sub tank T2 by the pump P2. The temperature of each tank and the liquid contained therein depends on the environmental temperature at which the inkjet recording device is installed, but is preferably in the range of, for example, 15 to 45 ° C.

Next, the configuration of the line head of the inkjet recording apparatus of the present invention will be described. FIG. 6 is a partial perspective view showing an example of the configuration of the line head. 7A and 7B are views schematically showing an example of the configuration of the line head, where FIG. 7A is a front view and FIG. 7B is a sectional view taken along the line AA of FIG. 7A. As shown in FIGS. 6 and 7, the line head used in the inkjet recording apparatus of the present invention includes a substrate 11 on which a heater 16 which is a heat generation resistor is formed, and a plurality of ejection ports 17 which are orifices for ejecting droplets. It is provided with a formed orifice plate 12. Further, the line head includes a liquid flow path 13 in which a heater 16 is arranged on an inner wall surface thereof that communicates with each discharge port 17, and a liquid supply port 14 that communicates with the liquid flow path 13. The heater 16 functions as a discharge pressure generating element. Further, the plurality of discharge ports 17 are formed so as to be arranged at positions corresponding to the heater 16 on the orifice plate 12.

In the line head used in the inkjet recording apparatus of the present invention, at least one inner wall surface of the liquid flow path 13 and the liquid supply port 14 is covered with a protective film 15 containing a hydrophilic material. The protective film 15 is located on the outermost surface in contact with the liquid, and the protective film 15 suppresses the growth of bubbles caused by the adsorption of bubbles in the liquid and the dissolution of the inner wall surface of the substrate 11 exposed to the liquid. be able to. The thickness of the protective layer 15 is preferably 5 to 200 nm, more preferably 5 to 150 nm, and particularly preferably 5 to 100 nm. The surface treatment with the protective film 15 is preferably performed on both the liquid flow path 13 and the liquid supply port 14.

The "hydrophilic material" in the present specification is a material having a static contact angle of 50 ° or less for pure water. The static contact angle can be measured using a general contact angle meter. In the examples described later, the static contact angle of pure water was measured using a contact angle measuring device (trade name “FACE CA-XA150”, manufactured by Kyowa Interface Science). The static contact angle of the hydrophilic material with respect to pure water is preferably 20 ° or more and 50 ° or less.

Examples of the hydrophilic material forming the protective film 15 include metals; compounds thereof such as oxides, nitrides, and carbides thereof. These hydrophilic materials can be used alone or in combination of two or more. As the metal, at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Al is preferable. Among them, at least one selected from the group consisting of Ti, V, Nb, Cr, Mo, and Al is preferable, and Ti is particularly preferable. Further, as the hydrophilic material forming the protective film 15, it is also preferable to use a non-metal such as Si; a compound such as an oxide, a nitride or a carbide thereof.

The formation of a protective layer on the surface of the heater 16 is optional. When the protective layer is provided, it may be a protective film similar to the inner wall surface of the liquid flow path 13 and the liquid supply port 14, or it may be a protective layer made of a different material. The protective film on the inner wall surface of the liquid flow path 13 and the liquid supply port 14 and the protective film on the surface of the heater 16 are preferably made of different materials, and more preferably made of a material containing different metals. preferable. Specifically, the inner wall surface of the liquid flow path 13 and the liquid supply port 14 is made of a material containing at least one metal selected from the group consisting of Ti, V, Nb, Cr, Mo, and Al. It is preferable to form a protective film. On the other hand, it is preferable to form a protective film on the surface of the heater 16 made of a material containing at least one metal selected from the group consisting of Zr, Hf, and Ta. On the surface of the substrate 11 on which the heater 16 and the drive circuit of the heater 16 are formed, there is usually a passivation layer that protects the wiring and integrated circuits (IC) from, for example, oxygen, moisture, and other sources of chemical damage. It is formed.

Next, a method for manufacturing a line head used in the inkjet recording apparatus of the present invention will be described. FIG. 8 is a schematic diagram showing an example of a method for manufacturing a line head. As shown in FIG. 8, the method for manufacturing the line head of the present embodiment includes the first step (a) of preparing the substrate 11 on which the heater 16 is formed and the surface of the substrate 11 on which the heater 16 is formed. It has a second step (b) of arranging a flow path type material 18 that can be selectively removed. In the method of manufacturing the line head of the present embodiment, the orifice plate 12 is further arranged so as to cover the flow path mold material 18, and the third step (c) of forming the discharge port 17 in the orifice plate 12 and the substrate 11 are penetrated. It has a fourth step (d) of forming the liquid supply port 14. Further, in the method for manufacturing the line head of the present embodiment, at least one of the fifth step (e) of removing the flow path mold material 18 to form a liquid flow path, and the liquid flow path 13 and the liquid supply port 14. It has a sixth step (f) of forming a protective film 15 containing a hydrophilic material on the inner wall surface of the above.

In the first step (a), a heater 16 which is a heat generation resistor functioning as a discharge pressure generating element and a drive circuit (not shown) thereof are formed on the substrate 11 by a general-purpose semiconductor process. The substrate 11 is made of, for example, silicon. Of both sides of the substrate 11, the surface on which the heater 16 is formed is the front surface, and the opposite surface is the back surface.

In the second step (b), a polymethylisopropenyl ketone, which is a UV (ultraviolet) resist that can be eluted and removed in a later step, is solvent-coated on the substrate 11. The solvent-coated UV resist is exposed to UV light and developed to form and arrange the flow path mold material 18.

In the third step (c), a cationically polymerized epoxy resin which is a negative resist is applied onto the surface of the substrate 11 on which the flow path type material 18 is arranged, and the ceiling of the liquid flow path 13 and each liquid flow path 13 are applied. Form a flow path wall that separates them from each other. The applied negative resist is exposed and developed using a photomask having a predetermined pattern, and the negative resist at the discharge port 17 and the electrode pad (not shown) is removed to form the orifice plate 12.

In the fourth step (d), a resist is applied to both sides (front surface and back surface) of the substrate 11, and a predetermined pattern having an opening corresponding to a position where the liquid supply port 14 is formed is applied to the resist on the back surface by a photolithography technique. Patterned by. Then, dry etching is performed using this resist as a mask to form a supply port 14 which is a through hole through the substrate 11. As the dry etching, for example, an ICP (Inductive Coupling Plasma) -RIE (Reactive Ion Etching) etcher can be used.

In the fifth step (e), the resist on both sides (front surface and back surface) of the substrate 11 is removed with a stripping solution, and then the resist is reapplied to the surface of the substrate 11. After that, it is immersed in methyl lactate while applying ultrasonic waves to dissolve the flow path type material 18 formed of a positive photosensitive resist or the like and let it flow out from the liquid supply port 14. As a result, the liquid flow path 13 is formed.

In the sixth step (f), the boundary between the substrate 11 and the orifice plate 12 is shielded as needed. Then, in this state, the membrane source is introduced into the liquid supply port 14 from the back surface side of the substrate 11. As a result, the protective film 15 containing a hydrophilic material can be selectively formed on the inner wall surface of the liquid supply port 14. On the other hand, if the film source is introduced from the surface side of the substrate 11, the protective film can be selectively formed on the inner wall surface of the liquid flow path 13. Further, if the film source is introduced in an unshielded state, a film can be formed on both the liquid flow path 13 and the liquid supply port 14. Examples of the film forming method include a plasma CVD (Chemical Vapor Deposition) method, a catalytic CVD method, a thin film deposition method, and a film forming method by a physical action or a chemical action such as a sputtering method.

Any recording medium may be used as a recording medium for recording an image by the inkjet recording method of the present invention. Among them, it is preferable to use a recording medium having no coated layer such as plain paper or uncoated paper, and a paper having permeability such as a recording medium having a coated layer such as glossy paper or art paper.

(liquid)
Hereinafter, each component constituting the liquid used in the liquid discharge method of the present invention, the physical properties of the liquid, and the like will be described in detail. The liquid used in the liquid discharge method of the present invention is an aqueous liquid containing a component having an anionic group. Examples of such a liquid include ink containing a coloring material, a reaction liquid used in combination with the ink, and clear ink. The reaction solution contains a reactant that reacts with a coloring material or the like in the ink. The clear ink contains substantially no coloring material. The liquid used in the liquid ejection method of the present invention may be ink, reaction liquid, or clear ink. The liquid used in the present invention does not have to be a so-called "curable liquid". Therefore, the liquid used in the present invention does not have to contain a compound such as a polymerizable monomer that can be polymerized by the addition of external energy.

[Components with anionic groups]
Examples of the component having an anionic group include a coloring material such as a dye or a pigment having an anionic group when the liquid is an ink. When a coloring material is used as a component having an anionic group, a self-dispersing pigment in which the anionic group is bonded directly to the particle surface or via another atomic group; a resin having an anionic group (resin dispersant) is used. It is preferably in the form of a resin-dispersed pigment or the like. In addition, when the liquid is a reaction liquid, examples of the component having an anionic group include a reactant and the like. Examples of the component having an anionic group that can be used in any liquid include a resin having an anionic group, an anionic surfactant, and a salt of a monovalent cation. Salts can generate anions by ionic dissociation. These components are adsorbed on the pinhole formed in the protective film containing the hydrophilic material covering the inner wall surface of the liquid flow path and the liquid supply port, and suppress the dissolution of the inner wall surface of the liquid flow path and the liquid supply port. It is effective.

As the component having an anionic group, it is particularly preferable to use a resin dispersant for dispersing the pigment. When the pigment dispersed by the resin dispersant is present in the ink, the steric repulsion effect is stronger than in the case where other components having anionic groups are present. Therefore, it becomes easy to be adsorbed on the inner wall surface of the liquid flow path and the liquid supply port, and the effect of suppressing the dissolution can be obtained at a higher level.

Examples of the anionic surfactant include various anionic surfactants such as a carboxylic acid type, a sulfonic acid type, a sulfate ester type, and a phosphoric acid ester type, and salts thereof. The content (% by mass) of the anionic surfactant in the liquid is preferably 0.1% by mass or more and 5.0% by mass or less, and 0.1% by mass or more and 1. It is more preferably 0% by mass or less.

The salt of a monovalent cation is a salt formed by binding a monovalent cation and an anion. Examples of the monovalent cation include alkali metal ion, ammonium ion, and organic ammonium ion. Examples of the alkali metal ion include ions such as lithium, sodium and potassium. Examples of the organic ammonium ion include those in which at least one hydrogen atom of the ammonium ion is substituted with an organic group. Anions that bind to monovalent cations include ^Cl- , ^Br- , I- ^{, ClO-} , ClO ^{2- ,} ClO _3- ^, ClO _4- , NO _2- ^, NO _3- ^, SO ₄ ^2- _, CO ₃ ^2- , HCO _3- ^, HCOO- ^, ( ^COO- ) ₂ , COOH ( ^COO- ), CH ₃ COO- ^, C ₂ H ₄ ( ^COO- ) ₂ , C ₆ H ₅ COO- ^, C ₆ H ₄ (COO-) ^- ) ₂ , PO ₄ ^3- , HPO ₄ ^2- , ^and H ₂ PO _4- . The content (% by mass) of the salt of the monovalent cation in the liquid is preferably 0.1% by mass or more and 3.0% by mass or less, and 0.1% by mass or more and 1. It is more preferably 0% by mass or less.

The charge amount of the component having an anionic group is preferably 0.005 mmol / g or more, and more preferably 0.005 mmol / g or more and 0.050 mmol / g or less. If the charge amount of the component having an anionic group is less than 0.005 mmol / g, the effect of suppressing the dissolution of the inner wall surface of the liquid flow path and the liquid supply port may be insufficient. The amount of charge of the component having an anionic group is a value measured for a liquid by an ion probe method and converted per 1 g of the liquid.

[Color material]
As the coloring material, either a dye or a pigment can be used. Examples of the dye include those having an anionic group. As the dye, a compound having a skeleton such as phthalocyanine, azo, xanthene, and anthrapyridone can be used. In addition, examples of the pigment include an inorganic pigment and an organic pigment. Considering the recording on plain paper, it is preferable to use the pigment as a coloring material. As the pigment, a resin dispersion type pigment using a resin as a dispersant, a self-dispersion type pigment having a hydrophilic group introduced on the particle surface of the pigment (self-dispersion pigment), and the like can be used. Pigments with different dispersion methods can also be used in combination. In the inkjet recording method of the present invention, it is preferable to use a resin-dispersed pigment as a coloring material.

As the resin dispersion type pigment, a resin dispersion type pigment using a polymer dispersant, a microcapsule type pigment in which the surface of the pigment particles is coated with a resin, and an organic group containing a polymer on the surface of the pigment particles are chemically used. There are resin-bound pigments that are specifically bonded. Pigments with different dispersion methods can also be used in combination. As the resin, it is preferable to use an acrylic resin having at least a unit having an anionic group such as (meth) acrylic acid and a unit having no anionic group such as a monomer having an aromatic ring or an aliphatic group.

Examples of the self-dispersion type pigment include those in which an anionic group is directly bonded to the particle surface of the pigment or via another atomic group. Examples of the anionic group include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. Examples of the counter ion of the anionic group include cations such as hydrogen atom, alkali metal, ammonium, and organic ammonium. Further, the other atomic group has a function of a spacer between the particle surface of the pigment and the ionic group, and the molecular weight is preferably 1,000 or less. Examples of other atomic groups include an alkylene group having about 1 to 6 carbon atoms; an arylene group such as a phenylene group and a naphthylene group; an ester group; an imino group; an amide group; a sulfonyl group; an ether group. Further, it may be a group in which these groups are combined.

The content (mass%) of the coloring material in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass, based on the total mass of the ink. The following is more preferable. Above all, it is particularly preferable that it is 2.0% by mass or more and 10.0% by mass or less. If the content of the coloring material is less than 2.0% by mass, the optical density of the recorded image may decrease. On the other hand, if the content of the coloring material is more than 10.0% by mass, the nozzle may be easily clogged.

[Reactant]
As the reactant, a polyvalent metal salt or an organic acid can be used. The polyvalent metal salt is composed of polyvalent metal ions and anions. The content (% by mass) of the reactant in the reaction solution is preferably 1.0% by mass or more and 50.0% by mass or less, and 2.0% by mass or more and 40.0 by mass, based on the total mass of the reaction solution. It is more preferably mass% or less. Above all, it is particularly preferable that it is 3.0% by mass or more and 30.0% by mass or less.

Examples of the polyvalent metal ion include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , Sr ²⁺ , and Ba ²⁺ ; Al ³⁺ , Fe ³ Trivalent metal ions such as ⁺ , Cr ³⁺ , and Y ³⁺ can be mentioned. Examples of anions include ^Cl- , ^Br- , I- ^{, ClO-} , ClO ^{2- ,} ClO _3- ^, ClO _4- , NO ^{2- ,} NO _3- ^, SO _{4 2-} , CO ₃ ^2- _{, and HCO 3 .} ^- , HCOO- ^, ( ^COO- ) ₂ , COOH ( ^COO- ), CH ₃ COO- ^, C ₂ H ₄ ( ^COO- ) ₂ , C ₆ H ₅ COO- ^, C ₆ H ₄ ( ^COO- ) ₂ , PO ₄ ^3- , HPO ₄ ^2- , and H ₂ PO ₄ ^-- and so on. The form of the polyvalent metal salt in the liquid may be either a partially dissociated state or a completely dissociated state.

Examples of organic acids include monocarboxylic acids such as formic acid, acetic acid, propionic acid and butyric acid; phthalic acid, isophthalic acid, terephthalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid. , Itaconic acid, sebacic acid, dimer acid, pyromellitic acid, dicarboxylic acid such as trimellitic acid; tricarboxylic acid such as citric acid; hydroxycarboxylic acid such as oxysuccinic acid, DL-apple acid, tartrate acid and the like. These organic acids may be salts. Of these, a carboxylic acid having an alkyl chain having 3 or less carbon atoms is preferable because of its high water solubility. Examples of the cation forming the salt of the organic acid include alkali metal ions such as lithium, sodium and potassium; ammonium ion; and organic ammonium ion.

[resin]
As the resin, a resin generally blended in a liquid used in a liquid ejection method such as an inkjet recording method can be used. The state of the resin in the liquid may be a state of being dissolved in an aqueous medium or a state of being dispersed as resin particles in the aqueous medium. As a component having an anionic group, a resin having an anionic group can also be used. Specific examples of the resin include acrylic resin, polyester resin, urethane resin and the like. Among them, acrylic resin and urethane resin are preferable because they can improve the discharge stability and the storage stability of the liquid. As the acrylic resin, for example, it is preferable to use a copolymer having a unit having an acid group and a unit having no acid group. As the urethane resin, for example, it is preferable to use a urethane resin obtained by reacting a polyol with a polyisocyanate. The urethane resin may be further reacted with a component serving as a chain extender or a cross-linking agent.

The content (% by mass) of the resin in the liquid is preferably 0.1% by mass or more, more preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the liquid. .. If the content of the resin is less than 0.1% by mass, the amount of the resin is too small, and it becomes difficult to sufficiently close the pinholes formed in the protective film. The effect of suppressing the dissolution of the inner wall surface may be insufficient.

[Aqueous medium]
The liquid contains water as an aqueous medium. As the water, it is preferable to use deionized water (ion-exchanged water). The content (% by mass) of water in the liquid is preferably 50.0% by mass or more and 95.0% by mass or less, and 60.0% by mass or more and 95.0% by mass or less, based on the total mass of the liquid. Is more preferable.

The liquid can further contain a water-soluble organic solvent as an aqueous medium. As the water-soluble organic solvent, any of those generally used for the liquid applied to the liquid ejection method such as the inkjet recording method can be used. Specific examples of the water-soluble organic solvent include alkyl alcohols having 1 to 4 carbon atoms, amides, ketones or keto alcohols, ethers, polyalkylene glycols, glycols, and alkylene groups having 2 to 6 carbon atoms. Alkylene glycols, alkyl ether acetates, alkyl ethers of polyhydric alcohols, nitrogen-containing compounds and the like can be mentioned. These water-soluble organic solvents can be used alone or in combination of two or more. The content (% by mass) of the water-soluble organic solvent in the liquid is preferably 3.0% by mass or more and 50.0% by mass or less, and 5.0% by mass or more and 30.0 by mass, based on the total mass of the liquid. It is more preferably mass% or less.

Normally, the "water-soluble organic solvent" means a compound in a liquid state, but in the present invention, a compound that is solid at 25 ° C. (normal temperature) becomes a liquid medium that dissolves in water to form a liquid. For convenience, it is included in the water-soluble organic solvent. Specific examples of the water-soluble organic solvent that is versatile as a liquid for inkjet ejection and is solid at 25 ° C. include 1,6-hexanediol, trimethylolpropane, ethyleneurea, urea, and polyethylene having a number average molecular weight of 1,000. Glycol and the like can be mentioned.

[Surfactant]
The liquid can contain a surfactant. The content (% by mass) of the surfactant in the liquid is preferably 0.1% by mass or more and 5.0% by mass or less, and 0.25% by mass or more and 3.0% by mass, based on the total mass of the liquid. % Or less is more preferable. Specific examples of surfactants include hydrocarbon-based surfactants such as ethylene oxide adducts of acetylene glycol, polyethylene glycol alkyl ethers, and polyoxyethylene polyoxypropylene block polymers; and fluorine such as perfluoroalkyl ethylene oxide adducts. Surfactant of the system; A silicone-based surfactant such as a polyether-modified siloxane compound can be mentioned. Above all, it is preferable to use a hydrocarbon-based surfactant. These surfactants can be used alone or in combination of two or more.

[Other ingredients]
In addition to the above-mentioned components, the liquid includes a resin, a pH adjuster, a rust inhibitor, a preservative, an antifungal agent, an antioxidant, and an anti-reduction agent in order to obtain a liquid having a desired physical property value as needed. Various additives such as agents may be contained.

[Physical characteristics of liquid]
The viscosity of the liquid at 25 ° C. is preferably 1.0 mPa · s or more and 10.0 mPa · s or less, more preferably 1.0 mPa · s or more and 5.0 mPa · s or less, and 1.0 mPa · s. It is particularly preferable that the content is 3.0 mPa · s or less. The surface tension of the liquid at 25 ° C. is preferably 28 mN / m or more and 45 mN / m or less. The pH of the liquid at 25 ° C. is preferably 5 or more and 9 or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. Unless otherwise specified, those described as "part" and "%" regarding the amount of components are based on mass.

<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
A styrene-acrylic acid copolymer (weight average molecular weight 10,000, acid value 200 mgKOH / g), which is a water-soluble resin, is dissolved in ion-exchanged water using potassium hydroxide having a neutralization equivalent of 1, and contains the resin. An aqueous solution of the resin dispersant having an amount of 20.0% was prepared. A mixture of 15.0 parts of carbon black, 30.0 parts of an aqueous solution of a resin dispersant, and 55.0 parts of water was placed in a sand grinder and dispersed for 1 hour. The coarse particles were removed by centrifugation, and the mixture was pressure-filtered with a microfilter (manufactured by Fujifilm) having a pore size of 3.0 μm, and then an appropriate amount of ion-exchanged water was added to obtain a pigment dispersion liquid 1. The content of the pigment in the pigment dispersion 1 was 15.0%, and the content of the resin (solid content) was 6.0%.

(Pigment dispersion liquid 2)
The solid content of a commercially available pigment dispersion (trade name "Cab-O-Jet470YA", manufactured by Cabot) was adjusted to prepare a pigment dispersion having a pigment content of 15.0%. The pigment dispersion 2 contains a self-dispersing pigment in which a phosphonic acid group is bonded to the surface of the particles of the yellow pigment via another atomic group.

<Preparation of aqueous resin solution>
A styrene-acrylic acid copolymer (weight average molecular weight 8,000, acid value 200 mgKOH / g), which is a water-soluble resin, is dissolved in ion-exchanged water using potassium hydroxide having a neutralization equivalent of 1, and the resin (solid) is dissolved. An aqueous solution of resin 1 having a content of (1) of 10.0% was obtained.

<Preparation of liquid>
Each component (unit:%) shown in the upper part of Table 1 was mixed and sufficiently stirred, and then pressure filtration was performed with a cellulose acetate filter (manufactured by Advantech) having a pore size of 1.20 μm to prepare each liquid. The amount of charge of the prepared liquid was measured with an ion probe type potassium electrode or calcium electrode (manufactured by HORIBA, Ltd.), and the obtained values were converted into 1 g of liquid and shown in the lower part of Table 1. From the value of this amount of charge, the number of moles of anionic groups present in the liquid was estimated.

<Evaluation>
The evaluations shown below were performed using the combinations of liquids and line heads shown on the left side of Table 2. The line heads used in Examples 1 to 3, 5 to 9, 12 , Reference Examples 4A, 10, 11, 13, 14, Comparative Example 3, and Reference Examples 3 and 4 carry out the above-mentioned steps 1 to 6. It was made by In each case, the thickness of the protective film 15 (FIG. 7 (b)) was about 100 nm, and the static contact angle for pure water was 30 °. On the other hand, the line heads used in Comparative Examples 1 and 2 and Reference Examples 1 and 2 were manufactured without performing only the sixth step. The evaluation results are shown on the right side of Table 2. In the evaluation criteria shown below, "AAAA", "AAA", "AA", "A", and "B" were set as acceptable levels, and "C" was set as an unacceptable level.

(Discharge stability)
An inkjet recording device having the configuration shown in FIG. 2 and further having the recovery mechanism shown in FIG. 4 and the supply mechanism shown in FIG. 5 was prepared. The main tank of this inkjet recording device was filled with the prepared liquids. Then, in Examples 1 to 3, 5 to 9, 12 , Reference Examples 4A, 10, 11, 13, 14 and Comparative Examples 1 to 3, a liquid is pumped to the sub tank and filled in the line head and its inside. A heater for temperature adjustment and a heater for discharge were used in combination to heat the liquid so that the temperature of the liquid was 60 ° C. In Reference Examples 1 to 4, the liquid was not heated. It was confirmed that the liquid was normally discharged from each nozzle by performing the pressure recovery operation by the recovery mechanism and the supply mechanism. Then, under the condition that 20 ng of liquid was applied per 1/600 inch square, 100 image patterns to be recorded on the entire surface of the A4 size recording medium were continuously recorded. Then, in order to confirm the presence or absence of the nozzles that did not eject, a solid image was recorded on the entire surface of an A4 size recording medium under the condition that 2 ng of liquid was applied per 1/600 inch square. At this time, for the liquid containing no coloring material, a commercially available transparency film was used as a recording medium in order to make it easy to confirm non-ejection. The recorded solid image was visually confirmed, and the ejection stability was evaluated according to the evaluation criteria shown below.
A: There was no nozzle that did not discharge.
C: There was a nozzle that did not discharge.

(Dissolution suppression)
First, the hydrophilic material shown in Table 2 was formed as a protective film on the silicon wafers in each of the directions (100), (110), and (111). After cutting a silicon wafer to an appropriate size, the back surface and end surface of the chip whose silicon surface is exposed are sealed with a photoresist material (trade name "OFPR-PR8PM", manufactured by Tokyo Ohka Kogyo Co., Ltd.) to form a sample chip. Made. The prepared sample chips were immersed in a closed container filled with each liquid and stored at 60 ° C. for 7 days. The mass of the chip after storage was determined from the mass of the chip before storage and the amount of silicon elution obtained by analyzing the liquid after storage by ICP. From these values, the silicon elution rate (%) is calculated according to the formula: silicon elution rate (%) = {(mass of chip before storage-mass of chip after storage) / mass of chip before storage} × 100. I asked. From the average value of the silicon elution rate for the three types of silicon wafers, the dissolution suppression was evaluated according to the evaluation criteria shown below.
AAAA: The average value of the silicon elution rate was less than 3%.
AAA: The average value of the silicon elution rate was 3% or more and less than 5%.
AA: The average value of the silicon elution rate was 5% or more and less than 10%.
A: The average value of the silicon elution rate was 10% or more and less than 30%.
B: The average value of the silicon elution rate was 30% or more and less than 50%.
C: The average value of the silicon elution rate was 50% or more.

In Reference Examples 1 to 4 in which the liquid was not heated, many unacceptable levels of unevenness occurred in the image pattern recorded during the evaluation of ejection stability.

Claims (9)

A liquid ejection method in which a liquid is ejected to a recording medium using an inkjet recording apparatus including a liquid, a line head for ejecting the liquid, and a heating mechanism for heating the liquid in the line head. There,
The liquid is an aqueous liquid containing a component having an anionic group.
Inside the line head, a liquid flow path having a discharge port for discharging the liquid and a liquid supply port communicating with the liquid flow path are formed, and at least the liquid flow path and the liquid supply port are formed. One of the inner wall surfaces is covered with a protective film made of titanium oxide, which is a hydrophilic material.
The charge amount of the component having an anionic group is 0.005 mmol / g or more, and the charge amount is 0.005 mmol / g or more.
The method of discharging the liquid from the discharge port is a method of using a liquid discharge heater.
The liquid in the line head is brought to 40 ° C. or higher and 70 ° C. or lower by a heater arranged so as to repeatedly energize the liquid discharge heater with a current that does not discharge the liquid or to make contact with the line head. A liquid discharge method characterized by heating. The liquid discharge method according to claim 1, wherein the component having an anionic group is at least one selected from the group consisting of the following (i) to (v).
(I) Self-dispersing pigment in which anionic groups are bonded directly to the surface of the particles or via other atomic groups (ii) Resin having anionic groups (iii) Anionic surfactants (iv) Polyvalent metal salts and A reactant that can generate anions in the liquid, selected from the group consisting of organic acids (v) Salts of monovalent cations that can dissociate in the liquid and generate anions. The liquid discharge method according to claim 1 or 2, wherein the liquid is at least one selected from the group consisting of the following (i) to (iii).
(I) Ink containing a color material (ii) Reaction liquid used in combination with an ink containing a color material (iii) Clear ink containing no color material used in combination with an ink containing a color material The liquid further contains a pigment and
The liquid ejection method according to claim 1 or 2, wherein the component having an anionic group is a resin dispersant for dispersing the pigment. The liquid discharge method according to any one of claims 1 to 4 , wherein the inner wall surfaces of both the liquid flow path and the liquid supply port are covered with the protective film. The liquid discharge method according to any one of claims 1 to 5 , wherein the surface of the protective film is negatively charged. The liquid discharge method according to any one of claims 1 to 6 , wherein the static contact angle of the hydrophilic material with respect to pure water is 50 ° or less. The liquid discharge method according to any one of claims 1 to 7 , wherein the charge amount of the component having an anionic group is 0.050 mmol / g or less. An inkjet recording apparatus comprising a liquid, a line head in which the liquid is filled, a line head for discharging the liquid, and a heating mechanism for heating the liquid in the line head.
The liquid is an aqueous liquid containing a component having an anionic group.
Inside the line head, a liquid flow path having a discharge port for discharging the liquid and a liquid supply port communicating with the liquid flow path are formed, and at least the liquid flow path and the liquid supply port are formed. One of the inner wall surfaces is covered with a protective film made of titanium oxide, which is a hydrophilic material.
The charge amount of the component having an anionic group is 0.005 mmol / g or more, and the charge amount is 0.005 mmol / g or more.
The method of discharging the liquid from the discharge port is a method of using a liquid discharge heater.
The liquid in the line head is brought to 40 ° C. or higher and 70 ° C. or lower by repeatedly energizing the liquid discharge heater with a current to the extent that the liquid does not discharge, or by a heater arranged so as to contact the line head. An inkjet recording device characterized by heating.

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