CN115851036A - Ink for ink jet, ink jet printer, and ink jet recording method - Google Patents
Ink for ink jet, ink jet printer, and ink jet recording method Download PDFInfo
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- CN115851036A CN115851036A CN202210720030.4A CN202210720030A CN115851036A CN 115851036 A CN115851036 A CN 115851036A CN 202210720030 A CN202210720030 A CN 202210720030A CN 115851036 A CN115851036 A CN 115851036A
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Abstract
Provided are an ink jet ink, an ink jet printer, and an ink jet recording method, wherein the ink jet ink can form a high-quality image on a recording medium having irregularities on the surface thereof while suppressing the generation of satellite droplets and mist while maintaining stable ink ejection performance even when the distance from the ink jet head to the recording medium is large. Description of the preferred embodimentsThe ink for ink jet contains a colorant and a resin, the content of water is less than 10% by mass, and when the dynamic surface tension at a surface life of 0.015 second measured at 25 ℃ by the maximum bubble pressure method is defined as gamma 1 and the dynamic surface tension at a surface life of 1.2 second is defined as gamma 2, the amount of change X in the dynamic surface tension per 1 second expressed by the following formula is 15mN/m or more, and X = (gamma 1) － γ2)/(1.2 － 0.015)。
Description
Technical Field
Embodiments of the present invention relate to an ink for inkjet and an inkjet printer.
Background
In recent years, with the rapid development of ink jet image forming technology, it is possible to output high-quality images comparable to photographic images. Inkjet is characterized in that an appropriate amount of ink can be accurately dropped onto a predetermined position in a non-contact manner, and the inkjet is applied to various application programs. Meanwhile, recording media and inks are various and vary depending on the application used. Among these, there is an increasing demand for printing by enlarging the distance between the discharge nozzle surface of the inkjet head and the recording medium surface, that is, by enlarging the gap, according to the unevenness of the recording medium surface.
In the case of low-speed printing and a small gap, the landing position of the main droplets is almost the same as the landing positions of the mist and the satellite droplets with respect to the landing of the ink on the surface of the recording medium, and therefore, the deviation of the landing positions of the mist and the satellite droplets from the landing positions of the main droplets has not been a problem in the past. However, as high-speed printing is performed and the gap is enlarged, a large deviation occurs between the landing position of the main droplets and the landing positions of the mist and the satellites, and this may cause deterioration of the print image quality.
As a technique for improving this situation, there is a method of increasing the static surface tension of the ink. Generally known are: as the static surface tension of the ink increases, the generation of mist and satellites, that is, the deviation of the landing positions of the mist and satellites from the landing positions of the main droplets can be reduced. However, when the static surface tension of the ink is increased to reduce the generation of mist and satellites, there is a problem that the ink is likely to cause the non-ejection of droplets when the ink is continuously ejected. This phenomenon is considered to be a cause of an unstable ejection state when ink droplets are ejected from the head due to the excessively high static surface tension of the ink.
In water-based ink jet inks, in order to improve desired performance, a technique for adjusting dynamic surface tension has been reported. However, there has been no ink jet ink proposed so far which can suppress the generation of mist and satellite droplets due to the deviation of the landing position of the ink while maintaining the ink ejection stability even when the distance (gap) between the ink jet head and the surface of the recording medium is increased with respect to the recording medium having irregularities on the surface.
Disclosure of Invention
The problem to be solved by the present invention is to provide: an ink jet ink and an ink jet printer capable of forming a high-quality image on a recording medium having irregularities on the surface thereof while suppressing the generation of mist and satellites while maintaining stable ink ejection performance even when the gap from the ink jet head to the recording medium is large.
According to embodiment 1, there is provided an ink for inkjet, including a colorant and a resin, wherein a content of water is less than 10% by mass, and wherein a change X of a dynamic surface tension per 1 second represented by the following formula is 15mN/m or more, X = (γ 1), where γ 1 is a dynamic surface tension at a surface life of 0.015 second measured at 25 ℃ by a maximum bubble pressure method, and γ 2 is a dynamic surface tension at a surface life of 1.2 seconds － γ2)/(1.2 － 0.015)。
According to embodiment 2, there is provided an inkjet printer including: an inkjet head that ejects ink toward a recording medium; and a medium holding mechanism that holds the recording medium so as to face the inkjet head, wherein the ink is the inkjet ink according to the embodiment.
Drawings
Fig. 1 is a perspective view showing a schematic configuration of an ink jet head provided in an ink jet printer according to embodiment 2.
Fig. 2 is an exploded perspective view showing a schematic configuration of a part of the inkjet head.
Fig. 3 is an explanatory diagram showing a configuration of the inkjet printer according to embodiment 2.
Fig. 4 (a) and 4 (b) are schematic plan views for explaining the method of evaluating the generation state of mist or satellite droplets on the recording medium according to the example.
Description of the symbols
1. An ink jet head; 10. an ink manifold; 11. an ink supply tube; 12. an ink return tube; 20. an actuator substrate; 21. an ink supply port; 22. an ink discharge port; 30. an actuator; 31. a wiring pattern; 40. a frame; 50. a nozzle plate; 60. a flexible printed substrate; 61. a drive circuit; 100. an ink jet printer; 101a, 101b, a cartridge; 102. 103, a paper feed roller; 104. 105, a conveying roller pair; 106. a pair of registration rollers; 107. a conveyor belt; 111. a negative pressure chamber; 112. 113, 114, a conveying roller pair; 115C (1), 115M (1), 115Y (1), 115Bk (1), an inkjet head; 116C, 116M, 116Y, 116Bk, ink cartridges; 117C, 117M, 117Y, 117Bk, tube; 118. a paper discharge tray; 119. a fan; n, a nozzle; p, a recording medium; d1, main liquid drops; d2, mist or satellite droplets.
Detailed Description
The embodiments will be described in detail below.
The "mist" and the "satellite droplets" may be treated differently, but may not be treated differently. That is, "mist" refers to ink separated from a main droplet dropped from a head of an ink jet printer and formed into mist, and "satellite droplets" refers to ink separated from the main droplet and remaining in droplet form, and as described above, the ink may be handled differently, but the ink is often handled as a general term for the above phenomenon without distinction. In the present specification, the terms "mist" and "satellite" are used as a general term for a droplet that lands on a portion other than the first target portion, that is, a droplet separated from the main droplet and lands deviating from the main droplet, without strictly distinguishing the terms from the mist and the satellite.
Ink for ink jet
The inkjet ink according to embodiment 1 is an inkjet ink to be ejected from an inkjet head of an inkjet printer.
The ink jet ink according to the present embodiment is an ink jet ink in which the amount of change X in the dynamic surface tension per 1 second represented by the following formula I is 15mN/m or more, where γ 1 is the dynamic surface tension at a surface life of 0.015 second measured at 25 ℃ by the maximum bubble pressure method, and γ 2 is the dynamic surface tension at a surface life of 1.2 seconds.
X = (gamma 1-gamma 2)/(1.2-0.015) (formula I)
The dynamic surface tension is a value measured at 25 ℃ by the maximum bubble pressure method, and can be measured, for example, by using a dynamic surface tensiometer (SITA pro line t 15) (manufactured by SITA Messtechnik GmbH). The term "surface life" also means "bubble life" (b.l. time), which is the life of a bubble generated by the maximum bubble pressure method, and means the time from the time when a new interface is generated in the probe tip of the dynamic surface tensiometer to the time when the bubble pressure reaches the maximum bubble pressure.
The change amount X of the dynamic surface tension calculated by the formula (I) is a change amount per 1 second of the dynamic surface tension during a surface lifetime from 0.015 second to 1.2 seconds, in other words, an inclination of the dynamic surface tension value during a surface lifetime from 0.015 second to 1.2 seconds. Here, for the reason described in the following paragraph, "0.015 seconds" of the surface life is selected from the viewpoint of the minimum surface life that can be measured in a dynamic surface tensiometer. On the other hand, during the period in which the dynamic surface tension value is in equilibrium with the passage of time, the surface life "1.2 seconds" of the surface life is selected as the surface life at the time when the value becomes a value close to the static surface tension value.
The reason why "0.015 second" is selected as the surface life from the viewpoint of the minimum surface life that can be measured by a dynamic surface tensiometer is as follows.
It is considered that the higher the surface tension of the liquid droplets when the ink is ejected from the ink jet head, the more easily the liquid droplets are aggregated into one droplet, and the mist and the satellite droplets, which are a phenomenon in which the liquid droplets are scattered in a small amount, are reduced. Since the ink is ejected from the inkjet head with a high ejection driving frequency and is formed into droplets in units of microseconds (μ s), the surface life of the dynamic surface tension is estimated to be very short to μ s units with respect to the instantaneous surface tension value of the droplets formed at the time of ejection. Further, it is considered that the surface tension in this instantaneous state is related to the aggregation of the discharged droplets, but a dynamic surface tension meter capable of measuring the dynamic surface tension up to μ s unit does not exist at present. Therefore, as described above, the minimum measurable surface life (0.015 seconds) was replaced with μ s.
The dynamic surface tension at 0.015 second and 1.2 second surface lives was measured, and it was found that the gradient (change amount per 1 second) from the static (1.2 second) to dynamic (0.015 second) surface tension value can be used as a parameter of an ink jet ink which can form an image with high image quality while suppressing generation of satellite droplets and mist, and the present invention was completed. In other words, when the amount of change X is 15mN/m or more, the surface tension of the droplets when the ink is ejected from the inkjet head is sufficiently high, the droplets are likely to aggregate into one droplet, and the generation of mist and satellites, which are a phenomenon in which the droplets are scattered in small amounts, can be suppressed.
In the present embodiment, the change amount X of the dynamic surface tension per 1 second between 0.015 second and 1.2 second of the surface life is 15mN/m or more as described above, and is preferably higher. The upper limit value is a matter of design depending on the specific application of the technology, and is not particularly set here.
The inkjet ink according to the present embodiment can suppress the generation of mist and satellite droplets without increasing the static surface tension, and therefore has excellent ejection stability. In the present embodiment, the static surface tension of the ink jet ink may be, for example, in the range of 20mN/m or more and 40mN/m or less. The static surface tension of the present embodiment is a value measured at 25 ℃ by the Wilhelmy method.
Hereinafter, components contained in the ink jet ink according to the present embodiment will be described.
The ink jet ink according to the present embodiment contains at least a colorant and a resin, and basically contains a solvent. The ink jet ink according to the present embodiment contains at least an organic solvent as the solvent, and may or may not contain water. Here, "not containing water" refers to an ink for inkjet that is intentionally produced so as not to contain water. For example, water contained in the ink due to water vapor contained in the atmosphere, water contained in the additive, or the like is treated as "water-free" rather than water as a solvent due to a cause not intended by the manufacturer. The water content in this case was "0 mass%".
In the ink jet ink according to the present embodiment, the content of water is less than 10% by mass based on the total mass of the ink. Here, "less than 10% by mass" relating to the content of water also includes the case where "no water" is contained in the above meaning, and therefore, the content of water in the ink jet ink according to the present embodiment is 0% by mass or more and less than 10% by mass. In the inkjet ink according to the present embodiment, the content of water is more preferably 0% by mass or more and 5% by mass or less.
Further, as the components contained in the ink jet ink according to the present embodiment, as long as the amount of change X in the dynamic surface tension represented by the above formula I is 15mN/m or more, colorants and resins generally used in ink jet inks and other arbitrary components can be appropriately used according to the purpose. The adjustment of the dynamic surface tension can be appropriately adjusted by selecting components contained in the ink for inkjet, the amount of the components to be blended, and the like. In general, there is a tendency that: the component having a large surface tension has a large influence on the dynamic surface tension. Therefore, for example, water has a higher surface tension than an organic solvent or an ultraviolet curable resin, and therefore, it is considered that the dynamic surface tension and the like are adjusted by paying attention to the blending ratio when water is used.
(coloring agent)
As the colorant contained in the ink jet ink according to the present embodiment, a pigment is suitably used. The pigment may be any pigment as long as it is a coloring material generally known as a pigment, has a desired optical coloring or coloring function, and can be dispersed in the ink. The pigment may be, for example, an inorganic pigment, an organic pigment, glass particles, or the like. The pigment may have properties such as a thermal indicating pigment (thermochromic pigment), or may have other properties such as magnetic properties, fluorescent properties, conductive properties, dielectric properties, and the like in addition to coloring properties and coloring properties. In this case, various functions can be provided to the image. In addition, a powder for improving heat resistance and physical strength can be added.
Examples of the inorganic pigment that can be used include titanium oxide, calcium carbonate, kaolin, aluminum, ceramics, glass, and the like, which are materials obtained as carbon black or ground mineral. In addition, synthetic inorganic pigments and the like can also be used, and examples thereof include red iron oxide, cadmium yellow, nickel titanium yellow, strontium yellow, hydrous chromium oxide, cobalt aluminate, synthetic ultramarine blue and the like.
Examples of the organic pigment that can be used include polycyclic pigments such as phthalocyanine pigments and anthraquinone pigments. Specific examples thereof include isoindolinone, isoindoline, azomethylfluorene, anthraquinone, anthrone, xanthene, diketopyrrolopyrrole, perylene, anthraquinone (anthrone), peryleneketone, quinacridone, indigo, quinacridone, diketopyrrolopyrrole, anthraquinone, perylene, perinone, indigo, dioxazine, quinacridone, perylene, indigo, anthraquinone (anthrone), xanthene, phthalocyanine, anthraquinone, indigo, phthalocyanine, azomethide, perylene, and the like. Azo pigments, lake pigments, fluorescent pigments, and the like can also be used.
Examples of the glass particles that can be used include colored glass particles, colorless glass particles, and the like, and colored or colorless glass composition mixture particles vitrified by heat treatment may be used.
The particle diameter of the pigment contained in the inkjet ink according to the present embodiment is preferably as small as possible, which enables inkjet ejection and can achieve a function.
The average particle diameter of the pigment is, for example, preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.01 to 1 μm. Here, the average particle diameter of the pigment is a cumulative average particle diameter analyzed based on the cumulative amount. For example, as for the average particle size of the pigment, an ink sample is diluted by about 500 times in a solvent, and the particle size of the diluted sample is measured by a dynamic light scattering method using a dynamic light scattering particle size measuring apparatus, and the cumulative average particle size can be calculated by cumulative analysis.
The pigment preferably has a volume cumulative particle diameter D90 of 1 μm or less, and a volume cumulative particle diameter D50 of 0.1 μm or more and 0.5 μm or less. Here, the volume cumulative particle diameter D90 is a particle diameter at which the value becomes 90% when the total volume of particles integrated from the small particle side to a certain particle diameter in the particle size distribution of the pigment is expressed as a percentage with respect to the volume of the entire particles, and the volume cumulative particle diameter D50 is a particle diameter at which the percentage becomes 50%. The volume cumulative particle diameter D90 and the volume cumulative particle diameter D50 were measured by a dynamic light scattering method.
As described above, the pigment contained in the ink jet ink according to the present embodiment has a cumulative average particle diameter in the range of 0.01 μm to 5 μm in one example, and in the range of 0.01 μm to 1 μm in another example, or a volume cumulative particle diameter D90 in the range of 1 μm or less, and preferably a volume cumulative particle diameter D50 in the range of 0.1 μm to 0.5 μm, and more preferably satisfies all of them.
The content of the pigment is preferably in a range of 1 to 30% by mass based on the total mass of the ink. When the content of the pigment is less than 1% by mass, it may be difficult to secure a sufficient color density when the pigment is a coloring material by subsequent processing. On the other hand, if it exceeds 30 mass%, the stability may be lowered. The content of the pigment is more preferably in the range of 1% by mass or more and 10% by mass or less based on the total mass of the ink. Among these, titanium oxide and the like, which are generally used as pigments for white inks, have a high specific gravity, and therefore, in this case, pigments may be prepared at a higher ratio than the above.
The ink jet ink according to the present embodiment may contain a dye as an auxiliary component of a pigment for color adjustment. As examples of the dye, dyes having low acidity and basicity and high solubility in a solvent, such as azo dyes, sulfur (building material) dyes, disperse dyes, fluorescent whitening agents, and oil-soluble dyes, are generally used. Among them, oil-soluble dyes such as azo dyes, triarylmethane dyes, anthraquinone dyes, and azine dyes are preferably used.
(resin)
The resin contained in the inkjet ink according to the present embodiment is not particularly limited, and may be appropriately selected according to the type of the medium, as long as it is dissolved or dispersed in an organic solvent to be described later, which is mixed with the ink. Examples of the resin include acrylic resins, polyester resins, phenol resins, polyamides, polyvinyl butyrals, cellulose acetate butyrates, nitrocellulose resins, polyurethanes, vinyl chloride-vinyl acetate copolymers, and the like. These can be used alone or in combination of 2 or more.
In the inkjet ink according to the present embodiment, an ultraviolet curable resin may be used, or a thermosetting resin may be used.
The ultraviolet curable resin may be a radical polymerizable compound which is polymerized by a radical polymerization initiator when irradiated with ultraviolet rays, and examples thereof include acrylic oligomers, acrylic monomers, N-vinyl compounds, vinyl esters, acrylamides, aromatic vinyl compounds, allyl compounds, and the like. Specific examples of the ultraviolet curable resin include urethane acrylate, acrylic resin acrylate, epoxy acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-dimethylaminoethyl acrylate, and 2-hydroxyethyl acrylate.
Examples of the photopolymerization initiator include: benzoin isopropyl ether, benzophenone, chlorothioxanthone, benzyl dimethyl ketal, acetophenone diethyl ketal, α -hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-phenyl propane, and the like.
The thermosetting resin is not particularly limited as long as it is cured by heating. Examples thereof include mixtures of isocyanate compounds, epoxy compounds, amines and amine derivatives.
(organic solvent)
The organic solvent contained in the inkjet ink according to the present embodiment is not particularly limited, but a solvent that does not cause any concern about corrosion is preferably used. Examples of such organic solvents include: aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, organic acid esters, ethers, ketones, and the like. From the viewpoint of safety and solubility of the resin and the like, organic acid esters are preferred as the organic solvent, and specifically, for example, acetic acid esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethyl 3-ethoxypropionate, 3-methoxybutyl acetate, and 3-methyl-3-methoxybutyl acetate are easily available, and thus preferred. Water-soluble esters such as propylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate are preferable because they can be used in either of oil-based inks and water-based inks.
(dispersing agent)
In the inkjet ink according to the present embodiment, a dispersant may be used as needed. As the dispersant, for example, any dispersant used in conventionally known solvent-based ink compositions can be used. As the dispersant, a polymer dispersant (resin) is preferably used. The main chain of such a dispersant is composed of a polyester, polyacrylic, polyurethane, polyamine, polycaprolactone, or the like, and has a polar group such as an amino group, a carboxyl group, a sulfone group, or a hydroxyl group as a side chain.
(surfactant)
In the inkjet ink according to the present embodiment, a surfactant may be used as needed. As the surfactant, any of anionic, cationic, amphoteric or nonionic surfactants can be used, and can be appropriately selected according to the purpose of addition. For example, a nonionic polyoxyethylene derivative which is liquid at room temperature and atmospheric pressure may be added for the purpose of suppressing volatilization of a solvent-based ink composition in a nozzle part, a tube, or the like, preventing curing, or improving resolubility during curing.
(other additives)
The ink jet ink according to the present embodiment may further include a conventionally known additive, if necessary. Examples of such additives include: viscosity modifiers, pH modifiers, surface tension modifiers, dispersion aids, sensitizers, leveling agents, defoaming agents, antioxidants, preservatives, antifungal agents, charge control agents, wetting agents, and the like.
The ink jet ink according to the present embodiment needs to have a viscosity suitable for ejection from a head nozzle of an ink jet printer. Therefore, the viscosity of the ink jet ink according to the present embodiment when ejected is, for example, 5 to 15mPa · s, and preferably 7 to 11mPa · s, as another example.
Ink jet printer
Hereinafter, an ink jet printer according to embodiment 2 will be described in detail with reference to the drawings. The same reference numerals are given to the constituent elements that perform the same or similar functions throughout the drawings, and redundant description is omitted.
The inkjet printer according to the present embodiment includes: an inkjet head that ejects ink toward a recording medium; and a medium protection mechanism for holding the recording medium in opposition to the inkjet head, wherein the inkjet ink according to embodiment 1 is used as the ink.
Fig. 1 is a perspective view showing a schematic configuration of an ink jet head provided in an ink jet printer according to embodiment 2. The ink jet head 1 shown in fig. 1 is of an on-demand type mounted on a head carriage of an ink jet printer. In the following description, an orthogonal coordinate system including X, Y, and Z axes is used. The direction indicated by the arrow in the figure is taken as a positive direction for convenience. The X-axis direction corresponds to the printing width direction. The Y-axis direction corresponds to a direction in which the recording medium is conveyed. The positive Z-axis direction is a direction opposite to the recording medium.
The inkjet head 1 includes an ink manifold 10, an actuator substrate 20, a frame 40, and a nozzle plate 50.
The actuator substrate 20 is rectangular with the X-axis direction as the longitudinal direction. Examples of the material of the actuator substrate 20 include: aluminum oxide (Al) 2 O 3 ) Silicon nitride (Si) 3 N 4 ) Silicon carbide (SiC), aluminum nitride (AlN), and lead zirconate titanate (PZT: pb (Zr, ti) O 3 ) And the like.
The actuator substrate 20 is superposed on the ink manifold 10 so as to close the open end of the ink manifold 10. The ink manifold 10 is connected to the ink cartridge via an ink supply tube 11 and an ink return tube 12.
A frame 40 is mounted on the actuator substrate 20. A nozzle plate 50 is attached to the frame 40. In the nozzle plate 50, a plurality of nozzles N are provided at predetermined intervals in the X axis direction so as to form 2 columns along the Y axis.
Fig. 2 is an exploded perspective view showing a schematic configuration of a part of the inkjet head 1, specifically, an exploded perspective view of the actuator substrate 20, the frame 40, and the nozzle plate 50. This ink jet head 1 is a so-called shear mode wall-sharing side-firing type.
The actuator substrate 20 has a plurality of ink supply ports 21 formed in a row at the center in the Y-axis direction at intervals along the X-axis direction. The actuator substrate 20 is provided with a plurality of ink discharge ports 22 spaced apart in the X-axis direction so as to form rows in the Y-axis positive direction and the Y-axis negative direction with respect to the rows of the ink supply ports 21.
A plurality of actuators 30 are provided between the center row of ink supply ports 21 and one row of ink discharge ports 22. These actuators 30 form a row extending in the X-axis direction. A plurality of actuators 30 are also provided between the center row of ink supply ports 21 and the other row of ink discharge ports 22. These actuators 30 are also formed in rows extending in the X-axis direction.
Each of the rows of the plurality of actuators 30 is composed of a 1 st piezoelectric body and a 2 nd piezoelectric body laminated on the actuator substrate 20. Examples of the material of the 1 st and 2 nd piezoelectric bodies include lead zirconate titanate (PZT) and lithium niobate (LiNbO) 3 ) Lithium tantalate (LiTaO) 3 ) And so on. The 1 st and 2 nd piezoelectric bodies are polarized in opposite directions to each other in a thickness direction.
A laminate composed of the 1 st and 2 nd piezoelectric bodies is provided with a plurality of grooves extending in the Y-axis direction and arranged in the X-axis direction. The grooves are open on the 2 nd piezoelectric body side and have a depth larger than the thickness of the 2 nd piezoelectric body. Hereinafter, a portion of the laminated body sandwiched between adjacent grooves is referred to as a channel wall. The channel walls extend in the Y-axis direction and are aligned in the X-axis direction. In addition, the groove between two adjacent channel walls is an ink channel for ink to flow through.
Electrodes are formed on the side walls and bottom of the ink channels. These electrodes are connected to a wiring pattern 31 extending in the Y-axis direction.
A protective film, not shown, is formed on the surface of the actuator substrate 20 including the electrodes and the wiring pattern 31 except for the connection portion with the flexible printed board, which will be described later. The protective film includes, for example, a plurality of inorganic insulating films and an organic insulating film.
The frame 40 has an opening. The opening portion is smaller than the actuator substrate 20 and larger than the area of the actuator substrate 20 where the ink supply port 21, the actuator 30, and the ink discharge port 22 are provided. The frame 40 is made of, for example, ceramic. The frame 40 is bonded to the actuator substrate 20 with an adhesive, for example.
The nozzle plate 50 includes: a nozzle plate substrate; and a liquid repellent film (not shown) provided on the medium-facing surface (the surface from which ink is ejected from the nozzles N). The nozzle plate substrate is made of a resin film such as a polyimide film.
The nozzle plate 50 is larger than the opening portion of the frame 40. The nozzle plate 50 is bonded to the frame 40, for example, by an adhesive.
The nozzle plate 50 is provided with a plurality of nozzles N. These nozzles N are formed in two rows corresponding to the ink channels. The nozzles N have larger diameters as they go from the opposite side of the recording medium toward the ink channels. The size of the nozzle N is set to a predetermined value according to the ink ejection amount. The nozzle N can be formed by performing laser processing using an excimer laser, for example.
As shown in fig. 1, the actuator substrate 20, the frame 40, and the nozzle plate 50 are integrated to form a hollow structure. The area enclosed by the actuator substrate 20, the frame 40, and the nozzle plate 50 is an ink flow chamber. The ink was circulated as follows: the ink is supplied from the ink manifold 10 to the ink flow chamber through the ink supply port 21, passes through the ink channel, and excess ink returns from the ink discharge port 22 to the ink manifold 10. A portion of the ink is ejected from the nozzle N for printing during the ink channel flow.
The flexible printed board 60 is connected to the wiring pattern 31 at a position on the actuator substrate 20 and outside the frame 40. The flexible printed board 60 is mounted with a drive circuit 61 for driving the actuator 30.
The operation of the actuator 30 will be described below. Here, the operation will be described focusing on the central ink channel among the adjacent 3 ink channels. The electrodes corresponding to the adjacent 3 ink channels are designated as a, B, and C. The channel walls are in an upright position without an applied electric field in a direction orthogonal to the channel walls.
For example, a voltage pulse having a potential higher than the potentials of the two adjacent electrodes a and C is applied to the central electrode B, and an electric field is generated in a direction perpendicular to the channel wall. In this way, the channel walls are driven in a shear mode, and the pair of channel walls sandwiching the center ink channel are deformed so as to expand the volume of the center ink channel.
Next, a voltage pulse having a potential higher than that of the central electrode B is applied to the two adjacent electrodes a and C, and an electric field is generated in a direction perpendicular to the channel walls. In this way, the channel walls are driven in a shear mode, and the pair of channel walls sandwiching the center ink channel are deformed so as to reduce the volume of the center ink channel. By this operation, pressure is applied to the ink in the central ink channel, and the ink is ejected from the nozzle N corresponding to the ink channel and landed on the recording medium. For example, all the nozzles are divided into 3 groups, and the above-described driving operation is time-division controlled in 3 cycles to perform printing on the recording medium.
Fig. 3 is a schematic view of the inkjet printer according to embodiment 2. The inkjet printer 100 shown in fig. 3 includes a housing provided with a paper discharge tray 118. The casing is provided with cassettes 101a and 101b, paper feed rollers 102 and 103, conveying roller pairs 104 and 105, registration roller pair 106, conveying belt 107, fan 119, negative pressure chamber 111, conveying roller pairs 112, 113 and 114, inkjet heads 115C, 115M, 115Y and 115Bk, ink cartridges 116C, 116M, 116Y and 116Bk, and tubes 117C, 117M, 117Y and 117Bk. The inkjet heads 115C, 115M, 115Y, and 115Bk are the inkjet heads 1 described with reference to fig. 1 and 2, respectively.
The cassettes 101a and 101b accommodate recording media P of different sizes. The paper feed roller 102 or 103 takes out the recording medium P corresponding to the size of the selected recording medium from the cassette 101a or 101b, and conveys the recording medium P to the conveying roller pairs 104 and 105 and the registration roller pair 106.
The conveying belt 107 is given tension by a driving roller 108 and two driven rollers 109. Holes are provided at predetermined intervals on the surface of the conveying belt 107. A negative pressure chamber 111 connected to a fan 119 for allowing the transport belt 107 to suck the recording medium P is provided inside the transport belt 107. Conveying roller pairs 112, 113, and 114 are provided downstream in the conveying direction of the conveying belt 107. Further, a heater for heating the printed layer formed on the recording medium P may be provided in the transport path from the transport belt 107 to the paper discharge tray 118.
Above the conveyor belt 107, 4 inkjet heads that eject ink onto the recording medium P according to image data are arranged. Specifically, an inkjet head 115C (1) that ejects cyan (C) ink, an inkjet head 115M (1) that ejects magenta (M) ink, an inkjet head 115Y (1) that ejects yellow (Y) ink, and an inkjet head 115Bk (1) that ejects black (Bk) ink are arranged in this order from the upstream side. As described above, the 4 inkjet heads are the inkjet heads 1 described with reference to fig. 1 and 2, respectively. Hereinafter, the inkjet heads 115C, 115M, 115Y, and 115Bk are collectively referred to as an inkjet head 1.
Above the inkjet heads 115C (1), 115M (1), 115Y (1), and 115Bk (1), there are provided a cyan (C) ink cartridge 116C, a magenta (M) ink cartridge 116M, a yellow (Y) ink cartridge 116Y, and a black (Bk) ink cartridge 116Bk, which respectively store the inks according to the present embodiment corresponding to these. These cartridges 116C, 116M, 116Y, and 116Bk are connected to the inkjet heads 115C (1), 115M (1), 115Y (1), and 115Bk (1) through tubes 117C, 117M, 117Y, and 117Bk, respectively.
The inkjet printer 100 includes: an ink-jet head 1; and a medium holding mechanism that holds the recording medium P opposite to the inkjet head 1. The medium holding mechanism also functions as a recording paper moving mechanism for moving the recording medium P. The medium holding mechanism includes a conveying belt 107, a driving roller 108, a driven roller 109, a negative pressure chamber 111, and a fan 119.
The following describes an image forming operation of the inkjet printer 100.
First, an image processing unit (not shown) starts image processing for recording, generates an image signal corresponding to image data, and generates a control signal for controlling the operations of the various rollers, the negative pressure chamber 111, and the like.
The paper feed roller 102 or 103 takes out the recording medium P of the selected size one by one from the cassette 101a or 101b according to control by the image processing unit, and conveys the recording medium P to the conveying roller pairs 104 and 105 and the registration roller pair 106. The registration roller pair 106 corrects skew of the recording medium P, and conveys the recording medium P at a predetermined point in time.
The negative pressure chamber 111 sucks air through the holes of the conveyor belt 107. Therefore, the recording medium P is sequentially conveyed to positions below the inkjet heads 115C (1), 115M (1), 115Y (1), and 115Bk (1) as the conveyor belt 107 moves in a state of being attracted to the conveyor belt 107.
The inkjet heads 115C (1), 115M (1), 115Y (1), and 115Bk (1) eject ink in synchronization with the timing of conveying the recording medium P according to control based on the image processing unit. Thereby, a color image is formed at a desired position on the recording medium P.
In the inkjet printer 100, the distance (gap) between the recording medium P held by the medium holding mechanism and the inkjet head 1 may be 2mm or more as an example, 3mm or more as another example, and 5mm or more as still another example.
If the gap between the ink jet head and the recording medium is enlarged, the accuracy of the landing position of the ink is lowered, and satellite droplets and mist are likely to be generated, and therefore, the gap cannot be set to be generally large from the viewpoint of image quality. For example, the prior art describes setting the gap between the inkjet head and the recording medium to 1mm. The present inventors have confirmed that the phenomenon that fogging and satellites become conspicuous when the gap exceeds 2mm is not sufficient for an ink jet ink that does not have the problem of fogging and satellites when the gap is 1mm. According to this embodiment, since the ink jet ink of the present embodiment in which the dynamic surface tension X represented by the above formula (1) is 15mN/m or more is used, even if the gap between the ink jet head and the recording medium is increased, the landing position accuracy is not lowered, and a printed matter with excellent image quality can be obtained. Therefore, the ink for inkjet according to the present embodiment and the inkjet printer using the same are particularly excellent in printing on a recording medium having irregularities on the surface. Examples of the recording medium having irregularities on the surface thereof include a woven fabric having a rough surface, a wallpaper, a toy having irregularities on the surface thereof, a plastic product, a sheet material having embossments or waves on the surface thereof, and the like.
Here, the gap between the inkjet head 1 and the recording medium P refers to a distance from a lower surface of the inkjet head (the surface of the nozzle plate 50) to a position where a perpendicular line to the lower surface intersects with the recording medium. When the recording medium is a structure having irregularities on the surface, the gap between the inkjet head 1 and the recording medium P means the shortest distance. In the present embodiment, the gap between the ink jet head 1 and the recording medium P can be appropriately set according to the unevenness of the surface of the recording medium P, and as described above, it is set to 2mm or more as an example, 3mm or more as another example, and 5mm or more as still another example.
After the color image is formed, the conveying roller pairs 112, 113, and 114 discharge the recording medium P on which the image is formed to the discharge tray 118. When a heater is provided in the transport path from the transport belt 107 to the discharge tray 118, the print layer formed on the recording medium P may be heated by the heater. When heating is performed by the heater, the adhesion of the printing layer to the recording medium P can be improved particularly when the recording medium P is non-permeable.
According to the ink for inkjet of the present embodiment, even when the distance from the inkjet head to the recording medium is large, the generation of satellite droplets and mist can be suppressed while maintaining stable ejection performance of the ink, and a high-quality image can be formed on the recording medium having irregularities on the surface.
Examples
Ink test sample
As ink samples, 13 inks a to M shown in table 1 below were prepared. These inks include an ultraviolet-curable ink containing a pigment, an acrylic oligomer and/or an acrylic monomer, an ultraviolet polymerization initiator or sensitizer, and a polymerization inhibitor and a dispersion aid, which are added as appropriate, and a solvent-based ink obtained by dissolving or dispersing a resin and a dispersant in an organic solvent and further dispersing a pigment therein. As specific pigments, acrylic oligomers, acrylic monomers, ultraviolet polymerization initiators, sensitizers, organic solvents, resins, and dispersion aids, materials generally used in ultraviolet curable and solvent-based inkjet inks can be used.
The mixing ratio of the above components in the inks a to M can be adjusted within a normal range. For reference, the mixing ratio of one ultraviolet curable ink is shown below from inks a to M.
An ink was prepared by mixing and dispersing the following raw material components at the following mixing ratios.
(an example of the mixing ratio of the raw Material ingredients)
[ measurement ]
For each ink sample, the static surface tension and the dynamic surface tension were measured by the following methods.
Measurement of static surface tension
The static surface tension of each ink sample was measured using a William-type surface tensiometer (DY-500, manufactured by Kyowa interfacial Chemicals Co., ltd.). Ink was placed in the measurement cell of the apparatus, and the platinum plate was immersed in the ink at 25 ℃ and wetted with the ink. At this time, the force by which the platinum plate was pulled in by the ink was read and measured as a static surface tension value. The measured values are shown in Table 1.
Measurement of dynamic surface tension
The dynamic surface tension of each ink sample was measured by the maximum bubble pressure method using a dynamic surface tensiometer (SITA pro line t15, manufactured by SITA Messtechnik GmbH). The dynamic surface tension was measured from the maximum pressure of the bubble corresponding to the surface lifetime by placing the needle of the device in the ink in the container, generating the bubble from the needle by changing the bubble generation rate (surface lifetime) from 0.015 second to 1.2 second at 25 ℃. Table 1 shows the dynamic surface tension γ 1 at a surface lifetime of 0.015 second, the dynamic surface tension γ 2 at a surface lifetime of 1.2 seconds, and the amount of change X in the dynamic surface tension per 1 second expressed by the following equation.
X＝(γ1－γ2)/(1.2－0.015)
Viscosity
The viscosity of each ink sample was measured. Viscosity was measured using "LVDV3T cone type" (BROOKFIELD ENGINEERING LABORATORIES, INC.). The measurement was performed using a CPA-42Z cone spindle under the condition of a rotation speed (rpm) before and after the torque became 30 to 50% at the temperature at the time of ejection. The measured values are shown in Table 1.
[ evaluation ]
An evaluation inkjet printer having a shared-mode inkjet head (trade name "CF1", manufactured by toshiba teger, nozzle density (300) dpi) and capable of adjusting the number of drops to 1 to 7 and the driving frequency to 4.8 to 13kHz was prepared. Using this inkjet printer, ejection stability and the generation state of mist and satellites were evaluated by the following methods. The evaluation results are shown in table 1.
Ejection stability
The evaluation was performed using SuperFine Paper manufactured by EPSON corporation as a recording medium. As printing conditions, the distance (gap) between the discharge nozzle surface of the ink jet head and the surface of the recording medium was set to 1mm, and the ink volume when 7 drops were discharged was 42pl (42X 10) as the driving voltage of the ink jet head 3 μm 3 ) The ink was ejected from all the nozzles (318 nozzles) for 5 minutes. Immediately after that, printing was performed on the recording medium, and printing missing of the print was observed, and 318 nozzles were counted as one missing with respect to one nozzle missing. This was repeated 5 times and the number of deletions per 10 minutes was counted. That is, the number of deletions was determined by (total of 5 deletions) × (10/25). As a determination criterion, the number of deletions per 10 minutes was 1.0 or less, and it was determined that the ejection stability was good. The evaluation results are shown in table 1.
Generation state of mist/satellite liquid droplet
As the recording medium, glossy paper IJ-RC-UF170 manufactured by Mitsubishi paper corporation was used for evaluation. As the printing conditions, there were set the conditions for printing,the distance (gap) between the discharge nozzle surface of the ink jet head and the surface of the recording medium was set to 3mm, and the ink volume when 7 droplets were discharged from the ink jet head was set to 42pl (42 × 10) as the driving voltage of the ink jet head 3 μm 3 ) The voltage of (3) is applied to discharge ink in 3 types of 1 drop, 2 drops and 3 drops, and the landing state of mist/satellite drops around the main drop of the printing medium is observed and determined for each drop by a microscope.
Fig. 4 is a schematic plan view for explaining a method of evaluating a generation state of mist or satellite droplets on a recording medium. When fig. 4 (a) is compared with fig. 4 (b), the number of mist or satellite droplets d2 whose landing positions are deviated from the main droplets d1 in fig. 4 (a) is smaller than that in fig. 4 (b), and the image quality is excellent. In the present evaluation method, an evaluation score is given for each droplet so that a print is 100 scores where mist or satellites d2 are hardly visible with respect to the main droplet d1 and the evaluation score decreases as the mist or satellites d2 increase. The average of the evaluation scores of 1 drop, 2 drops and 3 drops was calculated for each ink sample, and evaluated according to the following criteria. Evaluation a and B (average score exceeding 80 points) suppressed the generation of mist and satellite droplets, and showed excellent image quality. The evaluation results are shown in table 1.
A: the average score exceeds 90 points and is 100 or less
B: the average score is more than 80 and 90 or less
C: the average score is more than 70 and less than 80
D: an average score of more than 60 and 70 or less
E: an average score of 60 or less
From the results shown in table 1, it is understood that: the ink jet inks of examples 1 to 5 according to the present embodiment, in which the change amount of the dynamic surface tension per 1 second between 0.015 second and 1.2 second in the average lifetime is 15mN/m or more, have excellent ejection stability even when the distance between the ink jet head and the recording medium is large, and can form high-quality images with little generation of mist and satellite droplets.
While several embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications are included in the scope and spirit of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.
Claims (10)
1. An ink for ink jet printing, characterized in that,
contains a colorant and a resin, the content of water being less than 10% by mass, and the amount of change X in dynamic surface tension per 1 second represented by the following formula is 15mN/m or more when the dynamic surface tension at a surface life of 0.015 second measured at 25 ℃ by the maximum bubble pressure method is represented by gamma 1 and the dynamic surface tension at a surface life of 1.2 seconds is represented by gamma 2,
X＝(γ1－γ2)/(1.2－0.015)。
2. the ink jet ink according to claim 1,
the static surface tension is in the range of 20mN/m or more and 40mN/m or less.
3. The ink jet ink according to claim 1 or 2,
the colorant contains at least 1 pigment selected from organic pigments, inorganic pigments and glass particles, and the average particle diameter of the pigment is in the range of 0.01 [ mu ] m or more and 5 [ mu ] m or less.
4. The ink jet ink according to claim 1 or 2,
the viscosity of the ink for ink jet is 5 mPas to 15 mPas when the ink is ejected.
5. An inkjet printer, comprising:
an inkjet head that ejects ink toward a recording medium; and
a medium holding mechanism that holds the recording medium in opposition to the inkjet head,
the ink is the ink for inkjet according to any one of claims 1 to 4.
6. The inkjet printer of claim 5,
the recording medium is held by the medium holding mechanism such that a distance between the inkjet head and the recording medium is 2mm or more.
7. The inkjet printer of claim 6,
the distance between the ink jet head and the recording medium is 3mm or more.
8. An ink jet recording method, characterized by comprising:
ink is ejected toward a recording medium held opposite to the ink jet head,
the ink is the ink for inkjet according to any one of claims 1 to 4.
9. The inkjet recording method according to claim 8,
the recording medium is held so that the distance between the ink jet head and the recording medium becomes 2mm or more.
10. The inkjet recording method according to claim 9,
the distance between the ink jet head and the recording medium is 3mm or more.
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| JP2021155515A JP2023046744A (en) | 2021-09-24 | 2021-09-24 | Inkjet ink and inkjet printer |
| JP2021-155515 | 2021-09-24 |
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| CN101120064A (en) * | 2004-07-23 | 2008-02-06 | 太阳化学有限公司 | An ink-jet printing process and ink |
| JP2014094998A (en) * | 2012-11-07 | 2014-05-22 | Ricoh Co Ltd | Inkjet recording method |
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| CN104946015A (en) * | 2014-03-24 | 2015-09-30 | 富士施乐株式会社 | Ink, ink set, and recording device |
| CN104943377A (en) * | 2014-03-31 | 2015-09-30 | 精工爱普生株式会社 | Ink jet recording method and ink set |
| CN105793049A (en) * | 2013-12-11 | 2016-07-20 | 柯尼卡美能达株式会社 | Inkjet printing apparatus |
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2021
- 2021-09-24 JP JP2021155515A patent/JP2023046744A/en active Pending
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- 2022-06-23 CN CN202210720030.4A patent/CN115851036A/en active Pending
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| CN101120064A (en) * | 2004-07-23 | 2008-02-06 | 太阳化学有限公司 | An ink-jet printing process and ink |
| CN104755567A (en) * | 2012-10-24 | 2015-07-01 | 爱克发-格法特公司 | Radiation curable inkjet inks |
| JP2014094998A (en) * | 2012-11-07 | 2014-05-22 | Ricoh Co Ltd | Inkjet recording method |
| US20150035896A1 (en) * | 2013-08-02 | 2015-02-05 | Hiroshi Gotou | Inkjet recording method and inkjet recording device |
| CN105793049A (en) * | 2013-12-11 | 2016-07-20 | 柯尼卡美能达株式会社 | Inkjet printing apparatus |
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| CN104943377A (en) * | 2014-03-31 | 2015-09-30 | 精工爱普生株式会社 | Ink jet recording method and ink set |
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