Inkjet printer

Abstract

To provide a continuous type inkjet printer which can achieve drying promotion of printed ink at minimum cost.SOLUTION: An inkjet printer, which impacts ink droplets injected from a printing head onto a printed matter relatively moving in a horizontal direction using a printing head which stores a gun, a charge electrode and a deflection electrode in a cavity part, and has a cylindrical case formed with a slit passing charged ink droplets therethrough, and forms characters by a plurality of lines of printing dots, branches air compressed by a single compressor, supplies one air to the cavity part of the case and keeps the cavity part at a positive pressure, and sprays the other air onto a printing surface of the printed matter and promotes drying of ink.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a continuous ink jet printer, and more particularly to preventing smearing and transfer caused by wet ink. [Background technology]

[0002] Inkjet printers have a problem in that ink printed on a substrate in a wet state rubs against a substrate that has already been printed, causing the ink to fade or transfer, resulting in reduced print quality.

[0003] In order to solve the above-mentioned problems, conventionally, air is pumped out using a pump and the air is blown onto the wet printing surface to promote drying of the ink (see, for example, Patent Document 1).

[0004] However, the above-mentioned drying acceleration method requires a pump for delivering air and a mechanism for blowing air onto the printing substrate, which increases the cost of the inkjet printer.

[0005] Inkjet printers are broadly classified into continuous type and on-demand type based on the printing method used. Inkjet printers of the continuous type use a pump to eject ink from a nozzle and vibrate the ink, a charging electrode charges the ink droplets at the position where the ink separates into droplets, and a deflection electrode bends the trajectory of the ink droplets, causing them to collide with a specified position on the printing surface to form an ink dot. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-328253 A [Patent Document 2] JP 2018-83369 A Summary of the Invention [Problem to be solved by the invention]

[0007] The continuous ink jet printers described above use quick-drying ink, so there is almost no problem with smearing or transfer caused by wet ink.

[0008] However, recently, due to the need to avoid the organic solvent law and the smell of solvents, there is a tendency to avoid the solvents with short drying times that have been used up until now, and instead, solvents with long drying times that are not subject to the organic solvent law are being chosen. As a result, problems such as smearing and transfer caused by undried ink are becoming apparent.

[0009] On the other hand, in continuous-type inkjet printers, in order to eliminate contamination of component parts caused by ink mist generated by the ejected ink and to prevent dust from being sucked in through the gutter and clogging pipes, etc., which could cause malfunctions, the print head is covered with a case and a positive pressure is maintained inside the case (see Patent Document 2).

[0010] By maintaining a positive pressure inside the cover with the pressurizing means, it is possible to retard the progress of staining of the head components caused by the ink mist, and also to prevent foreign matter such as dust from entering the ink circulation system.

[0011] The object of the present invention is to provide an inkjet printer that can accelerate the drying of printed ink at a minimum cost by utilizing the air pressurizing means that is normally installed to create positive pressure inside the print head cover. [Means for solving the problem]

[0012] In order to achieve the above object, the inkjet printer according to the present invention comprises: A gun that applies a constant period of vibration to the ink being ejected to generate continuous ink droplets; a charging electrode for charging the ink droplets by applying a step-shaped voltage synchronized with a period of the ink droplets; a deflection electrode for deflecting the charged ink droplets vertically or horizontally according to the degree of charge, so that the ink droplets land on a printing surface of a substrate; a cylindrical case in which the gun, a charging electrode and a deflection electrode are housed in a hollow portion and in which a slit is formed through which the charged ink droplets pass; An inkjet printer that causes ink droplets ejected from the print head to land on a printing substrate that moves relatively in a horizontal or vertical direction, and forms characters with multiple rows of printing dots, Air compressed by a single compressor is split, one of the air flows is supplied to the cavity of the case to maintain the cavity at a positive pressure, and the other air flow is blown onto the printing surface of the printing material to promote drying of the ink. death, As a means for blowing air onto the printing surface, an air nozzle that blows air from a small diameter hole is used, The air nozzle is attached by wrapping a band around the outer circumferential surface of the case, and the position of the air nozzle can be adjusted by changing the attachment position of the band.

[0013] Also, The inkjet printer according to the present invention comprises: A gun that applies a constant period of vibration to the ink being ejected to generate continuous ink droplets; a charging electrode for charging the ink droplets by applying a step-shaped voltage synchronized with a period of the ink droplets; a deflection electrode for deflecting the charged ink droplets vertically or horizontally according to the degree of charge, so that the ink droplets land on a printing surface of a substrate; a cylindrical case in which the gun, a charging electrode and a deflection electrode are housed in a hollow portion and in which a slit is formed through which the charged ink droplets pass; An inkjet printer that causes ink droplets ejected from the print head to land on a printing substrate that moves relatively in a horizontal or vertical direction, and forms characters with multiple rows of printing dots, air compressed by a single compressor is branched, one of the air flows is supplied to a cavity in the case to maintain the cavity at a positive pressure, and the other air flow is blown onto a printing surface of the printing material to promote drying of the ink; As a means for blowing air onto the printing surface, an air nozzle that blows air from a small diameter hole is used. 、 A regulator that keeps the air pressure constant is attached to the tube that supplies one of the air streams to the hollow portion of the case, and a throttle valve that adjusts the amount of air is attached to the tube that supplies the other of the air streams to the air nozzle. Effect of the Invention

[0016] In this invention, a compressor installed to create positive pressure inside the print head case is utilized as a means of blowing air onto the ink on the printing surface, thereby reducing printer costs while preventing smudging and transfer caused by wet ink, thereby eliminating deterioration of print quality. [Brief description of the drawings]

[0017] [Figure 1] 1 is a perspective view showing the appearance of a print head according to the present invention incorporating an ink drying acceleration function. [Diagram 2] 2 is a partial cross-sectional front view showing the schematic configuration of a continuous-type ink-jet printer according to an embodiment of the present invention, including the print head of FIG. [Diagram 3] 3 is a diagram for explaining the operation when printing on a print substrate using the inkjet printer of FIG. 2. FIG. [Figure 4] FIG. 1 is a piping diagram of an air supply system. [Diagram 5] This figure shows examples of printing in which air is blown onto the printed surface to promote drying of the ink, and then the printed surface is rubbed with a wiper (a), and in which the printed surface is rubbed with a wiper without blowing air (b). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An inkjet printer according to an embodiment of the present invention will now be described with reference to the drawings.

[0019] Fig. 1 is a perspective view showing the appearance of a print head 1 incorporating an ink drying promotion function, and Fig. 2 is a partial cross-sectional front view showing the schematic configuration of a continuous-type inkjet printer (hereinafter referred to as "IJP") 10 according to this embodiment, including the print head 1. Fig. 3 is a diagram explaining the operation when printing on a substrate using the IJP 10 in Fig. 2.

[0020] The components of the IJP 10 according to this embodiment are roughly divided into components related to supplying ink to the print head 1 to perform printing (hereinafter, these are referred to as the "ink supply system") and components related to supplying pressurizing air and air for promoting drying of the ink to the print head 1 (hereinafter, these are referred to as the "air supply system"). First, the components of the ink supply system that supplies ink to the print head 1 to perform printing will be described.

[0021] <Ink supply system> 2, the IJP 10 is composed of a print head 1, an ink tank 2, and pumps 3a and 3b. Of these, the print head 1 is composed of a gun 12, a charging electrode 13, a detection electrode 14, a deflection electrode 15, a gutter 16, and pipes 17a and 17b, and these components are housed in a cylindrical case 11.

[0022] The gun 12 and other components that make up the print head 1 are actually arranged in close contact with the hollow portion 110 of the case 11, but Figure 2 shows a schematic arrangement to clearly explain the function of each component.

[0023] The gun 12 sprays ink droplets ID toward the side of a printing substrate (see FIG. 3, for example, a box in which a product is packed) 4, and is composed of a gun body 121, an ultrasonic vibrator 122, and a nozzle 123. Ink is pumped from the ink tank 2 by the pump 3a and supplied to the gun body 121 through the pipe 17a, and is sprayed from the hole of the nozzle 123 with vibrations added by the ultrasonic vibrator 122.

[0024] The ink column IP ejected from the hole of the nozzle 123 is separated into individual ink droplets ID by the vibration applied by the ultrasonic vibrator 122, and then charged by the charging electrode 13. After that, only the ink droplets ID required for printing are deflected by the deflection electrode 15 in accordance with the amount of charged charge, pass through the slit 111 formed in the front part of the case 11, and land on the printing surface of the substrate 4.

[0025] Fig. 3 shows a cosmetic case 4 moving at a constant speed on a belt conveyor (not shown) in the direction indicated by the arrow. For ease of viewing, Fig. 3 omits the case 11 of the print head 1, which is not related to the printing operation.

[0026] The surface of the decorative box 4, which is the substrate to be printed, is coated with a film made of polyethylene or polypropylene. After food products and other items are packed into the box, the manufacturing number, expiry date, etc. are printed on the film to form the final product.

[0027] As shown in Figure 3, when the cosmetic box 4 is moving in a direction perpendicular to the flight direction of the ink droplet ID, the position of the ink droplet ID that lands on the side of the cosmetic box 4 changes by changing the amount of deflection of the ink droplet ID, and by repeatedly deflecting the ink droplet ID in synchronization with the movement of the cosmetic box 4, a letter ("A" in the figure) is printed.

[0028] On the other hand, ink droplets ID that are not charged and ink droplets ID that are charged but are not used for printing are not deflected and jump directly into the gutter 16 for ink recovery and are recovered in the ink tank 2. The ink recovered by the gutter 16 is transferred by the pump 3b through the pipe 17b to the ink tank 2 and is reused.

[0029] The operation of the IJP 10 is controlled by a controller (not shown). The controller is composed of a CPU, memory (ROM, RAM, etc.), a timer, and a display, and controls the operation of the ultrasonic transducer 122 of the gun 12, the pulse power supply 131 of the charging electrode 13, the detection electrode 14, the DC power supply 151 of the deflection electrode 15, and the pumps 3a and 3b.

[0030] Specifically, the controller drives the pump 3a to apply pressure to the ink contained in the ink tank 2 and supply it to the gun body 121. The controller also controls the timing of the pulse voltage applied from the pulse power supply 131 to the charging electrode 13 based on a signal detected by the detection electrode 14, thereby adjusting the number and timing of the ink droplets ID to be charged. Furthermore, the controller adjusts the deflection amount of the ink droplets ID deflected by the deflection electrode 15 by controlling the voltage of the DC power supply 151.

[0031] <Air supply system> Next, the air supply system of the IJP 10 will be described with reference to the above-mentioned Figures 1 to 3 and newly added Figure 4. Figure 4 is a piping diagram of the air supply system 5. Before describing the air supply system, the features of the present invention will be described.

[0032] The feature of this invention is that it uses a single compressor to achieve two air-related functions. Specifically, it utilizes the compressor that supplies pressurized air to the print head, which is a standard feature of continuous IJP, to achieve the function of promoting the drying of ink that has landed on the printed material without adding a new compressor.

[0033] In food production sites, compressors are installed to drive air cylinders, etc. Air is supplied from the compressor through an air tube (hereinafter simply called "tube") 51, and first passes through a drain catch 52 to remove excess moisture, and then through a mist separator 53 to remove oil mist. These processes are performed to prevent equipment driven by air from breaking down due to moisture or oil mist.

[0034] The air AR then branches into two, and the air AR that passes through the tube 54a is supplied to the print head 1 and is used to create a positive pressure inside the case 11. On the other hand, the air AR that branches into the tube 54b is used to promote drying of the ink that has landed on the printing substrate 4.

[0035] The function of the air branched into tube 54a will now be described. A regulator 55 is attached midway through tube 54a to reduce the pressure of the air compressed by the compressor to an appropriate value, and air AR whose pressure has been adjusted by regulator 55 is supplied to case 11 of print head 1.

[0036] 2, holes through which the tubes 54a and 54b pass are formed in the lid 112 that seals the rear of the cavity 110 of the case 11, and the tip of the tube 54a is open to the cavity 110 of the case 11. The cavity 110 is sealed except for a slit 111 through which the ink droplets ID are ejected, and most of the air AR (indicated by the white arrow) supplied through the tube 54a remains within the case and increases the air pressure.

[0037] In a continuous type IJP, some of the ink ejected from the nozzle 123 floats in the surrounding atmosphere as ink mist and adheres to the surfaces of the components, causing stains, so it is necessary to periodically clean the components inside the case 11. In addition, dust can enter the ink circulation system through the gutter and clog pipes, causing malfunctions.

[0038] For this reason, the main components of the print head 1 are housed in the case 11, and the inside of the case 11 is kept at a positive pressure, which promotes the discharge of ink mist to the outside and prevents dust from entering the case 11. These measures make it possible to extend the cycle for cleaning the components and prevent clogging of pipes, etc., due to dust.

[0039] Next, a function of the air supplied to the air nozzle 57 through the tube 54b will be described. As shown in Fig. 4, the air AR branched to the tube 54b is supplied to the air nozzle 57 after the flow rate is adjusted by the throttle valve 56.

[0040] As shown in FIG. 2 above, tube 54b is inserted into hollow portion 110 of case 11 and passes through a hole formed in fixed block 61 attached to the outer periphery of case 11, and as shown in FIG. 1, air AR taken out from air outlet 62 passes through tube 54b again and is supplied to air nozzle 57, and is blown onto the printing surface of the printing material 4.

[0041] The reason why tube 54b is once inserted into hollow portion 110 of case 11 and then passed through a hole in fixed block 61 and reconnected to tube 54b is to integrate air nozzle 57 with print head 1. This configuration makes it easier to handle air nozzle 57 during maintenance and inspection.

[0042] As shown in FIG. 1, the air nozzle 57 is attached to the tip of a mounting fixture 63 , and the mounting fixture 63 is further fixed to the outer circumferential surface of the case 11 by a metal band 64 .

[0043] If the air nozzle 57 is attached to the outer peripheral surface of the case 11 using a band 64, the front-to-back and up-down positions of the air nozzle 57 can be easily changed by loosening the mounting fixture 63, making it easy to adjust the position of the air nozzle 57 relative to the printing surface.

[0044] The aforementioned Figure 3 shows the state in which air AR blown out from air nozzle 57 is blown onto ink that has landed on the printing substrate 4. In the experiment, the ink used was a 3-methyl-2-butanone solvent (75-90%) to which chromium complex salt (5-15%) was added as a black dye, and to which a small amount of m,p-cresyl glycidyl ether (1-10%) was added. Then, using the above-mentioned ink, printing was performed on the side of a decorative box 4 whose surface was coated with a film.

[0045] As a result of the experiment, it was found that by using a small-diameter air nozzle 57 with a hole diameter of about 0.5 mm and spraying air at a rate of 0.5 to 3 liters / min with the tip of the air nozzle 57 positioned about 45 mm away from the printing surface, the ink can be dried to the point where no rubbing occurs on the printed surface within 0.5 seconds after printing.

[0046] For reference, Figure 5 shows examples of printing in which air AR is blown onto the printed surface to accelerate the drying of the ink, and the printed surface is rubbed with a wiper 0.5 seconds after printing (a), and printing is performed without blowing air, and the printed surface is rubbed with a wiper 0.5 seconds after printing (b).

[0047] 5(a), the tip of the air nozzle 57 was placed about 45 mm away from the printing surface, and air was blown at a rate of about 1.2 L / min. The temperature during printing was 26° C. and the humidity was 60%.

[0048] As shown in Figure 5(b), when air is not blown onto the printed surface, the ink smudges and the characters become unreadable. In contrast, when air is blown onto the printed surface to promote the drying of the ink, as shown in Figure 5(a), the ink dries and no smudges occur.

[0049] As described above, by using the IJP according to the present invention, air is blown onto the ink that has landed on the printing surface, which promotes the drying of the ink and prevents the ink from smearing or transferring, thereby eliminating the deterioration of print quality caused by wet ink.

[0050] In addition, the present invention achieves the ink drying acceleration function without the need for a new air supply source by branching off the air that maintains positive pressure inside the print head case, which is a standard feature of continuous IJP. This makes it possible to keep the cost increase of IJP that comes with adding a new function to a minimum.

[0051] In the above embodiment, a cylindrical case is used as the print head case, and the main components are housed in the hollow portion of the case, but the shape of the case is not limited to a cylindrical shape. A case with a square or hexagonal cross section may be used depending on the shape and arrangement of the components.

[0052] In the above embodiment, the case where printing is performed on a substrate moving in a horizontal direction has been described, but the direction of movement of the substrate is not limited to this, and the ink drying promotion function can be introduced even when the substrate moves in a vertical direction, for example. In this case, the ink droplets are deflected in the horizontal direction, and the air nozzle is disposed above or below the print head. [Explanation of symbols]

[0053] AR Air 1 Print Head 2 Ink Tank 3a, 3b Pump 4 Printing material 5 Air supply system 10. Inkjet Printer 11 Cases 12. Gun 13 Charged electrode 14 Detection electrode 15 Deflection electrode 16 Gutter 17a, 17b pipes 51, 54a, 54b tubes 52 Drain catch 53 Mist separator 55 Regulator 56 Throttle valve 57 Air nozzle 61 Fixed Block 63 Mounting fixture 64 Bands 110 Cavity 111 Slit 112 Lid

Claims

1. A gun that applies a constant period of vibration to the ink being ejected to generate continuous ink droplets; a charging electrode for charging the ink droplets by applying a step-shaped voltage synchronized with a period of the ink droplets; a deflection electrode for deflecting the charged ink droplets vertically or horizontally according to the degree of charge, so that the ink droplets land on a printing surface of a substrate; a cylindrical case in which the gun, a charging electrode and a deflection electrode are housed in a hollow portion and in which a slit is formed through which the charged ink droplets pass; An inkjet printer that causes ink droplets ejected from the print head to land on a printing substrate that moves relatively in a horizontal or vertical direction, and forms characters with multiple rows of printing dots, air compressed by a single compressor is branched, one of the air flows is supplied to a cavity in the case to maintain the cavity at a positive pressure, and the other air flow is blown onto a printing surface of the printing material to promote drying of the ink; As a means for blowing air onto the printing surface, an air nozzle that blows air from a small diameter hole is used, The ink jet printer according to claim 1, wherein the air nozzle is attached to an outer peripheral surface of the case by wrapping a band around the outer peripheral surface of the case, and the position of the air nozzle is adjustable by changing the attachment position of the band.

2. A gun that generates continuous ink droplets by applying a constant periodic vibration to the ejected ink; a charging electrode for charging the ink droplets by applying a step-shaped voltage synchronized with a period of the ink droplets; a deflection electrode for deflecting the charged ink droplets vertically or horizontally according to the degree of charge, so that the ink droplets land on a printing surface of a substrate; a cylindrical case in which the gun, a charging electrode and a deflection electrode are housed in a hollow portion and in which a slit is formed through which the charged ink droplets pass; An inkjet printer that causes ink droplets ejected from the print head to land on a printing substrate that moves relatively in a horizontal or vertical direction, and forms characters with multiple rows of printing dots, air compressed by a single compressor is branched, one of the air flows is supplied to a cavity in the case to maintain the cavity at a positive pressure, and the other air flow is blown onto a printing surface of the printing material to promote drying of the ink; As a means for blowing air onto the printing surface, an air nozzle that blows air from a small diameter hole is used, an inkjet printer characterized in that a regulator that keeps the air pressure constant is attached to a tube that supplies one of the air streams to a hollow portion of the case, and a throttle valve that adjusts the amount of air is attached to a tube that supplies the other of the air streams to the air nozzle.

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