JP2005074733A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus which can obtain a good image by preventing poor ejection from a recording head from being caused by thickening of ink during storage thereof, and by making the ink properly cured on a recording medium. <P>SOLUTION: A dehydrator, which is composed of an intermediate tank 10 and a first heater 16 and which eliminates excess moisture included in the ink, is provided between a tank 13 for storing the ink, and the recording head 5 wherein a nozzle for ejecting the ink supplied from the tank 13 is formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus that adjusts moisture contained in ink.

  In recent years, an image recording apparatus using an ink jet recording method is often used because an image can be easily and inexpensively formed as compared with a method that requires plate making such as a gravure printing method or a flexographic printing method. It is becoming.

  In particular, in the field of image recording on products and product packaging using an ink jet recording apparatus, a non-ink-absorbing material such as a resin or metal is used as a recording medium for the product or product packaging. In order to fix the ink, a photocurable ink is used, and after the ink is ejected onto a recording medium, the ink is cured and fixed by, for example, irradiating light such as ultraviolet rays.

  UV curable inks are broadly classified into radical polymerization inks containing radical polymerization compounds and cationic polymerization inks containing cationic polymerization compounds as polymerizable monomers and photopolymerization initiators. Among them, cationic polymerization inks are attracting attention because they are cured well by irradiation with ultraviolet rays when recording an image because the polymerization reaction is hardly inhibited by oxygen in the air.

  However, in cationic polymerization inks, water and amines in the ink act as polymerization inhibitors, so if the ink touches the air for a certain period of time and the water evaporates, the polymerization will accelerate and the ink will thicken. As a result, ink supply failure or ejection failure may occur during image recording, and image quality may deteriorate.

Therefore, in order to prevent ejection failure due to ink thickening, an ink composition containing a colorant and a photopolymerizable monomer or oligomer and a photopolymerization initiator are provided in the ink supply path immediately before the recording head. There is known an ink jet recording apparatus that includes a mixing tank that mixes at least one reaction liquid contained therein and prepares ink immediately before the ink is ejected from the recording head (see, for example, Patent Document 1).
JP 2003-89261 A

  However, in the conventional ink jet recording apparatus, since ink is prepared immediately before ink is ejected from the recording head, there is a problem that the apparatus and the control are complicated and the cost is increased.

  For this reason, for example, an ink jet recording apparatus has been proposed in which the moisture content of the ink is maintained at a certain level or more by adjusting the humidity in the tank for storing the ink or by replenishing the ink with moisture for moisture retention. .

  However, if the ink contains excessive moisture, it will hinder the curing of the ink when an image is recorded. Therefore, after the ink has landed on the recording medium, the dot diameter increases on the recording medium and the ink There is a risk of blurring or color mixing, leading to a reduction in image quality.

  In view of this, the present invention prevents inkjet discharge from a recording head due to thickening at the time of ink storage, and allows ink to be cured well on a recording medium so that a good image can be obtained. An object is to provide an apparatus.

  In order to solve the above problems, an ink jet recording apparatus according to the present invention includes a tank for storing ink and a recording head formed with a nozzle for discharging the ink supplied from the tank. In an ink jet recording apparatus that forms an image by discharging the ink to a recording medium and curing it, a dehydrator that removes excess water contained in the ink is provided between the tank and the recording head. It is characterized by.

  According to the first aspect of the present invention, when the ink is stored in the tank, the polymerization is promoted by replenishing moisture for preventing the water in the ink from evaporating. Ink does not thicken, and ink ejection failure is suppressed during image recording. Even if moisture for moisture retention is replenished in this way, a dehydrator is provided between the tank and the recording head, and excess moisture is removed by this dehydrator, preventing ink curing failure. Is done. In addition, after the ink has landed on the recording medium, ink bleeding and color mixing due to the increase in the dot diameter on the recording medium are reduced, and the ink is cured well.

  According to a second aspect of the present invention, in the inkjet recording apparatus according to the first aspect, the dehydrator includes an intermediate tank that temporarily stores ink and a heating unit that heats the intermediate tank. Features.

  According to the second aspect of the present invention, even when the ink is replenished with moisture retaining moisture when the ink is stored in the tank, it is heated by the heating means while the ink is stored in the intermediate tank. Since excess water is removed, after ink has landed on the recording medium, ink bleeding and color mixing due to the increase in dot diameter on the recording medium are reduced, and the ink is cured well.

  According to a third aspect of the present invention, in the ink jet recording apparatus according to the first or second aspect, the communication tube that communicates from the dehydrator to the recording head and supplies the recording head with dehydrated ink. And a heating means for heating the communication tube and the recording head so as to keep the ink at a predetermined viscosity.

  According to the invention described in claim 3, since the ink from which excess water has been removed by the dehydrator is ejected from the recording head in a state where the predetermined viscosity is maintained by the heating means, ejection failure is further suppressed. The

  According to a fourth aspect of the present invention, in the inkjet recording apparatus according to any one of the first to third aspects, the ink is a photocurable ink that is cured by light, and the photocurable ink is used as the ink. A light irradiation device for irradiating light to be cured after being discharged from the recording head onto the recording medium is provided.

  According to the fourth aspect of the present invention, even when the photocurable ink is stored in the tank, even if the ink is replenished with moisture for moisture retention, excess water is removed by the dehydrator. After the curable ink has landed on the recording medium and before it is cured by the light irradiation device, the dot diameter of the photocurable ink is increased on the recording medium, and the occurrence of ink bleeding or color mixing is suppressed.

  The invention according to claim 5 is the inkjet apparatus according to claim 4, wherein the light irradiation device is an ultraviolet irradiation device that irradiates ultraviolet rays, and the ink is cured by being irradiated with ultraviolet rays. It is characterized by being ink.

  According to the fifth aspect of the present invention, when the ultraviolet curable ink is stored in the tank, excess water is removed by the dehydrator even when the ink is replenished with moisture. After the curable ink has landed on the recording medium and before being cured by the ultraviolet irradiation device, the dot diameter of the ultraviolet curable ink is increased on the recording medium, and the occurrence of ink bleeding or color mixing is suppressed.

  According to a sixth aspect of the present invention, in the ink jet recording apparatus according to the fourth or fifth aspect, the ink is a cationic polymerization type ink.

  According to the invention described in claim 6, even when the ink of the cationic polymerization type is stored in the tank, even if the ink is supplemented with moisture for moisture retention, excess water is removed by the dehydrator. After the cationic polymerization ink has landed on the recording medium and before it is cured by the light irradiation device, the dot diameter of the ink spreads on the recording medium and the occurrence of ink bleeding or color mixing is suppressed.

  According to the first aspect of the present invention, when the ink is stored in the tank, the moisture for moisturizing is replenished, thereby suppressing the ejection failure from the recording head due to the thickening at the time of storing the ink. In addition, since excess water is removed by the dehydrator before the ink is supplied to the recording head, the ink is cured well on the recording medium and a good image can be obtained.

  According to the second aspect of the present invention, when the ink is stored in the tank, the moisture retention moisture is replenished, thereby suppressing the ejection failure from the recording head due to thickening at the time of storing the ink. In addition, since excess water contained in the ink is removed by the heating means in the intermediate tank before the ink is supplied to the recording head, the ink is cured well on the recording medium and a good image is obtained. Can be obtained.

  According to the invention described in claim 3, since the ink from which excess water has been removed by the dehydrator is ejected from the recording head in a state where the predetermined viscosity is maintained by the heating means, ejection failure is further suppressed. As a result, a better image can be obtained.

  According to the fourth aspect of the present invention, when the photocurable ink is stored in the tank, by replenishing moisture for moisturizing, the recording head can increase the viscosity when storing the photocurable ink. In addition, since excessive moisture is removed by the dehydrator before supplying the photocurable ink to the recording head, the photocurable ink is cured well on the recording medium, A good image can be obtained.

  According to the fifth aspect of the present invention, when the ultraviolet curable ink is stored in the tank, the moisture retention moisture is replenished, thereby increasing the viscosity of the ultraviolet curable ink from the recording head. In addition, since excessive moisture is removed by the dehydrator before supplying the ultraviolet curable ink to the recording head, the ultraviolet curable ink is cured well on the recording medium, A good image can be obtained.

  According to the sixth aspect of the present invention, when the cationic polymerization ink is stored in the tank, the moisture content is replenished so that the recording head can increase the viscosity when the cationic polymerization ink is stored. In addition, since excessive moisture is removed by the dehydrator before supplying the cationic polymerization ink to the recording head, the cationic polymerization ink is cured well on the recording medium, A good image can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 shows an embodiment of an ink jet recording apparatus according to the present invention, which is a serial head type ink jet recording apparatus 1. As shown in FIG. 1, the inkjet recording apparatus 1 has a guide rail 2, and a carriage 3 is supported on the guide rail 2. The carriage 3 reciprocates in the scanning direction X along the guide rail 2 by a carriage drive mechanism (not shown).

  A recording head 5 is formed on the carriage 3 by forming nozzles (not shown) for ejecting yellow (Y), magenta (M), cyan (C), and black (K) inks to the recording medium 4. Is installed. The recording head 5 is covered with a box-shaped housing 6 having an open nozzle forming surface on which nozzles are formed.

  The ink used in the present embodiment is an ultraviolet curable ink that is cured by irradiating ultraviolet rays. Ultraviolet curable inks are broadly classified into radically polymerizable inks containing radically polymerizable compounds and cationically polymerizable inks containing cationically polymerizable compounds as polymerizable compounds. Both types of inks are used in this embodiment. As the ink used in the present embodiment, a hybrid ink in which a radical polymerization ink and a cation polymerization ink are combined may be used as the ink used in the present embodiment. However, cationic polymerization inks that have little or no inhibitory effect on the polymerization reaction due to oxygen are more excellent in functionality and versatility, and it is particularly preferable to use cationic polymerization inks.

  As the recording medium 4, a recording medium 4 made of various papers such as plain paper, recycled paper, glossy paper, various fabrics, various non-woven fabrics, resin, metal, glass and the like is applicable. In particular, as the recording medium 4 used in the present embodiment, a transparent or opaque non-absorbent resin film used for so-called soft packaging can be applied.

  The carriage 3 has light sources (not shown) on both sides in the scanning direction X of the recording head 5 and irradiates the ink ejected from the nozzles to the recording medium 4 with ultraviolet rays. An ultraviolet irradiation device 7 is provided. As the light source, a mercury lamp, a metal halide lamp, an excimer lamp, an ultraviolet laser, an LED (Light Emitting Diode), or the like is applicable. The light used here may be an electron beam, an X-ray, an infrared ray, or the like in addition to the ultraviolet ray.

  In addition, the inkjet recording apparatus 1 is provided with a transport mechanism (not shown) in which a plurality of transport rollers 8 that transport the recording medium 4 in the transport direction Y orthogonal to the scanning direction X are arranged. The conveyance mechanism is configured to intermittently convey the recording medium 4 by repeatedly conveying and stopping the recording medium 4 in accordance with the operation of the carriage 3 during image recording.

  The central part of the movable range of the carriage 3 is a recording area for recording on the recording medium 4, and this recording area is composed of a plate-like member and supports the recording medium 4 from the non-recording surface. 9 is provided.

  An intermediate tank 10 for temporarily storing ink is provided on the back side of the carriage 3 and below the recording head 5, and the intermediate tank 10 is connected to the recording head 5 via a communication pipe 11. Is communicated with a liquid chamber (not shown).

  The upper surface of the intermediate tank 10 is provided with a communication hole 12 for allowing ink to communicate with the atmosphere, and the ink back pressure is set to a negative pressure by making the ink liquid surface level lower than the nozzle formation surface of the recording head. The ink is reliably and accurately ejected from the nozzle.

  A tank 13 for storing ink is provided above the back side of the intermediate tank 10, and in this tank 13, the ink is 1 to 2% of moisturizing water for ink in a state suitable for recording an image. It is stored with the minute added. The tank 13 communicates with the intermediate tank 10 via the ink supply pipe 14, and the ink supply pipe 14 is provided with a pump 15 that forms an air flow and supplies ink from the tank 13 to the intermediate tank 10. ing.

  A first heater 16 as a heating means for heating the intermediate tank 10 is provided on the lower surface of the intermediate tank 10, and the first heater 16 evaporates moisture for moisture retention added when the tank 13 is stored. It has become. In the present embodiment, the intermediate tank 10 and the first heater 16 constitute a dehydrator.

  Further, a second heater 17 is provided on the peripheral surface of the communication pipe 11 and each surface of the casing 6 of the recording head 5 as a heating means for keeping the ink heated by the first heater 16 at a constant temperature. The second heater 17 is adapted to maintain a viscosity suitable for ejecting ink from the recording head 5.

  Next, the operation of this embodiment will be described.

  When image information is sent to the ink jet recording apparatus 1, the transport mechanism is activated to transport the recording medium 4 in the transport direction Y. When the recording medium 4 is conveyed below the carriage 3, the carriage driving mechanism is operated to reciprocate the carriage 3 in the scanning direction X, and a predetermined color from the nozzles of the recording head 5 based on predetermined image information. Ink is ejected. The ejected ink sequentially reaches the recording medium 4. Then, with the movement of the carriage 3, the ink that has landed on the recording medium 4 is sequentially irradiated with ultraviolet rays from the ultraviolet irradiation device 7, and the ink is cured on the recording medium 4. During this time, the conveyance mechanism operates to convey the recording medium 4 in the conveyance direction Y, whereby an image is recorded on the recording medium 4.

  Here, as ink is ejected from the recording head 5, ink is supplied from the intermediate tank 10 to the recording head 5, and ink is supplied from the tank 13 to the intermediate tank 10.

  In the tank 13, since the ink is stored in a state where 1 to 2% of moisture for moisture retention is added, the water in the ink evaporates, so that the polymerization is accelerated and the ink is thickened. It is suppressed.

  The ink is supplied from the tank 13 to the intermediate tank 10 and is temporarily stored in the intermediate tank 10, so that the ink is heated by the first heater 16 to evaporate the moisture retaining moisture. Note that vapor generated by heating the ink is released to the outside of the intermediate tank 10 through the communication hole 12 provided on the upper surface of the intermediate tank 10.

  Thereafter, the ink is supplied to the recording head 5 through the communication tube 11. At this time, the ink is heated by the second heater 17 and is maintained at a predetermined viscosity. When ejecting, ejection failure such as nozzle clogging is reduced.

  As described above, according to the ink jet recording apparatus 1 according to the present embodiment, when ink is stored in the tank 13, by supplying moisture for moisture retention, ink supply due to thickening during ink storage is performed. Defects are suppressed, and excess water contained in the ink is removed by the first heater 16 in the intermediate tank 10 before the ink is supplied to the recording head 5, so that the ink is good on the recording medium 4. When cured, a good image can be obtained.

  Further, since the ink from which excess water has been removed by the first heater 16 is ejected from the recording head 5 in a state where a predetermined viscosity is maintained by the second heater 17, ejection failure is suppressed.

  In the present embodiment, the intermediate tank 10, the communication pipe 11, and the recording head 5 are directly heated and heated by the heaters 16 and 17, but they may be heated and heated by radiant heat or a fan. A heater may be used. The heating means and the heating means are not limited to heaters. For example, the housing 6 of the recording head 5 is constituted by an inner wall and an outer wall, and hot water is circulated between the inner wall and the outer wall. It may be.

  In the present embodiment, the first heater 16 is provided in the intermediate tank 10 to be used as a dehydrator. However, a dehydrator may be provided separately from the intermediate tank 10.

  Further, in the present embodiment, the serial head type recording head 5 is used. However, the recording head 4 is provided above the recording medium 4 over the entire width of the recording medium 4, and ink is supplied to the conveyed recording medium 4. You may make it use the recording head 5 of the line head system which forms an image by discharging.

It is a figure which shows the structure of one Embodiment of the inkjet recording device by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 3 Carriage 4 Recording medium 5 Recording head 7 Ultraviolet irradiation device 10 Intermediate tank 11 Communication pipe 13 Tank 16 First heater (heating means)
17 Second heater (heating means)

Claims (6)

  An ink storage tank; and a recording head formed with a nozzle for discharging the ink supplied from the tank. The ink is discharged from the recording head to a recording medium and cured to form an image. An ink jet recording apparatus comprising: a dehydrator for removing excess water contained in the ink between the tank and the recording head.   The inkjet recording apparatus according to claim 1, wherein the dehydrator includes an intermediate tank that temporarily stores ink and a heating unit that heats the intermediate tank.   The dehydrator communicates with the recording head and has a communication tube for supplying the recording head with dehydrated ink. The communication tube and the recording head are heated to maintain the ink at a predetermined viscosity. The inkjet recording apparatus according to claim 1, further comprising a heating unit that performs heating.   The ink is a light curable ink that is cured by light, and a light irradiation device that irradiates light to be cured after the light curable ink is discharged from the recording head onto the recording medium is provided. Item 4. The ink jet recording apparatus according to any one of Items 1 to 3.   The inkjet apparatus according to claim 4, wherein the light irradiation device is an ultraviolet irradiation device that irradiates ultraviolet rays, and the ink is ultraviolet curable ink that is cured by irradiation with ultraviolet rays.   The ink jet recording apparatus according to claim 4, wherein the ink is a cationic polymerization type ink.

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