JP2008207514A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder with a constitution capable of preventing the drying and clogging of a nozzle and hardly changing the vehicle density etc. of ink remaining in a print head, even in the case of the print head such as a line head. <P>SOLUTION: When printing is not carried out, a cap 62 of a cap mechanism 60 abuts on the print head 10, and a closed space is formed between a nozzle forming face of the print head 10 and the cap 62. A liquid for generating a mist stored in a storage tank 70 is turned into the mist by a mist generator 68 and guided into the closed space. A vehicle of a component, except a pigment, among components of ink for performing the printing by the print head 10 is used as the liquid for generating the mist. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus.

  FIG. 3 is a plan perspective view showing an example of an ink jet print head used as a line head or the like. 4A is a cross-sectional view showing a dot forming portion formed on the print head, and FIG. 4B is a perspective view showing an overlapping state of each portion constituting the dot forming portion. The print head 10 includes a substrate 12, and a plurality of dot forming portions 14 are formed on the substrate 12. In order to form the dot formation part 14, as shown to Fig.4 (a), the board | substrate 12 is formed by laminating | stacking several layer 12a, 12b, 12c, 12d.

  In the first layer 12a, for example, a pressurizing chamber 16 having a longitudinal direction and having both ends in the longitudinal direction formed in an arc shape is formed. An ink flow path 18 is formed in the second layer 12 b and the third layer 12 c so as to communicate with the pressurizing chamber 16 on one end side in the longitudinal direction of the pressurizing chamber 16. A nozzle 20 having a smaller diameter than the ink flow path 18 is formed in the fourth layer 12 d so as to communicate with the ink flow path 18. Furthermore, on the other end side in the longitudinal direction of the pressurizing chamber 16, a supply port 22 is formed in the second layer 12b, and is connected to a common flow path 24 formed in the third layer 12c. On the first layer 12 a, a common electrode 26 having the same size as that of the substrate 12 is formed, and a piezoelectric layer 28 is formed on the common electrode 26. Further, individual electrodes 30 are formed on the piezoelectric layer 28 at positions corresponding to the pressurizing chambers 16 of the dot forming portions 14.

  As shown in FIG. 3, dot formation portions 14 are formed on the substrate 12 in a line in the width direction. Multiple rows of such dot forming portions 14 are arranged on the substrate 12. The nozzles 20 of the dot forming portions 14 in adjacent rows are arranged so as to be close to each other. Furthermore, as shown by the dotted line in FIG. 3, the common flow path 24 is formed so as to be connected to the supply ports 22 of all the dot forming portions 14. A joint portion 32 that communicates with the common flow path 24 is formed on the substrate 12, and a pipe or the like from the ink cartridge is connected to the joint portion 32.

  In the print head 10, ink is supplied from the common flow path 24 to the pressurizing chamber 16, the ink flow path 18, and the nozzle 20 through the supply port 22. In this state, when a voltage is applied to the individual electrode 30, the piezoelectric layer 28 bends as shown by a one-dot chain line in FIG. 4A, and the ink of the nozzle 20 is pushed out to the ink droplet. Is injected. When the piezoelectric layer 28 returns to its original shape, an amount of ink corresponding to the ink pushed out is supplied from the common flow path 24 and the nozzle 20 is filled with ink.

  In an ink jet recording apparatus using such a print head 10, a nozzle 20 having a small diameter is used in order to perform printing with high image quality and high resolving power. However, after printing, when the ink has not been used for a long period of time, the ink viscosity of the nozzle 20 portion may increase or the ink may solidify and become clogged with the nozzle 20. In such a case, high-quality printing may occur. Is impossible. Further, if a minute ink droplet other than the necessary droplet ejected from the nozzle 20 or its satellite adheres to the nozzle port ejection surface of the print head surface, the original printing function is impaired. In this case, for example, normal ink droplets from the nozzle 20 may not be ejected, or the ejection direction may change and so-called twist may occur.

  In order to solve such an inconvenient phenomenon, a reliability maintenance mechanism and a cleaning mechanism are attached to the ink jet recording apparatus. The reliability maintenance mechanism moves the print head from the print area to other areas during periods other than the print operation, covers the nozzle port with a concave cap, seals it, and discharges ink from the nozzle part, To remove abnormal ink (in which microbubbles are mixed), fill the nozzle with normal ink, enable highly reliable printing, and cap the nozzle port during the non-printing period. It covers and prevents the ink from drying.

As such a mechanism, for example, an ink jet printer provided with a backup device having a sponge impregnated with a non-volatile fluid and preventing the nozzle from drying by pressing the sponge against the print head when printing is stopped or when the power is turned off. (See Patent Document 1).
In addition, a cap for sealing the nozzle surface of the print head is provided, and the moisturizing liquid filled in the moisturizing liquid chamber in the cap is heated to evaporate the moisturizing liquid in the space sealed by the print head and the cap. There is an inkjet printer (see Patent Document 2).
In addition, a cap to be mounted on the print head is provided, the waste ink reservoir and the cap are connected by a flow path, one end of the fiber member is immersed in the waste ink stored in the waste ink reservoir, and the fiber member is passed through the flow path. There is an ink jet printer that is brought into contact with an absorbing member in a cap. In such an ink jet printer, the waste ink in the waste ink reservoir is absorbed by the absorbing member in the cap due to the capillary phenomenon of the fiber member, and the waste ink evaporates in the cap covering the print head, preventing the nozzle from drying. (See cited document 3).

JP-A-11-157090 JP-A-1-210350 Japanese Utility Model Publication No. 6-21939

However, when a sponge impregnated with a non-volatile fluid is pressed against the print head, the ink on the nozzle adheres to the sponge, and when it dries and thickens, the thickened ink adheres to the nozzle during the next capping. In the worst case, the recording quality is deteriorated and the nozzles are clogged. In addition, in the case of a print head in which a large number of nozzles are formed, such as a line head, it is difficult to press the sponge uniformly to all the nozzles, and there is a possibility that ink drying may occur in some of the nozzles. is there.
Further, when the nozzle surface of the print head is sealed with a cap and the moisturizing liquid is heated and evaporated in the cap, there is a problem that the temperature in the vicinity of the print head rises and the ink in the nozzle portion is accelerated. When the water content of the ink in the nozzle portion evaporates, the vehicle concentration of the ink remaining in the print head changes, which affects the dispersion of the ink components and the like, and the ink in the nozzle portion is discharged and discarded during operation. It is necessary and wasteful waste ink is generated.
Also, when the waste ink in the waste ink reservoir is absorbed by the absorbing member in the cap and evaporated, for example, with water-based ink, the ink is difficult to evaporate due to natural evaporation, and the cap is filled with sufficient ink vapor. May not be possible. In addition, if only water vapor is present in the nozzle portion, the vehicle concentration of ink remaining in the print head may change.

  Therefore, the main object of the present invention is to prevent the nozzles from being dried or clogged even in a print head such as a line head, so that the vehicle concentration of ink remaining in the print head is not easily changed. It is providing the inkjet recording device which has.

The present invention relates to a print head that ejects ink droplets from a nozzle in response to a print command, a cap mechanism that allows the cap to contact and detach from the print head, and a nozzle and a cap that are in contact with the nozzle. And a mist generating means for supplying mist to a closed space formed by the inkjet recording apparatus.
When the mist is supplied to the closed space formed by the nozzle and the cap in a state where the cap is in contact with the nozzle, the mist prevents the ink in the nozzle portion from drying without contacting the nozzle.

In such an ink jet recording apparatus, the mist generating means can be composed of an ultrasonic generator that mists a mist generating liquid with ultrasonic waves.
If an ultrasonic generator is used as the mist generating means, the mist generating liquid can be efficiently misted and the closed space can be filled with mist. In particular, even when using water-based ink that is difficult to evaporate, water-based mist having components similar to ink can be efficiently generated by using an ultrasonic generator.

The mist generated by the mist generating means is preferably a mist of at least a component that does not contain a pigment among the ink components.
As a mist that fills the closed space between the nozzle and the cap, by using a component that does not contain a pigment in the ink used for printing, it is possible to prevent a change in the vehicle concentration of the ink in the nozzle portion. it can.

  According to this invention, it is possible to prevent drying of the ink in the nozzle portion of the print head and clogging of the nozzle by filling the mist in the closed space formed by the nozzle and the cap. Further, by using a component that does not contain the pigment of the ink used as a mist, it is possible to prevent the ink vehicle concentration at the nozzle portion from changing. For this reason, it is not necessary to discharge ink at the nozzle portion during printing, and generation of waste ink can be suppressed.

  The above object, other objects, features, and advantages of the present invention will become more apparent from the following description of the best mode for carrying out the invention with reference to the drawings.

  FIG. 1 is an illustrative view showing an example of an ink jet recording apparatus of the present invention. The ink jet recording apparatus 50 includes, for example, a print head 10 as shown in FIG. As shown in FIG. 3, the print head 10 has a plurality of dot forming portions 14 formed therein, and can be used as a line head or the like.

  As shown in FIG. 2, the print head 10 is supported by a carriage 52, and the carriage 52 is movably supported by a guide shaft 54. The print head 10 is movable between a print area 56 and a home position 58 by a carriage 52 and a guide shaft 54. In the printing area 56, printing is performed by ejecting ink onto the recording paper. When printing is not performed, the print head 10 stands by at the home position 58.

  When the print head 10 is waiting at the home position 58, the cap mechanism 60 covers the cap 62 so as to cover the nozzle 20 formation surface of the print head 10. The cap 62 is formed so as to be able to come into contact with and disengage from the print head 10, and the cap 62 is detached from the print head 10 when the carriage 52 moves to the print area 56.

  For example, a pipe 64 is connected to the cap 62. A valve 66 is attached to the pipe 64, and the cap 62 is connected to the mist generating device 68 through the valve 66. As the mist generator 68, for example, an ultrasonic generator is used. Further, the mist generating device 68 is connected to the storage tank 70 by a pipe 64. The storage tank 70 stores mist generating liquid. Here, among the ink components used for printing, it is preferable to use a component not containing a pigment as the mist generating liquid. As the mist generating liquid, a cleaning liquid or the like can be used.

  In the ink jet recording apparatus 50, when the carriage 52 is waiting at the home position 58, the cap 62 is brought into contact with the print head 10 and the nozzle 20 forming surface is sealed. In this state, the mist generating liquid in the storage tank 70 is made mist by the mist generating device 68, and the obtained mist is guided to the closed space formed by the print head 10 and the cap 62. As a result, the nozzle 20 forming surface of the print head 10 is covered with mist, and the ink of the nozzle 20 is prevented from drying, and the nozzle 20 is prevented from being clogged. In particular, by using a component that does not include a pigment among the components of the ink used for printing as the mist generating liquid, the ink vehicle concentration at the nozzle 20 portion is less likely to change. Therefore, when printing is performed, it is not necessary to discharge ink from the nozzle 20 portion, and generation of waste ink can be suppressed.

  As described above, the mist is produced by the mist generator 68 such as the ultrasonic generator, so that the closed space formed by the print head 10 and the cap 62 is filled with a sufficient amount of mist. Therefore, for example, even when water-based ink is used, the water-based mist generating liquid that is hard to evaporate can be sufficiently misted by the mist generating device 68, and the ink in the nozzle 20 portion is dried. Can be prevented.

  Further, in the inkjet recording apparatus 50, the mist prevents the nozzle 20 forming portion from being dried, so that a foreign substance such as a sponge does not contact the nozzle 20 forming portion. Therefore, the ink does not adhere to the sponge and the nozzle 20 is not soiled by the ink.

  In addition, after sealing the nozzle 20 formation surface of the print head 10 with the cap 62, the mist density | concentration in closed space can be made substantially constant by driving the mist generating apparatus 68 only for a fixed time. Thus, by keeping the mist density in the closed space constant, the ink state of the nozzle 20 can be kept substantially constant. In order to keep the mist concentration in the closed space constant, a device for detecting the mist concentration may be provided in the cap 62. The installation position of the mist generating device 68 may be in the middle of the pipe 64 as shown in FIG. As described above, if the mist can be generated and sent to the cap 62, the mist generating device 68 can be installed at any position where the mist generating liquid is directly or indirectly misted. it can.

  As a colorant to be contained in the ink, C.I. I. Pigment Red 122 was used, and a pigment dispersion was prepared using a water-soluble resin. In order to obtain a pigment dispersion, C.I. I. A mixture comprising 30% by mass of pigment red 122, 15% by mass of John Crill 61 (acrylic-styrene resin, manufactured by Johnson), 10% by mass of glycerin, and 45% by mass of ion-exchanged water was prepared.

  The mixture having such a composition was dispersed with a ball mill using 0.5 mm zirconia beads until the average particle size became 100 nm to prepare a pigment dispersion. The average particle size was confirmed by diluting the pigment dispersion 5 times with ion-exchanged water and using a dynamic light scattering particle size distribution analyzer (LB-550, manufactured by HORIBA).

  Using the obtained pigment dispersion, the pigment dispersion was 20% by mass, glycerin was 10% by mass, 2-pyrrolidone was 5% by mass, hexylene glycol was 5% by mass, Olphine E1010 (acetylene diol) as a surfactant. EO adduct (manufactured by Nissin Chemical Industry Co., Ltd.) was mixed so that the content was 0.5% by mass and water was 59.5% by mass. did. Further, of the obtained inks, the vehicle was adjusted without adding a pigment.

  Using such an ink, using the above-mentioned vehicle as a mist generating liquid, printing with the ink jet recording apparatus shown in FIG. 1, sealing the print head with a cap, generating mist for 30 seconds, 7 days Printing was performed by leaving it to stand. As a result, there was no missing dot and a very good image could be obtained.

  Printing was performed by leaving it for 7 days after printing in the same manner as in the above-described example, except that water was used instead of the vehicle as the mist generating liquid. As a result, no dot omission occurred, but the print density of the first dot was slightly lower. The obtained image was good.

  As a comparative example, an ink jet recording apparatus having a reliability maintaining mechanism for pressing a sponge impregnated with a vehicle against a print head without using a mist generating apparatus was used, and printing was performed by leaving it for 7 days after printing. As a result, dot missing occurred in some places, and the obtained image was defective.

  As can be seen from the above embodiments, in the inkjet recording apparatus of the present invention, when the print head is on standby, the nozzle formation surface of the print head is filled with mist to prevent ink drying and nozzle clogging. Thus, good printing can be obtained.

It is an illustration figure which shows an example of the inkjet recording device of this invention. FIG. 2 is an illustrative view showing the periphery of a print head and a cap of the ink jet recording apparatus shown in FIG. 1. It is a plane perspective view which shows an example of the print head which has a nozzle. (A) and (b) are the illustrations which show the principal part of the print head shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Print head 12 Dot formation part 20 Nozzle 50 Inkjet recording device 52 Carriage 54 Guide shaft 60 Cap mechanism 62 Cap 68 Mist generator 70 Storage tank

Claims (3)

A print head that ejects ink droplets from nozzles in response to a print command;
A cap mechanism capable of contacting and detaching the cap with respect to the print head; and a mist for supplying mist to a closed space formed by the nozzle and the cap in a state where the cap is in contact with the nozzle An ink jet recording apparatus including a generating unit.   2. The ink jet recording apparatus according to claim 1, wherein the mist generating means is an ultrasonic generator that mists a mist generating liquid with ultrasonic waves.   3. The ink jet recording apparatus according to claim 1, wherein the mist generated by the mist generating unit is a mist of at least a component that does not include a pigment among the components of the ink. 4.

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