JPS62236748A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To enhance reliability by performing the stable emission of a liquid droplet from the point of time immediately after the reopening of recording, by supplying a thickening preventing liquid to a liquid flow passage through a semipermeable membrane apart from a recording liquid. CONSTITUTION:A current is supplied to a heat generating element 102 on the basis of a recording signal to heat the same and a recording liquid is emitted from an orifice under the pressure of air bubbles formed in the recording liquid contacted with the heat generating element 102 in a fluid flow passage 106 to perform recording. If there is a non-recording time over a long time, the viscosity of the recording liquid increases by the evaporation of a liquid component from the orifice and, therefore, a thickening preventing liquid is supplied to the recording liquid through a semipermeable membrane 110 to gradually replenish the evaporated part of the recording liquid component and the property of the recording liquid is not especially deteriorated not only at a non-recording time but also at a recording time to enable stable recording. A thickening preventing liquid replenishing port 112 is provided to a thickening preventing liquid chamber 113 and the liquid flow passage 106 is equipped with a thickening preventing liquid supply port 109 for supplying the thickening preventing liquid through the semipermeable membrane 110.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid that performs recording by ejecting and flying a recording liquid as droplets from a liquid ejection port and making the droplets land on a recording medium such as paper. The present invention relates to an ejecting recording head, particularly an on-demand type liquid ejecting recording head that performs ejection when a print signal is applied.

[Prior Art] A liquid jet recording method (inkjet recording method) is conventionally known in which recording is performed by ejecting and flying a recording liquid.

The inkjet recording device used in this method generally includes a liquid ejection opening (orifice) for ejecting the recording liquid as flying droplets, a liquid flow path communicating with the orifice, and a part of the flow path. , an inkjet recording head having an ejection energy generating means for applying ejection energy to the recording liquid in the flow path to form flying droplets.

FIG. 2 shows an example of such an inkjet recording head, in which 207 is an orifice, 202 is an ejection energy generating means, and 206 is a liquid flow path. 214 is the flow path 20
This is a liquid supply system that supplies recording liquid to 6. Recording is performed by driving the ejection energy generating means to supply ejection energy to the recording liquid in the liquid flow path, ejecting the recording liquid as flying droplets from the orifice, and causing the droplets to land on the recording medium. Let's do it.

The recording liquid used when recording with such an inkjet recording device generally consists of a recording agent such as a pigment or dye, and mainly water, or water and a water-soluble organic solvent or a water-soluble organic solvent for dissolving or dispersing it. It is formed by a non-aqueous solvent and a solvent component consisting of a non-aqueous solvent. In inkjet recording snowmaking, an orifice provided at the tip of a liquid flow path through which recording liquid is ejected is often constantly open to the outside air outside the apparatus, regardless of whether or not the apparatus is driven. Therefore, if recording is not performed for a long period of time, some of the solvent evaporates from the orifice into the outside air, and recording agent components and solvent components that are difficult to volatilize remain in the recording liquid. The composition of the recording liquid stagnant in the area changes and its viscosity increases, resulting in an increase in viscous resistance in the liquid flow path. Therefore, immediately after resuming recording after the printing material has stopped, droplet ejection failure is likely to occur in which droplets are not ejected even though the ejection signal is applied, resulting in defects in the initial printed area of the recorded image. There was a problem in that it caused

[Problems to be solved by the invention] The present invention has been made in view of the problems of the above-mentioned conventional examples.
When the recording liquid is not ejected for a long time without recording, the increase in the viscosity of the recording liquid due to the evaporation of liquid components as described above increases the viscous resistance of the liquid flow path. An object of the present invention is to provide a highly reliable inkjet recording head that can prevent droplet discharge failure and can stably discharge droplets immediately after resuming recording.

[Means for Solving the Problems] The above objects of the present invention are achieved by the following present invention.

In an inkjet recording head that includes an orifice for ejecting the recording liquid as droplets, a liquid channel communicating with the orifice, and a liquid supply system for supplying the recording liquid to the liquid channel, the liquid is An inkjet recording head characterized in that an anti-thickening liquid is supplied to the flow path through a semi-permeable ma, separate from the recording liquid.

That is, the present invention aims to prevent the thickening of the recording liquid, which causes the above-mentioned ejection failure, by supplying the thickening preventing liquid to the recording liquid in the liquid flow path through the above-mentioned semipermeable membrane. It is something that More specifically, for example, by bringing the anti-thickening liquid into contact with the recording liquid in the liquid flow path through the anti-thickening liquid supply port provided in the flow path, the above-mentioned effect can be achieved when droplets are not ejected. When the recording liquid components evaporate, the osmotic pressure difference between the recording liquid and the anti-thickening liquid created by this evaporation is used to
By gradually replenishing the recording liquid with anti-thickening liquid,
This is intended to prevent an increase in the viscosity of the recording liquid, which causes the ejection failure as described above.

As the semipermeable membrane in the present invention, for example, a cellophane membrane, a collodion membrane, a denitrifying collodion membrane, a gel cellophane membrane, a biological membrane, etc. can be used without particular limitation. A desired semipermeable membrane may be used, taking into consideration, for example, the solvent composition of the recording liquid used, the concentration of the recording agent, etc. (accordingly, the physical properties of the membrane, processability, economic efficiency, etc.).

The anti-viscosity liquid is not particularly limited as long as it can prevent the recording liquid from increasing in viscosity, but in general, low-viscosity liquids such as water or other low-viscosity solvents are preferred. be. Of course, the use of recording liquid may be used in some cases.

The present invention will be described below based on the drawings, but it goes without saying that the present invention is not limited to the following examples.

FIGS. 1(a) and 1(b) are diagrams for explaining an example of an inkjet recording head of the present invention, and FIG. 1(a) and FIG.
) is a perspective view of the head, and FIG. 1(b) is a sectional view taken along line AA' in FIG. 1(a).

In these figures, 107 is an orifice for ejecting the recording liquid as flying droplets, and 108 is an orifice +0718: an orifice plate provided.

The number and shape of orifices may be determined as desired.

106 is a liquid flow path communicating with the orifice 107;
104 is a channel wall.

Reference numeral 101 denotes a substrate on which is mounted an ejection energy generating means (heating element 102 in this example) that provides ejection energy to the recording liquid for forming flying droplets, and the ejection energy generating means has an orifice 107 on the substrate 101. It is set up correspondingly. The ejection energy generating means does not necessarily have to be a thermal energy generating means such as the heating element 102 described above, but may be a pressure energy generating means such as a pressure element described later.

A liquid chamber 114 serves as a liquid supply system that communicates with the liquid flow path 106 through a liquid supply port 103 provided on the substrate 101 and sends recording liquid to the flow path 106 .

115 is a liquid chamber wall, 117 is a head outer frame, and 116 is a vent for ventilation between the liquid chamber wall 115 and the head outer frame 117. In this example, since the head is a disposable type, replenishment of recording liquid from outside the head is not particularly considered.
It goes without saying that the recording liquid may be supplied to the liquid chamber 114 from a recording liquid storage means provided outside the head, as shown in FIG. 3, which will be described later.

110 is a semipermeable membrane, and 109 is a thickening prevention liquid supply port for supplying the thickening prevention liquid to the liquid flow path 106 via the semipermeable membrane ++01v. Reference numeral 113 denotes a thickening preventing liquid chamber as a thickening preventing liquid storage means, and 112 denotes a thickening preventing liquid supply port for replenishing the thickening preventing liquid to the liquid chamber 113. The anti-thickening liquid may be replenished at any time, or a means for replenishing the anti-thickening liquid may be provided separately from the liquid chamber 113, and the anti-thickening liquid chamber 11 is continuously supplied with the anti-thickening liquid.
In addition, the semipermeable membrane 110 does not necessarily have to be installed in contact with the anti-thickening liquid supply port 109, but in order to make the present invention effective, it is necessary to supply the anti-thickening liquid supply port +0.
9 is preferably provided near the orifice 107.

Although not particularly shown in FIG. 1, conductor wiring is provided on the substrate 101 to send recording signals for ejecting droplets from a recording signal supply source (not shown) to the heating element 102. . The heating element 102 is electrically heated by this recording signal, and this heating causes a bubbling phenomenon in the recording liquid in contact with the heating element 102 in the liquid flow path 106, and the pressure of the generated bubbles causes the recording liquid to be ejected from the orifice 107, allowing recording. will be carried out.

During recording when such droplets are constantly ejected, the recording liquid does not stay in the liquid flow path 106 for a long time, and the viscosity of the recording liquid does not increase as described above. Stable ejection of droplets is possible. However, during non-recording when droplets are not ejected for a long time, the viscosity of the recording liquid increases due to the evaporation of liquid components from the orifice 107 (particularly when the orifice 107 and the liquid flow path 1
06 near the orifice 107),
In conventional ink jet recording heads, droplet ejection failures tend to occur when recording is resumed. On the other hand, in the inkjet recording head of the present invention as exemplified above, since the anti-thickening liquid is supplied to the recording liquid through a semipermeable membrane, the viscosity of the recording liquid increases, which causes the ejection failure as described above. Moreover, by using a semipermeable membrane, the thickening prevention liquid is gradually supplied to the extent that it compensates for the evaporation of the recording liquid components. Even during recording, there is no particular change in the properties of the recording liquid, and stable recording can be performed.

FIGS. 3(a) and 3(b) are diagrams illustrating another example of the inkjet recording head of the present invention, and FIG.
a) is a perspective view of the head, FIG. 3(b) is FIG. 3(a)
It is a BB' sectional view in . The recording head of this example is not a disposable type as shown in FIG. 1, but is designed so that recording liquid can be replenished from outside the head.

In these figures, 310 is a semipermeable membrane, and 309 is a thickening prevention liquid supply port. Reference numeral 313 denotes a thickening preventing liquid chamber that communicates with the supply port 309 via a semipermeable membrane 310, and the thickening preventing liquid is supplied to the chamber 313 from the outside of the head through the thickening preventing liquid supply port 312.

307 is an orifice, and 306 is a liquid flow path.

314 is a liquid chamber communicating with the flow path 306, and 303 is a liquid supply port for supplying recording liquid from a recording liquid storage means (not shown) provided outside the head to the liquid chamber 314. 3
05 is a channel wall, 318 is a top plate as a cover for the channel, 30
4 and 315 are an outer wall of the liquid chamber and an inner wall of the liquid chamber, respectively.

A piezoelectric element 302 is mounted on the substrate 301 and serves as a means for ejecting energy. In the recording head of this example, a recording signal is applied to this piezoelectric element 302, and a volume change of the piezoelectric element 302 accompanying the application of the signal is used to eject droplets and perform recording. Even in this case, the anti-thickening liquid is supplied to the recording liquid through the semi-permeable membrane 310 during non-recording, and stable droplet ejection can be performed immediately after recording is resumed, as in the recording head of FIG.

Although not specifically explained above, when using a recording liquid as the anti-thickening liquid, the anti-thickening liquid storage means and the recording liquid storage means outside the head are not particularly separated, and the same recording liquid is used as the anti-thickening liquid. From the storage means to the liquid chamber 314 and the thickening prevention liquid chamber 31
A recording liquid may be introduced in Step 3.

FIG. 4 shows an inkjet bridge as an example of an inkjet recording apparatus using the inkjet recording head of the present invention, which utilizes the recording head illustrated in FIG. 1. In this printer, a recording head 406 mounted on a carriage 405 is mounted on rails 403 and 405.
The recording liquid is ejected while moving left and right above, and characters are printed on the recording medium using a dot matrix of the recording liquid. 402 is paper as the recording medium, and 401 is a platen that supports the recording medium.

Some of the embodiments of the present invention have been described above, but in the present invention, members of the recording head other than those in which the anti-thickening liquid is supplied separately from the recording liquid to the liquid flow path via a semipermeable membrane The configuration and formation method are not particularly limited, and may be any desired similar to those in conventional inkjet recording heads.

[Example] Examples of the present invention are shown below.

<Example 1> Using the inkjet recording head of the present invention illustrated in FIG. 1, this was installed in the inkjet printer illustrated in FIG. 4, and a printing test was conducted on a fixed-time HD. The results are shown in Table-1.

In the recording head shown in Fig. 1, the semipermeable membrane is a cellophane membrane, and the orifices are 'f3rM8 pieces/mm.
24 pieces were arranged in a straight line.

In the printing test, a recording liquid consisting of 30% by weight of ethylene glycol, 18% by weight of polyethylene glycol, 50% by weight of water and 2% by weight of a black water-soluble dye was used. %, Table-1
Recording was resumed after being left for 12 hours, 24 hours, and 72 hours as shown in FIG. At the time of restarting recording, the presence or absence of droplets was observed, and if any droplets were present, the number of droplets was counted to evaluate ejection stability. Note that water was used as the thickening prevention liquid.

<Example 2> A printing test similar to Example 1 was conducted except that the inkjet recording head was used as illustrated in FIG. 3. The results are shown in Table-1.

Comparative Example 1> A printing test similar to that of Example 1 was conducted except that the conventional inkjet recording head illustrated in FIG. 2 was used. The results are shown in Table-1.

<Comparative Example 2> Printing was carried out in the same manner as in Example 1, except that the inkjet recording head was a conventional recording head in which the anti-thickening liquid supply mechanism was removed from the inkjet recording head of the present invention illustrated in FIG. A test was conducted. The results are shown in Table-1.

As is clear from Table 1, in the conventional inkjet recording head, ejection failure occurred even when recording was resumed after being left unused for 12 hours, whereas in the inkjet recording head of the present invention, Even after 72 hours of standing, stable ejection was possible without droplets being lost. Further, even during recording, the droplet diameter did not particularly change, and the print quality was excellent.

[Effects of the Invention] As described above, the present invention makes it possible to provide a novel and highly reliable inkjet recording head that can stably eject droplets immediately after resuming recording.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams for explaining an example of an inkjet recording head of the present invention, and FIG. 1(a) and FIG.
) is a perspective view of the head, FIG. 1(b) is a sectional view taken along line AA' in FIG. 1(a), and FIGS. 3(a) is a perspective view of the head, and FIG. 3(a) is a perspective view of the head;
Figure (b) is a 8-8' sectional view in Figure 3 (a),
FIG. 4 is a diagram illustrating an example of a conventional inkjet recording head, and FIG. 4 is a diagram illustrating an example of an inkjet printer using the inkjet recording head of the present invention. 107.207,307-...Orifice 110.31
0--Semipermeable membrane 106.206.306--Liquid channel 102.202
．． 302--Discharge energy generating means 114.214
,314-...Liquid chamber +01,201,301-...Substrate 103.203.303...Liquid supply port 104.204
．． 305-...Flow path wall 115.215-...Liquid chamber wall 116.216...Vent hole

Claims (1)

[Claims] (1) A liquid comprising a liquid ejection port for ejecting the recording liquid as droplets, a liquid flow path communicating with the liquid ejection port, and a liquid supply system for supplying the recording liquid to the liquid flow path. 1. A liquid jet recording head, characterized in that an anti-thickening liquid is supplied to the liquid flow path separately from the recording liquid through a semipermeable membrane.