JPH0729416B2 - Liquid jet recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a liquid for recording by ejecting and ejecting recording liquid as droplets from a liquid ejection port and landing the droplets on a recording medium such as paper. The present invention relates to an ejection recording head, and more particularly to an on-demand type liquid ejection recording head that ejects when printing is applied.

[Prior Art] A liquid jet recording method (inkjet recording method) has been conventionally known in which recording is performed by ejecting and flying a recording liquid.
An ink jet recording apparatus used in the ink jet recording method used in the method is generally a liquid ejection port (orifice) for ejecting and ejecting a recording liquid as flying droplets, a liquid flow path communicating with the orifice, and the flow path. And an ink jet recording head having a discharge energy generating means for giving discharge energy for forming flying droplets to the recording liquid in the flow path.

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 landing these droplets on the recording medium. is there.

The recording liquid used for recording by such an ink jet recording apparatus is generally a recording agent portion such as a pigment or a dye, and mainly water for dissolving or dispersing it, or water and a water-soluble organic solvent or It is formed by a solvent component composed of a non-aqueous solvent. In an inkjet recording apparatus, an orifice provided at the tip of a liquid flow path through which a recording liquid is discharged is often open to the outside air outside the apparatus regardless of whether the apparatus is driven. Therefore, when recording is not performed for a long time, a part of the solvent evaporates from the orifice into the outside air, and the recording agent component or the solvent component which is hard to volatilize remains in the recording liquid. The composition of the recording liquid staying in the part changes and the viscosity increases, and as a result, the viscous resistance of the liquid flow path increases. Therefore, immediately after the recording is restarted after the printing is paused, the ejection signal is not ejected even though the ejection signal is applied. The ejection failure of the droplets easily occurs, and the initial print portion of the recorded image is defective. There was a problem to be solved.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems of the above conventional example,
When the non-ejection state of the recording liquid without recording is continued for a long time, the increase in the viscosity of the recording liquid due to the evaporation of the liquid components as described above is caused to increase the viscous resistance of the liquid flow path immediately after the restart of recording. An object of the present invention is to provide a highly reliable inkjet recording head capable of preventing defective ejection of droplets and stably ejecting droplets immediately after restarting recording.

Another object of the present invention is to arbitrarily change the size of the liquid droplets ejected from the orifice, whereby the recording liquid concentration (printing density) per unit area on the recording medium surface can be changed. Another object of the present invention is to provide a novel inkjet recording head capable of expressing gradation.

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

In a liquid ejecting head that ejects a recording liquid from an ejection port to perform recording, an ejection energy generating unit that generates energy for ejecting the recording liquid from the ejection port, and the ejection port is an ejection port formed in a piezoelectric body. A liquid jet recording head, which is an outlet, and whose opening area is changed by driving the piezoelectric body, and the ejection opening is larger than the opening area when the liquid jet recording head is used. , A liquid jet head that is used by narrowing the opening area when not in use.

That is, the present invention utilizes the reversibility of the deformation of the piezoelectric body due to the voltage application and the variability of the deformation amount. By forming an orifice in such a piezoelectric body, the orifice area can be arbitrarily changed. It was done. More specifically, for example, at the time of non-recording in which the liquid droplets are not ejected, a voltage is continuously applied to the piezoelectric body to reduce the orifice area, which causes the ejection failure of the liquid droplets as described above. It was intended to prevent the increase of. Further, at the time of recording, the orifice area is appropriately changed by arbitrarily adjusting the amount of voltage applied to the piezoelectric body at the time of recording by, for example, ON-OFF or applying several kinds of pulse voltages, thereby ejecting droplets. The size is arbitrary, and gradation expression is also possible.

In the present invention, known piezoelectric materials such as Rochelle salt, barium titanate, and lead titanate can be used without particular limitation. Specifically, these piezoelectric bodies are used, for example, in a desired form such as a piezoelectric member obtained by boring a hole used as an orifice in a plate-shaped member or the like made of the piezoelectric body so as to make the orifice area variable.

Hereinafter, the present invention will be described with reference to the drawings, but it goes without saying that the present invention is not limited to the following examples.

1 and 2 are views for explaining an example of the ink jet recording head of the present invention. FIG. 1 is a perspective view of the head, and FIG. 2 is a sectional view taken along the line AA 'in FIG. .

In these figures, 1 is an orifice plate as a piezoelectric member, and 2 is an orifice provided in the orifice plate 1. The number of orifices and the shape may be as desired. Reference numeral 16 is a liquid flow path communicating with the orifice 2.

Reference numeral 3 denotes a substrate on which a well-known electrothermal converter (not shown) is mounted as a discharge energy generating means for giving the recording liquid ejection energy for forming flying droplets, and the electrothermal converter is the substrate 3 It is provided above the orifice 2. The discharge energy generating means does not necessarily have to be the heat energy generating means such as the electrothermal converter, but may be the pressure energy generating means using the above-mentioned piezoelectric body or the like. Reference numeral 10 is an adhesive layer for fixing the substrate 3 and the orifice plate 1.

Reference numeral 4 is a conductor wiring portion that sends a recording signal for discharging droplets from a recording signal supply source (not shown) to the electrothermal converter on the substrate 3. The electrothermal converter is electrically heated by this recording signal, and by this heating, a bubbling phenomenon occurs in the recording liquid in contact with the electrothermal converter in the liquid flow path 16, and the recording liquid is discharged from the orifice 2 by the pressure of the generated bubbles. , Recording is done.

It should be noted that conductor wiring (not shown) for sending a recording signal from the conductor wiring portion 4 to the electrothermal converter is independently provided on the substrate 3 separately from the wiring portion 4, and 9 is a substrate. 3 is a thin metal wire (in this example, a gold wire having a diameter of 30 μm) for electrically connecting the above wiring on 3 and the conductor wiring portion 4. Reference numeral 8 is a resin sealing member for protecting the connection portion between the gold wire 9 and the substrate 3 and the conductor wiring portion 4. The resin sealing member 8
Was formed by using an epoxy-novolak type resin that is widely used as an IC package, molding the resin with a mold, and heating and curing.

7 is a fluid flow path by a hole (not shown) formed in the substrate 3.
The ink tank is a liquid chamber that communicates with 16 and stores the recording liquid 11 sent to the flow path 16, and is a deformable rubber tank in this example. Reference numeral 6 is a main body case of the recording head, which is made of acrylic in this example. still,
The body case 6, the ink tank 7, and the resin sealing member 8 are fixed to each other with an adhesive.

Reference numeral 5 is a conductor wiring portion for sending an electric signal from a voltage supply source (not shown) to the orifice plate 1 as a piezoelectric member. The voltage applied to the orifice plate 1 through the conductor wiring portion 5 controls the orifice area, prevents evaporation of the liquid component during non-recording, and controls the size of ejected droplets during recording.

3 to 4 are views for explaining the detailed configuration of an orifice plate as an example of the piezoelectric member used in the ink jet recording head shown in FIGS. 1 and 2, and FIG. FIG. 4 is a perspective view and FIG. 4 is a sectional view taken along the line AA ′ in FIG.

The orifice plate 1 is constructed by providing a plate-shaped member 17 made of the above-described piezoelectric material with a hole having a desired size as the orifice 2. Reference numerals 13-1 and 13-2 are metal plating layers as electrodes, and in order to polarize the piezoelectric body by applying a voltage and to cause the orifice plate 1 to deform toward the center of the orifice, electrodes 13-1 and 13-2 are provided.
It is divided into -1 and 13-2.

The ink jet recording head of the present invention has been described above mainly using the case where a piezoelectric member such as an orifice plate is used as the piezoelectric body. However, the present invention is not limited to using such a piezoelectric member, and the piezoelectric body is not limited thereto. May be, for example, one in which the entire outer circumference of the orifice or a part thereof is simply plated. Of course, the member structure and forming method of the recording head other than providing the orifice in such a piezoelectric body are not particularly limited, and may be the same desired one as in the conventional ink jet recording head.

[Examples] Examples of the present invention will be shown below.

<Example 1> Barium titanate was used as the piezoelectric material, a plate-like member 17 having an appearance as shown in Fig. 3 was prepared, and then an orifice 2 having a diameter of 51 µ was provided by perforation. Then, this plate-shaped member
After Ni plating and gold plating as electrodes 17 were sequentially applied, the conductor cap 12 as shown in FIG. 4 was provided by etching to complete the orifice plate 1 as shown in FIG.

The gap width 12 between the electrodes 13-1 and 13-2 is 0.2
μ, and the thickness of the plating layer was 5 μ for the Ni plating layer and 1 μ for the gold plating layer.

Using the orifice plate 1 thus obtained,
It was assembled to the ink jet recording head described in FIGS. 1 and 2 above. At this time, both electrode portions of the piezoelectric body and the conductor wiring portion 5 were connected to each other by brazing via a thin metal wire whose circumference was insulated.

This inkjet recording head was mounted on an inkjet printer, and a recording test described later was conducted.

<Example 2> The piezoelectric material of Example 1 was changed to PZT (PbZr _0.5 Ti).
An ink jet recording head was prepared in the same manner as in Example 1 except that the _0.5 O ₃ ) powder was replaced with a composite piezoelectric material hardened with an epoxy resin, and the same recording test as in Example 1 was carried out.

<Example 3> The same piezoelectric substance as barium titanate as in Example 1 was used.
A plate-shaped member 14 having an appearance as shown in the figure was created.
After that, the same perforation, Ni plating, gold plating, and etching for forming a gap as in Example 1 were performed, and then the plate member 14 was formed into a square hole having substantially the same size as the member 14 as shown in FIG. An orifice plate was obtained by sticking the acrylic plate 15 having 18 with an adhesive. The orifice plate thus completed was assembled into an ink jet head by the same method as shown in Example 1, and then the same recording test as in Example 1 was conducted.

With respect to the inkjet recording heads of Examples 1 to 3 described above, the results are shown in Table 1 in which the inkjet recording heads were actually mounted on an inkjet printer, left for a certain period of time, and then printed on recording paper. The conditions for leaving were that the ambient temperature was 20 ° C. and the humidity was 20%, and it was reused after being left for 2 hours.

As is clear from Table-1, in any of the examples, the one in which the orifice diameter was reduced by applying the voltage to the piezoelectric body when the printer was not used did not apply the voltage when the printer was not used, It can be seen that the ejection failure of the recording liquid immediately after the restart of use of the printer is greatly improved, as compared with the case where the orifice diameter is not made small (that is, the same state as the ink jet recording head of the conventional example). This is considered to be due to the effect of suppressing the evaporation of the recording liquid component by reducing the orifice diameter. By the way, in Example 1, the number of pulses applied to the electrothermal converter as the ejection energy generating means until the start of droplet ejection was reduced to about 1/3, while in Example 2, it was reduced to about 1
It has decreased to / 4. By the way, in Example 3, the effect of improvement is about 1/2, which is lower than in Examples 1 and 2, but
It is considered that this is because the amount of displacement of the piezoelectric body due to voltage application was small, that is, the orifice diameter when the printer was not used was larger than in other examples.

As is apparent from these examples, the evaporation speed of the recording liquid component can be reduced by reducing the orifice area during non-recording in which the liquid droplets are not ejected, and thus the recording liquid in the liquid flow path can be reduced. The speed of increase in the viscous resistance of was relieved, and stable recording could be resumed without causing ejection failure even after being left for a long time.

[Effects of the Invention] As described above, by forming an orifice in a plate-shaped piezoelectric body and making the orifice area variable, it is possible to perform stable ejection of liquid droplets immediately after resuming recording. You can now provide the head. Further, such variability of the orifice area enables gradation expression, and such gradation expression can be performed by only one orifice without disposing a plurality of orifices having different sizes. As a result, the inkjet recording head can be made compact and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of an ink jet recording head of the present invention, FIG. 2 is a sectional view taken along the line AA ′ of FIG. 1, and FIGS. 3 to 4 are views illustrating an example of an orifice plate. 5 to 6 are views for explaining another example of the orifice plate. 1 ... Orifice plate 2 ... Orifice 3 ... Substrate 4, 5 ... Conductor wiring part 6 ... Main body case, 8 ... Resin sealing member 7 ... Ink tank, 10 ... Adhesive layer 9 ... Thin metal wire, 12 ... Gap 11 ... Recording liquid, 13 ... Electrode 14, 17 ... Plate member, 15 ... Acrylic plate 16 ... Liquid channel, 18 ... Square hole

Claims (4)

[Claims] 1. A liquid ejecting head for ejecting a recording liquid from an ejection port to perform recording, and ejection energy generating means for generating energy for ejecting the recording liquid from the ejection port, and the ejection port being a piezoelectric body. A liquid jet recording head, which is a discharge port that is provided and whose discharge area is changed by driving the piezoelectric body. 2. The liquid jet recording head according to claim 1, wherein the discharge port is used with a smaller opening area when the liquid jet recording head is not used than when the liquid jet recording head is used. . 3. The liquid jet recording head according to claim 1, wherein the ejection opening is used by changing the opening area of the ejection opening to change the size of the ejected droplet. 4. The liquid jet recording head according to claim 1, wherein the ejection energy generating means is an electrothermal converter.