JPH02108544A - inkjet print head - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drop-on-demand type ink jet print head.

[Prior Art] Traditionally, drop-on-demand type inkjet printing devices use a piezoelectric crystal thin plate as an actuator, and the deformation due to the piezoelectric effect is used to generate the ink volume movement speed on the upper surface of the ink ejection nozzle. type printheads have been used.

[Problems to be Solved by the Invention] In such conventional techniques, the problem was how to mount piezoelectric crystal diaphragms with high density.

[Means for Solving the Problems] The present invention utilizes the property of generating heat or heat absorption when electricity is applied to the electrically connected parts of two different semiconductors or two different metal compounds or alloys. This is an inkjet print head, and when the expansion/contraction or phase transformation due to temperature changes of the members due to heat generation/endotherm causes deformation of the movable mechanism, this deformation acts on the movement of liquid ink to eject ink. It is characterized by being configured to perform the following.

[Function] In the above configuration, when a semiconductor or metal is energized, one part of the alloy or semiconductor, etc., generates heat while the other part absorbs heat at the joint with another alloy or semiconductor. have the tendency to behave as if This is known as the "Bertier effect." If a thin plate made of a material with such properties is configured to generate heat on one side and absorb heat on the other side, a temperature distribution will occur in the thickness direction, causing deformation of the thin plate. Alternatively, a shape memory alloy or the like can be used to cause direct deformation due to temperature changes. At this time, if the deformation is configured to be transmitted to the liquid ink, the ink will move, and some of the ink will become droplets and be ejected from the nozzle to form printed pixels on the paper.

[Example] FIG. 1 is a block diagram of an inkjet print head used in one example of the present invention. Here, 11 is a nozzle plate, and a diaphragm made of members 15 to 20 is attached to each nozzle 12 at a position facing it. Further, 15.18 is an electrode, and different semiconductor thin pieces 19.18 are electrodes.
20 is crimped. Furthermore, polysulfone films 16 and 17 with a thickness of 100 microns are adhered to both sides thereof. These are sealed by containers 13, 14 and form one print head.

Next, FIG. 2 shows a block diagram of a printing apparatus using the print head shown in FIG. 1. Here, the entire structure shown in FIG. 1 is referred to as a print head 9. The print head 9 is mounted on a head carriage 8 whose position is controlled along a guide shaft 6.7 by a drive motor and drive belt.

Further, the printing paper is conveyed in the direction of arrow 5 by paper holding rollers 2.3 and paper feed roller 4, and printed by print head 9 that repeatedly moves in the direction of arrow 10. The configuration and operation are common.

Returning to FIG. 1, the printing operation will be described. When printing,
Ink is supplied into the container 13, 14 through an ink supply hole 21. The electric current i15 is driven by a well-known complementary push-pull circuit using bipolar transistors. For this reason, the electrode 15.18, the semiconductor 19
．． Current can be passed through the portion constituted by 20 in both positive and negative directions. Here, the case where the semiconductor 19 has a high potential is referred to as "current flows in the positive direction." When current is applied in the positive direction to the electrode 15 with an energy of about 1 millijoule, the semiconductors 19 and 20 generate heat on the side in contact with the electrode 18 due to the Beltier effect, and absorb heat on the side in contact with the electrode 15. At this time, the temperature difference between the two sides was about 20 degrees Celsius. Therefore, polysulfone film 17 thermally expands, while polysulfone film 16 contracts. Therefore, the diaphragm as a whole is curved downward in FIG. 1, and ink is ejected from the nozzles. Following this, the current direction is made negative and the electrode 15
When energized, the semiconductor absorbs heat on the side in contact with the electrode 18, and generates heat on the side in contact with the electrode 15. Therefore, the temperature gradient that has already occurred in the thickness direction is rapidly relaxed,
The shape of the diaphragm returns to almost horizontal. Since one printing pixel is formed by this procedure, the inkjet print head of the present invention repeatedly conducts positive and negative energization in accordance with the printing information of each pixel, making it possible to print using the so-called dot matrix method. .

In the above configuration, the polysulfone film has a larger coefficient of linear expansion than metal, so it is suitable for generating strain as the temperature rises. In addition, thermal conductivity is inferior to metal, so
This has the effect of preventing temperature changes caused by the Beltier effect from being alleviated by the transfer of heat to the ink. Therefore,
It is clear that resins other than polysulfone can also be applied to the members 16 and 17 of the embodiment in FIG. 1 in the present invention if these conditions are equivalent.

Next, another embodiment will be described. FIG. 3 is a configuration diagram of an embodiment of the present invention using a diaphragm fixed on one side. In this embodiment, ink is ejected when the 36 cantilever structures vibrate at positions facing the nozzles. Figure 3 A-A'
A cross-sectional view of is shown in FIG. This has a structure in which thin metal films 24 and 25 are deposited on both sides of a semiconductor 29, and a resin layer is further bonded. Here, the resin layers 23 and 26 have a thickness of 5
A 0 micron polysulfone film was used. In this way, by using a material with lower thermal conductivity than metal, this example prevents the amount of heat generated by the Bertier effect from being conducted to the ink, which has a large heat capacity, and supplies more than necessary amount of heat. The configuration was made without. The semiconductor thin piece 29 is doped at a high concentration in the shaded area 22 and has high electrical conductivity. In addition, 27 and 28 were doped with different impurities, so that the well-known "Peltier effect" could be generated. The highly doped layer 22 is electrically connected to a vapor-deposited metal thin film 24.25 which, as is clear from FIG. 3, is intended to be used as a drive electrode.

As shown in the above embodiments, by providing appropriate thermal insulation, the effects of "heat generation" and "endotherm" used in the present invention can be improved.
It can be constructed so that it acts only on a portion with a very small heat capacity. By using this, a shape memory alloy, which conventionally could not improve responsiveness due to the large amount of heat associated with phase transformation, can be used as an actuator for ejecting ink droplets.

The cross-sectional shapes at 80 degrees are shown in Figure 5 (A) and (
A small piece of a rectangular shape memory alloy as shown in B) is used in a structure whose cross section is shown in FIGS. use Then, the entire print head is heated with a heater to about 70 degrees Celsius, and electricity is applied to the shape memory alloy electrode 30 shown in FIG. The temperature rises to 80 degrees Celsius, and the entire body deforms into the shape shown in FIG. Subsequently, when the current direction is reversed, the side in contact with the electrode 30 generates heat, and the shape becomes as shown in FIG. 7. The point that these series of operations perform printing is the same as in the above-mentioned embodiment.

Further, in this example, an ink containing wax as a main component having a melting point of 65 degrees Celsius was prepared and used. This is advantageous in that it has a smaller heat capacity than aqueous solution inks, and is also effective in shortening the time required for solidification and drying after printing.

All of the above embodiments had in common that the actuator was placed in liquid ink, but the following embodiment
The actuator based on the "Peltier effect" and the liquid ink are separated by a partition wall, and a configuration diagram thereof is shown in FIG.

In this embodiment, the polysulfone film 33 on the upper surface of the ink cavity 37 formed on the head substrate 34 is deformed to cause ink to be ejected from the nozzle 35. Ink is supplied from the ink supply hole 36. Also, 19.20 is a small semiconductor piece, 38.39 is an electrode, 3
2 is a resin plate. The operation is common to the other embodiments described above.

[Effects of the Invention] As is clear from the configuration of the embodiments described above, the printing apparatus of the present invention has a feature that the diaphragm of the print head can be manufactured by easy means such as bonding members together.

Therefore, it is more advantageous than using a piezoelectric element in constructing a high-density print head that requires many diaphragms per unit length. In addition, since the thermal history can be controlled in the current direction, the thermal response is faster than other methods.
It can be said that it is excellent.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a print head used in an embodiment of the printing apparatus of the present invention. FIG. 2 is a configuration diagram of a printing apparatus according to an embodiment of the present invention. FIG. 3 is a configuration diagram of a print head using another diaphragm. FIG. 4 is a configuration diagram of the diaphragm portion in the embodiment of FIG. 3. FIG. 5 is a sectional view showing the shape of the shape memory alloy used in the example at high temperature. FIG. 6 is a sectional view of the diaphragm. FIG. 7 is a sectional view of the diaphragm. FIG. 8 is a configuration diagram of a print head according to another embodiment. 1...Print paper 2.3...Paper holding roller 4...Paper feed roller 6.7...Guide shaft 8...Head carriage 9...Print head 11...Nozzle plate 12. ... Nozzle 13.14 ... Container 15.18 ... Electrode 19.20 ... Semiconductor thin piece 21 ... Ink channel 23.26 ... Resin layer 24.25 ... Metal vapor deposition film 2 .27.28.29... Semiconductor 0.31... Shape memory alloy small piece 2.33... Resin layer 4... Head substrate 5... Nozzle 6... Ink supply hole 7... Ink cavity 8.39...Electrode plate and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki and one other person Figure 2/9. zo half set 1-6 z′? Heiton stop layer 1z Nospa 1 shi Fig. 3 30.31 j #6

Claims (1)

[Claims] When electricity is applied to the electrically connected parts of two different semiconductors or two different metal compounds or alloys,
This is an inkjet print head that uses the property of generating heat or heat absorption, and when the expansion/contraction or phase transformation of the member due to the temperature change accompanying the heat generation/endotherm causes deformation of the movable mechanism, this deformation is An inkjet print head characterized in that it is configured to eject ink by acting on the movement of ink.