JPH0437551A - Head for ink jet printer - Google Patents

Abstract

PURPOSE:To print characters on a matter to be printed even if an ink printer head is maintained at high temperature as ink ejection orifices are arranged on an almost flat surface by setting differences in a shortest distance formed between ejection orifices and the surface of a matter to be printed at a printing temperature below a specified size value. CONSTITUTION:Where the coefficient of thermal expansion of a material used for a nose plate 5 is larger than that of a material used for a head case 3, an ink jet head 2 is significantly curved instead of being flat at a temperature applied when it is manufactured. However, when ink is ejected at high temperature, the head 2 is almost flat and ink kept at high temperature is ejected and therefore, stable character printing is ensured. If the temperature is maintained at a specified high level so that the difference in distance between nozzles 4 and a matter to be printed 6 is insignificant, print quality becomes high and if the distance is 1 mm or less, satisfactory print quality is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet printer head. More specifically, the present invention relates to a structure of a plurality of ejection port groups for ejecting ink of an inkjet printer head that has different temperatures during printing and non-printing.

[Conventional technology]

Conventional inkjet printer heads have been constructed so that a plurality of ink ejection orifice groups are substantially coplanar during manufacture.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, in order to improve printing stability, the inkjet printer head is maintained at a predetermined temperature higher than the external environmental temperature and when printing, ink is ejected mainly due to thermal expansion. There was a technical problem in that the surface containing a plurality of jet nozzle groups was curved, and the distance from the surface of the printing object such as paper was different for each jet nozzle group, resulting in uneven printing. .

Therefore, the present invention solves these technical problems,
The purpose is to provide an inkjet printer head that has a plurality of ink jet nozzle groups arranged on a substantially flat surface and can perform stable printing on a printing substrate even when maintained at high temperatures. be.

[Means to solve the problem]

The head for an inkjet printer of the present invention mainly includes a plurality of jetting ports for jetting ink, a means for jetting the ink, and a means for setting a predetermined temperature for printing. In an inkjet printer head that performs printing by jetting onto a printing material, the difference between the shortest distances between each of the plurality of jetting port groups and the surface of the printing material under the temperature at which the printing is performed is 1 mm or less. It is characterized by being installed so that

[For production]

According to the above configuration of the present invention, the difference in thermal expansion of each material constituting the inkjet printer head is reduced, or the increase due to thermal expansion is taken into consideration to By setting the ink ejection ports to be small at the time of manufacture so that they are arranged on substantially the same plane, it is possible to obtain stable, uniform, and good printing.

〔Example〕

FIG. 1 is a partial sectional view of the main components showing one embodiment of the present invention. FIG. 2 is a partial cross-sectional view of FIG. 1 taken along a cutting plane A that passes through the centers of a plurality of nozzles 4 for ejecting ink, and shows the configuration during cooling when no printing operation is being performed. It is.

The main components of the present invention and the operation of the inkjet printer head will be explained below using FIG. The inkjet head 2 was filled with ink 1 maintained at a moderately high temperature (70° C. to 190° C. in this example) to form a liquid having a predetermined viscosity. At this time, the ink 1 was heated through the inkjet head 2 using a heater 17 which is a heating device.

As shown in the figure, the inkjet head 2 is configured as a line-type head surrounded by a head case 3 and a nozzle plate 5 having a plurality of nozzles 4 for ejecting ink. The vibrator 6 was installed in the inkjet head 2 via a spacer 10 so as to maintain a constant distance from the nozzle plate 5, and at substantially the same pitch as the nozzle 4. The vibrator 6 had a diaphragm 8 having electrical conductivity and a piezoelectric body 7 bonded together as shown in the figure, and a thin film electrode 9 was formed on the other surface of the piezoelectric body 7.

The piezoelectric body 7 was polarized by applying a DC voltage between the diaphragm 8 and the thin film electrode 9 for a long time. When a predetermined pulse voltage is applied to the vibrator 6 using the drive power supply 11 to discharge the accumulated charge, the vibrator 6 returns to its original position shown in the following section, and the ink droplet 14 is directed to the nozzle 4. The ink was ejected in the ejection direction 13 and a good print was formed on the printing material 16. After 2, the same amount as the ejected ink droplets 14 was supplied in the supply direction 15 from an ink 1 supply section (not shown).

By applying appropriately modulated drive voltages from the drive power supply 11 to the plurality of vibrators 6, a large number of ink droplets 14 were ejected onto a printing medium 16 such as paper, and good printing was obtained. Next, the main materials and shapes used in the present invention will be explained. Ink 1 is prepared by heating and dissolving dye dissolving aids such as paraffin wax, carnauba wax, and behenic acid at a ratio of 1 to 60 weight percent each, and adding a black dye such as nigrosine and other dyes at a similar rate of 1 to 8 weight percent. The solution was used. Viscosity when kept at high temperature is 2-30mPa-5
is a constant value in the range of . In addition to these, the ink 1 may be a non-linear fluid liquid in which carbon black, fine particles of pigment, and fine particles to which dyes or pigments are attached or bonded are mixed in an organic material that has the above-mentioned viscosity at high temperatures. The head case 3 is made of a material that provides appropriate thermal conductivity, such as ceramics such as silicon and alumina. The nozzle plate 5 and the spacer 10 are made of the same material or a combination of materials with a small difference or ratio of thermal expansion coefficients. In particular, the spacer 10 is made of a conductive material or an insulating material with a conductive film formed on its surface in order to serve as a common electrode for the diaphragm 8. The materials of the nozzle plate 5 and spacer 1G used in the present invention include, for example, metals such as nickel, copper,
Tantalum, molybdenum, iron/nickel alloy, iron, iron/nickel/cobalt alloy, stainless steel, chromium, and alloys containing at least one of these. In other materials,
Glasses, alumina, ceramics such as silicon nitride, silicon, sapphire, etc. were used.

Good operation was also obtained with heat-resistant plastics such as polyimide, polyethersulfone, polyetheretherketone, and polyphenylsulfone. Nozzle 4 has a diameter of 2
A predetermined constant value was set between 0 μm and 300 μm in consideration of the shape of the ink droplet 14 and the spacer. The piezoelectric body 7 is made of lead zirconate titanate-based ferroelectric ceramics exhibiting a piezoelectric effect, and a thin film electrode 9 is formed by vapor deposition, sputtering, or plating to a thickness of 0.1 μm to 2 μm.
It was formed to a constant value between 0 μm.

In Fig. 1, when maintaining a high temperature at a predetermined temperature to achieve good printing, the average distance between the printing material 6 and each of the plurality of nozzles 4 is constant within 0.3 + * m to 5 ■ l. value(
It is preferably a constant value of 0.3 to 1.5 mm). At this time, the difference in distance between them was at most 1 dragon. The smaller the difference between each, the better the print quality will be, but 11
Within this range, generally good print quality was ensured.

Next, FIG. 2 shows a cross-sectional view of the above-mentioned head for an inkjet printer with good printing, cooled at a temperature between 1° C. per hour and 12° C. per second to the temperature at which it was manufactured. Figure 2 shows nozzle plate 5.
This is a case where the coefficient of thermal expansion of the material used for the head case 3 is larger than the coefficient of thermal expansion of the material used for the head case 3. As shown in the figure, at the manufacturing temperature, the inkjet head 2 is not flat but curved, but as mentioned above, when held at a high temperature and ejecting ink, it becomes almost flat and stable printing can be achieved. . Here, the principle of the method for manufacturing the inkjet head 2 of the present invention will be briefly explained. The inkjet head 2 of the present invention is made by joining the above-mentioned components using an alloy that melts at high temperatures. - For example, the melting temperature was adjusted by changing the composition ratio of the gold/tin alloy, and the melting temperature was set to be 5°C to 150°C higher than the predetermined high temperature required for printing. By doing this, by maintaining the temperature above the melting temperature of the alloy and gradually cooling it, it was possible not only to securely fix each of the components at the ink jetting temperature of the inkjet head 2, but also to reduce residual stress. A head with good printing stability was obtained, with little deformation. Contrary to this example, when the coefficient of thermal expansion of the material used for the nozzle plate 5 was smaller than that of the material used for the head case 3, the inkjet head 2 bent, contrary to FIG. (set convex upward)
When printing was carried out while maintaining the temperature in both cases, similar good results were obtained as long as the difference in the shortest distances between the plurality of nozzles 4 and the printing substrate 6 was 11 or less, as described above.

Further, even if the temperature of the external environment changes, since the inkjet head 2 is maintained at a higher temperature using the heater 17, it is hardly affected by the change, and the ink viscosity is also constant, resulting in stable printing. This will be explained more clearly using FIGS. 3(a) and 3(b). FIG. 3(a) is a cross-sectional view when the temperature is maintained at a predetermined high temperature, and shows a plurality of nozzles 4 and a printing material 6.
B and C, which are an example of the distance between the two, were almost equal in size and the difference was 1 mm or less, and good printing was obtained.

When this temperature is lowered to the manufacturing temperature, which is the temperature at which the inkjet head 2 is bonded and cooled, the entire body bends as shown in FIG. As shown in the figure, the difference was large for 1C'. That is, in the embodiment of the present invention, by taking advantage of these phenomena in advance and considering the coefficient of thermal expansion of the constituent parts of the inkjet head 2 in advance, the nozzle 4 of the inkjet head 2 and the printing substrate 6 when ejecting ink at high temperatures are
The present invention provides an inkjet printer head that can maintain the distance within a certain range and provide stable print quality.

〔Effect of the invention〕

As described above, according to the present invention, in order to print at a higher temperature than the external environment, even if the temperature of the external environment changes, by maintaining the inkjet printer head at a higher temperature, the viscosity of the ink can be reduced. Not only can stable ink jetting be obtained by keeping the distance constant, but also the distance between the multiple nozzles formed in the inkjet head and the printing material can be kept constant during ink jetting, so the distance between the multiple jetted ink droplets can be kept constant. The distance traveled by each printer is also constant, which also has the effect of enabling high-quality printing. In addition, since the deflection of the head can be reduced when ejecting ink, the direction of the ejected ink droplets is also aligned and beautiful printing can be performed at equal intervals.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 are sectional views of main components each showing an embodiment of the present invention. 4... Nozzle 6 ・ ・ ・ Vibrator 17 ・ ・ ・ Heater and above Applicant: Seiko Epson Corporation Representative Patent attorney: Kizobe Suzuki (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] Mainly composed of a plurality of ejection ports for ejecting ink, means for ejecting the ink, and means for setting a predetermined temperature for printing, and performs printing by ejecting the ink onto the substrate. The head for an inkjet printer is characterized in that the head is installed such that the difference between the shortest distances between each of the plurality of ejection port groups and the surface of the printing medium is 5 mm or less under the temperature at which the printing is performed. head for inkjet printers.