JPH0255140A - Ink-jet head and manufacture thereof - Google Patents

Abstract

PURPOSE: To lower the wettability of ink in the vicinity of a nozzle and to produce an ink droplet of a uniform shape with high frequency by forming a coating layer out of a polymeric material, in an ink jet head whereon the coating layer is so provided as to surround the nozzle. CONSTITUTION: A discharge surface 18 of a nozzle plate 16 has a layer of a coating material 50 and this is provided selectively on the area of an ink jet head surrounding a nozzle 20, in the same way as in the nozzle, and prevents substantially the surface of the surrounding area from being wetted by an ink droplet of a phase change ink component discharged from the nozzle 20. The material adopted generally as the coating material 50 is a polymeric material, suitably a fluorocarbon polymer having a necessary ink contact angle and surface energy level. In order to apply the coating material 50 to the ink jet head 10, thermal vapor deposition of fluorocarbon resin and deposition of colloidal fluorocarbon in electroless nickel are conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet head, and more particularly to an inkjet head that can prevent wetting of nozzles by phase change ink and a method for manufacturing the same.

[Conventional technology]

Inkjet printers having one or more heads with one or more nozzles are increasingly used to produce images or documents on paper or other print media. Inkjet printers with multiple inkjet nozzles are used to form color images.
Each nozzle receives a supply of ink of a different color.

These colored inks, alone or in combination, are applied onto the recording medium to produce a complete color print. Typically, all of the colors needed for printing are generated from cyan, magenta, and yellow inks. Black ink may also be added to the above ink mixture for printing textile materials and for faithful four-color printing.

In a typical arrangement, the recording medium is mounted on a rotating drum or is advanced through a typewriter-like mechanism, with the printer head (with the inkjet head mounted on a moving platform) oriented axially of the drum. Do you exercise or
Or, on the above-mentioned type-like mechanism, the movement alternates back and forth. , as the head scans the recording medium in a spiral trajectory or performs an alternating motion, ink droplets are ejected from tiny external nozzles toward the print medium, creating a recording. An image is formed on the media. A suitable control device synchronizes the ejection of the ink drops with the rotating drum or typewriter mechanism.

[Problem to be solved by the invention]

Various devices or methods are known for printing images on recording materials with inks based on aqueous materials. A significant problem when printing images with ink jets using water-based inks is that the ink ejection surface becomes wet. Ink deposits on the ink ejection surface surrounding the nozzle that ejects the ink droplets cause the ink droplets exiting the device to be uneven in size and reduce image quality. Therefore, methods have been provided for treating the ejection surface of an inkjet device with a non-wetting material to prevent ink deposits from spreading across the ejection surface from the ink drop ejection nozzles of the inkjet device. In US Pat. No. 4,533,569, the inner surface of a glass nozzle is cleaned with hydrofluoric acid and covered with a protective material such as ethylene glycol, glycerin, etc. After anionic pretreatment, an anti-wetting agent, such as a long chain of anionic non-wetting material, is applied to the fluid nozzle to enhance the quality of the ink droplets. US Pat. No. 4,623,906 discloses a three-layer coating for glass or silicon inkjet nozzles containing silicon nitride or aluminum nitride. In US Pat. No. 4,343,013, the nozzle plate of an inkjet printer is made of glass and covered with a material that has non-wetting properties to the aqueous properties of the ink components. Tetrafluoroethylene and certain silicone-based materials are useful for this purpose because they have the non-wetting properties mentioned above. In US Pat. No. 4,368,476, a water-repellent layer of non-wetting material of silicon fluoride is provided on the surface surrounding the jet nozzle. US Patent No. 4643
No. 948, the nozzle plate from which the ink is ejected is coated with a non-wetting coating containing each of a partially fluorinated alkylsilane and a perfluorinated alkane. In U.S. Pat. No. 4,728,393, the nozzle plate of an electrostatic deflection type inkjet printer has a mirror finish,
Completely covered with a thin film of Teflon resin. However, in this case the Teflon coating is used for static control and not for ink drop formation. Ink droplet formation is facilitated by air assistance and mesa-like geometry mechanisms.

For this reason, inkjet works without a Teflon coating. Other articles related to the wettability of fluorocarbon polymeric layers include the IBM Technical Disclosure publication by B. D. Washou entitled "Highly Non-Wettable Surfaces by Plasma Polymer Deposition of Tetrafluoroethylene" 26, No. 4, page 2074, and an article in the Journal of Polymer Science by A. J. G. Alan et al. entitled "Wettability of polymeric layers of perfluorinated carbon: Effect of roughness." Includes the article on page 1 of volume 39.

Another inkjet printing technology uses non-aqueous, phase-change inks to replace inks based on aqueous materials in inkjet devices.
Ink: Ink whose phase changes from solid to liquid when heated, for example. (hereinafter referred to as phase change ink) have been used. The phase change ink is solid at room temperature, but becomes a liquid at the operating temperature of the ink side so that it can be jetted onto a recording medium to form a predetermined pattern. The ink that is ejected to form a pattern becomes solid on the recording medium. Just as water-based inks have the problem of non-uniform ejected ink droplets due to surface wetting as described above, similar problems occur with phase change inks. This problem can be solved, both conceptually and at a practical level, by specifically improving the structure of the inkjet nozzle. Some examples are mesas, ink blobs, tube constrictions, and dissimilar liquid masses. However, in these configurations, the cost required to make them can be higher than the desired water rate. This is especially the case when the jet ports are arranged in a row.

Therefore, ink components, including phase change ink components, produce reproducible, uniform ink droplets and thus print images with desired properties on recording media without the need for significant expense in inkjet nozzle design. There is a need for an inkjet head that can do this.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inkjet head and a method for manufacturing the same, which can reduce the wettability of ink near a nozzle and generate uniformly shaped ink droplets with high frequency.

Other objects of the present invention are to enhance the addressing performance of ink droplets,
The objective is to improve image quality and image positioning accuracy.

Still another object of the present invention is to provide an inkjet head that can reduce the number of inkjet heads installed in a printer or improve printing speed, and a method for manufacturing the same.

SUMMARY OF THE INVENTION The present invention provides inkjet printing by utilizing phase change ink components to achieve the desired characteristics of ink droplet generation described above.The method and apparatus of the present invention are employed. Inkjet printers for phase change inks can achieve important image printing properties on print media without costly reconfiguration of the nozzle design. By using the method and the inkjet printhead of the present invention, printed images produced by phase change inks can be printed without any loss in quality, as the ink droplets are well-shaped and deposited in precise locations. , (1) and clear images can be provided.

In ink ejection devices based on water-based materials,
By reducing the wettability of the ejection surface of an inkjet head, ink drop properties can be improved. This is achieved by coating these surfaces with a material that inherently exhibits a much lower surface energy than the water-based ink. The low surface roughness of the coating material results in a relatively high ink contact angle well above the minimum angle required to inhibit wetting on the surface near the nozzle ejecting the ink. Therefore, for inks based on aqueous materials, the conditions for producing high quality ink droplets are easily achieved.

Applicants believe that the large surface energy differences that existed between various coating materials and water-based inks, i.e., differences of at least about 20 dynes/cm, are due to the large surface energy differences between these coating materials and phase change inks. I am aware that it did not exist originally. Therefore, a coating material that can significantly suppress the wettability of the ejection surface in the case of aqueous inks will not work as well in the case of phase change inks.

It has been discovered by this application that the above-described images can also be formed with phase change ink components by using an inkjet head with some type of nozzle plate. This nozzle plate forms at least one discharge nozzle, which does not need to be specially devised. This is accomplished by increasing the contact angle of the ink within the area surrounding the ejection nozzle to a predetermined water percentage, thereby preventing wetting of the previously surrounding surface area by the phase change ink components. be done. The contact angle of this ink is increased by providing ll'J of certain coating materials on the ejection surface of the inkjet head. When the ejection surface is coated in accordance with the teachings of the present invention, the ink droplets of each liquefied phase change ink component are substantially uniform in size and shape and are capable of being ejected according to a predetermined pattern, thus A precisely positioned printed image can be formed on the recording medium with virtually no loss of quality.

An improvement in inkjet printheads is thus provided by providing a layer of coating material on the surface area of the printjet head surrounding each of the ejection nozzles. With this coated surface area surrounding the nozzle, the contact angle with the phase change ink increases to at least about 50° at an operating temperature of at least about 70°C. This coating material is treated in the surrounding area being coated to maintain a high contact angle with the ink in the area surrounding the nozzle. Thus, at operating temperatures, upon prolonged exposure of the surrounding area to the ink components, the contact angle will be at least as large as the contact angle on the surrounding area of the untreated coating material. Approximately 20%
is thick (which substantially prevents wetting of the surrounding surface area by the ink components. By this method, the inkjet printhead uses a phase change ink to print the above-mentioned individual A plurality of ink droplets can be ejected, and a printed image can be formed on a print medium with precisely determined positions without deterioration of quality.

The above-mentioned and other objects, features and advantages of the present invention will become more apparent from the detailed description of the preferred embodiments taken in conjunction with the drawings.

〔Example〕

FIG. 1 shows a cross-sectional view of an inkjet head of the present invention for printing with phase change ink components on print media. The inkjet head (10) includes a body portion (12) within which is a single compartment ink chamber (14). The ink chamber (14) is closed by a plate (16) forming a wall of the ink chamber.

The outer part of the nozzle plate (16) is the discharge surface (18). The outside of the nozzle (20) ejecting ink drops formed by the nozzle plate (I6) forms an area surrounding the nozzle (20), which extends from the ink chamber (14) to the outside of the inkjet head (10). Passing through. The nozzle plate (16) may be provided with a single nozzle (20), or multiple nozzles and associated ink chambers may be provided as appropriate. The ink chamber (14) consists of a section (22) and a section (24), and is generally circular in cross section, although it is not necessary to do so. part(
24) is adjacent to the wall (16) and the outer nozzle (20) and is bounded by the inner wall (26) of the body portion (12). Section (22) has a larger diameter than section (24) and is bounded by an inner wall (28). Although parts (22) and (24) are symmetrical about axis (30) as shown, this is not necessary.

The phase change ink in the melted state enters the ink receiving inlet (3).
2) and flows through the ink passageway (34);
The ink chamber (14) within the inkjet head (10) is filled. The end of the ink chamber opposite the outer nozzle (20) is covered with a flexible membrane (38) such as stainless steel.
) is closed by. Piezoelectric ceramic disk (36
) is coated with metal on both sides and adhered to the membrane (38), and serves as a pressure pulse generating element. However, other configurations using piezoelectric ceramics may also be used. A pressure pulse is generated in the ink chamber (14) in response to an electrical pulse applied to the piezoelectric disc. This causes an ink droplet to come out of the nozzle (20). The ink droplets travel toward the print medium where they create the desired printed image.

The emitting surface (18) of the nozzle plate (16) has a layer of coating material (50) which is selectively applied in the area surrounding the nozzle (20) of the inkjet head as well; Ink droplets of the phase change ink component ejected from the nozzle (20) are substantially prevented from wetting the surface of the surrounding area.

By providing a surface coating layer (50),
Surface wetting is substantially reduced and the contact angle of the ink on the coating layer is substantially increased. Typically, the contact angle is determined by ASTM (American 5oC).
ety ofTesting Material:
It is measured by the method described in the American Society for Testing and Materials standard D72445. Further, the contact angle typically varies at least at operating temperatures of about 70°C, preferably at least 100°C, and most preferably at least 1
At the operating temperature of the phase change ink of 50° C., the peripheral region is substantially maintained over the extended exposed portion for the phase change ink. In this way, the coating layer (50
), the contact angle of the ink components generated by employing the present invention is maintained at least 50°, preferably at least 55°, more preferably at least 6
It is maintained at 0°. The coating material is this material,
after immersion or aging in a phase change ink at a temperature of 150° C. for a period of at least 24 hours;
The coating material is evaluated by measuring the contact angle of the phase change ink. The angle between a given phase change ink and coating material is
Measurements are made with a goniometer bearing model No. 100-00-115 manufactured by e-Hart Inc.

To maximize the contact angle, the difference between the surface energy of the coating material and the surface tension energy of the phase change ink components must be minimized. To be more specific,
The surface energy of the coating material is at least about 4 d y compared to the surface energy of the phase change ink components.
nes/cm, -layer preferably 6 dy
It is desirable to be lower by nes/cm. Preferably, the surface energy of the coating material and the surface tension energy of the phase change ink are measured by a goniometer as described above.

The materials commonly employed as coating materials (50) are polymeric materials, preferably fluorocarbon polymers having the required ink contact angles and surface energy levels as previously described. The fluorocarbon polymer selected is a DuPont Teflon trademarked polymer, specifically Teflon PTFE.
(Bo'J-r dorafluoroethylene), and Teflon PFA (polyperfluoroalkoxybutadiene), or a fluorocarbon dispersion that is a dispersion of either Teflon PTFE or Teflon PFA. A preferred dispersion is an electroless nickel dispersion, such as the Teflon PTFE dispersion described above in Richardson Industries Model 75-A and Model 75-R "Dynaplate" products. A colloidal fluorocarbon polymer dispersed within.

Coating material (5) on the inkjet head (10)
There are various ways to apply 0). These methods include thermal evaporation of the fluorocarbon polymer, dipping, sprying or spin coating of aqueous fluorocarbon dispersions with subsequent thermal curing treatment.
coating), precursors
or) Deposition of the fluoropolymer onto the substrate by plasma polymerization of monomers and deposition involving colloidal fluorocarbons in electroless nickel. A preferred method is thermal evaporation of the fluorocarbon resin and deposition of the G colloidal fluorocarbon in electroless nickel.

Long exposure in ink, coating layer (50)
To better keep the surface energy low, the polymeric material is annealed by heating following deposition. This controlled heating often takes the form of a thermal cycle in which the coating layer (50) undergoes separate heat treatment steps at separate annealing temperatures to complete the process. The preferred annealing temperature in each heat treatment step is about 150°C to 500'C, more preferably 200'C to 400'C.

Although most phase change ink components can be employed as part of the subject matter of the present invention, suitable phase change ink components are those that are effective at the elevated operating temperatures previously discussed. By way of example, phase change ink components include phase change ink carrier components, preferably resinous materials containing fatty amides along with tackifiers, plasticizers and colorants. A preferred fatty amide resin material is a combination of a tetraamide mixture and stearyl stearamide.

Head Construction Here, a phase change inkjet printer head of the present invention is shown that includes a nozzle plate covered by a layer of coating material. This also provides the method of the present invention for producing positionally accurate printed images with substantially no loss of quality with phase change ink components. The subject coated device is compared to a similar printer head with an uncoated nozzle plate.

In this way, the experiment was carried out using a jet printer head as shown in Fig. 1, and as described in "Method of Forming a Coating Layer", a coating layer (50) of Teflon PFA (polyperfluoroalkoxybutadiene) was used. Droplets of phase change ink were created with and without phase change ink.

The jet heads are identical in construction, consisting of layers of chemically etched stainless steel that are integrally attached to a monolithic unit.

Jetting is characterized by the point in the ink drop formation process and the maximum number of ink drops ejected per second when jetting failure occurs. This characteristic extends from the ink aperture to the axial position approximately 1 mm downstream from the ink aperture to the imaging device.
Observed using an electrical delay circuit and a strobe light. The imaging device consists of a microscope mounted perpendicular to the trajectory of the ink drop. The microscope is connected to a video camera, and the video camera is connected to a monitor. The magnification of the device was approximately 250x. A strobe light illuminates the ink droplets.

The device is controlled by a delay circuit that is triggered by the drive signal leading to injection.

This delay circuit made it possible to measure the ink drop formation process over time.

The fatty amide ink components used were as follows. Union Camp Tetraamide 39.2%, Steryl Stearamide 49.0%, Herculs Inc.
, ) tackifier Foral 105 manufactured by
9.8%, and Monsanto Company (Monsant
.

Plasticizer Sanity Sizer 278-
is 2%. The operating temperature during each injection was 160°C. Union Camp's Tetraamide is
1 mole of dimer acid, 2 moles of ethylene diamine, 2
It is made by the combination of moles of stearic acid. Because the surface is coated and annealed, the contact angle is when the ink and surface are heated to 150°C.
The temperature is at least 60°C. When the surface is uncoated, the contact angle is at most 20 @ at 150°C.

The voltage of each jet is such that when each jet produces ink drops at a rate of 1000 drops per second, each ink drop produces 350 drops per second.
It is set so that it reaches lrnm downstream of the nozzle within microseconds. A distance of 1 mm was chosen because it is a good representation of how far the print medium is from the jet nozzle in a printer device. As the firing frequency increases, the time required for an ink droplet to travel 1 mm, and respective changes in ink droplet size and shape are recorded.

FIG. 3 compares the performance of the two injection devices. This graph shows that an ejector without a coating on the nozzle cannot produce as many ink drops per second as an ejector with a nozzle with such a coating. There is. When attempting to generate 2000 ink drops per second, an uncoated ejector will fail due to meniscus wetting around the nozzle. An ejecting device coated with the coating can be operated even when ejecting 10,000 or more ink droplets per second. In either case, a single ink drop is formed at each production frequency until the ejector is no longer driven.

The maximum drop production frequency that an ejector can drive directly affects the architecture of the print engine. The time required by a printer to produce a printed image is directly related to the number of ejectors available for printing, as well as the maximum number of ink drops produced per second from each ejector. This data indicates that, for a given copy time, a printer with an uncoated jet will require five times as many jets as a printer with a coated jet. Otherwise, for the former printer, the latter printer's approx.
It will take twice as long to print.

The difference between the absolute maximum and absolute minimum of the time required for an ink drop to travel 1 mm as a function of repetition rate (this is
(defining the range) also affects the print engine architecture.

This range as a function of repetition rate is directly limited by certain ink drop positioning errors. This error is determined by the maximum addressability (which is defined as the number of dots placed per inch) that the jetting device is capable of printing, which is based on the theoretical bitmamp placement rather than the physical dot placement on the media. It is related to

). The maximum addressability in the print direction can be expressed in relation to the change in time of the ink droplet to the medium as follows:

nD=1/(VΔt) where n is a positive number that determines the tolerance for the position of the ink droplets, D is the number of dots per unit inch, and ■ is the medium on which the ink droplets are being ejected. and the relative velocity of the ejector, and ΔL is the range of time it takes for the ejector to reach the print medium at its repetition rate when it is printing. A typical value for n is 3, assuming that 1/3 of the dot placements is the maximum tolerable placement error.

If, for example, the error is greater than this value, the information conveyed by these dots will be meaningless on the medium, even though the same number of dots can be placed in one inch. Therefore, the maximum addressability that can be meaningful is low. From this equation, for given n and ■, as Δt increases, addressability decreases. If the addressability is constant, the relative speed can also be decreased to compensate for the increase in Δt.

If (2) is small, the printing time will be longer unless more ejectors are added to keep the printing level constant.

As can be seen from FIG. 3, the time required for an ink droplet to travel 1 mm increases rapidly for an uncoated ejector until the ejector becomes inoperable. The range of ΔL for this uncoated injector was about 120 microseconds. For coated injectors, the range of Δt is
It took only 25 microseconds. Therefore, the presence of the coating improves Δt to about 115.

From this discussion, this difference of 115 in ΔL is
Given n and V, the addressability of the coated injector is 5
You can see that it means twice as much. Otherwise, the printing time of the injector being coated is
115 of print time for uncoated injector
It can also be said that Similarly, the number of coated injectors could be 115 to achieve similar print times and addressability as with uncoated injectors.

<Method of Forming Coating Layer> This example shows a preferred method of applying the coating material of the present invention. There are several electron beam evaporation devices on the market for applying coating layers that are similar to our device.

One such device is the CHA Industries Electron Beam Evaporator, Model #5E600. Second
The figure is a perspective view of the electron beam evaporation device, and as shown in FIG.
). The specimen is made from stainless steel, the type used to make inkjet heads. The electron beam evaporator (6o) is equipped with a bell-shaped lid (62) and a temporary base (64)! Supported by these, a sealed vacuum deposition chamber (66) is formed. The source of this polymeric coating material is polyperfluoroalkoxybutadiene, which is a Teflon PFA rod (68) within a metal retaining cup (72). The deposition chamber (66) is evacuated by a pump (not shown) in communication therewith. Sample holding stand (74)
is attached toward the top of the bell-shaped M (62). The coupon (70) is placed on the sample holder (74) directly above the rod (68). Electron beam source (76
) is located directly below the retaining cup (72).

The vacuum deposition chamber (66) is evacuated to an initial pressure of about 5.times.10-' Torr and, upon evaporation, a pressure of about 5.times.10-' Torr. The power of the electron beam is maintained at approximately 300 watts during operation. The coupon is heated to approximately 120° C. by an infrared lamp (78) located above the coupon in the bell-shaped lid. Even though the electron beam source is below the holder, the beam is generated at an angle, deflected by the magnetic field, and focused into the holder.

The polymeric rod (68) is heated to between 300°C and 600°C by an electron beam source (76).

The electron beam vaporizes the polytetrafluoroethylene material and its vapor is concentrated onto it to coat the coupon.

Coating layers with a thickness of about 400 nm to 600 nm are produced by this method.

The coated samples are sequentially annealed in a Held type furnace under a nitrogen atmosphere for a total processing time of approximately 1.75 hours. This belt furnace is divided into five temperature zones of substantially identical dimensions. The belt moves at a constant speed, and the sample passes through each temperature range for the same amount of time. The temperature of each region may be the same as or different from that of adjacent regions. In this example,
Processing cycle: 200°C → 400°C → 400°C
The temperature order is →400°C →200°C.

The effect of coating the surface on the ink ejection surface surrounding the nozzle of a phase change inkjet is demonstrated in coated and uncoated coupons made from stainless steel of the type used in the fabrication of inkjet heads. This can be determined by comparing the wettability with other materials. One is PF
The wettability of two samples, one coated with A and the other uncoated, was as follows:

a, The contact angle of the phase change ink on the annealed coating surface, measured at 150°C, was measured to be approximately 68″ before aging.

The surface tension of phase change ink at 150°C is approximately 24.5d.
It was ynes/cm. The energy of the unaged coated surface is 16
It was measured as dynes/cm. The contact angle of the phase change ink on the uncoated sample is:
When measured under similar conditions, it was only about 20'.

b. After aging the sample by immersing it in the ink at t s o 'c for 72 hours, the contact angle of the coated and annealed surface is approximately 60' at a temperature of 150 °C. was measured. 15
The surface tension of phase change ink at 0°C is also approximately 2
It was measured to be 4.5 dynes/cm. In addition, the energy of the aged coating surface is approximately 20 dyn.
It was measured as es/cm. The contact angle of an uncoated sample after aging was measured under similar conditions and was approximately 15°.

C. As explained in <Coating layer formation method>,
The sample coated by Teflon PFA was 1
Aging was performed by immersion in the ink for 72 hours at 50°C. These coated samples were
Not annealed prior to aging. The contact angle of the phase change ink on these samples was approximately 72@ before aging and was measured from 40'' to 43'' after aging.

Therefore, treated (annealed) and aged fluorocarbon polymers maintain high contact angles during extended exposure to phase change inks at operating temperatures and exhibit superior quality compared to their untreated counterparts. It has been found that printed images of the type already described can be positioned even more precisely, without any loss in quality.

<Others><Coating layer formation method> is a coating layer formed by dispersing fluorocarbon polymer, in this case,
It was repeated employing a mixture with a dispersion of polymer in nickel.

In this experiment, a commercially available electroless nickel mixture is utilized in the Richardson Industries Dynaplate formulation. Although most of these formulations are nickel phosphate based, boron nickel mixtures are used therein. 150 m/1 iter of Richardson Industries' 752A, 50 m1/1 iter of Richardson Industries' 752A, and mixed with DuPont's 30 submicro PTFE emulsion with 800 m1 of distilled water. , used as a coating material.

Stainless steel coupons were placed in the coating mixture described above at a temperature of 85°C-90°C for 10 minutes.
Soak for 30 minutes to 0.0001 inch to 0.00 inch
Form a coating layer 0.04 inches thick. The samples are then annealed at a temperature of 300° C. for 1 hour in a nitrogen atmosphere.

The contact angle of the ink on the sample is 6 before aging.
After aging at 0° it was 58°. This aging was performed in the same manner as in (method for forming coating layer).

Thus, the required contact angles can be produced by coated ink-end heads, aged or unaged fluorocarbon polymers, and especially the fluorocarbon polymer dispersions mentioned above, along with other treatments. Furthermore, it has therefore been confirmed that even with phase change inks, it is possible to print in the manner described above, with no loss of quality and with precisely positioned images.

(Effects of the Invention) In the present invention, a coating layer made of a polymer material is provided to surround the nozzle, or a coating layer made of a polymer material is provided to surround the nozzle.
Since the ink layer is heat-treated and/or agitated, the wettability of the ink near the nozzle can be reduced. Therefore, uniformly shaped ink droplets can be generated with high frequency, and the addressability of the ink droplets is increased. Therefore,
Image positioning also becomes more accurate without degrading the image quality of printing. Furthermore, the number of inkjet heads installed in the printer can be reduced and the printing speed can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an inkjet head of the present invention, FIG. 2 is a perspective view of an apparatus for applying a coating layer to the material of the head shown in FIG. It is a graph for comparing the ink ejection mode between an inkjet head and an inkjet head not provided with a coating layer. In these figures, (10) is an ink side head, (20) is a nozzle, and (50) is a coating layer.

Claims (1)

Claims: 1. An inkjet head provided with a coating layer surrounding a nozzle, characterized in that the coating layer is made of a polymer material. 2. A method for manufacturing an inkjet head, comprising: providing a coating layer to surround a nozzle; and subjecting the coating layer to heat treatment or aging treatment.