JPH05124198A - Ink jet head and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Purpose] To facilitate the initial filling of ink and to easily discharge the generated bubbles. As a result, the device for discharging bubbles can be simplified, the cost of the recording device can be reduced, and the ink consumed for discharging bubbles can be greatly saved. Further, it is possible to eject an ink droplet having a uniform jetting direction and a stable flight speed, in which entrainment of bubbles does not occur. In an inkjet head for recording characters / images with liquid ink, a nozzle plate 10 has a crater portion 13, and a head inner wall 14 and an ink supply path 15 that are in contact with the crater portion 13 and the ink 11 have a hydrophilic surface. Is being processed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head for recording characters and images with liquid ink and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as inks used in ink jet recording systems, water-based inks have been mainly used from the viewpoint of odor and safety, and various water-soluble dyes are mixed with water or a mixed solvent of water and a water-soluble organic solvent. Water-based inks that have been dissolved in water and added with various additives as needed are currently used.

When a water-based ink is used in an ink jet head, if the water repellency of the nozzle surface is insufficient, the ink adheres unevenly to the nozzle surface, which impairs the straightness of the ejected ink droplets and disturbs printing. The trouble sometimes occurred.

Therefore, by using electrostatic powder coating, vacuum deposition, etc., fluorine-containing resin particles are attached to the nozzle surface to make it water repellent, or a solvent-soluble fluorine-containing polymer solution is applied,
There is provided a method in which a fluororesin is dispersed in a nickel plating solution to form a water-repellent film by electroplating.

If the ink wettability of the inner wall of the head and the ink supply path is poor, air bubbles may be left in the ink flow path when the ink is filled, or the air bubbles generated in the flow path may be discharged. Since it is difficult to discharge even if the operation is performed, problems such as dot omission and print disorder may occur.

In order to improve the wettability of the inner wall of the head and the ink supply path with the ink, Japanese Patent Laid-Open No. 60-24957 discloses that the surface is treated with a polar group by acid treatment or plasma treatment. There has been proposed a method of producing a hydrophile to make it hydrophilic.

Further, Japanese Patent Publication No. 54784/1990 proposes a method of improving the wetness by heating a dye aqueous solution in a state of being in contact with the ink flow channel surface and adsorbing or permeating the dye in advance on the flow channel surface. ing.

[0008]

However, with the above-mentioned conventional techniques (1), (1) it was difficult to obtain a smooth surface without pinholes.

(2) Durability was not obtained due to insufficient adhesion strength.

Regarding the conventional hydrophilic treatments 1 to 3,
(1) Although the initial wettability can be secured, since the durability is poor, the effect of the hydrophilic treatment is lost if the ink is not filled in the head and the supply path for a long time.

There are problems such as the above.

Further, as the biggest problem, it is very difficult to perform both hydrophilic treatment and water repellent treatment on the same head, because they give mutually opposite characteristics, and the yield is poor and the reliability is high. It was impossible to avoid increasing the cost to secure the property.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide an ink jet head capable of easily ensuring a high printing quality for a long period of time and a manufacturing method thereof. ..

[0014]

The ink jet head of the present invention is an ink jet head for recording characters / images with liquid ink, in which the nozzle plate has a crater portion, and the crater portion and the ink are in contact with the head inner wall and the ink. It is characterized in that the supply path is hydrophilically surface-treated.

An oxide layer is formed as the surface treatment layer.

Further, the oxide layer is composed of SiO ₂ , Al ₂ O ₃ and Ti.
It is characterized by comprising oxide fine particles selected from at least one selected from the group consisting of O ₂ , ZrO ₂ and MgO.

Further, the crater portion of the nozzle plate, the inner wall of the head in contact with the ink and the contact angle of the pure water at room temperature with pure water are 10 degrees or less.

Further, in a method of manufacturing an ink jet head for recording characters / images with liquid ink, a sol or a solution in which fine oxide particles are dispersed or dissolved is formed in a crater portion of a nozzle plate, an inner wall of the head in contact with ink and an ink supply passage. It is characterized in that an oxide layer is formed by coating.

[0019]

In the ink jet head of the present invention as set forth in claim 1, the ink is uniformly wetted by surface-treating the crater portion of the nozzle plate, the inner wall of the head in contact with the ink, and the ink supply path with hydrophilicity. There is also no entrainment of ink and non-uniform deposition of ink on the surface of the nozzle plate. Therefore, it is possible to eject ink droplets having a uniform ejection direction and a stable flight velocity.

Further, since only the crater portion is wet with the ink, the nozzle end surface is not contaminated with the ink, and even if the ink is solidified and dried in the crater portion, the solidified and dried ink film serves as a cap. Further, it is possible to prevent the viscosity of the ink inside the head from increasing, and it is possible to easily recover the ink by simple preliminary ejection or cleaning.

Further, when the ink is filled, bubbles are not left in the ink flow path, and bubbles generated in the flow path can be easily discharged, so that long-term reliability can be ensured. it can.

The oxide fine particles used as the surface treatment layer of the ink jet head used in the present invention described in claim 2, particularly the oxide fine particles described in claim 3, have a large specific surface area, are active, and have many hydroxyl groups. have.

If these oxide layers are formed on the crater portion of the nozzle plate, the inner wall of the head in contact with the ink and the ink supply path, a stable hydrophilic film with excellent adhesion strength can be obtained.

According to the fourth aspect of the present invention, the crater portion of the nozzle plate that has been subjected to the hydrophilic treatment, the inner wall of the head that is in contact with the ink, and the contact angle of pure water at room temperature of the ink supply path are 10 degrees or less. When the contact angle is larger than 10 degrees, the ink is non-uniformly adhered to the nozzle surface, which hinders the straightness of the ink droplets and induces flight bending, or
The reliability that the bubbles cannot be discharged in the portion where the flow velocity is slow inside the head and the ink filling and the bubble discharge depend on the head structure is deteriorated. (Note that the contact angle means an angle θ formed by the tangent line between the droplet surface and the sample surface and the sample surface after dropping pure water 61 onto the horizontally fixed sample shown in FIG. 6 and leaving it to stand for 1 minute. According to the method for producing an inkjet head described in claim 5, after applying a sol or solution in which oxide fine particles are dispersed or dissolved to the crater portion of the nozzle plate, the head inner wall in contact with the ink, and the ink supply path, When dried at a temperature at which the dispersion solvent evaporates, a hydrophilic film that is stable and highly durable to heat and any solvent can be formed with appropriate adhesion strength.

[0025]

EXAMPLES The ink jet head of the present invention and the method for producing the same will be specifically described below.

FIG. 1 is a cross-sectional view of essential parts showing a basic embodiment of an ink jet head according to the present invention. As shown in the figure, in the inkjet head of this embodiment, the nozzle plate 10 has a crater portion 13, and the crater portion 13, the head inner wall 14 in contact with the ink 11 and the ink supply passage 15 are hydrophilically surface-treated. There is. 16 is a surface treatment layer. With such a configuration, the ink 11 is uniformly wetted, so that entrapment of air bubbles and uneven adhesion of the ink to the surface 10a of the nozzle plate are prevented.
Therefore, it is possible to eject the ink droplets 12 having a uniform ejection direction and a stable flight speed.

As the surface treatment layer which can be used in the present invention, acid treatment, alkali treatment, plasma treatment, corona discharge treatment, dye adsorption layer, plating treatment, oxide treatment and the like can be used. As the type of processing, S
Non-metal oxides such as iO ₂ , Al ₂ O ₃ , TiO ₂ , Zr
Metal oxides such as O ₂ and MgO, and composite compounds thereof are the most effective.

Specifically, alumina sol 100, 200, 520 manufactured by Nissan Kagaku Co., Ltd., Snowtex 20, 30, 40, C, N, O, S, 20L, O of silica sol.
L, zirconia sol NZS-20A, NZS-30A,
NZS-30B, NTL agent 2003, 2102, 210
2, 2103, 5402, 3007, 3008, 500
7, 6008, Glaskers 90, 10 of Nittaku Research Institute Co., Ltd.
1A, 300, 401, 700, 950, 1000, 1
100, 1500, organic coat of Matsumoto Pharmaceutical Co., Ltd., Sumicerum of Asahi Chemical Industry Co., Ltd., Cerama coat of Odec Co., Ltd., normal temperature glass G- of Fujitoku Co., Ltd.
It can be used by diluting 401GT, Adelite of Asahi Denka Kogyo KK, Aerosil of Nippon Aerosil, etc. with a stock solution or a diluting solvent, and mixing them individually or by mixing.

The above-mentioned examples of the treatment liquid are particularly preferable for the ink jet head of the present invention, and the treatment liquid used in the present invention is not limited to these.

As a manufacturing method, after assembling the ink jet head, sufficient washing with alkali, water and alcohol, and then circulating the treatment liquid and drying it are also performed. After taping or masking, dip, spin coat, etc., apply and dry, then taping,
It is also possible to remove the masking and assemble and bond.

Further, in the ink jet head of the present invention, the piezoelectric element pushes out the flexible ink in response to the input pulse,
Piezoelectric head flying as recording droplets from the nozzle, the heating element heats up in response to an input pulse, causing the ink to boil instantaneously, and the ink ejected by the bubbles generated at that time is ejected by the nozzle. Bubble type and thermal ink jet type that are ejected from the ink and fly as recording droplets, or
A piezoelectric element array formed by arranging piezoelectric elements in which piezoelectric materials and conductive materials are alternately laminated in layers is fixed at one end,
It is possible to use a laminated piezoelectric element vertical vibration type, in which ink is ejected by vertical vibration with the other end facing the nozzle opening with the other end free, a Gould type, a stem type, a static control type, etc., but there is no limitation on the recording method. Not something to do.

Hereinafter, the present invention will be described in detail by giving Examples and Comparative Examples, but the present invention is not limited to these.

(Embodiment 1) A piezoelectric head is used in which a piezoelectric element 21 pushes a flexed ink 22 in response to an input pulse shown in FIG. A stainless nozzle plate having a crater portion 31 shown in FIG. 3 was used.
Polysulfone was used as the material for the inner wall 25 of the head and the ink supply path 26.

[0034] As the sol oxide fine particles are dispersed, oxide composition _{SiO 2 -ZrO 2 -Na 2 O =} 35: 60: 5
Was used as a sol having a solid content of 1% by weight and an average particle diameter of 0.02 μm dispersed in a solvent containing ethanol as a main component.

The head inner wall 25 and the ink supply path 26 are set to K
OH 1% by weight, glycerin 20% by weight, ethanol 10
5% by weight, 61% by weight of ion-exchanged water, 5
After circulating with a pump for a minute, it was rewashed with ethanol, and the treatment liquid was circulated with water for 1 minute and dried at 80 ° C. for 1 hour to form a treatment layer.

(Example 2) Using a head manufactured by laminating stainless steel, as a sol in which oxide fine particles are dispersed, a room temperature glass G-401GT (SiO manufactured by Fujitoku Co., Ltd.) is used.
_2- ZrO ₂ = 35: 65, solid content 28% by weight, viscosity 8c
Washing and treatment were carried out in the same manner as in Example 1 using P) diluted with isopropanol to a solid content of 1% by weight.

(Example 3) Using a head manufactured by laminating photosensitive resin (nozzle plate is nickel), as a sol in which fine oxide particles are dispersed, Snowtex N (SiO ₂ approx. Using 20% by weight and a viscosity of 3 cP) diluted with methanol to a solid content of 1% by weight, washing and treatment were carried out in the same manner as in Example 1.

(Embodiment 4) After cleaning and drying the first and second substrates 41 and 42 made of polycarbonate shown in FIG. 4, the adhesive portion 43 is masked with taping or a resist to obtain a sol in which fine oxide particles are dispersed. , Nissan Chemical Industries, Ltd. alumina sol 520 (Al ₂ O ₃ about 20% by weight, viscosity about 50
cP) was diluted with ethanol to a solid content of 1% by weight, applied by dipping and spin coating, dried at 80 ° C. for 1 hour, then the mask was removed and assembled with an adhesive.

An untreated head having the same structure as in Examples 1 to 4 was used as a comparative example.

The evaluation items, evaluation methods and evaluation results of the examples and comparative examples are shown below.

(Contact Angle) Table 1 shows Examples 1 to 4 and Comparative Example 1
4 to 4, the contact angle between the inner wall of the head and the crater portion of the nozzle plate after 1 minute of pure water dropping, and the rubbing test with silicone rubber of the crater portion of the nozzle plate 2000 times
The result of having measured the contact angle after 3000 times and 5000 times with an automatic contact angle meter (CA-Z type manufactured by Kyowa Interface Science Co., Ltd.) is shown.

[0042]

[Table 1]

From Table 1, it can be seen that Examples 1 to 4 have dramatically improved wettability as compared with Comparative Examples 1 to 4.

(Ink Filling / Air Bubble Discharging) The suction pump 51 shown in FIG. 5 (the suction pump has a pressure of -15 cmH).
A suction amount of about 0.02 cc / s is used in about g, and the time until the ink jet heads of Examples 1 to 4 and Comparative Examples 1 to 4 can be completely filled with the ink having the following composition is measured,
Then, after leaving the inkjet head at 70 ° C. for 5 days, the suction pump 51 shown in FIG.
Table 2 shows the results of measuring the time until the ink 54 is sucked through the cap 53 and the bubbles inside the head inner wall and the supply path can be completely discharged.

Ink Composition Dye C. I. Food Black 2 3% by weight Glycerin 10% by weight 2-Pyrrolidone 3% by weight Ethanol 4% by weight Ion-exchanged water 80% by weight

[0046]

[Table 2]

From Table 2, it can be seen that Examples 1 to 4 have better ink filling properties and bubble discharging properties than Comparative Examples 1 to 4.

(Printing Stability) Using the ink having the above composition,
The time for stable and continuous ejection was measured at room temperature, the number of missing dots generated during continuous printing was counted, and the total number of printed lines was divided by the number of missing dots to calculate the average number of printed lines.

◯: 50,000 lines or more Δ: 20,000 lines to 50,000 lines ×: 20,000 lines or less Table 3 shows the evaluation results of Examples and Comparative Examples.

[0050]

[Table 3]

From Table 3, it can be seen that Examples 1 to 4 are capable of stable ejection for a long time as compared with Comparative Examples 1 to 4.

[0052]

According to the ink jet head of the present invention, in the ink jet head for recording characters / images with liquid ink, the nozzle plate has a crater portion, the inner wall of the head in contact with the crater portion and the ink and the ink supply path. The hydrophilic surface treatment facilitates initial filling of the ink due to its affinity with the inside of the head and inside the flow path, and the bubbles generated can be easily discharged, ensuring long-term reliability. In addition to simplifying the device for discharging bubbles, it is possible to reduce the cost of the recording apparatus, and it is possible to significantly reduce the ink consumed for discharging bubbles. In addition, since the initial filling of ink is easy, it is possible to transport and store it with the inside of the flow path empty, and it is possible to reduce transport costs. Also it has the effect that in.

Further, there is an effect that it is possible to eject ink droplets having a uniform jetting direction and a stable flying velocity, in which entrainment of bubbles does not occur.

Further, there is an effect that the surface of the nozzle plate is not contaminated with ink and the viscosity of the ink inside the head can be prevented (that is, clogging can be prevented). Further, according to the method of manufacturing an inkjet head of the present invention, the hydrophilic treatment can be performed with an extremely simple apparatus and process, which is safe in manufacturing and the cost can be significantly reduced, and its effect is great.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a basic embodiment of an inkjet head of the present invention.

FIG. 2 is a cross-sectional view showing a piezoelectric control type recording head used in an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a nozzle plate used in the inkjet head of the present invention.

FIG. 4 is a sectional view showing a piezoelectric control type recording head used in another embodiment of the present invention.

FIG. 5 is a schematic diagram of an ink jet recording apparatus equipped with a recovery pump.

FIG. 6 is an explanatory diagram of a contact angle.

[Explanation of symbols]

 Nozzle plate 10a Nozzle plate surface 11 Ink 12 Ink drop 13 Crater 14・ Head inner wall 15 ・ ・ ・ ・ ・ ・ Ink supply channel 16 ・ ・ ・ ・ ・ Surface treatment layer 21 ・ ・ ・ ・ Piezoelectric element 22 ・ ・ ・ ・ ・ ・ Ink 23 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Nozzle 24 ・・ ・ ・ Recorded liquid droplets 25 ・ ・ ・ ・ ・ Head inner wall 26 ・ ・ ・ ・ Ink supply path 31 ・ ・ ・ ・ ・ ・ Crater part 41 ・ ・ ・ ・ ・ ・ First substrate 42 ・ ・ ・... Second substrate 43 ... Adhesive part 51 ... Suction pump 52 ... Nozzle 53 ... Cap 54 ... Ink 61 ... ·····Pure water

Claims (5)

[Claims] 1. An ink jet head for recording characters / images with liquid ink, wherein a nozzle plate has a crater portion, and the crater portion, an inner wall of the head in contact with ink, and an ink supply path are hydrophilically surface-treated. An inkjet head characterized in that 2. The ink jet head according to claim 1, wherein an oxide layer is formed as the surface treatment layer. 3. The oxide layer is SiO ₂ , Al ₂ O ₃ , T
The inkjet head according to claim 2, characterized in that it comprises oxide fine particles selected from at least one selected from the group consisting of iO ₂ , ZrO ₂ , and MgO. 4. The inkjet head according to claim 1, wherein the crater portion of the nozzle plate, the inner wall of the head in contact with the ink, and the contact angle of the pure water at room temperature with pure water are 10 degrees or less. .. 5. A method of manufacturing an ink jet head for recording characters / images with liquid ink, wherein a sol or solution in which oxide fine particles are dispersed or dissolved is formed in a crater portion of a nozzle plate, a head inner wall in contact with ink, and an ink supply path. A method for manufacturing an inkjet head, which comprises forming an oxide layer by applying.