JPH106494A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the water repellency of an ink jet head by putting a surface treated layer having repellency formed with fluoride pitch on the spouting face side surface of a nozzle forming member formed with nozzle holes for spouting ink. SOLUTION: This ink jet head is formed in such a way that a liquid chamber member formed with a plurality of liquid chambers and ink flow paths is laminated corresponding to each piezoelectric element of a piezoelectric element part arranged plurality on the substrate as an energy generating means, and a nozzle plate 5 having a plurality of nozzles 4 formed is provided for spouting ink droplets in front corresponding to each ink flow path. The nozzle plate 5 includes a surface treated layer 7 with repellency being a layer consisting of fluoride pitch with a substantially uniform thickness on the entire spouting face side surface of a nozzle forming member 6 with nozzle holes formed therein. The fluoride pitch is obtained by heating pitch under a fluorine atmosphere, i.e., the fluoride pitch is made by replacing hydrogen in pitch to fluorine and further addition reacting fluorine into a double bonded part.

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, and more particularly to an ink-jet head having a water-repellent surface treatment layer provided on a discharge-side surface of a nozzle forming member for forming a nozzle hole.

[0002]

2. Description of the Related Art A drop-on-demand (DOD) type ink jet recording apparatus used in a printer, a facsimile, a copying machine, or the like, includes, for example, a plurality of nozzles for discharging ink droplets, a liquid chamber in which the nozzles communicate, and an ink in the liquid chamber. Using an ink-jet head having an electromechanical conversion element such as a piezoelectric element or a thermomechanical conversion element such as a thermal resistor (heater) for pressurizing the ink,
Only when a recording signal is input, ink droplets are ejected from the nozzles to fly, and high-speed, high-resolution recording is performed.

[0003] As described above, the ink-jet head drives the energy generating means (actuator) such as a heater and a piezoelectric element to eject ink droplets (ink droplets) from the nozzles to perform recording. The shape, accuracy, and the like affect the ink droplet ejection characteristics (ink droplet ejection performance), and the characteristics of the surface of the member forming the nozzle affect the ink droplet ejection characteristics.
For example, when the ink adheres to the periphery of the nozzle and an uneven ink pool (so-called uneven wetting) occurs, the ejection direction of the ink droplet is bent, the size of the ink droplet varies, or the ink droplet flies. It is known that inconvenience such as unstable speed occurs.

Therefore, it has been known that the surface of the nozzle forming member (the ejection side surface of the nozzle hole) is subjected to a water-repellent (ink-repellent) surface treatment (water-repellent treatment) to improve the uniformity. I have. Examples of the water repellent treatment include a method of applying a water repellent such as a silicon-based water repellent and a fluorine-based water repellent (see JP-A-55-65564), and a method of performing a surface treatment with fluoroalkoxysilane or the like ( JP-A-56-8
No. 9569), a method of forming a plasma polymerized film of a fluorine-based compound or a silane-based compound (JP-A-64-87).
359), a method of treating with a fluorosilicone coating agent (see JP-A-2-39944),
There is a method of forming a water-repellent layer by fluorinated polymer eutectoid plating (see JP-A-63-3963 and JP-A-4-294145).

[0005]

However, recently, inks having improved wettability have been used in order to improve the fixability to paper, water resistance, and the like. A water-repellent surface treatment layer does not provide a sufficient water-repellent function, which is a problem in achieving high image quality.

[0006] The present invention has been made in view of the above points, and has as its object to improve the water repellency of an ink jet head.

[0007]

According to a first aspect of the present invention, there is provided an ink jet head comprising a surface treatment layer having a water repellent surface on a discharge surface side of a nozzle forming member having a nozzle hole for discharging ink. In the ink jet head provided with the above, the surface treatment layer was formed with a pitch fluoride.

According to a second aspect of the present invention, in the inkjet head of the first aspect, the pitch fluoride is coated by a vapor deposition method.

A third aspect of the present invention is the ink jet head according to the first aspect, wherein the pitch fluoride is coated by a solvent coating method.

According to a fourth aspect of the present invention, in the ink jet head, a water-repellent surface treatment layer is provided on a discharge surface side surface of a nozzle forming member having a nozzle hole for discharging ink. It was configured to be formed by composite plating in which the pitch was eutectoid.

According to a fifth aspect of the present invention, there is provided an ink jet head having a water-repellent surface treatment layer provided on a discharge surface side surface of a nozzle forming member having a nozzle hole for discharging ink. The outermost surface of the plating film formed by the composite plating with the eutectoid pitch was covered with the fluoride pitch.

According to a sixth aspect of the present invention, in the inkjet head according to any one of the first to fifth aspects, the hole diameter of the surface treatment layer is smaller than the hole diameter of the nozzle forming member.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is an external perspective view of an ink jet head to which the present invention is applied, FIG. 2 is an enlarged perspective explanatory view of a nozzle plate of the ink jet head according to the first embodiment of the present invention, and FIG. 3 is a schematic view in the nozzle arrangement direction of FIG. FIG.

This ink jet head is provided with a piezoelectric element member 2 on which a plurality of piezoelectric elements as energy generating means are arranged on a substrate 1, and a plurality of liquid chambers and ink corresponding to each piezoelectric element of the piezoelectric element member 2. A nozzle plate 5 having a plurality of nozzles 4 for ejecting ink droplets corresponding to the respective ink flow paths is provided on the front surface by stacking liquid chamber forming members 3 each having a flow path.

The nozzle plate 5 is provided with a water-repellent surface treatment layer 7 on the discharge surface side surface of the nozzle forming member 6 in which the nozzle holes 6a are formed as shown in FIGS. 2 and 3.
The nozzle 4 is formed as a whole by the nozzle hole 6a and the hole 7a of the surface treatment layer 7. The nozzle forming member 6 is formed by, for example, punching a metal plate such as nickel electroforming, SUS, Ni, or Al, an organic material such as polyimide, polyether sulfone, or polyphenylene sulfide, or a ceramic such as alumina or barium titanate. The nozzle holes 6a are formed. The drilling method may be any method as long as it matches the material, and punching, electric discharge machining, excimer laser machining, or the like can be used.

A surface treatment layer 7, which is a layer made of fluorinated pitch, having a substantially uniform thickness is formed on the entire surface on the discharge surface side of the nozzle forming member 6. The thickness of the fluorinated pitch layer (surface treatment layer) 7 is in the range of about 1 to 10 μm. When the thickness is 1 μm or less, the surface is not sufficiently durable against wiping, and when a foreign substance such as paper comes into contact with the surface, physical defects are likely to occur. In addition, when the thickness is set to 10 μm or more, the ink droplet ejection characteristics of each nozzle 4 may be varied. Although the diameter of the nozzle hole 6a depends on the performance of the recording apparatus, it is about 20 to 35 μm in order to obtain a high resolution of 600 dpi or more.

Here, the fluorinated pitch will be described.
Fluorinated pitch is a substance obtained by heating pitch in a fluorine atmosphere. The pitch is a mixture of compounds having a basic structure of an aromatic six-membered ring structure of various sizes and a structure in which aromatics forming a six-membered ring plane are cross-linked by an aliphatic hydrocarbon group such as methylene. The hydrogen in the pitch is replaced with fluorine, and further the fluorine is added to the double bond to form a fluorinated pitch. Hydrogen is almost completely fluorinated.

The feature of this fluorinated pitch is that it has a “—CF ₃ group” which is hardly present in PTFE (polytetrafluoroethylene) or fluorinated graphite. As a result, very high repellency to water can be obtained, and sufficient repellency to easily wet ink can be ensured, and high-quality recording can be performed.

That is, the ink used for ink jet recording has a lower surface tension than water to improve the permeability to paper. At present, however, an ink containing a pigment or the like in order to improve the image quality, In other words, ink that is easy to get wet is used. This tends to contradict the property (repellency) required for the nozzle surface of the ink jet head, and tends to be incompatible with conventional PTFE or other linear fluorine-based polymer materials. However, by covering with a pitch fluoride layer as in the present invention, it is possible to sufficiently cope with such easily wet ink.

Next, a method of coating the nozzle plate with the fluorinated pitch will be described. When a water repellent treatment is applied to the nozzle plate, firstly, the water repellent treatment layer does not enter the inner wall surface of the nozzle hole, while the inner wall surface of the nozzle hole and the inside of the liquid chamber improve ink filling properties and reduce air bubble entrapment. For this reason, it is necessary to have a property of easily getting wet with ink. Second, it is necessary to form a uniform water-repellent treatment layer, and the non-uniform treatment layer may cause a variation in ejection characteristics between nozzles necessary for realizing a multi-nozzle and a line head. Become.

From such a viewpoint, a method of coating pitch fluoride by a vapor deposition method can be adopted. The pitch fluoride evaporates in an environment of about 400 ° C. or more, has a vapor deposition property, and shows high uniformity by vapor deposition. Can be formed. In this case, after depositing the fluoride pitch on the nozzle forming member 5 having the nozzle holes formed therein, the nozzles can be formed using a fine hole processing method such as punching or excimer laser processing. According to this method, no fluorinated pitch layer is formed on the inner wall of the nozzle hole.

It is also possible to adopt a method of coating pitch fluoride with a solvent coating method. Since the pitch fluoride is soluble in a fluorine-based solvent having a similar structure such as C ₆ F ₆ , the solution in which the pitch fluoride is dissolved can be uniformly applied to the surface of the nozzle forming member 6. This is P
TFE and the like have a very high solvent resistance and are extremely efficient in terms of the construction method as compared with the case where the solvent cannot be applied. As a coating method, a spin coating method, a screen printing method, an octopus printing method, a transfer method, or the like can be employed. In the case of the spin coating method, the coating film thickness can be easily controlled by adjusting the number of rotations of the coater with respect to the viscosity of the pitch fluoride solution. Further, by using the solvent coating method, it is easy to selectively form a surface treatment layer on the surface of the nozzle forming member, and a more functional surface treatment layer can be formed.

Next, an ink jet head according to a second embodiment of the present invention will be described with reference to FIG. 4 which is a schematic sectional view in the nozzle arrangement direction. In this example,
The nozzle plate 5 is provided with a surface treatment layer 8 made of a plating film formed on the surface of the nozzle forming member 6 by composite plating with eutectoid pitch. Thus, by forming by composite plating, a nozzle surface having excellent water repellency and excellent wiping resistance can be obtained.

Here, the particle size of the fluorinated pitch does not exceed 5 μm, and the average particle size is about 0.5 μm. Since the nozzle hole diameter is about 20 to 50 μm, 5 μm
Fluorinated pitch particles exceeding m are not preferable because they increase the non-uniformity of the nozzle surface and the nozzle edge portion, and increase the dispersion of the ink ejection characteristics. The content of the pitch fluoride is not particularly limited as long as composite plating is possible because the higher the content, the higher the water repellency.

For the lower limit of the content of pitch fluoride, for example, when the surface treatment layer 8 is formed by pitch fluoride-nickel composite plating, the pitch fluoride eutectoid ratio (content Evaluation of the contact angle of water with respect to the rate (%) is as shown in FIG. In the figure,
Δ indicates the contact angle of the PTFE plate on which the surface treatment layer was formed by the composite eutectoid plating of PTFE.

As can be seen from this figure, in the region where the content of pitch fluoride is 10 vol% or more, a contact angle exceeding 109 ° which is the contact angle of water of the PTFE surface treatment layer is obtained. Therefore, in order to realize water repellency higher than that of the PTFE surface treatment layer, it is preferable that the amount of the pitch fluoride contained in the composite plating be 10 vol% or more.

As a means for forming the composite plating, a known method can be used, and there is no particular limitation. Further, the metal base material is not limited to nickel, but may be a metal such as copper, chromium, zinc, tin, or an alloy thereof. However, composite plating using nickel as a metal base material is a very versatile method, and has the advantage of being excellent in cost and ink resistance. Further, when the electroless plating method of forming a mixture of nickel and phosphorus as the metal base material is used, the accuracy of the plating film thickness can be improved, and a highly integrated head can be obtained.

Next, an ink jet head according to a third embodiment of the present invention will be described with reference to FIG. 6, which is a schematic sectional view in the nozzle arrangement direction. In this embodiment, the nozzle plate 5 is provided with a plating film 9 formed on the surface of the nozzle forming member 6 by the composite plating in which the fluorinated pitch is eutectoid as in the second embodiment. A surface treatment layer 11 formed by covering the surface with pitch fluoride 10 is provided.

In this case, as the method for forming the pitch fluoride 10 on the plating film 9, the above-described vapor deposition method or solvent coating method can be used. In addition, the method is not particularly limited as long as it is a method capable of forming a uniform thin film such as an electrodeposition coating method.

By covering the outermost surface of the plating film with the pitch fluoride as described above, sufficient water repellency can be ensured even for ink which cannot be handled by composite plating. That is, since the surface obtained by the composite plating has a surface roughness of the order of microns, it may not have sufficient water repellency with respect to ink having low surface tension and high wettability. Thus, by further coating the outermost surface of the composite plating with pitch fluoride, the surface smoothness of the plating film can be improved, and higher water repellency can be obtained.

Next, an ink jet head according to a fourth embodiment of the present invention will be described with reference to FIG. 7, which is a schematic sectional view in the nozzle arrangement direction. In this embodiment, the minimum diameter (hole diameter) D1 of the hole 7a of the surface treatment layer 7 is smaller than the minimum diameter (nozzle hole diameter) of the nozzle hole 6a of the nozzle forming member 6.

As described above, by making the hole diameter of the surface treatment layer 7 smaller than the nozzle hole diameter of the nozzle forming member 6,
Energy at the time of ink ejection can be efficiently transmitted to the ejected droplets (ink droplets), the droplet speed increases, the ejection efficiency increases, stable ejection characteristics can be obtained, and the printing quality can be improved. it can.

Further, by forming the hole 7a of the surface treatment layer 7 to have a tapered cross section and continuing to the nozzle hole 6a, there is no step between the nozzle hole 6a and the hole 7a of the surface treatment layer 7, This makes it difficult for air bubbles to stay or be drawn into this portion, thereby preventing jet down, and furthermore, the jet direction is further stabilized by the continuation of the inner wall surface of the nozzle hole from the inner wall surface of the surface treatment layer. Quality can be improved.

Here, the hole diameter of the surface treatment layer 7 is
It is preferable to set it to 50% or more and less than 100% with respect to the diameter of a. The hole diameter of the surface treatment layer 7 is 10
If it is 0%, the hole diameter of the surface treatment layer 7 and the nozzle hole diameter become the same, and it becomes impossible to efficiently transmit the energy at the time of ink ejection to the ejected droplet (ink droplet). It may affect injection characteristics. By setting the above range, it is possible to improve the injection efficiency and stabilize the injection characteristics.

An example of a manufacturing process of an ink jet head as in this embodiment will be described with reference to FIGS. 8 to 11. As shown in FIG. 8A, a nozzle hole 6a is formed by an electroforming method. The formed nozzle forming member 6 is formed. By forming the nozzle forming member by the electroforming method, the nozzle hole has a tapered shape, and it is easy to eliminate the step between the nozzle hole and the hole of the surface treatment portion and to make it smooth.

Then, a negative dry film resist 15 is laminated on the back side of the discharge surface of the nozzle forming member 5 as shown in FIG. At this time, the laminating temperature and the pressure are adjusted so that a protruding portion 15a in which a part of the dry film resist 15 protrudes from the nozzle hole 6a to the ejection surface side as shown in FIG. The amount of protrusion from the surface of the protrusion 15a is set according to the thickness of the surface treatment layer to be formed.

Thereafter, as shown in FIG. 3C, the entire surface is exposed by irradiating ultraviolet rays (UV light) from the back side of the discharge surface of the nozzle forming member 6, thereby forming a dry film resist as shown in FIG. 15 cures to become a cured dry film resist 16. At this time, since the nozzle forming member 6 serves as a mask, the protruding portion 15 protruding from the nozzle hole 6a to the ejection surface side as shown in an enlarged view in FIG.
As for a, only the portion facing the nozzle hole 6a is hardened to form the hardened protruding portion 16a.

Then, by developing this, as shown in FIGS. 8 (e) and 10, a tapered projection 17 which protrudes from the nozzle hole 6a to the discharge surface side.
The dry film resist pattern 17 having “a” is completed. In this case, by using an exposure device or a developing device capable of adjusting the exposure amount and / or the development time, for example, as shown in FIG. Is relatively thick, and as shown in FIG. 3B, when the exposure amount is reduced and the development time is extended, the protruding portion 17a is relatively thinned.
The shape of the protrusion 17a can be easily changed and set.

Next, as shown in FIG. 10F, a surface treatment layer 7 made of pitch fluoride is formed. Note that the thickness of the surface treatment layer 7 at this time is preferably smaller than the thickness (height from the surface of the nozzle forming member 5) of the protrusion 17a of the dry film resist pattern 17. This is because, when the thickness of the surface treatment layer 7 is larger than the thickness of the protrusion 17a, the surface treatment layer 7 rides on the protrusion 17a, so that sufficient accuracy cannot be obtained. This is because there is a possibility of causing peeling failure.

Thereafter, by removing the photoresist pattern 17, the surface treatment layer 7 having the tapered holes 7a formed on the surface of the nozzle forming member 6 having the nozzle holes 6a formed as shown in FIG. The formed nozzle plate 5 is obtained. Although the surface treatment layer 7 is used here, it is also possible to apply a layer obtained by composite plating of pitch fluoride as in the above-described embodiment, or a layer obtained by coating the outermost surface of this plating film with pitch fluoride.

In the above embodiment, an example in which the present invention is applied to a piezo actuator type ink jet head using a piezoelectric element as an energy generating means has been described. However, a so-called bubble jet type ink jet using a heater as the energy generating means has been described. It can also be applied to heads. Further, the nozzle forming member is not limited to one having a structure separate from a member forming a liquid chamber for pressurizing ink by energy generating means, but may be applied to a member integrally forming with the member forming the liquid chamber. Can be.

Further, in the above-described embodiment, an example in which a plate-shaped member is used as the nozzle forming member has been described. However, the nozzle is formed by combining a plurality of members (for example, a member having a groove and a member covering the groove). The present invention can be similarly applied to a case where a hole is formed. Furthermore, in the above-described embodiment, the example in which the surface treatment layer is provided on the entire surface of the nozzle forming member has been described.

[0043]

As described above, according to the ink jet head of the first aspect, the surface treatment layer formed with the fluorinated pitch is provided on the discharge surface side surface of the nozzle forming member in which the nozzle holes for discharging the ink are formed. With this configuration, the water repellency is improved, good water repellency is obtained even for ink with high wettability, stable ink droplet ejection characteristics are obtained, and a highly reliable and durable ink jet head is provided. Obtainable.

According to the ink jet head of the second aspect, in the ink jet head of the first aspect, the pitch fluoride is coated by a vapor deposition method, so that a uniform surface treatment layer of the pitch fluoride is formed at low cost. be able to.

According to the ink jet head of the third aspect, since the ink jet head of the first aspect is configured such that pitch fluoride is coated by a solvent coating method, the surface treatment layer can be selectively formed. The surface treatment layer can be provided more functionally.

According to the fourth aspect of the present invention, there is provided a structure in which a nozzle-forming member having a nozzle hole for discharging ink is provided with a surface treatment layer formed by composite plating of eutectoid pitch on the discharge surface side surface. As a result, the water repellency is improved, good water repellency is obtained even for inks having high wettability, stable ink droplet ejection characteristics are obtained, and wiping durability is also improved. Thus, a highly durable inkjet head can be obtained.

According to the fifth aspect of the present invention, the outermost surface of the plating film formed by the composite plating of eutectoid pitch on the discharge surface side surface of the nozzle forming member having the nozzle hole for discharging the ink is formed. With a surface treatment layer formed by coating with a modified pitch, the water repellency is further improved, good water repellency is obtained even for highly wettable ink, and stable ink droplet ejection characteristics Is obtained,
Further, wiping durability is improved, and an ink jet head having high reliability and durability can be obtained.

According to the ink jet head of claim 6, in the ink jet head of any one of claims 1 to 5, the hole diameter of the surface treatment layer is smaller than the hole diameter of the nozzle forming member. Efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is an external perspective view of an inkjet head to which the present invention has been applied.

FIG. 2 is an enlarged perspective view illustrating a nozzle plate of the inkjet head according to the first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view in the nozzle arrangement direction of FIG. 2;

FIG. 4 is a schematic cross-sectional view of a nozzle plate according to a second embodiment of the present invention in a nozzle arrangement direction.

FIG. 5 is a diagram showing an example of a relationship between a pitch fluoride content and a contact angle in a pitch fluoride composite plating film;

FIG. 6 is a schematic sectional view of a nozzle plate according to a third embodiment of the present invention in a nozzle arrangement direction.

FIG. 7 is a schematic sectional view of a nozzle plate in a nozzle arrangement direction according to a fourth embodiment of the present invention.

FIG. 8 is a process chart illustrating an example of a method for manufacturing the nozzle plate of FIG. 7;

FIG. 9 is an enlarged view of a main part of FIG. 8 (c).

FIG. 10 is an enlarged view of a main part of FIG. 8 (d).

FIG. 11 is an explanatory diagram for explaining a relationship between an exposure amount, a development time, and a shape of a dry film resist pattern;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Piezoelectric element part, 3 ... Liquid chamber forming member, 4 ... Nozzle, 5 ... Nozzle plate, 6 ... Nozzle forming member, 7,
8, 11: Surface treatment layer.

Claims (6)

[Claims] 1. An ink jet head having a water-repellent surface treatment layer provided on a surface on a discharge surface side of a nozzle forming member having a nozzle hole for discharging ink, wherein the surface treatment layer is formed with a pitch fluoride. Characteristic inkjet head. 2. The ink jet head according to claim 1, wherein said pitch fluoride is coated by a vapor deposition method. 3. The ink jet head according to claim 1, wherein said pitch fluoride is coated by a solvent coating method. 4. An ink jet head in which a surface treatment layer having water repellency is provided on a discharge surface side surface of a nozzle forming member in which a nozzle hole for discharging ink is formed, wherein the surface treatment layer is a composite of eutectoid pitch fluoride. An ink-jet head formed by plating. 5. An ink jet head having a water-repellent surface treatment layer provided on the ejection surface side of a nozzle forming member having a nozzle hole for ejecting ink, wherein said surface treatment layer is a composite of eutectoid pitch fluoride. An inkjet head, wherein the outermost surface of a plating film formed by plating is coated with a fluoride pitch. 6. The ink jet head according to claim 1, wherein a hole diameter of the surface treatment layer is smaller than a hole diameter of the nozzle forming member.