JPH11240153A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ink repellency, sliding properties, wear resistance and peeling resistance by forming an ink repellent coating film provided around the opening part of an ink discharge nozzle, of a diamondlike carbon, in an ink jet recording head having an ink flow path comprising the ink discharge nozzle or the like. SOLUTION: When a pulsed voltage is applied to a piezoelectric element 3, a vibration plate 2 is displaced to an ink pressure chamber 13 side to push an ink out of a nozzle flow path 12 and thus the ink is discharged from the ink nozzle 11. In this ink jet recording head, a diamondlike carbon coating film(DLC coating film) 4a is formed as an ink repellent coating film which forms a nozzle face 18. That is, a gas of methane and hydrogen mixed at a molar ratio of 2:1 is introduced as a feedstock gas into the nozzle face 18 which is the opening part of the ink nozzle 11 using an RF plasma CVD device to form a DLC coating film 4a, which contains a large amount of a hydrogenated carbon and is self-lubricating so that is shows outstanding sliding properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head used in an ink jet recording apparatus for recording by ejecting ink as small droplets from nozzles.

[0002]

2. Description of the Related Art A method of recording by ejecting ink from a minute ink nozzle and attaching the ink to a recording medium such as paper is known.
It is known as an ink jet recording method. As one of the methods, there is an on-demand type ink jet recording head (hereinafter, simply referred to as a recording head).

FIGS. 2 and 3 show a recording head of this type.
FIG. 2 is a plan view showing an ink flow path 10 of the flow path substrate 1 and the like, and FIG. 3 is a cross-sectional view showing the structure of a recording head. The flow path substrate 1 made of glass, metal, silicon, plastic material, or the like is formed on the ink nozzles 11 by etching, machining, molding, or the like.
A plurality of ink flow paths 10 including a nozzle flow path 12, an ink pressurizing chamber 13, an ink supply path 14, and a throttle flow path 15, and a groove serving as an ink reservoir 16 and an ink inlet 17 connected to these ink flow paths 10 are formed. Have been. A vibration plate 2 made of glass, metal, or the like is laminated and integrated on the flow channel groove side of the flow channel substrate 1 to form an ink flow channel 10 and the like.
A piezoelectric element 3, which is an electromechanical transducer, is adhered to the opposite surface of the vibration plate 2 corresponding to.

The piezoelectric element 3 of the recording head having such a configuration
When a pulse-like voltage is applied to the diaphragm 2, the diaphragm 2 is displaced toward the ink pressurizing chamber 13, the volume is rapidly reduced, and the ink corresponding to the reduced volume is pushed out from the nozzle flow path 12, The ink is ejected from the ink nozzle 11 and adheres to a recording medium (not shown). In order for the recording head to be a recording head that can withstand practical use, it is necessary that the surface where the opening of the ink nozzle 11 is located, that is, the nozzle surface 18 is a surface to which ink does not easily adhere. If the ink easily adheres to the nozzle surface 18, the ink adheres to the periphery of the nozzle opening, and the adhered ink affects the ink droplet ejected from the ink nozzle 11, and the ejection speed of the ink droplet and the ink droplet The size and the flight direction become unstable. As a result, the printing accuracy such as the accuracy of the size (dot diameter) of the ink point recorded on the recording medium and the accuracy of the spotting position deteriorates. Therefore, in order to prevent such adhesion of the ink around the ink nozzle 11, the nozzle surface 18 is required to have an ink repellent function.

[0005] Further, a recording apparatus equipped with a recording head, such as a printer or a facsimile, often has a cleaning mechanism for cleaning and protecting the nozzle surface 18. This mechanism includes a rubber blade, a sponge, a cloth, etc. as a member for wiping the nozzle surface 18,
The nozzle surface 18 is wiped with the member periodically or in accordance with a necessary instruction (referred to as wiping) to remove ink, dust, and the like attached to the nozzle surface 18, thereby ensuring printing accuracy. For this reason, the nozzle surface 18 is required to have abrasion resistance, peeling resistance, and slidability that withstand wiping for cleaning, in addition to the above-described ink repellency.

The materials of the flow path substrate 1 and the vibration plate 2 include:
As described above, glass, metal, silicon, plastic materials, and the like are used, and any of these materials is a material to which ink easily adheres. Therefore, in order to satisfy the above-described conditions required for the nozzle surface 18, it is indispensable to perform a process for imparting ink repellency to the nozzle surface 18. Conventional methods for imparting ink repellency to the nozzle surface 18 include the following methods.

1) A method in which a solvent solution containing silicone oil is applied to the nozzle surface 18 and baked. 2) A method in which a solvent solution containing a fluorine compound is applied to the nozzle surface 18 and baked. 3) A method of forming a film on the nozzle surface 18 by eutectoid plating of a fluorine-containing compound-containing material and nickel.

4) A method of forming a film of chromium or titanium nitride on the nozzle surface 18 by vapor deposition or sputtering. The results of comparative study of the effectiveness of these methods are shown in Table 1, 1) to 5).

[0009]

[Table 1] The contact angles shown in Table 1 are the contact angles for pure water at room temperature, and for comparison, the contact angles of the glass substrate are also shown. This contact angle required for the nozzle face 18 is at least 75 degrees, preferably
80 degrees or more. The slidability indicates the damage of the wiping material, where ○ indicates no damage and × indicates damage. Abrasion resistance, peeling resistance and chemical resistance are evaluated by the number of wiping times at normal temperature that can withstand,
In the case of withstanding 50,000 wipings, ○ was given. In the case of less than 10,000 wipings, x was given. If the effect of wiping is due to abrasion of the film, it is evaluated in the column of abrasion resistance. The result was marked.

[0010] In the method of baking silicone oil of 1), desired ink repellency can be obtained, but it cannot withstand wiping. In the method of baking a fluorine-based compound of 2), the abrasion resistance and the peeling resistance are insufficient, so that it cannot be adopted particularly in a printer used under severe conditions. In the eutectoid plating of 3), there is a problem that nickel is corroded due to long-term contact with the ink, the contact angle is reduced, and the adhesion to the base is deteriorated. It is fatal that the sputtered films 4) and 5) have a small contact angle and cannot secure the most important ink repellency.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the conventional nozzle surface treatment technology, and to provide an ink-repellent property that does not easily adhere to ink and a sliding property that does not damage the wiping member. It is an object of the present invention to provide a recording head provided with an ink-repellent film having resistance, abrasion resistance and peeling resistance against wiping, and chemical resistance not corroded by ink.

[0012]

According to the present invention, there is provided an ink flow path comprising a nozzle or the like for discharging ink pressurized by ink pressurizing means, and an ink-repellent film around an opening of the nozzle. In the ink jet recording head provided, the ink repellent film is made of diamond-like carbon (the invention of claim 1).

Diamond-like carbon as an ink-repellent film has the necessary ink-repellent properties, has a high adhesion strength to the nozzle surface, has excellent slidability, has abrasion resistance that can withstand wiping, and has an ink-repellent property. It has chemical resistance that does not corrode. In the invention of claim 1, the thickness of the diamond-like carbon is 0.5 μm to 3 μm (the invention of claim 2).

The diamond-like carbon having a thickness of less than 0.5 μm is easily peeled off by wiping under the influence of the irregularities of the underlayer, and the abrasion resistance of the diamond-like carbon exceeding 3 μm is reduced due to the internal stress remaining in the film. And it becomes easy to peel off. In the invention of claim 1 or claim 2, the diamond-like carbon is diamond-like carbon generated by a plasma CVD method (the invention of claim 3).

The diamond-like carbon produced by the plasma CVD method contains a large amount of hydrogenated carbon therein and has a self-lubricating property. As a result, the coefficient of friction of the film becomes small.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the ink jet recording head according to the present invention will be described with reference to examples. FIG.
FIG. 2 is a cross-sectional view illustrating a structure of an example. The parts having the same functions as those of the prior art are denoted by the same reference numerals.

This embodiment has the same structure as that of the recording head of the prior art shown in FIGS. 2 and 3, except that the ink repellent film (the ink repellent film shown in FIG. 4) A diamond-like carbon film (hereinafter abbreviated as DLC film) 4a is formed. This will be described in detail below. A silicon wafer is used as the substrate 1 and ink channels are formed by dry etching.
A groove of 10 or the like was formed, and a vibrating plate 2 made of glass was joined to the surface by electrostatic joining to be integrated. Using an RF plasma CVD apparatus, a gas obtained by mixing methane and hydrogen at a molar ratio of 2: 1 was introduced into the nozzle surface 18 which is the opening of the ink nozzle 11 in this configuration.
The DLC film 4a was formed under the conditions of 15 Pa and RF power of 50 to 110 W, and the characteristics as an ink-repellent film were evaluated. The thickness of the formed DLC film was 0.25 to 5 μm, and the evaluation results are shown in Tables 1 and 2.

[0018]

[Table 2] Table 1 also shows the evaluation results of the ink-repellent film according to the prior art. 6) to 8) in Table 1 correspond to this example, and 6) indicates D
The case where the thickness of the LC film is 0.5 to 3 μm,
The case where the thickness of the film is less than 0.5 μm, and the case 8) where the thickness of the DLC film exceeds 3 μm. Table 2 shows the results of the wiping test performed in the embodiment and the fluorine-based water-repellent film which is the most practical level in the prior art, that is, the film formed by applying a solvent solution containing a fluorine-based compound to the nozzle surface 18 and baking it. It is shown.

In Table 1, when the thickness of the DLC film is less than 0.5 μm (case (7)), it cannot withstand 50,000 wiping operations and its abrasion resistance is insufficient. This is presumably because the smaller the film thickness is, the more affected by the unevenness of the base. On the other hand, when the DLC film exceeds 3 μm [8]
In this case, the abrasion resistance is reduced and the film is easily peeled off. This is presumably because, as the film thickness increases, the internal stress remaining in the film increases, so that the film itself is easily broken and the adhesion strength decreases. The thickness of the DLC film is 0.
In the case of 5 to 3 μm, it has excellent characteristics satisfying all evaluation items.

As the fluorine-based water-repellent film in Table 2, a fluorine-based water-repellent film manufactured by Asahi Glass Co., Ltd., which is sold under the trade name CYTOP, was used. The thickness was 0.3 to 0.8 μm, and a 0.5 μm recording head having a fluorine-based water-repellent film was used for the wiping test. The thickness of the DLC film of the example used in this test is 2 μm. The conditions of the wiping test are as follows.

Material of the wiper: Polyurethane The amount of bite of the wiper into the nozzle surface: 0.5 mm Test temperature: 5 ° C., 23 ° C., 35 ° C. It is based on the general warranty that the life of the printer is 5 years or 50,000 A4 size prints. That is, the numerical value set as the wiping that is normally performed every five sheets is performed every one sheet is 50,000 times.

According to the results shown in Table 2, the DLC film withstands 50,000 wiping operations except at 5 ° C. It is presumed that the worse result at 5 ° C. is attributable to an increase in the abrasion force at a low temperature because the hardness of the wiper material increases as the temperature decreases. On the other hand, in the case of the fluorine-based water-repellent film, the upper limit is 20,000 wipings, indicating that the DLC film is clearly superior.

The nozzle surface 18 is coated with DL by RF plasma CVD.
When the C film 4a is formed, the inner surface of the ink nozzle 11
Although an LC film is formed, its penetration depth is about 10 μm and does not adversely affect the ink ejection characteristics. Rather, the ink repellency of the ink nozzle inner surface near the nozzle surface 18 stabilizes the ink meniscus. It is considered that the adhesion of the ink to the nozzle surface 18 is more completely prevented.

A DLC film and a Cytop film were formed on a glass substrate instead of the film formed on the nozzle surface 18 of the recording head, and the peeling resistance was evaluated by a grid test specified in Japanese Industrial Standards. However, in this test, it was confirmed that the DLC film was superior. Further, the ink ejection characteristics at room temperature were tested using a recording head with a DLC film and a recording head with a CYTOP film, and no difference was observed between the two under the same driving conditions.

In the above embodiment, a method using an RF plasma CVD apparatus was used as a method for forming the DLC film 4a, but similar results can be expected with a method using a DC plasma CVD apparatus. Also, the case of the edge shooter type recording head as shown in FIGS. 2 and 3 has been described. It will be clear that the present invention is not limited to the method using the plate 2. Further, in this embodiment, the case where the DLC film 4a is formed directly on the nozzle surface 18 has been described. However, the case where the DLC film is formed on a separately prepared nozzle plate and the nozzle plate is bonded to the nozzle surface 18 It will be apparent that the same effect can be exerted also in the case of.

[0026]

According to the present invention, there is provided an ink flow path comprising a nozzle or the like for discharging ink pressurized by the ink pressurizing means, and an ink-repellent film around the opening of the nozzle. In the ink jet recording head, the ink repellent film is made of diamond-like carbon. Diamond-like carbon as an ink-repellent film is
It has the required ink repellency, high adhesion strength to the nozzle surface, excellent slidability, and has chemical resistance not to be corroded by ink in addition to abrasion resistance to withstand wiping. A recording head provided with an ink-repellent film having an ink repellency that is difficult to perform, a sliding property that does not damage the wiping member, an abrasion resistance and a peeling resistance that withstands wiping, and a chemical resistance that is not corroded by the ink. It can be provided (the invention of claim 1).

In the first aspect of the present invention, the thickness of the diamond-like carbon is 0.5 μm to 3 μm. 0.5
Diamond-like carbon with a thickness of less than μm is easily peeled off by wiping under the influence of the irregularities of the base, and diamond-like carbon with a thickness of more than 3 μm is likely to have reduced abrasion resistance and to be easily peeled off due to internal stress remaining in the film. Therefore, diamond-like carbon having a thickness in the above range is most suitable as the ink-repellent film (the invention of claim 2).

In the first or second aspect of the present invention,
Diamond-like carbon is diamond-like carbon generated by a plasma CVD method. Plasma C
The diamond-like carbon produced by the VD method contains a large amount of hydrogenated carbon therein and has a self-lubricating property, and as a result, the coefficient of friction of the film is reduced. A film can be provided (the invention of claim 3).

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of an ink jet recording head according to the present invention.

FIG. 2 is a plan view showing a flow path of a flow path substrate of the inkjet recording head.

FIG. 3 is a cross-sectional view showing the structure of an example of a conventional ink jet recording head.

[Explanation of symbols]

 Reference Signs List 1 flow path substrate 10 ink flow path 11 ink nozzle 12 nozzle flow path 13 ink pressurization chamber 14 ink supply path 15 throttle flow path 16 ink reservoir 17 ink injection port 18 nozzle surface 2 vibration plate 3 piezoelectric element 31 adhesive layer 4 repellency Ink film 4a DLC film

Claims (3)

[Claims] An ink jet recording head having an ink flow path comprising a nozzle or the like for discharging ink pressurized by an ink pressurizing means and having an ink repellent film around an opening of the nozzle. An ink jet recording head, wherein the ink film is made of diamond-like carbon. 2. The diamond-like carbon having a thickness of 0.5
2. The ink jet recording head according to claim 1, wherein the thickness is from 3 μm to 3 μm. 3. Diamond-like carbon is plasma C
3. The ink jet recording head according to claim 1, wherein the ink jet recording head is a diamond-like carbon produced by a VD method.