JP3242676B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
The present invention relates to an ink jet head for performing printing on paper or the like.

[0002]

2. Description of the Related Art Ink droplets fly from nozzle openings,
Ink jet recording for forming images and characters on paper is widely used because of its low noise, high speed, and high printing quality. In the ink jet head, the accumulation of the ink liquid around the nozzle opening disturbs the flying direction of the flying ink droplet, and changes the flying speed of the flying ink droplet. The accumulation of the ink liquid occurs and grows due to seepage of the ink liquid, residues of the flying ink droplets, and the like. Preventing the generation and growth of ink pools around the nozzle openings is necessary to ensure the quality of images and characters to be created. There have been many proposals for performing ink-repellent treatment around the nozzle openings in order to eliminate the accumulation of ink liquid around the nozzle openings. The ink-repellent treatment means that the ink-repellent film is hardly wetted, that is, an ink-repellent film is formed.

[0003] Fluororesins have excellent solvent resistance and are hardly wetted by many solutions. Therefore, when a fluorine resin film is used as the ink repellent treatment, a great effect can be obtained.

As a conventional method for forming a fluororesin film, there is a method of applying a fluororesin dispersed in a solution to a base material, drying the solvent, and then forming a film of the fluororesin by melting. As a coating method at this time, transfer, dipping, spin coating, roll coating, brush coating, spraying and the like are used. As other conventional methods for forming a fluororesin film, a method by thermal evaporation of a fluororesin, which is disclosed in JP-A-2-55140, or a method of depositing a fluororesin during plating, followed by heat treatment. There is a method of forming a resin film. Such a conventional method is such that fluororesin particles are once adhered onto a base material, and then connected by heat treatment to obtain a stronger and more ink-repellent film than before heat treatment. It is. Therefore, the heat treatment heats to a temperature higher than the melting point of the fluororesin.

[0005]

According to the above-described heat treatment, crystal growth occurs in the fluororesin. Fluororesin becomes crystals with a dendritic appearance, and the length of the branches is
If it is long, it can reach tens to tens of microns. At this time, as the crystal grows, it absorbs the surrounding fluorine resin. For this reason, with the growth of the dendritic crystals, the density of the film quality increases, and the unevenness of the surface increases.

It is important that the ink-repellent treatment to be applied to the nozzle forming member has a property that it is hard to be wet with the ink liquid, and that the property must last for a long time. First, even when exposed to the ink liquid for a long time,
It is required to maintain the property that the ink liquid is not easily wetted. In addition, the nozzle forming member is close to the recording paper, and there is adhesion of dust generated due to the conveyance of the recording paper. The nozzle forming member performs a cleaning operation to remove the attached dust, but it must endure this. The cleaning operation refers to a series of operations for mechanically cleaning the surface of the nozzle forming member with a rubber plate, a cloth material, a brush, or the like.

[0007] Since the film formed by the above-described conventional technique has unevenness in the film density, the ink liquid is allowed to enter the rough portion, and the ink liquid corrodes the nozzle forming member. Also, the adhesion of the ink liquid component to the nozzle forming member grows, which causes the ink repellency to deteriorate. Furthermore, during the cleaning operation, the grown dendritic crystals are shaved off, and in extreme cases, the large crystals are peeled off from the nozzle forming member. Therefore,
The problem that the ink-repellent film made of a film in which the dendritic crystals of the fluororesin have grown greatly has poor initial ink repellency, long-term ink liquid resistance, or poor durability against mechanical abrasion. Having.

An object of the present invention is to provide an ink-repellent treatment of a fluororesin applied around the nozzle opening of an ink jet head.
An object of the present invention is to improve the reliability of an ink jet head by improving the ink liquid resistance and the cleaning operation resistance.

[0009]

Means for Solving the Problems To achieve such a problem
In the present invention in order, a nozzle member having a plurality of nozzle openings, a pressure generator disposed in correspondence with the nozzle opening, by actuating the pressure generator, the nozzle opening in the inkjet head of ejecting ink droplets from the nozzle openings to increase the ink pressure between parts and the pressure transducer, the periphery of at least the nozzle openings, the composite plating layer of fluorine resin and metal are formed The composite plating layer has a melting point or higher.
The heated, that is subsequently cooled in a 100 degrees / minute or more is to branch <br/> length 5 microns or less dendrite formation.

[0010]

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

The nozzle forming member 1 having the nozzle opening 1a is connected to a pressure generator corresponding to the nozzle opening 1a by a spacer 5. The pressure generator includes the laminated piezoelectric transducer 2, the pressure plate 3 and the elastic plate 4. The piezoelectric transducer 2 is made of, for example, lead zirconate titanate-based composite perovskite ceramic material, silver, or
Conductive materials such as silver-palladium alloy and platinum are alternately laminated. In the driving method, displacement is generated by giving a constant potential difference to the conductive material layers sandwiching the ceramic material of each layer. Each conductive material layer has an end face 2
d or exposed at the end face 2c, and routed to the side face so as not to be short-circuited by the external electrode 2e. The piezoelectric transducer 2 includes a fixed portion 2b which is an inactive portion that does not contribute to pressure generation.
And a free portion 2a which is an active portion that changes in volume with application of a voltage. The piezoelectric transducer 2 is fixed on the common electrode 6c of the fixed substrate 6 with a conductive adhesive. The reason why the conductive adhesive is used is to fix the piezoelectric transducer 2 and to provide two functions for taking out the individual electrodes.

The electrode facing the individual electrode is the end face 2
d, and are electrically connected by a common electrode plate 8 as a common electrode. Free part 2a of piezoelectric transducer 2
A pressure plate 3 is fixed to an end of the plate with an adhesive. Further, the pressure plate 3 is joined to the elastic plate 4. In the present embodiment, a plurality of nozzle openings 1a are provided,
Are also arranged to correspond to this. The space between the nozzle opening 1a and the elastic plate 4 is filled with an ink liquid (not shown).

The piezoelectric transducer 2 to which a voltage is applied in the standby state is in a contracted state compared to the free length. When a print command is issued by an external electric circuit, the applied voltage is released and the piezoelectric transducer 2 returns to the free length. This operation causes the pressure plate 3 to vibrate, raises the ink liquid pressure through the elastic plate 4, and causes the droplet to fly from the nozzle opening 1a. The ink-repellent processing performed on the nozzle forming member in the present embodiment will be described. FIG. 2 shows a conceptual diagram of various film qualities of an ink-repellent film made of dendritic crystal fluororesin. The nozzle forming member is manufactured by nickel electroforming.

FIG. 2 shows a state in which a composite plating in which a fluororesin is dispersed in a growing plating film and on the film surface is formed by a nickel plating solution in which a fine powder of a fluororesin is dispersed by a dispersant. In this embodiment, Nimflon (made by Uemura Kogyo), which is electroless fluororesin composite nickel plating, was used as the composite plating. Since the fluororesin used in Nimflon is PTFE (ethylene tetrafluoride resin), the heat treatment after the formation of the plating film was performed at 350 ° C., which exceeds its melting point of 327 ° C. After heat treatment,
By adjusting the cooling conditions, the branch length level of the dendritic crystals of the fluororesin film was set. The cooling condition specifically refers to a cooling rate.

FIG. 3A shows a PTFE film formed by extremely slow cooling at a cooling rate of 1 degree / minute. According to the result of measurement by an electron microscope, the branch length of the dendritic crystal has grown to an average of 10 μm or more.

FIG. 3 (b) is formed under cooling conditions of 100 ° C./min. The branch length of the dendritic crystal is 5 μm or less.

FIG. 3 (c) is formed by rapid cooling at 5000 ° C./min. The branch length of the dendritic crystal is 2 μm or less. The sample of the nozzle forming member having the crystal length varied as described above was immersed in an ink liquid and subjected to a corrosion resistance test. Table 1 shows the results.

[0018]

[Table 1]

The ink liquid used for the evaluation will be described. The ink liquid in the present embodiment is a so-called hot melt ink which is solid at room temperature and used as an ink liquid in a heated and melted state. The composition of the ink liquid mainly contains paratoluenesulfonamide, ethylbenzenesulfonamide, 3,4-diethylbenzenesulfonamide, para-N-butylbenzenesulfonamide, N-cyclohexyl-paratoluenesulfonamide, and a dye. The evaluation temperatures are all 150 ° C.

From Table 1, it is apparent that there is a relationship between the branch length of the dendritic crystal and the ink resistance, and the shorter the branch length of the dendritic crystal, the longer the life.

Next, the cleaning operation resistance was tested. In this embodiment, wiping with a rubber plate is employed as the cleaning operation. The cleaning conditions will be described. Using a rubber plate having a hardness of 40 degrees made of silicone rubber and a plate thickness of 2 mm, the pressure of the rubber plate against the nozzle forming member was adjusted to 10 grams per centimeter by a testing device in which the nozzle forming member was adjusted. Repeated wiping was performed, and the contact angle with the above-described ink liquid was measured.
Table 2 shows the results. The contact angle is used as a guide because it is an index of the degree of difficulty in wetting with the ink liquid. Both the wiping and the contact angle measurement are performed at a nozzle forming member temperature of 130 degrees.

[0022]

[Table 2]

As shown in Table 2, the branch length of the dendritic crystal is 1
In the case of exceeding 0 micron, the contact angle sharply decreases while the number of rubbing is relatively small. Such a decrease in the contact angle increases the probability of occurrence of ink accumulation around the nozzle opening. That is, there is little decrease in the contact angle,
This shows that the durability is inferior to that of an ink-repellent film having a dendritic crystal with a branch length of 5 μm or less or 2 μm or less.

As described above, one embodiment of the ink jet head of the present invention employs a hot-melt ink using a coating of PTFE resin composite nickel electroless plating.
Although a description has been given of the case where a piezoelectric transducer is used as the pressure generator, the present invention is not limited to this. A solution application in which a fluororesin is dispersed may be used as a coating method. A similar effect can be obtained with a fluorine resin other than PTFE, such as FEP. Further, the ink liquid may have a composition containing water or another solvent and a dye or pigment as main components. Further, the present invention can be easily applied to a so-called thermal inkjet type ink jet head in which a heat generating element is used as a pressure generator and ink droplets fly by the pressure of ink liquid vapor generated by heat generation.

[0025]

According to the ink jet head of the present invention, a nozzle forming member having a plurality of nozzle openings, a pressure generator arranged corresponding to the nozzle openings, and the pressure generator are operated to operate the nozzle. In an ink jet head that raises the ink pressure between the nozzle opening and the pressure transducer and causes ink droplets to fly from the nozzle opening, at least the periphery of the nozzle opening is covered with a composite plating of fluororesin and metal, Since dendritic crystals having a branch length of 5 μm or less are formed, the dendritic crystals are uniformly dispersed during the composite plating. Therefore, there is no variation in the ink repellency of the ink repellent film, and at the same time, the cleaning by the wiper is performed. Even if the dendrites are scraped off, the dendrites have a small unit volume, so the dendrites in the composite plating can be maintained in a dispersed state for a long time. That. Therefore, the ink-repellent film has an effect of maintaining uniform ink-repellency for a long period of time and providing a highly reliable ink-jet head without bending of ink droplets.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ink jet head of the present invention.

FIG. 2 is a diagram illustrating an ink-repellent film made of a fluororesin in a dendritic crystal state.

FIG. 3 is a diagram showing a change in length of a resinous crystal when a cooling rate is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle forming member 1a Ink-repellent film 2 Piezoelectric transducer 3 Pressure plate 4 Elastic plate 5 Spacer 6 Fixed substrate 7 FPC 8 Common electrode 101 Nozzle forming member 101a Nozzle opening 102 Fluororesin

Continuation of the front page (56) References JP-A-1-280566 (JP, A) JP-A-2-301429 (JP, A) JP-A-2-30540 (JP, A) JP-A-2-153744 (JP) , A)

Claims (2)

(57) [Claims] 1. A nozzle forming member having a plurality of nozzle openings, a pressure generator arranged corresponding to the nozzle openings, and operating the pressure generator to form the nozzle openings and the nozzle openings. In an ink jet head for increasing the ink pressure between the pressure converter and the ink droplets to fly from the nozzle openings, a composite plating layer of a fluororesin and metal is formed at least on the periphery of the nozzle openings , The composite plating
The layer is heated above its melting point and then
Cooled by Branch lengths of 5 microns or less dendrite Louis ink Jefferies bract heads are formed above. Wherein said dendrites branch length is 2 microns or less der Louis ink GETS bract head.