JPS5812765A - Ink jet head - Google Patents

Abstract

PURPOSE:To obtain an ink jet head consisting of lesser numbers of easily processable parts from a synthetic resin base with integrally molded head and tank and a flexible film closely bonded with the opening of the tank. CONSTITUTION:A pressure chamber 2 and supply chambers 4 and 5 are formed on the surface of an ink-proof plastic base plate 1 molded by injection molding method, and also a supply tube 6 through which ink is supplied from outside is formed. A conductive film is formed on the surface of a vibration plate made of a vibration plate made of the same material as the base plate 1 and a piezo- electric element 8 for electrode is attached to the surface of the vibration plate 7. The vibration plate 7, the base plate 1, and the piezo-electric element 8 are assembled by bonding them by a solvent or a dope cement or melting the surface of the base plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inkjet printing apparatus, and particularly to a method of manufacturing an inexpensive inkjet head.

Among inkjet printing, ink-on-demand printing is attracting attention because its head has a simple configuration and multiple nozzles can be easily obtained.

Various proposals have been made for head manufacturing methods, some of which have been put into practical use. However, all of them had drawbacks such as high manufacturing costs and poor durability of the head. For example, U.S. Pat. No. 4,189,734 describes making an inkjet head from a photosensitive glass ceramic, such as Corning's Photoceram. In general, photosensitive glass tends to be very expensive because it is difficult to control temperature during the manufacturing process. Furthermore, since the photosensitive glass becomes opaque upon completion, it is difficult to inspect whether the head substrate and diaphragm are completely bonded.

Swedish Patent No. 564,585 (U.S. Pat. No. 398)
8745), it is stated that the respective substrates are stacked one on top of the other and the connection is tightened with several screws. In this case, the board can be made by molding plastic or the like.

In this way, the board itself can be manufactured at low cost, and the cost of screwing it together is not that high. However, in order to completely seal the flow paths of the pressurized chamber, nozzle, etc., it is necessary to make each substrate extremely flat. In general, molded plastic does not fit this [1]. In particular, in a multi-nozzle head in which a large number of nozzles are integrated, many nozzles must be fixed using a small number of common screws, and it is difficult to completely seal all flow paths. In addition, since the pressing force between the substrates is weak in the flow path away from the fixing screw, there is a risk that the adjacent flow path may be short-circuited as the piezoelectric element deforms.

In order to eliminate these drawbacks, it is conceivable to bond the substrates forming the flow channels with an adhesive. However, the adhesive often flows into the nozzle, which has a small cross-sectional area, and seals the nozzle. Further, the adhesive applied to the channel wall peels off from the channel wall after a certain period of time due to the influence of the ink, blocking the nozzle.

Another head manufacturing method has been put into practical use, in which the tip of a tubular glass is made thinner to form a nozzle, and a tubular piezoelectric element is placed over the glass to form a head. However, this method requires a very high production cost of the piezoelectric element. !
, the high density integration of a large number of nozzles reduces the
If il L <, the cost also increases as the number of nozzles increases.

As mentioned above, the heads that have been conventionally designed or put into practical use are very sophisticated, but they have the disadvantage of being unreliable if they are to be made at low cost.

Therefore, an object of the present invention is to reduce head manufacturing costs.

Another object of the invention is to obtain a reliable head.

The present invention will be explained below with reference to Examples.

FIG. 1 is a perspective view showing an inkjet head according to an embodiment of the present invention. 1 is an injection-molded plastic substrate having corrosion resistance against ink, and a pressure chamber 2.
Nozzle 3. Supply route 4. A supply path 5 is formed, and a supply pipe 6 for supplying ink from the outside is formed. 7 is board 1
The diaphragm is made of the same material and has a conductive film formed on its surface. 8
is a piezoelectric element with electrodes formed on its surface. 9゜1
0 is a positioning hole and a mounting groove for attaching the inkjet head to the main body.

In the above configuration, the diaphragm 7, the substrate 1, and the piezoelectric element 8 are bonded together using a solvent or doped cement. A solvent or dope cement that has a lower viscosity can be used than the epoxy-based adhesives that are generally used for assembling inkjet heads.

Therefore, it is possible to coat the surface of the substrate 1 or the diaphragm 7 very thinly, to a thickness of several microns at most. Therefore, the nozzle is less likely to be sealed with adhesive during adhesion. Also, after coating the surface of the substrate 1 and the diaphragm 7 with a solvent "!" or dope cement, leave it for a while to evaporate some of the solvent and then apply pressure bonding to prevent the sealing of the nozzle from forming. .

The solvent has softened the thin layer on the surface of the diaphragm 7 by one inch of the substrate, so if the substrate 1 and the diaphragm 7 are stacked and pressurized from both sides, the material substrate 1 can be removed without sealing the nozzle. ′! , or the surface of the diaphragm 7 may have some unevenness. Therefore, each channel is completely sealed.

Furthermore, if annealing is performed after adhesion and the solvent is completely evaporated, there is only 5-methylene of the same substance as the substrate on the flow channel wall, which causes peeling and nozzle clogging due to the influence of ink, just like adhesive. That's not the case. Since the substrate, the diaphragm, and the adhesive layer are made of the same material, the VC melts evenly and the substrate and the diaphragm do not separate.

In addition, as a specific example, the substrate and the diaphragm are made of polysulfon or ABS, and trichlorethylene,
If melt bonding is performed using methylene chloride or the like, reliable bonding without sealing the nozzle is possible.

Methyl ethyl ketone (
Methyl ethyl ketone), Methyl isobutyl ketone
etone) etc. can also be used. Further, polymethyl methacrylate 14 can also be bonded to polycarbonate using ethylene dichloride (Ethyl θn θclichloride θ). The polysulfone mentioned above, AB
If a transparent grade is selected from among S, polymethyl methacrylate, and polycarbonate, there is an advantage that the condition of the bonded part can be visually confirmed from the outside after bonding, and inspection can be easily performed. You can also check the condition of the ink inside, and check for clogging and air bubbles = 6.
- It is easy to take measures against problems such as contamination.

Transparent plastics include polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polystyrene, acrylonitrile-styrene [1
Polymers, ethylene vinyl acetate copolymers, etc. can also be used.

In the case of polysal 7on, A B fE, polyether sulfon, etc., if the surface is scratched, it will not be possible to check the condition of the ink inside, but it will prevent ink evaporation, gas intrusion, etc. The effect will be higher. tiHighly heat resistant polysulfon, polyethersulfon,
For polycarbonate, dry plating using vapor deposition or sputtering can increase the effectiveness of preventing ink evaporation and gas intrusion.

By fusing the substrate made of the above-mentioned thermoplastic resin with relatively low crystallinity with an organic bath agent suitable for the substrate, a complete seal can be achieved without sealing the nozzle.

In particular, Polysal 7-on and AB'S have stable solvent adhesion, and have excellent corrosion resistance against alkaline inks.1Especially, in order to improve quick drying during recording, strong alkalis with a pH of about 12.5 are used to protect against tar inks. You can use it without any problem. Plating also protects against ink evaporation, etc.
F can do it. In addition, if transparent grade is used, it has many advantages such as easy inspection of bonded parts, making it the most suitable synthetic resin for inkjet heads.

In the embodiment shown in FIG. 1, an example was described in which the surfaces of the substrates were melted and fused using a solvent. Next, an example in which a thermoplastic resin is fused by heat will be described.

The ABS board and diaphragm are placed in a jig and pressurized to bring the temperature near the thermal deformation temperature. By appropriately selecting the pressure and temperature, it is possible to fusion-seal only the necessary portions without substantially deforming the substrate. According to this method, since no solvent flows into the nozzle, adhesion without sealing the nozzle is possible. However, the flatness of the substrate is required;
If the temperature and pressure are not carefully controlled, there will be problems such as incomplete adhesion, or the substrate will be severely deformed and the nozzle will be crushed. Further, there is a problem in that a considerable period of time is required for pressurization.

It is also conceivable to adhere the substrates by ultrasonic fusion as a type of thermal fusion. In this case, in addition to the above-mentioned amorphous plastic (Amorphous Re5in), acetal s nylon (Nylo
n) *Crystalline plastics (Cry-stallinθRθθin) such as polyester (Polyθθter) and polypropylene (Polypropylene)
can also be used. However, although ultrasonic fusion can be applied to nozzles with a large cross-sectional area, there is a problem in that nozzles with a small cross-sectional area are often sealed.

As can be seen from the above examples, according to the present invention, since the surface of the substrate is melted and bonded, the adhesive may peel off during use.
It does not cause any nozzle pressure. Also, the sealing is done perfectly.

In addition, as can be seen in the embodiment shown in Fig. 1, the nozzle 3, supply path 4, supply path 5, etc. are integrally formed on the substrate 1, so parts processing is easy, and the number of parts is small, making it easy to handle delicate parts during assembly. Positioning is uncomfortable.

In the embodiment shown in FIG. 1, the number of nozzles is one. Further, an example in which there are two supply paths 4 and 5 is shown. These head shapes do not limit the present invention, and the present invention can be applied to a head as shown in FIG. 2, for example. As in the example of FIG. 1, a plurality of supply channels 5, pressurizing chambers 2, and nozzles 3 are each arranged. When many nozzles are arranged in this way, it is inevitable that the pressure chamber 2
The distance from the nozzle 3 to the nozzle 3 becomes longer, and the flow path resistance increases.

Therefore, it becomes difficult to eject ink. To prevent this, if the nozzle 3 has a depth of, for example, 50μ, it is effective to make the pressure chamber 2, flow path 11, etc. deep to about 200μ. In this way, plastic injection molding is very suitable for increasing the characteristics of the head by varying the depth of the flow path depending on the location. Although it is possible to change the depth of the flow path by etching the photosensitive glass described above, the manufacturing process increases and the cost increases. Plastic injection molding can improve properties without increasing costs. Furthermore, the supply section 12 that receives ink supply from the tank can be simultaneously molded by injection molding.

FIG. 3 shows another embodiment to which the present invention is applied.

Figure 3 shows that the flow channels shown in Figure 2 are formed on both sides of the substrate.
A cross section of a head with nozzles X2=24 nozzles is shown. (
a) When the thickness of the diaphragm 7 is thin as shown in the figure, a portion of the ink 12 accumulates on the front surface of the head as ink 12' during printing. Due to this influence, the ejected ink droplet 13 bends inward and flies. Since the flying direction of the ink droplets 13 changes depending on the degree of wetting, the print quality is not very good. Loss 11fj
The thickness of the shield 7 has an optimum value depending on the piezoelectric element, etc., and cannot be made too thick. Therefore, if (1)) the front side of the head is made thick like the diaphragm 7' as shown in the figure,
Regardless of the degree of wetting, the state of the ink 12' near the nozzle 3 forms a surface perpendicular to the nozzle 3, and the ink droplet 13 flies in the direction of the nozzle 3 without blood dripping. In addition, as shown in (c), a groove 1' is provided in the substrate 1 so that the ink 12' is connected to the nozzle 3.
If the front surface of the head is wetted symmetrically around the center, the ink droplets 13 will fly without being bent. In this way, by taking advantage of the advantages of plastic injection molding, the shapes of the substrate and diaphragm can be made into special shapes to improve characteristics without increasing costs.

FIG. 4 shows how the inkjet head of the present invention is attached to a printer.

The inkjet head described in the embodiment of Fig. 21,
22 is a tube made of vinyl chloride, 25 is an ink tank made of vinylidene chloride, or a type of polyethylene, 24 is ink, 25 is rubber, 26 is a flexible circuit board, 27
is a diaphragm electrode, 25 is a piezoelectric element electrode, 29 is a set screw,
3o is a paper feed roller, 31 is a recording paper, 32 is a carriage,
33 is a guide shaft.

In the above configuration, the carriage 32 reciprocates along the guide shaft 33 perpendicular to the paper plane of FIG. 4 by means (not shown). Paper feed roller 3 synchronizes with the reciprocating motion.
o, the recording paper 31 is fed one dot at a time. A control circuit (not shown) sends an injection signal suitable for the position of the carriage to the piezoelectric element electrode 2 via the flexible substrate 26.
8. Ink is applied to the diaphragm electrode 27 and ink is ejected to record on the recording paper 31Vc. In this way, by the movement of the carriage 32- and the paper feed roller 30, printing is performed using ink droplets like a TV scanning line.

When the ink in the ink tank 23 is used up due to ink consumption, the set screw 29 is loosened and the head 21 is replaced with a new one along with the inflator 23 and tube 22. According to this method, air is not mixed into the ink due to the connection between the ink tank and the head, and even if the nozzle becomes clogged due to ink coagulation, it can be easily replaced. Of course, instead of using a set screw, other methods such as fixing with a spring can also be considered.

FIG. 5 shows an embodiment of a print head that is a further development of the present invention.

It consists of a substrate 51, a head section 52 in which a pressurizing chamber 2, a nozzle 3, and a supply channel 5 are molded, and a tank section 53 that stores ink, and is integrally molded by injection molding. Reference numeral 54 denotes a porous plastic ring filter, which is placed on the substrate 51 as shown in the figure. 55 is an ink bag made of vacuum-formed synthetic resin film, which is a laminated film of saponified ethylene-vinyl acetate copolymer and polyethylene to prevent evaporation and gas intrusion into the ink bag 16-. A filter 54 is placed between the substrates 51, and a plate 56 is bonded with a solvent. Further, the ink bag 55 is placed in the tank portion 53 and the surrounding area is sealed by heat sealing. Furthermore, the piezoelectric element 8 is bonded to the bottom surface of the head portion 52. In this example, a piezoelectric element 8 is attached to the substrate 51 to serve as a lively plate. Further, the piezoelectric element 8 is common to each pressurizing chamber 2, and the electrode 57 is divided so as to correspond to each pressurizing chamber. Ink injection hole 58
After injecting the tank into the tank portion 53, the injection hole 58 is sealed by bath melting with heat.

6 and 5 schematically show how the head shown in FIG. 5 is attached to a printing device. A notch 61 provided in the tank portion 53 engages with a protrusion 63 provided in the carriage 62, thereby fixing the head and the tank.

At this time, the electrode 57 and a common electrode (not shown) are crimped onto the connection electrode 64 provided on the carriage 62 to establish an electrical connection. The carriage was moved along axis 33 in the same manner as shown in FIG. 4, and printing was performed. As shown in FIG. 4, since there are four nozzles, the movement stroke of the carriage is only about the same as in the example of FIG.

Furthermore, since the tank portion 53 is a rigid body, it is easy to handle when attaching the head and tank to the carriage. Also, in the event that the nozzle hits your eye or air is generated within the head, you can recover by pressing the ink bag 55 with your finger. Further, if the shape of the ink bag 55 is made to bulge outward so that negative pressure is generated within the ink bag as ink is consumed, ink can be prevented from flowing out from the nozzle in any position.

In the practical example shown in FIGS. 5 and 6, the head and ink tank are integrally made by pultrusion molding, so that an inkjet printing device with a small number of parts, high reliability, and easy handling can be obtained.

In the embodiment shown in FIG. 5, the pressurizing chamber 2, nozzle 3, etc. are connected to the substrate 51
Although these channels are molded toward the plate 56, they may also be molded toward the plate 56. Further, the filter 54 may be made by injection molding at the same time as the nozzle etc. instead of being a separate part. As the film for the one-length ink bag 55, vinylidene chloride, aluminum vapor-deposited film, aluminum foil laminated film, etc. can also be used. However, it is difficult to completely prevent air from entering the tank. Therefore, if the filter 54 is made of polyvinyl formal, etc., which has good wettability with ink,
It also has the effect of an air trap, and even if air enters the tank, it can prevent air from entering the head. Furthermore, if the filter 54' is lengthened and allowed to drip into the tank section 53 as shown in FIG. 7, even if air 71 fills the vicinity of the supply section of the head, ink can be replenished by the capillary force of the filter 54'.

Note that an epoxy adhesive can be used to bond the piezoelectric element and the diaphragm, or the piezoelectric element can be heated and embedded into the diaphragm by taking advantage of the fact that it is a synthetic resin.

Further, the conductive film on the diaphragm can be formed by plating, vapor deposition, sputtering, or the like. It is also possible to adhere metal foil. It is also conceivable to solder conductive wires 61 and 82 to both sides of the piezoelectric element 8 and adhere them to the imaging plate 7, as shown in FIG. 8, to form a conductive film on the diaphragm.

As described above, according to the present invention, synthetic resin substrates are fused without using adhesives, so there is no nozzle sealing, and a complete seal can be achieved even if the surface of the injection-molded substrate is rough. Ru. Also, the number of parts is very small and the cost can be reduced. In particular, if transparent plastic is used, the bonded portion can be easily confirmed and the number of inspection steps can be reduced. Since the manufacturing cost of the head is reduced in this way, the head can be replaced at the same time as the ink tank. Secondly, there is no problem such as air getting mixed into the ink, which is the case when only the ink tank is replaced, and the reliability can be improved.

Although the above example shows an inkjet head manufactured by injection molding, it is also possible to manufacture it by a method such as surface pressing.

In the above embodiment, the same synthetic resin is used for the diaphragm and the substrate 11, but resins with extremely high compatibility such as ABB resin and A8 resin can be used for the substrate and the diaphragm 17-. -! Since the elastic modulus of synthetic resins is generally low, there is little deflection in the direction perpendicular to the plane due to radial displacement of the piezoelectric element. To improve this, it may be possible to use a material with a high elastic modulus, such as glass, for the diaphragm (and substrate). It is also conceivable to use a polymer piezoelectric material to serve as both a diaphragm and a piezoelectric element.

As stated above, according to the present invention, the pressurizing chamber, nozzle, supply path, supply pipe, etc. are all integrally molded by pultrusion molding, thereby reducing the number of parts, and problems such as rust caused by ink on metal heads. It does not occur and assembly is easy. Furthermore, if the ink tank and head are replaced at the same time when the ink tank runs out of ink or the head malfunctions, reliable printing can be achieved without air getting mixed into the ink when the tank and head are connected. I can do it.

Note that the present invention can also be applied to inkjet heads other than the ink-on-demand type.

It has many advantages as mentioned above, and many applications such as various printers, blocks, facsimile machines, copying machines, etc. can be considered.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the invention, Fig. 2 is a plan view showing another embodiment of the invention, and Fig. 3 shows a cross-sectional shape near the nozzle of the embodiment shown in Fig. 2. 4 is a side view showing how the head shown in FIG. 1 is attached to the printer, FIG. 5 is a view showing still another embodiment of the present invention, and FIG. A side sectional view showing the installation of the
FIG. 7 is a diagram showing an embodiment of the present invention, and FIG. 8 is a diagram showing an example of electrode arrangement L11f of a piezoelectric element in the present invention. 1... Substrate 2... Pressure chamber 6... Nozzle 5.
... Supply path 12 ... Ink 21 ... Head 2
5... Ink tank 52... Head section 56...
・Tank part 55... Ink bag 64... Connection electrode
54...filter Figure 3 Figure 6 7/ Figure 7) Figure 8

Claims (1)

[Claims] In a winkjet printing device that records liquid ink from a nozzle onto a recording medium, a synthetic resin base body is formed by integrally molding a head part and a tank part, and the opening of the tank part is covered. An inkjet head comprising an adhesively bonded flexible film.