JP3206615B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called on-demand type ink jet head for printing by discharging ink droplets from nozzles and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a conventional ink jet head, a common ink chamber and a groove-like ink flow path are formed on the upper surface of a flat flow path substrate. Are joined by an adhesive. The ink flow path includes an ink supply path communicating with the common ink chamber,
The pressure chamber includes a pressure chamber that communicates with the ink supply path, and a communication path that communicates the pressure chamber with the nozzle. A pressure means such as a piezoelectric element is provided on the outer surface of the flow path substrate cover so as to face the pressure chamber. Normally, the flow path substrate and the flow path substrate lid are made of the same material such as plastic or glass, so that the four wall surfaces of the flow path are made of the same material and all have the same elastic modulus. . Further, in order to generate a pressure by deforming one of the wall surfaces of the flow channel by the pressurizing means, a material having a small rigidity and a small deformation is used as a material of the flow channel.

[0003] As a method of manufacturing such an ink jet head, an adhesive is applied to the joint surface of the flow path substrate when the flow path substrate and the flow path substrate lid are joined together when the material is plastic. In this method, the flow path substrate lids are brought into contact with each other and pressed to join them together, or a solvent is applied to the joining surfaces to be melt-bonded (for example, Japanese Patent Publication No. 60-377).
No. 97).

However, in the method of applying an adhesive or a solvent, the adhesive or the like may flow into the ink flow path and adversely affect the performance, or may block the ink flow path.
Instead of using an adhesive or the like, the ink flow path is sealed by pressing and holding the flow path substrate and the flow path substrate lid using a screw or an elastic member, or joined by heat compression (for example, And JP-A-63-120659).

Further, when the material is glass, it is bonded by heat fusion (for example, Japanese Patent Application Laid-Open No. 62-8316).

[0006]

When the wall surface is a hard surface having the same elastic modulus as in the above-described ink jet head, the pressure wave generated in the flow path is reflected by the wall surface until the vibration is attenuated. It takes a long time, and therefore, the meniscus decay time on the nozzle surface becomes long, so that the response frequency of the head must be reduced, which causes a problem that the printing speed is reduced.

Also, in the method of sealing the ink flow path by pressing and holding without using an adhesive or a solvent, the smoothness of the joint surface between the two is required, and it is difficult to secure the sealing property of the ink flow path. is there. In order to obtain smoothness, glass or metal (stainless steel) is suitable for the flow path substrate. However, when glass is used, it is necessary to form an ink flow path by etching, and there is a problem that the number of steps is increased due to the etching, which leads to an increase in cost.

[0008] In order to facilitate the manufacture, it is desirable to use plastic, but in the case of heat compression,
Heating causes the whole to rise to a temperature higher than the melting temperature, thereby deforming the flat channel substrate. In addition, there is a problem that the characteristic change due to the temperature of the plastic is slow and large in variation.

[0009] It is an object of the present invention, Kotodea to provide an inkjet head capable of increasing early attenuation of the vibration of the ink in the ink flow path, a response frequency of the head
You.

[0010]

According to the present invention, there is provided a pressure chamber having one end communicating with a nozzle opening and the other end communicating with a common ink chamber via an ink supply port. Pressurizing means fixed to one wall surface of a pressurizing area of the pressurizing chamber, and pressurizing the ink by changing the volume of the pressurizing chamber, wherein the pressurizing means of the pressurizing chamber is fixed.
A layer having a lower rigidity than a wall surface forming the pressure chamber is formed on an inner surface of a wall surface of the pressure chamber other than the wall surface.

[0011]

[0012]

[0013]

[Function] Unnecessarily attenuating the pressing force by the pressurizing means.
And rigidity of the vibration wave of ink in the pressurized chamber after ink droplet ejection
Attenuate earlier with lower layers.

[0014]

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIGS. 1 and 2, the overall structure of an embodiment of the ink jet head of the present invention will be described. The flow path substrate 1 is a molded article made of polysulfone or the like which is strong against ink and is suitable for adhesion. A groove-shaped ink flow path 1b is engraved, and a nozzle 1a communicating with the ink flow path penetrates in the thickness direction. It has been drilled. As shown, the flow path substrate 1
Is provided on the front surface of the central portion of the nozzle, and the nozzles 1a are penetrated through the protrusion 1c by excimer laser processing or the like. An ink flow path 1b engraved on the back surface of the flow path substrate 1 and communicating with the nozzle 1a substantially orthogonally includes a plurality of pressure chambers 1d.
, And each pressurizing chamber 1d and each nozzle 1a
And ink supply paths 1f which communicate with the respective ink supply holes 2a to be described later.

Behind the flow path substrate 1, a first substrate 2 serving as a flow path substrate lid for sealing the ink flow path is laminated, and both are joined by a sheet adhesive 3. A plurality of ink supply holes 2a are formed in the first substrate 2 so as to penetrate in the thickness direction. The ink supply holes 2a are formed by excimer laser processing or the like, and are formed in the ink supply path 1f. It is open. The sheet-like adhesive 3 is, for example, a sheet-like adhesive obtained by impregnating a rubber-based substrate with an epoxy resin or the like. This sheet-like adhesive 3 has ink supply holes 2a in advance.
A hole 3a is formed corresponding to.

As described above, since the flow path substrate 1 and the first substrate 2 are joined by the sheet adhesive 3, the nozzle 1
FIG. 3 is an enlarged cross-sectional view of the ink flow path 1e in the vicinity of a. Among the four wall faces of the ink flow path 1e, three wall surfaces a, b, and c are made of poly- It is composed of sulfan, but the other wall d is a sheet-like adhesive 3
Therefore, one wall surface d is a wall surface having a different elastic modulus.

Behind the first substrate 2, a second substrate 4 is bonded by a sheet-like adhesive 5 similar to the above. On the front side of the second substrate 4, a large-area common ink chamber 4a is formed so as to be orthogonal to and communicate with the ink supply holes 2b. An opening 4b for supplying ink is provided at the center of the common ink chamber 4a, and a filter 6 is joined to the opening 4b by heat fusion, so that dust and the like in the ink can be removed from the common ink chamber 4a. To prevent intrusions. In the sheet-like adhesive 5, holes 5a are formed in advance corresponding to the ink supply holes 2b as described above.

On the front surface of the flow path substrate 1, a pressure means is provided at a position facing the pressure chamber 1d. That is, the pressurizing means is formed by laminating a plurality of vibrating plates 7 made of a metal such as phosphor bronze or brass and a plurality of piezoelectric elements 8. 1 Each piezoelectric element 8 is joined to a predetermined electrode of a flexible cable 9 on which a pattern electrode electrically connected to an external driver IC (not shown) for driving a piezoelectric element is formed by a conductive paste or the like. A common electrode (not shown) is formed on the front surface of the flow path substrate 1 by a conductive paste. The common electrode is electrically connected to the respective vibration plates 7 to which the respective piezoelectric elements 8 are joined, and a predetermined pattern of the flexible cable 9 is formed. The electrodes and the conductive paste are electrically connected.

An embodiment of the method for manufacturing an ink jet head according to the present invention will now be described. The sheet-like adhesive 3 is interposed between the flow path substrate 1 and the first substrate 2, and the two are joined by applying pressure and heating. The sheet adhesive 3 is obtained by impregnating a rubber base material with an epoxy adhesive.
A sheet having a thickness of 20 to 60 μm is used.

As an example, an aging treatment in which a sheet-like adhesive 3 having a thickness of 40 μm was held at 60 ° C. for 120 hours was performed. This suppresses the flow of the adhesive impregnated in the sheet adhesive 3.

The bonding surface of the first substrate 2 has a surface roughness of 5 μm.
m, and the aged sheet-like adhesive 3 is placed on this surface with the holes 3a and the ink supply holes 2a aligned with each other, and a pressure of 15 ± 1.5 kg / cm ² is applied. While heating to 150 ° C. As a result, the sheet adhesive 3 is in a semi-cured state, and is temporarily fixed to the first substrate 2.

The semi-cured sheet adhesive 3 is
The surfaces of the flow path substrate 1 on which the ink flow paths are formed are aligned and brought into contact with each other, and while applying a pressure of 15 ± 1.5 kg / cm ² ,
Heat to 50 ° C. As a result, the sheet adhesive 3 is in a completely cured state, and the flow path substrate 1 and the first substrate 2 are joined.

As shown in FIG. 2, when the flow path substrate 1 and the second substrate 4 are bonded to the upper and lower surfaces of the first substrate 2 with the sheet-like adhesives 3, 5, the above-described steps are performed. The sheet adhesives 3 and 5 are simultaneously subjected to an aging treatment, and the sheet adhesives 3 and 5 are temporarily fixed to both surfaces of the first substrate 2 in the above step, and the flow path substrate 1 and the second substrate 4 are May be joined at the same time.

The conditions for the aging treatment in the process and the conditions for the temporary fixing in the process include the thickness of the base material, the flowability of the resin used as the adhesive, the pressure, the heating temperature, and the surface roughness of the joint surface. Therefore, the condition is determined in consideration of all of these.

Before reaching the above conditions, the inventor carried out the aging treatment at 80 ° C. for 100 hours. In this case, the adhesive was excessively hardened, and the part which could not be temporarily fixed in the process was used. Has occurred.

Further, the present inventor performed the temporary fixing in the process by setting the pressure to 10 ± 1.5 kg / cm ² under the same other conditions. In this case, the bonding strength of the temporary fixing was used. Was not sufficiently obtained, and a portion where the sheet-like adhesive ran into the ink flow path was formed.

The sheet adhesive may be formed using an adhesive other than the epoxy resin.

When ink is ejected by the ink jet head of the present invention, when a driving signal from a driver IC is supplied to the piezoelectric element 8 through the flexible cable 9, the piezoelectric element 8 is deformed to The substrate 1 is bent toward the inside of the pressurizing chamber 1d, whereby the ink in the pressurizing chamber is pressurized to generate pressure. By this pressure, the ink passes through the communication path 1e and is ejected from the nozzle 1a. After the ejection, the voltage applied to the piezoelectric element 8 becomes 0, and the piezoelectric element 8 is bent outward by reaction and the pressure in the pressurizing chamber 1d becomes negative. By this negative pressure, ink is supplied from the common ink chamber 4a to the pressure chamber 1d through the ink supply hole 2a and the ink supply path 1f.

When the ink passes through the ink flow path due to the pressure applied to discharge the ink droplets , if all the wall surfaces of the flow path are formed of a uniform and highly rigid material as in the prior art, Since the pressure wave generated in the road continues to be reflected on the wall surface, it takes a long time for the vibration to attenuate. In contrast
The piezoelectric element 8 of the wall surfaces a, b, c, and d is fixed.
On at least one of the unwalled walls a, c, d,
A layer of the sheet-like adhesive 3, that is, a wall constituting the pressure chamber 1 d
If there is a layer having a lower rigidity than the surface, the layer of the adhesive 3
Without weakening the pressure when ejecting ink droplets.
Since the vibration of the ink after click ejection is absorbed, vibration early
Period . As a result , the next drive signal can be applied earlier and the printing speed can be improved.

[0031]

As described above, in the present invention,
One end is connected to the nozzle opening, and the other end is fixed to the wall of the pressurized area of the pressurized chamber, which communicates with the common ink chamber via the ink supply port. Pressurizing means for pressurizing, wherein the pressurizing means of the pressurizing chamber is fixed.
Since a layer having a lower rigidity than the wall constituting the pressurizing chamber is formed on the inner surface of the wall of the pressurizing chamber other than the wall of the pressurizing chamber, the pressure applied by the pressurizing means is not unnecessarily attenuated and the ink droplets are ejected. Vibration waves of the subsequent ink can be attenuated early by the layer having low rigidity, thereby enabling high-speed printing.

[0032]

[0033]

[0034]

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing one embodiment of an ink jet head of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

FIG. 3 is an enlarged sectional view showing an ink flow path near a nozzle in FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 flow path substrate 1d ink flow path (pressurized chamber) 1e ink flow path (communication path) 1f ink flow path (ink supply path) 2 flow path substrate lid (first substrate) 3 sheet adhesive a, b, c Wall surface of ink channel d Wall surface of ink channel with different elastic modulus

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Go Hayakawa 934-13 Shiwatari Yotsukaido-shi, Chiba Seikosha Co., Ltd. Chiba Works (56) References JP-A-5-8388 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055

Claims (3)

(57) [Claims] A pressurizing chamber having one end connected to a nozzle opening and the other end communicating with a common ink chamber via an ink supply port; varying the chamber volume and a pressurizing means for pressurizing the ink, before
An inkjet head in which a layer having a lower rigidity than a wall constituting the pressure chamber is formed on an inner surface of a wall surface of the pressure chamber other than a wall surface to which the pressure unit of the pressure chamber is fixed . 2. The ink jet head according to claim 1, wherein the layer is formed of an adhesive for joining members forming the pressure chamber. 3. The ink jet head according to claim 2, wherein the adhesive is a sheet in which a rubber base material is impregnated with an epoxy resin.