JP3149890B2 - 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 recording head of an on-demand type ink jet printer which forms an ink image on a recording medium such as recording paper by discharging ink droplets in response to a print signal.

[0002]

2. Description of the Related Art There are roughly three types of recording heads of so-called on-demand type ink jet printers which fly ink droplets in response to a print signal. The first type is a so-called bubble jet type in which a heater for instantaneously evaporating ink is provided at the tip of a nozzle, and ink droplets are generated and fly by the expansion pressure at the time of ink vaporization. In the second type, a part of a container forming an ink chamber is constituted by a discharge energy generating element which is deformed by applying a voltage, and the ink is discharged by the pressure in the container caused by the deformation of the discharge energy generating element. It is intended to fly as drops. And the third type is
A discharge energy generating element is provided in an ink chamber provided with a nozzle, and the ink pressure in the ink chamber is changed by expansion and contraction of the discharge energy generating element, so that the ink flies from the nozzle as droplets. These types of on-demand type inkjet heads are known in which an ink chamber wall is formed in one layer and in which two or more layers are formed.

The former case has an advantage that the number of parts is reduced, the number of assembling steps is reduced, and the device can be manufactured at low cost. As the material, an ink-resistant metal, resin, glass or film is used. As a processing method, press, photoetching, injection molding, electroforming, and exposure forming are generally used. However, as shown in FIGS. 6 and 7, in the case of a press, the processing limit is up to W: T = 1: 1.
When W: T = 1: 2, processing becomes difficult anymore. Here, W is the width of the ink chamber wall, and T indicates the depth of the ink chamber. L indicates the width of the ink chamber. Also, in photo etching, the processing limit is up to L: T = 1: 1, and when L: T = 1: 2, processing becomes similarly difficult. In the case of molding, if W is too small, the resin does not turn, and molding is difficult. In the case of electroforming, W: T
= 1: 1 is the limit, and the thickness T
Is also subject to restrictions. From the above, when the ink chambers are arranged in a high-density array, for example, when the pitch is 1/180 inch, the shape and the processing method are also restricted. If the pitch is 1/180 inch, L is about 100 microns, W
May be on the order of 40 microns and T may be on the order of 50 to 150 microns. In such a case, it is necessary to appropriately select the material, the processing method, and the processing size, and this has been a major obstacle to high density.

[0004] On the other hand, in the latter case, that is, by making the ink chamber wall two or more layers, the above-mentioned restriction is greatly relaxed.
There is an advantage that the depth of the ink chamber and the shape of the wall of the ink chamber can be relatively freely set. In addition, if the ink chamber wall is formed of two or more layers of photosensitive resin or the like, fusion and lamination can be performed, so that it is not necessary to use an adhesive for joining the ink chamber formed as a single layer and other components adjacent thereto. In addition, it is possible to eliminate the risk of adverse effects on the ejection characteristics, such as the protrusion of the adhesive at the joining portion and the resulting mixing or clogging of the ink.

However, when the ink chamber wall is formed of two or more layers, one of the ink chamber wall layers and the other layer are positioned at the time of bonding in any of the bonding, bonding and brazing methods. Method and accuracy are important. That is, as shown in FIG. 7, when joining the two layers of ink chamber walls, misalignment is likely to occur, which reduces the cross-sectional area of the joining surface and reduces the rigidity of the ink chamber walls. There was a problem.

[0006]

SUMMARY OF THE INVENTION The miniaturization of the recording head,
As the density is increased, the pitch between adjacent ink chambers becomes smaller. Therefore, the ejection energy generating element and the ink chamber become smaller, and the width of the ink chamber and the width of the ink chamber wall are further restricted. Therefore, the importance of a processing method for creating a required shape is increased. However, as described above, general processing methods for creating the ink chamber wall include pressing, photoetching, molding, and electroforming, but in any case, the depth and width of the ink chamber are limited due to restrictions on processing limits. It is difficult to set the required size. As a solution to such a problem, a member forming the ink chamber wall has a structure of two or more layers. However, as described above, there is a problem of positioning and accuracy, and it is not satisfactory. Was. Therefore, an object of the present invention is to realize a head having a simple configuration that does not require high precision for positioning between ink chamber walls formed of two or more layers and does not cause a reduction in rigidity of the ink chamber walls due to misalignment. It is in.

[0007]

In the ink jet head of the present invention, one of the ink chamber walls is formed on the first substrate side, and the other of the ink chamber walls is formed on the opposing second substrate on the side of the ejection energy generating element. In the ink jet head in which the two are joined, the width of the ink chamber wall formed on the first substrate side and the width of the ink chamber wall formed on the second substrate side are made different, and a step is provided on the ink chamber wall. It is characterized by. Further, the width of the ink chamber wall on the second substrate side is smaller than the width of the ink chamber wall on the first substrate side.

[0008]

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention, in which parts are disassembled after assembly. FIG.
3 and 4 are partial cross-sectional views illustrating the same embodiment in more detail.
FIG. 2 is a partial cross-sectional view of the embodiment cut in the AA direction in FIG. FIG. 5 shows another embodiment.

In these figures, reference numeral 1 denotes a first substrate. A plurality of nozzles 2 are provided on the first substrate 1. 3
Denotes an ink chamber forming substrate on the first substrate side, and 6 denotes an ink chamber forming substrate on the elastic member side described later. The ink chamber forming substrates 3 and 6 include a first substrate 1 and an elastic member 11 serving as an elastic wall.
(Corresponding to the second substrate) and the reservoir 4,
7 and ink chambers 5 and 8 are formed. The elastic member 11 has a laminated structure including the metal sheet 9 and the insulating member 10. The ink chamber forming substrate 3 is formed by exposing a photosensitive resin film to the first substrate 1 and then exposing the same. The ink chamber forming substrate 6 is also formed by laminating the elastic member 11 and exposing the same. . After that, the ink chamber forming substrate 3 laminated on the first substrate 1 and the ink chamber forming substrate 6 laminated on the elastic member 11 are tightly joined by fusion, and then tightly joined on the head frame 14.

The ejection energy generating element 22 serving as a driving source for ejecting ink droplets has one half surface in the longitudinal direction fixed to a fixed base 21 and the other end not fixed to the elastic member 11. The fixed base 21 is provided with a conductive wiring pattern 24 of a positive electrode and a negative electrode, and applies an electric field controlled by the control board 13 to the discharge energy generating element 22 via a lead frame 25. 11 is a head frame. Reference numeral 12 denotes a mounting hole which penetrates through the inside of the head frame 14, and supports a fixed base 21 for positioning the ejection energy generating element 22 in the X and Y directions (see XYZ coordinates in FIG. 1). Note that the Z direction of the ejection energy generating element 22 is
After the elastic member 11 is joined to the head frame 14, the tip of the discharge energy generating element 22 is positioned in contact with the elastic member 11.

Reference numeral 31 denotes an ink supply pipe for supplying ink 51 from an ink reservoir (not shown). Ink supply pipe 31
Are press-fitted to the head frame 14. The ink flow path passes through the ink connection port 32 in the head frame 14 and the ink communication port 33 in the elastic member 11, and the reservoirs 4 and 7 of the ink chamber forming substrates 3 and 6, and the ink chambers 5 and 8.
Is in communication with The above is the schematic configuration.

The structure will be described in more detail with reference to FIG. In the ejection energy generating element 22, the positive electrode 41 and the negative electrode 42 face each other. The positive electrode 41 is electrically connected to the wiring pattern 24 on the fixed base 21, particularly to the positive electrode conductive pattern at the same time as the bonding. The negative electrode 42 is electrically connected to the wiring pattern 24 on the fixed base 21, particularly to the negative electrode conductive pattern, by the common plate 23. The wiring pattern 24 and the control board 15 are connected by a lead frame 25, and the connection portions are fixed with solder. The fixing plate 21 is bonded and fixed to the head frame 14 in a state where the ejection energy generating element 22 is in contact with the insulating member 10 of the elastic member 11.

On the other hand, the ink chambers 5 and 8 and the reservoirs 4 and 7 which are filled with the ink 51 are provided with the ink chamber forming substrates 3 and 6 respectively.
And the first substrate 1 and the elastic member 11. In the conventional case, the ink chamber forming substrates 3 and 6 can be formed by etching of glass, lamination of thin metal plates, exposure forming of photosensitive resin, injection molding of resin, and the like. Therefore, instead of etching and injection molding of resin, which are restricted in processing, exposure forming of photosensitive resin is used.
FIGS. 3 and 4 are diagrams in which FIG. 1 is cut along the AA section so that the ink chamber wall appears. As shown in FIG.
The ink chamber wall width W1 on the ink chamber forming substrate 3 side and the ink chamber wall width W2 on the ink chamber forming substrate 6 side are different. Also,
The thickness of the ink chamber wall on the side of the ink chamber forming substrate 3 is T1,
Assuming that the thickness of the ink chamber wall on the side of the ink chamber forming substrate 6 is T2, T1 and T2 are different in thickness and have a step. This is to absorb a positional shift generated when the ink chamber wall on the ink chamber forming substrate 3 side and the ink chamber wall on the ink chamber forming substrate 6 side are joined in the assembling process, and as shown in FIG. Is generated, the cross-sectional area of the joint surface between the ink chamber wall on the ink chamber forming substrate 3 side and the ink chamber wall on the ink chamber forming substrate 6 side is ensured. Therefore, the rigidity of the ink chamber wall does not decrease, and the rigidity of the ink chamber wall initially targeted is secured. In order to do so, the dimensional difference between the ink chamber wall width W1 on the ink chamber forming substrate 3 side and the ink chamber wall width W2 on the ink chamber forming substrate 6 side is equal to or less than twice the positional deviation due to assembly. It needs to be big. Also, changing the thickness T1 of the ink chamber wall on the ink chamber forming substrate 3 side and the thickness T2 of the ink chamber wall on the ink chamber forming substrate 6 side in accordance with W1 and W2 improves the effect of securing rigidity. , More effective. That is, W
This is because as 1 / T1 and W2 / T2 increase, the rigidity further increases. If rigidity is not ensured, there are the following adverse effects. In order for the ink droplet to be ejected from the nozzle 2, the ejection energy generating element 22 needs to be displaced in the Z direction.
At this time, depending on the behavior of the ejection energy generating element 22, the internal pressure of the ink chamber changes, or changes to a negative pressure. At this time, a force acts on the ink chamber wall to expand or contract the volume of the ink chamber. If the ink chamber wall rigidity is insufficient, the ink chamber wall itself vibrates and interferes with changes in the internal pressure of the adjacent ink chamber. This hinders stable ejection of ink droplets and adversely affects print quality. Therefore, securing the rigidity of the ink chamber wall leads to stable ejection of ink droplets.

By the way, as shown in FIG. 3, as an additional effect, the dimension B can be increased, which means that the length of the flexure of the elastic plate 9 increases, and as a result, the shear stress applied to the elastic plate is reduced. It will be. If the thickness per sheet is sufficiently thin, the ink chamber wall can be formed by laminating thin metal plates.

On the other hand, FIG. 5 is a view showing another embodiment, in which the ink chamber wall has three layers, and the shape thereof has a small width at the center. By doing so, the contact area with each component adjacent above and below the ink chamber wall is increased, and accordingly,
There is an advantage that the bonding strength increases and the bonding is stable. Also, by creating a portion where the width of the central portion of the ink chamber wall is reduced, there is an advantage that even if the ink dries, it can be supplied by capillary action. In any case, by forming the ink chamber wall with two or more layers, the shape of the ink chamber wall can be formed more freely, which is a great advantage for more stable ejection of ink droplets.

On the other hand, the first substrate 1 covering the upper surface of the ink chamber forming substrate 3 is formed by a plurality of ink chambers 5,
8 each with one nozzle 2 opened, 0.1mm
Made of stainless steel. The elastic member 11 covering the lower surface of the ink chamber forming substrate 6 has a laminated structure in which a photosensitive resin is coated as an insulating member 10 on a thin metal plate 9 formed to a thickness of 5 μm or less by nickel electroforming. Eggplant
The thin metal plate 9 is preferably thinner in order to efficiently transmit the expansion and contraction of the ejection energy generating element 22 to the ink chambers 5 and 8, but has such a thickness that the ink 51 in the ink chambers 5 and 8 does not exude.

In the ink droplet discharging operation, in FIG. 2, an electric field is applied to the positive electrode 41 and the negative electrode 42 of the discharging energy generating element 22 from the control board 15 through the lead frame 25 and the wiring pattern 24 in accordance with the print signal. The ejection energy generating element 22 to which the electric field is applied tends to contract in the longitudinal direction (vertical direction in the figure). At this time, the lower half of the ejection energy generating element 22 is fixed to the fixed base 21 held by the head frame 14 and cannot be contracted and displaced. On the other hand, the upper half of the ejection energy generating element 22
The elastic member 11 is contracted and displaced without receiving other constraints.
Pull. The metal sheet 9 of the elastic member 11 pulled by the ejection energy generating element 22 bends downward, and as a result, the volumes of the ink chambers 5 and 8 expand. When the ink chambers 5 and 8 expand, the ink 51 flows from the reservoirs 4 and 7 through the ink supply port 3a. Next, when the electric field of the discharge energy generating element 22 is released, the discharge energy generating element 22 is released.
Expands to the original length and compresses the ink chambers 5, 8. An ink droplet is ejected from the nozzle 2 at this pressure. The above is the ink droplet ejection operation.

As described above, as the density of the ink chambers increases, the ratio of the depth of the ink chamber to the width of the wall of the ink chamber increases. This not only makes it difficult to form the ink chamber walls, but also makes it difficult to ensure rigidity. However, as described above, the ink chamber wall is composed of two or more layers,
In addition, by providing a step on the wall of the ink chamber, it is possible to easily form the ink chamber, and it is possible to absorb a positional shift due to assembly. In addition, the rigidity of the ink chamber wall can be ensured.

[0019]

As described above, in the ink chamber wall composed of two or more layers, by providing a step between the width of the ink chamber wall on the first substrate side and the width of the ink chamber wall on the second substrate side, the following steps can be performed. There is an effect like

1. It is possible to prevent a decrease in rigidity of the ink chamber wall caused by a positional shift caused by joining of the ink chamber walls.

2. The shape of the ink chamber wall can be created more freely. Therefore, it is possible to set the shape and size of the ink chamber that stabilizes the ejection characteristics.

3. High density arrangement of the ink chambers becomes possible.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of one embodiment of the present invention.

FIG. 2 is a partial sectional view of the embodiment.

FIG. 3 is a partial sectional view of the embodiment.

FIG. 4 is a partial step view of the embodiment.

FIG. 5 is a partial cross-sectional view of another embodiment of the present invention.

FIG. 6 is a partial cross-sectional view illustrating a problem of a conventional example.

FIG. 7 is a partial cross-sectional view illustrating a problem of a conventional example.

FIG. 8 is a partial cross-sectional view for explaining a problem of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 3, 6 Ink chamber formation board 5, 8 Ink chamber 2 Nozzle 4, 7 Reservoir 9 Metal thin plate 10 Insulation part 11 Elastic member 14 Head frame 21 Fixed plate 22, 101 Discharge energy generation element 23 Common plate 24 Wiring pattern 25 Lead frame 31 Ink supply pipe 32 Ink connection port 33 Ink connection port 51 Ink 102, 103, 104, 105, 106 Ink chamber wall 110 Second substrate

Continuation of front page (56) References JP-A-2-299854 (JP, A) JP-A-5-50602 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2 / 045 B41J 2/055

Claims (2)

(57) [Claims] 1. An ink jet apparatus comprising: one of ink chamber walls formed on a first substrate side; and another ink chamber wall formed on a second substrate on a side of an ejection energy generating element facing the first substrate, and the two are joined together. An ink jet head, wherein a width of an ink chamber wall formed on a first substrate side is made different from a width of an ink chamber wall formed on a second substrate side, and a step is provided on the ink chamber wall. 2. The ink jet head according to claim 1, wherein the width of the ink chamber wall on the second substrate side is smaller than the width of the ink chamber wall on the first substrate side.