JPH06297711A - Ink jet head - Google Patents

Abstract

PURPOSE:To provide an ink jet head corresponding to the increase of a printing speed, the enhancement of printing quality or yield and density and a multinozzle system and excellent in operation efficiency, response, printing quality and durability. CONSTITUTION:In an ink jet head wherein ink passages are formed from a photosensitive resin member, a supply passage 2d wherein an ink flow direction coincides with the thickness direction of the photosensitive resin member is arranged at the position where each pressure chamber 2a arranged corresponding to a pressure generator 30 communicates with a reservoir 2b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an inkjet recording device such as a printer that forms an ink image on a recording medium such as recording paper, and more specifically, to an inkjet head.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 11, an on-demand type ink jet head includes a plurality of nozzles 21 having a constant opening diameter, a plurality of pressure chambers 2a communicating with each of the nozzles 21 and a pressure generator for applying a pressure. 30 and a plurality of supply paths 2d that connect the pressure chamber 2a and the reservoir 2b.

Conventionally, as a method of producing such an ink jet, a method of forming a flow path by adhering plates after forming fine grooves by cutting or etching on a plate of glass or metal, Kosho 62-59672
As disclosed in Japanese Patent Publication No. 4-166066 and Japanese Patent Publication No. 4-16066, there is known a method of forming a flow path by laminating a photosensitive resin having grooves.

[0004]

However, in the structure of the conventional ink jet head, the accuracy of the supply path is not improved, and more specifically, the flow path resistance value that most affects the ink ejection characteristics of the ink jet head is varied, and the heads and the nozzles vary. The amount of ink and the speed vary, resulting in a decrease in printing speed and a decrease in printing quality and yield.

The on-demand type ink jet head is
Since the ink droplets are ejected only when necessary, it is necessary to eject the ink droplets having a constant weight and a constant speed in both continuous ejection and intermittent ejection. As a result of detailed observation and analysis of the conventional ink droplet ejection characteristics, the present inventor has found that the following three states mainly occur. Therefore, the shape of the ink droplet will be described with reference to the drawings, focusing on the state of the meniscus. In FIG. 8A, the nozzles 21 are sufficiently filled with the ink 110, and the meniscus 111 held by the surface tension of the ink 110 in the nozzle openings 10 is in a static neutral position. From this state, it was found that when ink droplets are ejected by pressure propagation from the pressure generator, the ink droplets fly out and become round ink droplets 120a as shown in FIG. 8B. Figure 9
The meniscus 111 in (a) is largely drawn in by the vibration after ink ejection. When the ink droplets are ejected in this state, the ink droplets become the ink columns 120b as shown in FIG. 9B, and the speed is faster and the weight is smaller than that of the round ink droplets 120a. It was Further, as shown in FIG. 10A, when the meniscus 111 is ejected from a state in which the meniscus 111 is largely raised due to vibration,
As shown in FIG. 10B, the ink droplet has a node such as 120c, and is sometimes torn to become two droplets, and sometimes excessive ink is ejected, so that the ink is not supplied to the next ejection. It was found that the next ink droplet became small in time, or in the worst case, ink could not be supplied and air bubbles were drawn in, resulting in missing dots. From these, it was found that the position of the meniscus should be kept as constant as possible in order to eject ink droplets of constant weight and speed.

Next, the behavior of the meniscus will be described. The meniscus is centered around a static position

[0007]

[Equation 1]

A vibration represented by Where A and φ
Is an arbitrary constant determined by initial conditions, and ω is obtained from the compliance of the meniscus and the flow path, the resistance R of the flow path, and the inertance M. k is called a damping constant and is represented by k = R / M (2). In FIG. 11, the supply path 2d generally controls the resistance R and the inertance M of the flow path. In FIG. 11, the supply passage 2d has a rectangular cross section, but since it is complicated, a circular pipe passage will be described. R and M are R = 8πηL / S ² (3) M = Lρ / S (4) η: viscosity coefficient of ink L: flow path length S: flow path area
ρ: It is represented by the specific gravity of the ink. Therefore, the attenuation constant k is k = 8πη / (ρS) (5).

In order to eject ink droplets having a constant weight and speed, in order to keep the meniscus position X as constant as possible, it is necessary to make the constant A smaller and k larger than the above equation (1). As the ejection efficiency is improved, that is, the ink flow rate flowing through the nozzle 21 is larger than that of the supply passage 2d, the energy applied to the pressure generator 30 is reduced and A is reduced. Since the discharge efficiency is determined by the flow path resistance ratio between the nozzle 21 and the supply path 2d, it is effective to increase the resistance R of the supply path 2d.
Therefore, in order to keep the meniscus position X as constant as possible, it is necessary to increase the constants R and k.
The flow passage area S is dominant in both R and k according to the above-described equations (3) and (5). Therefore, it was found that the flow path area S is the most important parameter in order to keep the meniscus position X as constant as possible.

From the above, the deterioration of the flow path area accuracy results in the deterioration of the characteristics, that is, the responsiveness, the variation of the ink amount and the speed between the heads and the nozzles, and the decrease of the printing speed, the deterioration of the printing quality and the yield. I found out that

In the structure of the conventional ink jet head, since the channels having the grooves are bonded to each other, the structure shown in FIG.
As described above, the ink flow direction of the supply path 2d is parallel to the plane of the flow path substrate, and the depth varies depending on time when etching glass or the like, and when the photosensitive resin is used, the substrates are joined to each other. Since the flow path is crushed at the time of laminating or laminating, the supply path area and the above S are remarkably changed. for that reason,
As described above, there are problems of responsiveness, printing speed, printing quality and yield.

Therefore, the present invention solves such a problem, and its purpose is to cope with a high density and a high number of nozzles, enable high-accuracy simple assembly, and have a high operating efficiency. Another object of the present invention is to provide an inkjet head having high responsiveness, high print quality and excellent durability.

[0013]

An ink jet head in which a pressure generating substrate provided with a pressure generating body and a plurality of photosensitive resins are laminated, and an ink flow path is formed by the pressure generating substrate and the photosensitive resin member, A supply path in which the ink flow direction and the thickness direction of the photosensitive resin member coincide with each other is provided at a position where each pressure chamber arranged corresponding to the pressure generator communicates with the reservoir.

[0014]

In general, a photosensitive resin is used as a resist for fine processing of semiconductor elements and the like. Since it is a medium for fixing a fine pattern on a wafer, the precision in the plane direction is very good, and processing in the submicron order is also possible. Compared with this, in the thickness direction, if it is a dry film type, the thickness variation of the material is several μm, even for liquid materials there is a thickness variation of several μm when masking or squeegeeing. Several μm is possible.

Therefore, according to the above-described structure and manufacturing method of the present invention, the area accuracy of the supply path is improved, and the flow path resistance value, which has the greatest influence on the ink ejection characteristics of the ink jet head, approaches the ideal value as close as possible. Therefore, it is possible to improve the ink ejection characteristics, that is, improve the responsiveness, and reduce the variation in the ink amount and speed between the heads and nozzles, which improves the printing speed, the printing quality and the yield.
In addition to high density and multi-nozzle, high precision and easy assembly are possible.
It is possible to provide an inkjet head having high responsiveness, high print quality, and excellent durability.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the ink jet head of the present invention. In the figure, reference numeral 3 is a pressure generating substrate provided with a pressure generating body 30, and as the pressure generating body 30, a heating element or a piezoelectric element is generally used. When a heating element is used as the pressure generator 30, pressure is generated by heating the ink in the vicinity, and when a piezoelectric element is used, the pressure is generated by mechanical vibration of this element. A signal input electrode (not shown) is connected to the pressure generator 30. The flow path substrate 2 forming the ink flow path is formed by laminating photosensitive resin to form a groove, and is sandwiched between the pressure generating substrate 3 and the nozzle plate 1 having a plurality of nozzles 21 to form a space serving as a flow path. . Nozzles 21 corresponding to the flow paths are formed in the nozzle plate 1, and ink droplets are ejected from the nozzle openings 10 by the pressure generated by the pressure generator 30 described above. A pressure chamber 2a is formed in the flow path substrate 2 corresponding to the pressure generator 30 described above, and the reservoir 2b has a size in which the flow path resistance is sufficiently small in order to sufficiently supply the ink to all the pressure chambers 2a. Has been formed. Pressure chamber 2
a and the nozzle 21 are connected to the pressure chamber 2a by the nozzle communication passage 2c.
The reservoir 2b and the reservoir 2b are communicated with each other by a supply path 2d. Furthermore, the ink flow direction of the supply path 2d and the thickness direction of the photosensitive resin member are the same, and the supply path 2d controls the flow path resistance of all flow paths.

With the conventional structure shown in FIG. 11, the supply path 2d is formed.
Has a depth variation of about ± 5 μm, and since the supply path 2d is generally formed with a depth of about 30 μm and a width of about 40 μm, the flow path resistance value varies about ± 40%. On the other hand, in the structure as shown in FIG. 1 of the present embodiment, when the supply path 2d has a rectangular cross section of 10 μm, the width has a deviation of about ± 0.5 μm, but the flow path resistance value is about ± 20%. The variations were as follows. As a result, the response was improved by about 20%, the print quality was improved, and the yield was also improved by about 20%.

2A and 2B show the second embodiment of the present invention. As shown in FIG. 2A, by forming the step on the pressure chamber 2a side into a step 40, even if the ink has a large contact angle and a large surface tension, and the wettability is poor, the stagnation point becomes small, so that the stagnation of bubbles is reduced. However, dot dropouts are reduced and reliability is further improved. Although the stepped step 40 is not provided on the reservoir 2b side, providing the stepped step 40 on the reservoir 2b side is also effective. In order to manufacture the supply path 2d having such a step-like step as described above, FIG.
As described above, the dry film photoresist 60 and the dry film photoresist 62 are stacked to form different patterns.

FIG. 3 shows a third embodiment of the present invention. In the case where air bubbles are poorly discharged due to the physical properties of the ink and it is necessary to further reduce the stagnation point, it is possible to eliminate the step between the reservoir 2b and the pressure chamber 2a as shown in FIG. Also, at this time, taking into account the pattern deviation, etc.
Even if a step of about m is provided, there is almost no effect on the bubbles.

FIG. 4 shows a fourth embodiment of the present invention. Fourth
In the embodiment, the supply path 2d has a circular shape. In the supply path 2d having a circular cross section as shown in FIG. 4, even if the exposure conditions, the thickness of the photosensitive resin, the cross-sectional dimensions of the supply path 2d, the development conditions and the like are changed, the defective development is unlikely to remain and the shape is stable. Could be formed.

The manufacturing methods of Examples 1 to 4 described above will be described below. FIG. 5 shows a manufacturing process of the flow path forming layer on the side of the nozzle plate 1. The inner surface of the nozzle plate 1 shown in FIG. The dry film photoresist 51 is laminated while applying heat or pressure.
Since the dry film photoresist 51 does not have fluidity but has adhesiveness, it can be easily adhered to the nozzle plate 1 even if some external force is applied (FIG. 5B).

Next, a pattern for positioning (not shown) formed on the nozzle plate 1 or the nozzle 21.
Then, the photomask M1 is positioned on the photomask M1 so as to be aligned with. As shown in FIG. 1, the photomask M1 has a nozzle communication path 2c which communicates with the nozzle 21 and a pattern of a region for forming the reservoir 2b which are previously formed as opaque portions a and b.

Therefore, as shown in FIG. 5C, an amount of light insufficient for causing a curing reaction, for example, light energy of about 90 mJ / cm 2 is applied from above the photomask M1 to the dry film photoresist. When the parallel light 51 is irradiated onto the surface of the dry film photoresist 51 that hits the opaque portions a and b, the nozzle communication path 2c portion communicating with the nozzle 21 and the reservoir 2b become the unexposed portion 51A, and the other transparent portion c, that is, These peripheral portions become a semi-cured portion 51B which is in an intermediate state of the curing reaction, that is, which is insoluble in the solvent but has adhesiveness. Next, the unexposed portions 51A are removed from these dry film photoresists 51 using a solvent such as trichloroethane (FIG. 5 (d)).

On the other hand, the flow path forming layer provided on the pressure generating substrate 3 side is formed by the process shown in FIG. At this time, when a heat generating element is used as the pressure generator 30, before the dry film photoresist is laminated, the heat generating element is provided on the inner surface of the substrate, that is, the flow path molding surface at the portion corresponding to the pressure chamber, and the signal input electrode is provided. Is also provided. When a piezoelectric element is used as the pressure generator 30, it is provided after the flow path substrate is completed.

First, a dry film photoresist 5 of the same type as the dry film photoresist 51 provided on the nozzle plate 1 is formed on the inner surface of the pressure generating substrate 3, that is, the flow path forming surface.
5 is laminated (FIG. 6A). And FIG. 6 (b)
As shown in FIG. 5, a photomask M5 having opaque parts f and g formed on the pressure chamber 2a and the reservoir 2b is formed on the photomask M5.
Position and irradiate with light of an amount such that the dry film photoresist is semi-cured, for example, light energy of about 90 mJ / cm2, the pressure chamber 2a and the reservoir 2b become the unexposed portion 55A and other transparent portions. The h, that is, the peripheral portion thereof, becomes the semi-cured portion 55B. Then, the dry film photoresist 55 on the unexposed portion 55A is removed by a solvent to form a flow path forming layer as shown in FIG. 6C.

Subsequently, a dry film photoresist 53 for forming the supply path 2d is laminated, and the dry film photoresist 53 may be laminated on either the nozzle plate side or the substrate side provided with the pressure generator 30. It is possible to obtain a similar structure.

A dry film photoresist 53 is laminated on the nozzle plate side (FIG. 7 (a)).
As shown in (b), a photomask M3 provided with opaque portions k and n is located at the portion where the nozzle communication passage 2c and the supply passage 2d are formed, and the amount of light is such that the dry film photoresist is semi-cured. For example, when light energy of about 90 mJ / cm 2 is applied, the nozzle communication passage 2c and the supply passage 2d become the unexposed portion 53A, and other transparent portions m, that is, the peripheral portions thereof become semi-cured portions 53B. Then, the dry film photoresist 53 on the unexposed portion 53A is removed by a solvent to form a flow path forming layer as shown in FIG. 7C.

When the flow path forming layer on the side of the nozzle plate 1 and the flow path forming layer on the side of the pressure generating substrate 3 which have been molded through the above-mentioned respective steps are pressure-heat bonded, they are thermally polymerized and as shown in FIG. Both can be integrally bonded to each other to provide ink resistance.

If a positive photosensitive resin is used, the dry film photoresist 51 and the dry film photoresist 53 for forming the supply path 2d can be developed at the same time. When the dry film photoresist 53 for forming the supply path 2d is laminated on the pressure generating substrate 3 side, the dry film photoresist 53,
55 can be developed at the same time.

The above construction is merely an example, and even if a liquid photosensitive resin is used, the same effect can be obtained with the same structure.

Regarding the perforating step having such a structure, a laser beam processing which is usually used is also effective in addition to the above-described manufacturing method by development.

[0033]

As described above, in the ink jet head of the present invention, the area accuracy of the supply path is improved, that is, the flow path resistance value, which has the greatest influence on the ink ejection characteristics of the ink jet head, approaches the ideal value as close as possible. Therefore, the ink ejection characteristics are improved, that is, the response is improved, and the variation in ink amount and speed between heads and nozzles is reduced, which improves printing speed, improves printing quality and yield, and increases density and In addition to supporting nozzles,
It is possible to provide an inkjet head which is highly accurate and can be easily assembled, and which has high operation efficiency, high responsiveness, high printing quality, and excellent durability.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an inkjet head of the present invention.

FIG. 2 is an explanatory view showing an example in which a step-like step is provided in a supply path.

FIG. 3 is an explanatory view showing an embodiment in which the step of the supply path is eliminated.

FIG. 4 is an explanatory view showing an embodiment in which the supply passage has a circular cross-sectional shape.

FIG. 5 is an explanatory view showing a forming process of the flow path forming layer on the nozzle plate side.

FIG. 6 is an explanatory view showing a forming process of the flow path forming layer on the pressure generating substrate side.

FIG. 7 is an explanatory view showing a molding process of a photosensitive resin layer for forming a supply path.

FIG. 8 is an explanatory diagram of an ink droplet shape when ejecting from a state where the meniscus is at a static neutral position.

FIG. 9 is an explanatory diagram of an ink droplet shape when ejecting from a state where a meniscus is greatly drawn.

FIG. 10 is an explanatory diagram of an ink droplet shape when ejecting from a state where a meniscus is largely raised.

FIG. 11 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

1 ... Nozzle plate 2 ... Flow path substrate 2a ... Pressure chamber 2b ... Reservoir 2c ... Nozzle communication path 2d ... Supply path 3 ... Pressure generation Substrate 10 ··· Nozzle opening 21 ··· Nozzle 30 ··· Pressure generator 40 ··· Step-like steps 51, 53, 55, 60, 61 ··· Dry film photoresist 51A , 53A, 55A ... Uncured dry film photoresist 51B, 53B, 55B ... Semi-cured dry film photoresist M1, M3, M5 ... Photomask a, b, f, g, k, n ... Opaque portion c, h, m ... Transparent portion 110 ... Ink 111 ... Meniscus 120a ... Round ink droplet 120b ... Ink column 120c ...・Ink droplets with a

Claims (1)

[Claims] 1. An ink jet head in which a pressure generating substrate having a pressure generating body and a plurality of photosensitive resins are laminated, and an ink flow path is formed by the pressure generating substrate and the photosensitive resin member. An ink jet head, characterized in that a supply path in which an ink flow direction and a thickness direction of the photosensitive resin member coincide with each other is provided at a position where each pressure chamber arranged correspondingly communicates with a reservoir.