JPH0422700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inkjet head, and more particularly to an inkjet head for generating recording ink droplets used in so-called inkjet recording systems.

[Prior Art] An inkjet head applied to an inkjet recording system generally includes a fine ejection opening (orifice), an ink passage, and an ink ejection pressure generating section provided in a part of the ink passage.

One way to create such an inkjet head is, for example, by cutting or etching a glass or metal plate to form fine grooves, and then joining the plate with these grooves to another suitable plate. A known method is to form an ink passage within a head.

However, the head obtained by the above method has a problem in that the straightness of the ejected ink droplets is often impaired. This is particularly due to the fact that the ejection openings (orifices) of the heads are made of different materials, resulting in differences in ink leakage around the periphery of the orifices.

In addition to this, if ink is ejected for a long time or vibration is applied to the head, the ink that leaks from the orifice may adhere to a part of the area around the orifice, and the ink pool may coalesce. Since the created and ejected ink droplets are pulled in that direction, the straightness of the ink droplets is impaired.

Conventionally, in order to eliminate such problems, an orifice plate was created by etching a metal plate or a photosensitive glass plate to form an orifice, and this was attached to the head body to create an inkjet head. It is proposed that.

However, in this method, the orifice is formed by etching, so the orifice obtained may be distorted due to the difference in etching rate, and the shape of the orifice may vary, making it difficult to create an orifice plate with good dimensional accuracy. It was difficult to do so.

Further, when forming the discharge port using an orifice plate using a metal plate, it is necessary to apply a resist material to the metal surface and remove the resist material after etching in order to form the desired discharge port by etching.

When etching metal plates or photosensitive glass, a strong acid etching solution is used, which sometimes poses health and safety problems.

In the case of photosensitive glass, it was necessary to pay close attention to cracking and chipping of the material during handling operations.

Therefore, the conventional orifice plate includes inefficient elements in its manufacturing operation, and many problems remain to be solved in terms of mass productivity and yield efficiency.

Furthermore, in inkjet heads manufactured using this method, the adhesive used to attach the orifice plate to the head body often flows into the extremely fine orifices and ink passages and blocks them. There are also some inconveniences.

SUMMARY OF THE INVENTION The main object of the present invention is to provide an inkjet head that overcomes the above-mentioned problems of the prior art and has additional features.

That is, the first object of the present invention is to provide an ink jet head that guarantees the straightness of ejected ink droplets over a long period of time.

Another object of the present invention is to provide an inkjet head that is precise and highly reliable. Another object of the present invention is to provide an ink jet head in which the ink passage including the orifice is finely machined with high precision and faithful to the design.

It is another object of the present invention to provide a multi-orifice type ink jet head that can be manufactured with a high yield by a simple method and has excellent durability in use.

[Means for Solving the Problems] The ink jet head of the present invention, which has achieved the above objects, includes a head body having an ink passage, and an orifice communicating with the ink passage for ejecting ink. and an orifice plate having an orifice plate joined to the head main body, wherein the orifice plate has a pattern of non-transmissive portions in the orifice portion for light and a peripheral edge of the orifice. By irradiating the surface of the photosensitive resin material with light through a mask having a pattern that combines a transparent part and a non-transparent part in the area excluding the area, a cured area and an uncured area are formed in the surface area. It is characterized in that it is formed by forming a roughened area of the surface portion excluding the periphery of the orifice by dissolving and removing the uncured area.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

FIGS. 1 to 5 are schematic diagrams for explaining the structure of the ink jet head of the present invention and the manufacturing procedure thereof.

First, as shown in FIG. 1, a desired number of ink ejection pressure generating elements (ejection energy generating elements) 2 such as heating elements or piezoelectric elements are placed on a suitable substrate 1 made of glass, ceramics, plastic, metal, etc. (Two in the figure) are provided, and the head main body 4 is created by joining this substrate 1 to another plate 3 in which grooves for ink passages are formed. Incidentally, in the figure, 5-1, 5-
2 are ink ejection ports (orifices) in the head body 4. Note that when a heating element is used as the ink ejection pressure generating element 2, this element generates ink ejection pressure by heating ink in the vicinity. Further, when a piezoelectric element is used, ink ejection pressure is generated by mechanical vibration of this element. And these elements 2
Although not shown, a signal input electrode is connected thereto.

Since the structure of the head body 4 is not directly related to the gist of the present invention, other detailed explanations thereof will be omitted.

Next, as shown in FIG. 2, after cleaning and drying the orifice side end surface of the head body 4,
At this time, the orifice side end surface may be roughened. ) Dry film photoresist 6 (film thickness, approximately 25μ~) heated to about 80℃~105℃ is applied to this end face.
100μ) at a speed of 0.5 to 0.4 f/min and a pressure of 1 to 3 Kg/cm ³ . At this time, the dry film photoresist 6 is partially fused and fixed to the head body 4, and will not peel off from the head body 4 even if considerable external pressure is applied thereafter.

Next, as shown in the schematic cross-sectional view of FIG. 3, a photomask 7 having master patterns 7a and 7b corresponding to the orifice of a desired shape is superimposed on the dry film photoresist 6 fixed to the orifice side end surface of the head body 4. After that, exposure is performed from the upper part of this mask 7, as shown in the schematic cross-sectional view of FIG. Note that since the patterns 7a and 7b do not transmit light, the areas of the dry film photoresist 6 covered by these patterns 7a and 7b are not exposed. At this time, the mask patterns 7a and 7b respectively correspond to the orifice 5 of the head body 4.
-1 and 5-2, accurate alignment is performed using a well-known method. Furthermore, the area of the dry film photoresist 6 covered by the mesh pattern 7c is not completely masked and is therefore slightly exposed. In addition, the patterns 10a and 10b on the periphery of the patterns 7a and 7b corresponding to the orifices are arranged to provide annular exposure as shown in the figure. This is because the peripheral edge of the orifice itself becomes roughened in the subsequent development process, which impairs the straightness of the ejected ink droplets.

When exposed as described above, patterns 7a and 7b
In other words, the exposed photoresist 6 undergoes a polymerization reaction, hardens, and becomes insoluble in the solvent. On the other hand, the unexposed photoresist 6
does not harden and remains solvent soluble. After such an exposure operation, the dry film photoresist 6 is immersed in a volatile organic solvent such as trichloroethane to dissolve and remove the unpolymerized (uncured) photoresist, resulting in a cured photoresist film 6H.
Through holes 8-1 and 8-2 shown in FIG. 5 are formed according to patterns 7a and 7b, and undissolved removed portions 11-2 at the periphery of the orifice are formed according to patterns 10a and 10b, as shown in FIG. 1 and 11-2 are formed, and a finely uneven surface 9 shown in FIG. 5 is formed on the outer surface excluding the orifice periphery according to the pattern 7c. Thereafter, the cured photoresist film 6H left on the orifice side end surface of the head body 4 is further cured in order to improve its solvent resistance. The method is thermal polymerization (at 130°C to 160°C).
It is best to use a combination of either heating (heating for about 10 to 60 minutes) or irradiation with ultraviolet rays.

In this way, the cross-sectional shape of the through holes 8-1 and 8-2 formed by the cured photoresist film 6H corresponding to the orifice plate is made into a desired shape (not shown) such as circular or square. be able to. Further, the vertical cross-sectional shape of the through holes 8-1 and 8-2 can also be arbitrarily changed from a tapered shape toward the ink ejection direction as shown in FIG. 5 to a widened shape, a straight shape, etc. .

The dry film photoresist used in the above examples can be said to be a suitable photosensitive resin for the present invention because it is easy to handle and the thickness can be easily and precisely controlled. Examples of such film types include DuPont's permanent photopolymer coating.
RISTON, solder mask 730S, 740S, same
There are photosensitive resins commercially available under trade names such as 730FR, 740FR, and SM1.

In the embodiment of the present invention, mask patterns 7a,
When each of the holes 7b is made circular with a diameter of 60μ, the through holes 8-1 and 8-2 actually formed in the cured photoresist film 6H (thickness: 50μ) can be obtained with an accuracy of about ±5μ. For reference, when a through hole equivalent to that of the above embodiment is formed by etching on a silicon flat plate with a thickness of 50 μm, the accuracy is approximately ±15 μm.

Also, the orifices 5-1, 5-2 and the through hole 8-
In the case of the present invention, the positional deviation with respect to 1 and 8-2 is approximately ±5μ, but in the latter method, it is considerably large as ±30μ. As a result, the landing accuracy of the ink ejected from the head provided with each of the above-mentioned orifice plates is about five times better in the present invention.

The degree of unevenness formed on the surface of the orifice plate, that is, the degree of roughness, can be controlled quite freely (by adjusting the exposure amount) by the coarseness and density of the mesh in the mesh mask 7c (FIG. 3). can do.

In addition, the mask for roughening the surface of the orifice plate is not limited to the mesh type used in the above embodiments, but can also be radial or parallel linear. Also good.

[Effects] The effects of the ink jet head according to the present invention explained in detail above are as follows: 1. Since the orifices are made of the same material and are formed with extremely high dimensional accuracy, the ejected ink droplets are excellent in straightness, and the ink droplets are The size of is also made uniform.

2 The face surface of the orifice plate is designed to exhibit uniform wettability with ink, making it difficult for ink to accumulate around the orifice and stabilizing the straightness of ink droplets even when driven for long periods of time. Ru.

3. Since a large number of orifices of uniform size and shape can be molded at the same time, it is easy to create a high-density multi-array ink jet head, and it is also easy to handle during the manufacturing process, and is excellent in mass production.

4. The orifice can be formed into a desired shape depending on the photomask used.

5. Since the self-adhesive property of photoresist is utilized, there is no need to use a separate adhesive, and there is no risk of blocking ink passages such as orifices due to the adhesive flowing in.

6. The alignment accuracy between the head body and the molding orifice is good, and the alignment operation is easy.

7. Since it is not necessary to use an etching solution (strong acids such as hydrofluoric acid), it is advantageous in terms of safety and health.

8. By roughening the surface except for the periphery of the orifice, it is possible to prevent the periphery of the orifice itself from becoming rough in the development process and to prevent the straightness of ejected ink droplets from being impaired.

Many things can be listed.

[Brief explanation of drawings]

1 to 5 are explanatory diagrams of embodiments of the present invention. In the figure, 4 is the inkjet head body, 5
-1, 5-2 is an orifice, 6 is a dry film photoresist, 6H is a cured photoresist film,
8-1 and 8-2 are through holes, and 11-1 and 11-2 are orifice peripheral parts.

Claims (1)

[Scope of Claims] 1. A head body having an ink passage; and an orifice plate communicating with the ink passage and having an orifice for discharging ink, the orifice plate being joined to the head body; In the ink jet head, the orifice plate includes a mask having a pattern of a non-transmissive part in the orifice portion and a pattern of a combination of a transmissive part and a non-transmissive part in an area other than the periphery of the orifice. By irradiating the surface of the photosensitive resin material with light through the photosensitive resin material, a cured region and an uncured region are formed on the surface, and the orifice of the surface is dissolved and removed. An inkjet head characterized by being formed by roughening the area except for the periphery of the inkjet head.