JP2897499B2 - Thermal 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 thermal ink jet head in which at least a part of the ink passage or the like which is in contact with ink is formed of a thermosetting resin layer.

[0002]

2. Description of the Related Art Conventionally, in a thermal ink jet head, as described in JP-A-61-249767, a polyimide resin or a polyamide resin is used as a material for forming a portion in contact with ink such as an ink flow path. The use of a thermosetting resin such as the above has been proposed, and the durability as an ink jet recording head has been improved, and high reliability can be obtained.

On the other hand, as described in JP-A-62-33648, a concave portion for the purpose of limiting the growth region of bubbles or preventing air from being caught from a nozzle (this concave portion is Pits.)
A thermal ink jet head in which a heating element is arranged in the concave portion is known, and a thermosetting resin is effectively used for forming the concave portion.

In the thermal ink jet head proposed in Japanese Patent Application No. 2-212525, a concave portion is formed by a thermosetting resin layer, and the boundary of the concave portion is set inside the boundary of the heat generating region of the heat generating element. Things. In this structure, the life of the electrode can be prolonged by protecting the step portion near the electrode where a failure easily occurs with a thermosetting resin.

By the way, as a method of forming a thermosetting resin layer, usually, a varnish of a desired resin is applied to a substrate such as glass, ceramic or a Si wafer, and then a desired pattern is formed. A method of curing the applied resin layer by performing the method is employed.

However, by performing the heat treatment, the applied resin layer thermally contracts, and as a result, the edge of the pattern formed by the heat-treated resin layer rises in a frame shape. FIG. 9 is a model diagram for explaining the phenomenon. In the figure, 10 is a heater substrate,
17 is a thermosetting resin layer, 20 is a channel substrate,
FIG. 9A is a cross-sectional view showing a state after pattern exposure and development, and shows a state before heat curing.
(B) shows the state after the heat curing treatment. When the thermosetting resin layer 17 in the state shown in FIG. 9A is heat-treated at, for example, 400 ° C., thermal contraction occurs in the film thickness direction and also in the plane direction. In the curing, the edge portion proceeds first. Since the dimension of the portion where the thermosetting resin layer 17 is in contact with the heater substrate 10 does not change, a large distortion is generated in the thermosetting resin layer 17 and the end has a high height as shown in FIG. The raised portion a of the height h occurs in a frame shape.

An example of the degree of excitement will be described. P which is a photosensitive polyimide varnish as a thermosetting resin layer
robimide (registered trademark) (Ciba-Geigy)
Was heated at 350 ° C. for 2 hours. When the resin layer thickness before curing is 55 μm, the film thickness after curing is 33 μm
And a swell having a height of 8 μm occurred thereon. Further, Py, which is another photosensitive polyimide varnish, is used.
It heated at 350 degreeC for 2 hours using ralinPI2722 (made by Du-Pont). When the thickness of the resin layer before curing was 55 μm, the thickness after curing was 33 μm, and a swelling height of 8 μm occurred thereon.

When such a phenomenon occurs, the following problems occur when assembling an ink jet recording head. That is, as a method for forming the nozzles of the ink jet recording head, as shown in FIG. 10, a heat acting portion (not shown) is formed on the heater substrate 10 and pits are formed thereon using the above-described resin. After the thermosetting resin layer 17 is formed in a desired pattern, a nozzle 21, an ink supply port 23,
A method of bonding the channel substrate 20 on which the filter 24 and the like are formed, or as shown in FIG.
A method of forming a nozzle 21 by covering the top with a top plate 30 is adopted. However, in any case, as long as heat treatment is performed in a normal forming method, a phenomenon in which the edge of the pattern of the thermosetting resin layer always rises in a frame shape occurs.

[0009] The frame-like bulge at the end of such a pattern has a large correlation with the resin film thickness, and becomes larger as the thickness increases. Therefore, when the film thickness is small,
Although this does not cause much problem, if practicality as an ink jet recording head is considered, at least 5 to 1
Since a relatively thick resin film of about 00 μm is required, the above-described frame-shaped swell is inevitable in the conventional method. As a result, the thermosetting resin layer cannot be completely adhered to the channel substrate or the top plate, thereby lowering the yield and remarkably reducing the reliability as an ink jet recording head.

The frame-shaped bulge at the end of the pattern has a strong correlation not only with the film thickness of the resin but also with the temperature at the time of heat treatment for curing the resin (hereinafter referred to as the curing temperature). It has been found that the higher the temperature, the greater the climax. One example is the same Pr as in the above example.
A case in which a resin film having a thickness of 55 μm before curing is heated for 2 hours using obimide will be described. At a curing temperature of 200 ° C., the film thickness after curing is 50 μm, on which a swelling of 2 μm occurs. On the other hand, at a curing temperature of 400 ° C., the film thickness after curing is 30 μm, and a swelling of 10 μm is generated thereon. Pyra
Even in the case of lin PI2722, the film thickness before curing is 55
When the μm resin film is heated for 2 hours, the curing temperature is 200 ° C.
Then, the film thickness after curing becomes 50 μm, and 1 μm
At the curing temperature of 400 ° C.
The film thickness after curing was 30 μm, and a swell of 9 μm was generated thereon.

When the curing temperature is lowered, the height of the rise is reduced. However, the resin layer cannot be completely cured at a low curing temperature. In the case of the polyimide resin as described above, the imidation ratio, which is a measure of curing, is such that the curing temperature is 4%.
It is known that at a temperature of 00 ° C., it reaches 95% or more, whereas at a curing temperature of 200 ° C., it stays around 80%.

In the thermal ink jet head proposed in Japanese Patent Application No. 3-240516, a thermosetting resin layer is composed of multiple layers, and at least the lowermost thermosetting resin layer is sufficiently thermoset. FIG. 7 is a cross-sectional view of the vicinity of the heat action area. In the figure, 10 is a heater substrate, 11 is a heat storage layer, 12 is a common electrode, 13 is an individual electrode,
14 is a heater layer, 15 is a heater protective film, 16 is an electrode protective film, 17a and 17b are thermosetting resin layers, 18 is a pit, 20 is a channel substrate, 21 is a nozzle, and 22 is an ink flow path. The pits 18 are composed of two thermosetting resin layers 1
7a, 17b and pit 1 near the electrode
The boundary of No. 8 was set inside the boundary of the heating region of the heater layer 14. Also, of the thermosetting resin layer, the lowermost layer 17
a is sufficiently imidized. With this structure, by forming a multilayer structure, it is possible to form a concave portion having a depth sufficient to define a bubble generation region, and at the same time, to sufficiently heat the lowermost layer of the multilayer thermosetting resin layer. The purpose is to cure and protect the heater from the disappearance of bubbles and the chemical action of ink. That is, since the thermosetting resin layer having a higher imidation rate has a higher protective effect on the heater layer 14, the imidization rate of the lowermost layer 17 is set to, for example,
A high protection effect is aimed at at 85% or more. Further, in order to suppress the swelling height after thermosetting, which hinders the adhesion between the channel substrate 20 and the thermosetting resin layer 17b on the heater substrate 10, the imidation ratio of the upper thermosetting resin layer 17b is set to 85%. The thermosetting resin layer is formed below.

However, in this thermal ink jet head, in the heat treatment step required to sufficiently imidize the lowermost layer of the thermosetting resin layer, large thermal stress accumulates in the lowermost layer, and As a result, the adhesive strength between the heater layer and the lowermost layer is weakened. As a result, there is a problem that the protective effect of the thermosetting resin layer as the heater protective film cannot be sufficiently obtained. The details will be described below.

FIG. 8 is an enlarged view of the vicinity of the individual electrode 13 in FIG. In the figure, the same parts as those in FIG. b indicates the position of the boundary of the heat action area. The cross-sectional shape of the lowermost layer 17a of the thermosetting resin layer before the ink discharge operation is performed after manufacturing the head is formed in close contact with the heat generating surface as shown in FIG. As described above, a large stress is accumulated in the lowermost layer 17a due to the shrinkage caused by the heat treatment performed to make the imidization ratio of the lowermost layer 17a 85% or more. Since the magnitude of this stress is maximum at the outermost peripheral portion of the thermosetting resin layer, it takes the largest value at the interface where the lowermost layer 17a is in contact with the heater protective film 15. As a result, this large stress causes the adhesive strength between the heater protective film 15 and the lowermost layer 17a to be weakened. In this state, the lowermost layer 17a of the thermosetting resin layer after ejecting about 100 million ink droplets
As shown in FIG. 3B, the cross-sectional shape of FIG. 3B is such that a portion close to the heater heat-generating portion is cut off. As a result, the intrusion of ink from the scraped portion is allowed, the effect of the pit layer as a protective film is weakened, and the problem that the heater is likely to fail occurs. Alone is not enough.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it has been proposed to reduce the height of a thermosetting resin after curing, thereby providing a channel substrate, a top plate and a heater. The yield in the bonding process with the substrate is high, and the thermosetting resin layer in the vicinity of the heat generating portion is almost completely cured, and the stress accumulated in the thermosetting resin layer due to the thermosetting is reduced. It is another object of the present invention to realize a thermal inkjet head having an excellent effect as a protective film or a partition wall of a thermosetting resin layer.

[0016]

According to the present invention, in the first aspect of the present invention, a concave portion for defining a bubble generation region is formed by a thermosetting resin layer comprising a plurality of layers, and a heating element is formed at the bottom of the concave portion. And, in the thermal inkjet head in which the boundary of the concave portion is set inside the boundary of the heat generating region of the heat generating element, at least the lowermost layer of the thermosetting resin layer is formed by a set of small blocks adjacent to each other. And a thermosetting resin layer composed of a plurality of layers on a substrate having a heating element for generating air bubbles. In a thermal inkjet head in which a partition forming a flow path is formed and a top plate is joined on the partition, at least the lowermost layer of the thermosetting resin layer is adjacent to each other. Together they are formed by a set of small blocks which is characterized in that it is fully thermoset.

The imidization ratio of at least the lowermost thermosetting resin layer can be 85% or more, preferably 95% or more. The opening size of the thermosetting resin layer above the lowermost layer may be larger than the opening size of the lowermost thermosetting resin layer. The thermosetting resin layer may be formed by setting the curing temperature of the lower layer higher than the curing temperature of the upper layer.

[0018]

According to the present invention, in a thermosetting resin layer composed of a plurality of layers, at least the lowermost layer is formed by a set of small blocks adjacent to each other, and is sufficiently thermoset to form at least the lowermost layer. Is distributed between the small blocks adjacent to each other, and the occurrence of large stress can be suppressed. Therefore,
Since the adhesive strength is sufficiently secured, the function as a heater protective film or a partition can be stably maintained for a long time. Further, by forming a plurality of thermosetting resin layers, a concave portion having a depth sufficient to define a bubble generation region, or a flow channel having a height sufficient to secure a required ink flow rate. Can be formed.

[0019]

FIG. 2 is a perspective view of a completed thermal ink jet head obtained by bonding a heater substrate and a channel substrate according to a first embodiment of the present invention, and FIG.
FIG. 3 is a schematic cross-sectional view of the vicinity of a heat action area. In the figure, the same parts as those in FIG. The heater substrate 10 and the channel substrate 20 are formed on a Si substrate by photolithography. After bonding the two, the two are cut by a dicing saw, and the head shown in FIGS. 1 and 2 is manufactured.

The configuration of the heater substrate 10 will be described in more detail. In this embodiment, the heat storage layer 11 is a thermal oxide film formed on a Si substrate, and the heater layer 14
It is formed by polysilicon (poly-Si).
The common electrode 12 and the individual electrode 13 are formed of Al, and the electrode protection layer 16 thereon is SiO ₂ . As the heater protection layer 15, two layers of a Si ₃ N ₄ film and a Ta film are used, and Ta is an upper layer. Thermosetting resin layer 17a, 1
7b is formed on the heater protection layer 15 and the electrode protection layer 16. Since the electrode protection layer 16 formed under the thermosetting resin layer 17a is made of SiO ₂ , heat conduction is not good. In this embodiment, the boundary of the heat action region is located at the end of the electrode protection layer 16 as shown by b. Therefore, the boundary between the thermosetting resin layers 17a and 17b is set closer to the center of the heat generating portion, which is inside the boundary of the heat action region.

Each of the thermosetting resin layers 17a and 17b has the above-mentioned Probimide (registered trademark) (Ciba-Gei).
gy). That is, in this embodiment, the pit layer is composed of two thermosetting resin layers 17a and 17b. Hereinafter, a method for forming the pit layer will be described. (A) A varnish of a thermosetting resin is applied on a heater substrate on which a film other than the pit layer has been formed to a predetermined thickness by a method such as spin coating or roll coating. (B) Perform baking and dry the varnish of the thermosetting resin. (C) Exposing the thermosetting resin varnish through a mask corresponding to a desired pattern. (D) Develop by a method suitable for the thermosetting resin varnish to form a desired pattern. (When a thermosetting resin having no photosensitivity is used, after (b), an appropriate resist is applied, and then exposure and development are performed.) (E) Baking at a predetermined temperature for a predetermined time To cure the thermosetting resin layer.

In this embodiment, the above-described steps (a) to (e) are repeated twice to form a pit layer having a two-layer structure. The film thickness of the first thermosetting resin layer 17a before the curing in the step (a) is 9 μm, and the curing temperature and the curing time in the step (e) are 400 ° C. and 2 hours. As a result, the film thickness of the first layer was 5 μm, and FIG.
The height of the swelling indicated by h described in (B) was only 1 μm because the film thickness was thin.

Next, a second thermosetting resin layer 17b was formed. The film thickness before curing in step (a) of the second layer is 2
The curing temperature and the curing time in the step (e) are 200 ° C. and 2 hours. As a result, the film thickness of the second layer was 20 μm, and the height of the swelling shown by h in FIG. 9B was only 1 μm due to the low curing temperature.

The protrusion of 1 μm in height after the formation of the first layer was absorbed and flattened after the application in the step (a) of the second layer. However, the unevenness of the first layer itself having a thickness of 5 μm is substantially maintained. As a result, the total film thickness of the first and second layers was 25 μm, and the height of the protrusion was 1 μm. Since the height of the swell was only 1 μm, it did not hinder the adhesion to the channel substrate 20 in FIG.

FIG. 1B shows the lowermost thermosetting resin layer 1.
It is explanatory drawing of the plane pattern of 7a. The hatched area with diagonal or vertical lines is the area where the lowermost layer of the thermosetting resin layer is formed, and the second layer above it is the pit 1
The film is formed on the entire surface except for No. 8. Lowermost thermosetting resin layer 1
7a are 20 to 20 adjacent to each other with an interval of 5 μm.
It is formed by a set of small blocks having a size of 40 μm. By performing a heat treatment necessary for setting the imidation ratio of the layer 17a to 85% or more, stress occurs in each small block. However, since the magnitude of the stress generated in the lowermost layer depends on the size of each small block, the magnitude of the stress is much smaller than that of the thermosetting resin layer described in FIG. Further, the portions hatched by vertical lines are the portions that play the greatest role as the protective film. The block shape of this portion is preferably such that the length in the left-right direction in the figure is short. As a result, the heater protection layer 15 shown in FIG.
The magnitude of the stress generated in the portion in contact with is suppressed. Accordingly, since the adhesive force at the interface where the lowermost thermosetting resin layer 17a is in contact with the heater protective layer 15 is sufficiently maintained, the function of the lowermost thermosetting resin layer 17a as a protective film is maintained for a long time. can do. Since the small blocks are adjacent to each other at a short interval, the upper surface thereof becomes flat after the thermosetting resin layer is formed thereon, and does not hinder the adhesion with the channel substrate 20. .

FIG. 3 is an explanatory view of a plane pattern of the lowermost thermosetting resin layer 17a in the second embodiment of the thermal ink jet head of the present invention. As described above, the part that plays the largest role as the protective film is the one shown in FIG.
Similar to (B), this is a portion hatched by a vertical line. Therefore, in this embodiment, a large block is used as a block other than the portion hatched by the vertical line. Also in this embodiment, the first
As in the embodiment, the function of the lowermost thermosetting resin layer 17a as a protective film can be maintained for a long period of time.

FIG. 4 is an explanatory view of a plane pattern of the lowermost thermosetting resin layer 17a in the third embodiment of the thermal ink jet head of the present invention. 1B and 3, the hatched portions are regions where the lowermost layer of the pit layer is formed. The bold line at the center is the boundary between the pits 18, and the second layer is formed on the entire surface excluding the pits 18. Also in this embodiment, as in the first and second embodiments, the function of the lowermost thermosetting resin layer 17a as a protective film can be maintained for a long period of time.

FIG. 5 is a perspective view of a main part of a fourth embodiment of the thermal ink jet head of the present invention. In the figure, 1
0 is a heater substrate, 21 is a nozzle, 30 is a top plate, 31
a and 31b are thermosetting resin layers. In this example,
Unlike the first to third embodiments, the thermosetting resin layer 31
a and 31b are used for forming a partition. The used thermosetting resin is the above-mentioned Probimide (registered trademark), but it is of course possible to use other thermosetting resins. Also in this embodiment, the above (a)
By repeating the steps (e) to (e) twice, the partition walls can be formed with the two-layer structure of the thermosetting resin layers 31a and 31b. The manufacturing conditions for the first and second layers were exactly the same as in the first embodiment. As a result, the thickness of the partition wall finally manufactured was 25 μm, and the height of the protrusion was 1 μm. The height of the swell was only 1 μm, and did not hinder the adhesion to the top plate 30 as in the above-described embodiment. In this embodiment, the present invention is applied to the production of a thermal ink jet head, but it is also applicable to the production of other ink jet recording heads requiring a partition or recording heads of other systems.

FIG. 6 is an explanatory view of a plane pattern of a lowermost thermosetting resin layer in a fourth embodiment of the thermal ink jet head of the present invention. As in FIG. 1 (B),
The shaded portion is the region where the lowermost thermosetting resin layer 31a of the partition layer is formed, and the second layer is formed on the entire surface of the partition wall. (A) shows two blocks in a direction parallel to the direction of the nozzle. FIG. 2B is a diagram in which the image is further divided into blocks at right angles to form a block. As in the above-described embodiment, the adhesive force between the heater substrate 10 and the partition wall 31a can be increased. In addition,
The pattern and size of the blocking are not limited to the embodiment, and can be appropriately designed.

[0030]

As apparent from the above description, according to the present invention, the following effects can be obtained. (A) By forming the lowermost layer of a pit layer of a thermosetting resin by a set of small blocks adjacent to each other,
Since the stress generated in the lowermost layer is reduced and the adhesive force with the heater substrate is sufficiently ensured, a large protective effect as a heater protective film can be maintained for a long time. (B) By forming the lowermost layer of the partition wall made of a thermosetting resin by a set of small blocks adjacent to each other, stress generated in the lowermost layer is reduced, and the adhesive force between the heater substrate and the heater substrate is sufficiently ensured. Therefore, the function as a partition for forming the ink flow path can be stably maintained over a long period of time. (C) By making the thermosetting resin layer more multilayer,
A concave portion having a depth sufficient to define a bubble generation region, or a flow channel having a height sufficient to secure a necessary ink flow rate can be formed. (D) The flatness of the pit layer on the nozzle surface after cutting is improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of a thermal inkjet head according to the present invention.

FIG. 2 is a perspective view of the thermal inkjet head according to the first embodiment of the present invention.

FIG. 3 is an explanatory view of a plane pattern of a thermosetting resin layer of a second embodiment of the thermal ink jet head of the present invention.

FIG. 4 is an explanatory view of a plane pattern of a thermosetting resin layer of a third embodiment of the thermal ink jet head of the present invention.

FIG. 5 is a perspective view of a main part of a fourth embodiment of the thermal ink jet head of the present invention.

FIG. 6 is an explanatory diagram of a plane pattern of a thermosetting resin layer of a fourth embodiment of the thermal inkjet head of the present invention.

FIG. 7 is a cross-sectional view of a thermal ink-jet head having a multi-layered thermosetting resin layer in the vicinity of a heat action area.

8 is an enlarged cross-sectional view of the vicinity of an individual electrode before and after ejection of ink droplets of the thermal inkjet head of FIG.

FIG. 9 is an explanatory diagram of a heat-treated state of a thermosetting resin layer.

FIG. 10 is a perspective view of a conventional thermal inkjet head.

FIG. 11 is a perspective view of a main part of another example of a conventional thermal inkjet head.

[Explanation of symbols]

10 heater substrate, 11 heat storage layer, 12 common electrode,
13 individual electrodes, 14 heater layers, 15 heater protective films, 16 electrode protective films, 17, 17a, 17b, 31
a, 31b thermosetting resin layer, 18 recess, 20 channel substrate, 21 nozzle, 22 ink flow path, 30
Top board.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yutaka Mori 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd.Ebina Office (72) Inventor Shinji Tabata 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. In-house (72) Inventor Naoshi Kotake 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Office (72) Inventor Hiroshi Ikeda 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Jiro Minabe 2274 Hongo, Ebina-shi, Ebina-shi, Kanagawa Prefecture Inside the Fuji Xerox Co., Ltd.Ebina Office (72) Inventor Makoto Misawa 2274, Hongo, Ebina-shi, Kanagawa Prefecture Inside the Ebina Office of Fuji Xerox Co., Ltd. 224743 (JP, A) 64-45650 (JP, A) JP Akira 63-191647 (JP, A) (58 ) investigated the field (Int.Cl. ^6, DB name) B41J 2/05

Claims (2)

(57) [Claims] 1. A concave portion for defining a bubble generation region is formed by a plurality of thermosetting resin layers, a heating element is provided at a bottom portion of the concave portion, and a boundary of the concave portion is generated by the heat generating element. In the thermal ink jet head set inside the boundary of the region, at least the lowermost layer of the thermosetting resin layer is formed by a set of small blocks adjacent to each other, and is sufficiently thermoset. Ink jet head. 2. A thermal ink jet apparatus comprising: a substrate having a heating element for generating air bubbles; and a partition for forming an ink flow path formed by a plurality of thermosetting resin layers, and a ceiling plate joined to the partition. In the head, at least the lowermost layer of the thermosetting resin layer is formed of a set of small blocks adjacent to each other and is sufficiently thermoset.