JP3248268B2 - Inkjet recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for performing printing by vaporizing ink by heat and controlling the ejection of ink droplets using the pressure of generated bubbles.

[0002]

2. Description of the Related Art Conventionally, as a thermal ink jet recording head, there has been known a thermal ink jet recording head having a thick film insulating layer for forming pits as described in Japanese Patent Application Laid-Open No. 1-148560.

FIG. 4 is a sectional view of a main part of a conventional ink jet recording head having pits. In the figure, 1 is a heater substrate, 2 is a heat storage layer, 3 is an electrode, 4 is a heater, 5 is an insulating layer, 6 is a protective layer, 7 is a thick insulating layer, 8 is a pit, 10 is a channel, and 11 is an ink reservoir. , 12 is a channel substrate, 13 is a nozzle surface, and 14 is an injection nozzle port. The thick film insulating layer 7 is made of a photosensitive resin, for example, photosensitive polyimide, and pits 8 are formed on the heater 4. The pits 8 are provided for defining the direction of bubble growth. When the heater 4 is energized and heated according to the print signal, bubbles are generated by the heat transmitted to the ink side, and the ink droplets are ejected. After the power supply to the heater 4 is turned off, the heat is quickly diffused toward the heater substrate 1 and the heater 4 is cooled. When the bubbles grown between the heating surface and the ink disappear, and the ink comes into contact with the heating surface, heat is also released to the ink side. Reference numeral 15 denotes an arrow representing heat radiation.

As described above, the heat is normally dissipated to the heater substrate side and the ink side. However, since the thick insulating layer forming the pits is also a heat insulating layer, heat is dissipated to the ink side. It has a difficult structure.

By the way, in such a thermal ink jet recording head, when the power supply to the heater is repeated for printing, the heater substrate side stores heat and the head temperature rises. There is a problem that the ink density becomes too large, the print density becomes too high, or bubbles protrude from the ejection nozzle opening, so that normal ink droplet ejection is not performed.

In order to solve this problem, a temperature sensor is attached to the recording head, and the temperature detected is 40 to 50 ° C.
When the above is achieved, control such as temporarily suspending the printing operation or turning on the cooling means is performed. However, by adopting such means, although the printing quality is maintained, a reduction in printing speed and an increase in cost due to the installation of cooling means cannot be avoided.

Japanese Patent Application Laid-Open No. Hei 2-258352 discloses that the cross-sectional area of an ink reservoir is increased at a central portion where heat easily accumulates so as to improve the escape of heat to ink. However, even if such a method is applied, the problem of heat storage of the entire head cannot be solved.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an ink jet recording head which has a simple structure and can prevent heat storage in a recording head portion, thereby preventing a decrease in printing speed. It is intended to do so.

[0009]

According to the present invention, ink is ejected by the pressure of bubbles generated by heating the ink,
In an ink jet recording head having a first pit on a heating section for defining a growth direction of the bubble, the ink jet recording head has a second pit between the first pit and a nozzle ejection port, and the first pit has A protective layer using a metal film provided extends to the bottom of the second pit to thermally conductively connect the first pit and the second pit, and
The heat of the pit is accelerated from the second pit to the ink to improve the heat radiation.

[0010]

According to the present invention, the thick insulating layer is opened by providing the second pit between the first pit and the nozzle injection port. Then, the second pit and the first pit on the heating unit are extended from the first pit to the first pit by extending a protection layer using a metal film provided on the first pit to the bottom of the second pit. Since the two pits are thermally conductively connected, the heat of the first pit is accelerated to dissipate heat from the second pit to the ink, thereby improving heat dissipation and preventing heat accumulation.

Therefore, when the heater is energized and heated repeatedly, heat is generated. However, since the heat is radiated to the ink side between the heater and the nozzle orifice, a large amount of heat is generated. The absorbed ink is ejected, and the recording head can be efficiently cooled.

The heat conductive connection between the two pits can be made simpler by extending the protective layer of the heater, which is a metal layer having good heat conductivity, to the nozzle side.

[0013]

1 and 2 are views for explaining an embodiment of an ink jet recording head according to the present invention. FIG. 1 is a sectional view of a main part, and FIG. 2 is a plan view showing the vicinity of a pit. In the figure,
The same parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. 8 is a first pit and 9 is a second pit.

A process for fabricating the ink jet recording head of this embodiment will be briefly described. A silicon wafer is used as the heater substrate 1, and the thermal storage layer 2 uses an SiO ₂ layer formed as a thermal oxide film of the silicon wafer. A heater 4 is deposited on the heat storage layer 2 using Poly-Si, TaAl, or the like by vapor deposition or sputtering. If necessary, the resistance is adjusted to a desired value by doping with an impurity and the like, and is patterned into a desired shape.

Then, an electrode or the like is deposited as an electrode layer and patterned to form an electrode 3. The insulating layer 5 is made of SiN
And a PSG, and the protective layer 6 is patterned thereon. The protection layer 6 is for protecting the heater from cavitation damage and ink corrosion, and is made of a metal layer such as Ta. As shown in FIG. 2, the protective layer 6 is patterned so as to be separated separately from the adjacent channel,
The pit 8 and the second pit 9 have a common bottom.

The thick film insulating layer 7 is formed by using photosensitive polyimide, and the first pit 8 and the second pit 9 are opened by photolithography. In the pit layer, CIBA-
Probide (registered trademark) 34 manufactured by GEIGY
8, Selectilux (registered trademark) HTR3-20
Or a photosensitive resin such as a dry film resist is formed by spin coating or lamination, and a desired pit layer pattern is obtained by exposure and development.

On the other hand, the channel substrate 12 is a silicon substrate having a (100) crystal plane on its surface, and the channel 10 and the ink reservoir are formed by an anisotropic etching method utilizing a difference in etching rate from the (111) crystal plane. 11 is formed. The detailed preparation method is described in JP-A-2-265754.

The channel substrate 12 on which the channels 10 and the ink reservoirs 11 are formed is coated with an epoxy adhesive by a selective coating method as described in JP-A-63-34152. Is bonded to the thick film insulating layer 7.

Thereafter, the position of the nozzle surface 13 is cut by a dicer to expose the nozzle surface 13, the opening of the wire bonding pad portion at the electrode wiring end is cut, and cut and separated into individual chips. The separated chip is adhered to an aluminum heat sink (not shown) with a silver epoxy, and an ink manifold, a printed wiring board, and the like are assembled.

The operation of the thermal ink jet head according to the above-described embodiment is the same as that of the conventional one in terms of ink ejection. However, the heat storage generated when the heater is repeatedly energized is transmitted through the protective layer 6 using a metal film.
The ink is efficiently absorbed by the ink existing in the second pits 9 and is discharged to the outside of the recording head together with the ejected ink droplets.
Therefore, it is possible to obtain a head that does not easily store heat.

Further, in this embodiment, since the metal protective layer which easily conducts heat is divided and patterned between the adjacent heaters,
Thermal crosstalk is small, and excellent print quality independent of the print pattern can be obtained.

FIG. 3 is a plan view showing the vicinity of pits in another embodiment of the ink jet recording head of the present invention. In the figure, the same parts as those in FIG.
In this embodiment, on the second pit 9 side,
The protective layer 6 is commonly integrated. Since the protective layer 9 on the first pit side is separated between adjacent heaters, thermal crosstalk is small. The protection layer on the second pit side is common, and the protection layer 6 of each heater is connected via this portion.
The thermal crosstalk does not cause much problem because the heat is dissipated to the ink on the pit side and the thermal resistance is larger than that when the protective layer between the adjacent heaters is directly connected. On the second pit side, heat is also dissipated in the direction of the adjacent pits, so that heat dissipation characteristics are improved.

Incidentally, the heat conductive connection between the first pit and the second pit is not limited to the protective layer, and an appropriate method such as connection between the side walls of the pit can be adopted.

[0024]

As is apparent from the above description, according to the present invention, the heat accumulation generated when the heater is repeatedly energized is mainly absorbed by the ejected ink droplets, so that the heat can be efficiently radiated. Thus, heat storage of the head can be suppressed. As a result, even when continuous printing is performed, there is an effect that the downtime can be reduced and the reduction in printing speed can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of an ink jet recording head of the present invention.

FIG. 2 is a plan view of the vicinity of a pit of the inkjet recording head of FIG.

FIG. 3 is a plan view near a pit of another embodiment of the ink jet recording head of the present invention.

FIG. 4 is a cross-sectional view of a main part of a conventional inkjet recording head.

[Explanation of symbols]

1 heater substrate, 2 heat storage layers, 3 electrodes, 4 heaters,
Reference Signs List 5 insulating layer, 6 protective layer, 7 thick insulating layer, 8 pits, 9 second pit, 10 channels, 11 ink reservoirs, 12 channel substrate, 13 nozzle surface, 14
Injection nozzle opening.

Claims (1)

(57) [Claims] 1. An ink jet recording head having a first pit on a heating section for ejecting ink by a pressure of a bubble generated by heating of the ink and defining a growth direction of the bubble, wherein the first pit is provided. A second pit between the first pit and the nozzle injection port, and a protective layer using a metal film provided on the first pit extends to the bottom of the second pit to form the first pit and the second pit. 2. An ink jet recording head in which two pits are thermally connected to accelerate heat radiation from the first pit to ink from the second pit to improve heat radiation.