JPH0768758A - Thermal ink jet head - Google Patents

Abstract

PURPOSE:To provide a thermal ink jet head in which a filter function part is precisely formed in the head and which can stably inject against dust. CONSTITUTION:A plurality of heat generators 1a, 1b, 1c,... are formed in a heater wafer 10 made of Si, and a polyimide layer 9 is formed thereon. Pits 2a, 2b, 2c,..., a common slit 3 and a bypass pit 4 are formed on upper parts of the generators 1a, 1b, 1c by etching. On the other hand, nozzle channels 5a, 5b, 5c,..., ink channels 6a, 6b, 6c,... and an ink reservoir are formed of ODE at a channel wafer 10 made of Si. Ink is passed from the reservoir through the bit 4 and the channels 6a, 6b, 6c,.... In the case of passing, dust is trapped to eliminate invasion of the dust to the slit 3 and the channels 5a-5c.

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 for recording by generating bubbles in ink by heat generated from a bubble generating resistor and discharging the ink from nozzles by the generated bubbles. .

[0002]

2. Description of the Related Art As a flow path structure of a conventionally known thermal ink jet head, for example, Japanese Patent Application Laid-Open No. Sho 61-61 is known.
As described in JP-A-230954, the first
Of the Si substrate (heater substrate) and the second Si substrate (channel substrate), a heating element is formed on the first Si substrate, and ODE (anisotropic etching) is used on the second Si substrate. Some have nozzles and ink reservoirs.

Further, as described in Japanese Patent Application Laid-Open No. 1-148560, in order to reliably control the nozzle length, the nozzle portion and the ink reservoir are formed as independent grooves, respectively, and between them. There is used a means for connecting the two with a concave portion (bypass portion) provided in the polyimide on the heater substrate. However, in the ink flow path of the thermal inkjet head thus formed, since the bypass portion is narrow and bent, dust in the ink is likely to collect in the bypass portion. The dust accumulated in the bypass portion hinders the ink supply to the nozzles, deteriorates the repeated ejection characteristics of the nozzles, and has a problem that the ejection drop becomes small, or the ejection becomes impossible at all. On the other hand, it is extremely difficult to eliminate dust mixed in the ink or in the head during the manufacturing process, and some dust is stochastically mixed.

In order to solve this problem, for example, in Japanese Patent Application No. 4-351842, a communication groove for connecting a plurality of nozzles is provided in the polyimide on the heater substrate between the bypass portion and the heater. As a result, the bypass portion functions as a filter, and ink is supplied from other nozzles by the communication groove even if dust is accumulated in the bypass portion, so that a head flow path structure with stabilized ejection characteristics can be obtained. You can This structure excels in trapping dust, but since the bypass portion that serves as a filter is formed on the polyimide side, the precision during processing is low. Therefore, the nozzle array density is high,
When the nozzle size is small, there is a problem that sufficient processing accuracy cannot be obtained. In particular, when patterning the polyimide by etching, it is difficult to reduce the flow path resistance by widening the opening while improving the filtering accuracy because the processing limit is the same dimension as the film thickness of the polyimide. ..

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and even when nozzles are arranged at a high density, a filter function portion can be accurately formed inside the head, and dust can be removed. It is an object of the present invention to provide a thermal ink jet head that can perform stable jetting.

[0006]

According to the present invention, there is provided a thermal ink jet head comprising a heater substrate having a bubble generating resistor and a channel substrate having a plurality of nozzle channels, ink reservoirs, and ink supply ports, wherein the channels are provided. A substrate is provided with a plurality of ink channels between a plurality of nozzle channels and an ink reservoir, and a polyimide layer is provided on the heater substrate, and the polyimide layer has at least the resistor for bubble generation. An upper concave portion, a groove connecting the nozzle channel and the ink channel formed on the channel substrate, and a groove connecting the ink channel and the ink reservoir formed on the channel substrate are provided. It is characterized by being. The groove connecting the nozzle flow path and the ink flow path may be formed to connect a plurality of nozzle flow paths.

[0007]

According to the present invention, the plurality of ink channels provided on the channel substrate side function as a filter. Since this ink flow path can be formed in the channel substrate by ODE, for example, it is possible to obtain high dimensional accuracy. Since ODE has a small processing limit dimension, it is possible to provide a large number of fine ink flow passages, and even fine dust can be trapped in this ink flow passage portion. At this time, for example, a plurality of ink flow paths can be formed corresponding to one nozzle flow path, and by increasing the number of flow paths, it is possible to reduce the resistance of the filter while maintaining the filtering effect. As a result, it is possible to suppress deterioration of the ejection characteristics due to dust.

[0008] Further, by connecting a plurality of nozzle channels in the nozzle arrangement direction by means of a groove connecting the nozzle channel and the ink channel provided in the polyimide layer, dust is accumulated in the ink channel corresponding to a certain nozzle. However, even if the ink flow is obstructed, the ink can be supplied from the surrounding nozzles through the groove connecting the nozzle flow path and the ink flow path provided in the polyimide layer, and further the deterioration of the ejection characteristics can be suppressed. be able to.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing a flow passage structure in an embodiment of an ink jet head of the present invention, FIG. 2 is a sectional view of the flow passage at the center of the nozzle, and FIG. It is a top view. In the figure, 1, 1a, 1b and 1c are heating elements, 2, 2a, 2b and 2c are pits, 3 is a common slit, 4 is a bypass pit, 5, 5a, 5b and 5c are nozzle channels, 6, 6a, 6b and 6c are ink flow paths, 7 is an ink reservoir, 8 is a heater wafer, 9 is a polyimide layer,
10 is a channel wafer and 11 is dust.

The thermal ink jet head is constructed by bonding a channel wafer 10 and a heater wafer 8 having a polyimide layer 9 formed thereon. The heater wafer 10 is made of, for example, Si and has a plurality of heating elements 1.
a, 1b, 1c, ... And a common electrode (not shown), individual electrodes, etc. are formed. A polyimide layer 9 is formed thereon. The polyimide layer 9 has heating elements 1a, 1b,
Pits 2a, 2 defining the bubble formation area on top of 1c
, b, 2c, ..., The common slit 3, and the bypass pit 4 are formed by etching, for example. On the other hand, the channel wafer 10 is also made of, for example, Si, and has nozzle flow paths 5a, 5b, 5c, ...
a, 6b, 6c, ..., The ink reservoir 7 is, for example, O
Formed in DE.

As shown in FIG. 2, the ink flow reaches the nozzle channel 5 from the ink reservoir 7 through the bypass pit 4, the ink channel 6, and the common slit 3. Of the dust 11 that has entered the ink reservoir 7, large dust is trapped in the bypass pit 4. The dust 11 that has passed through the bypass pit 4 enters the ink flow path 6. However, since the portion of the ink flow path 6 is bent and has a narrow cross-sectional area, the dust 11 is reliably trapped. The dust that has not been trapped in the ink flow path 6 is so small that it does not clog the nozzle flow path 5 and is discharged to the outside as ink is ejected.

When large dust or air bubbles are trapped in the ink flow path 6, the fluid resistance in the ink flow path 6 becomes large, and the ink supply to the nozzles becomes insufficient, resulting in small dots and ejection failure such as misjet. Cause of. At this time, as shown in FIG. 3, ink is supplied from an adjacent nozzle or a nozzle in the vicinity through a common slit 3 connecting the channels, thereby supplementing the ink supply to the nozzle that is short of ink. be able to. As a result, the ink supply shortage can be suppressed to a level that is not noticeable as the actual image quality.

FIG. 4 is a sectional view of the flow path at the center of the nozzle in another embodiment of the ink jet head of the present invention, and FIG.
[Fig. 4] is a plan view of a flow path structure. Reference numerals in the figure are the same as those in FIGS. 1 to 3. In this embodiment, the ink flow paths 6 are arranged at a ratio of two to one nozzle. In such a configuration, the individual ink flow paths 6
And the filtering performance in the ink flow path 6 can be improved. The resistance of one ink flow path is large, but since the two ink flow paths correspond to one nozzle, the total flow path resistance is low, and sufficient ink supply to the nozzles is required. You can Such a thin ink flow path cannot be formed in the polyimide layer 9, but can be formed in the channel wafer 10 by ODE, for example.

The number of ink flow paths 6 is not limited to those in these embodiments, and three ink flow paths 6 are formed for one nozzle or three ink flow paths 6 for two nozzles. Can be formed at various ratios.

In the above-mentioned two embodiments, the common slit 3 is constructed so as to communicate with all the nozzles, but the common slit 3 can be formed by dividing it into several nozzles. For example, in the case of driving the heating element 1 in a divided and simultaneous manner, several nozzles that are not driven simultaneously may be used as a block, and a common slit 3 communicating with each block may be provided. With this configuration, it is possible to prevent the influence of crosstalk between nozzles that are driven at the same time.

Further, the common slit 3 is formed in each nozzle channel 5
It is also possible to provide each for each ink flow path 6. In the embodiment shown in FIGS. 1 to 3, since the nozzle flow path 5 and the ink flow path 6 correspond to each other, if the ink flow path 6 is clogged with dust, printing failure may occur. In the embodiment shown in FIG. 5, since a plurality of ink flow paths 6 are provided for one nozzle flow path 5, even if one ink flow path 6 is clogged with dust, Ink can be supplied by the ink flow path 6. In these configurations, it is possible to avoid ink ejection failure by separately providing a communication groove in the polyimide layer in the middle of the nozzle flow path 5, for example, as described in Japanese Patent Application No. 4-351842 mentioned above. Is possible.

Further, although the bypass pit 4 is formed in a common slit shape in the above-mentioned embodiment, for example, the bypass pit 4 is formed individually corresponding to each nozzle, or as a groove common to several nozzles. Can be formed. Further, the ink flow path 6 side of the bypass pit 4 may be formed in a comb shape so as to be an individual flow path, the ink reservoir 7 side may be formed in a comb shape, or the ink flow path 6 side and the ink reservoir 7 side may be formed. The bypass pit 4 can have various shapes, such as a comb-shaped structure in which both parts are connected to each other between the ink flow path 6 and the ink reservoir 7.

[0018]

As is apparent from the above description, according to the present invention, a plurality of ink channels are provided between the nozzle channel of the channel substrate and the ink reservoir, and the ink reservoir is provided in the polyimide layer of the heater substrate. By providing the ink flow path and the ink flow path, and the groove connecting the ink flow path and the nozzle flow path, the ink flow path functions as a filter, clogging of the nozzle due to dust can be prevented, and ejection failure can be avoided. . Since this ink flow path can be formed by ODE, a fine filter can be formed with high accuracy, and even fine dust can be trapped. With such a nozzle channel filter, it is not necessary to provide a separate filter, and the number of parts can be reduced.
Since the nozzle flow path is originally formed by ODE, the filter portion can be formed without increasing the number of steps. Further, since the bypass portion functions as a filter even after the two substrates are adhered to each other, the filter effect is exerted even on dust mixed in the dicing process, the head assembly process, etc., and stable characteristics are obtained regardless of the processing environment. The effect is that you can.

[Brief description of drawings]

FIG. 1 is a perspective view showing a flow path configuration in an embodiment of an inkjet head of the present invention.

FIG. 2 is a cross-sectional view of the flow path at the center of the nozzle in one embodiment of the inkjet head of the present invention.

FIG. 3 is a plan view of a flow path configuration in an embodiment of the inkjet head of the present invention.

FIG. 4 is a sectional view of a flow path at the center of a nozzle in another embodiment of the inkjet head of the present invention.

FIG. 5 is a plan view of a flow path configuration in another embodiment of the inkjet head of the present invention.

[Explanation of symbols]

1, 1a, 1b, 1c heating element, 2, 2a, 2b, 2c
Pit, 3 common slit, 4 bypass pit,
5, 5a, 5b, 5c Nozzle channel, 6, 6a, 6b,
6c ink flow path, 7 ink reservoir, 8 heater wafer, 9 polyimide layer, 10 channel wafer, 1
1 garbage.

Claims (2)

[Claims] 1. A thermal inkjet head comprising a heater substrate having a bubble generating resistor and a channel substrate having a plurality of nozzle channels, an ink reservoir and an ink supply port, wherein the channel substrate has a plurality of nozzle channels. A plurality of ink flow paths between the ink reservoir and the ink reservoir, and a polyimide layer on the heater substrate,
In the polyimide layer, at least a concave portion above the bubble generating resistor, a groove that connects the nozzle channel and the ink channel formed in the channel substrate, and,
A thermal ink jet head characterized in that a groove connecting the ink flow path and the ink reservoir formed in the channel substrate is provided. 2. The thermal inkjet head according to claim 1, wherein the groove connecting the nozzle flow path and the ink flow path is formed so as to connect a plurality of nozzle flow paths.