JPH06143579A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To provide an ink jet recording head in which mixture of dust with a channel is prevented without increasing the manufacturing cost and an injecting malfunction due to clogging of dusts can be prevented. CONSTITUTION:Channel groves 3 and an ink reservoir 4 are formed on a channel board 1 by anisotropically etching. An insulting layer 8, a thick resin layer 9 are formed on a heater board 2. A first recess 10 provided with a heater 7 in a bottom and a second recess 11 for bypassing an unetched part 6 of the board 1 to communicate the groove 3 with the reservoir 4 are formed on the layer 9. Channel side parts 15 of the second recess are connected, and the reservoir 16 is so individually divided as to correspond to the grooves. Dusts, etc., are trapped to the individually divided reservoir side part 16 to supply ink from the connected part.

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 recording by ejecting ink droplets from nozzles by the pressure of vapor bubbles generated by heat generated by a heater.

[0002]

2. Description of the Related Art The ink jet recording system is capable of high-speed recording and produces almost no noise during recording.
Since it can print directly on plain paper and does not require fixing processing, it is drawing attention because it can be downsized.

The technique for producing an ink jet recording head described in Japanese Patent Laid-Open No. 61-230954 discloses a channel portion which constitutes a nozzle for ejecting ink and a channel portion from the outside to the channel portion by anisotropic etching of a Si wafer. An ink reservoir portion that supplies ink is created. This wafer is called a channel wafer.
The anisotropic etching technology for Si wafers utilizes the fact that the etching rate differs depending on the crystal plane.
In particular, it is general to utilize the fact that the etching rate of the {111} crystal plane is very slow compared to other crystal planes. When a silicon substrate having a (100) crystal face on the surface is used, a pattern with square or rectangular openings is
It is known that they can be formed with extremely high precision, and that the shape of connecting them deteriorates the accuracy of the connecting portion. Therefore, in the channel wafer, as shown in the perspective view of the main part of FIG. 6, the channel groove 3 formed by anisotropic etching and the ink reservoir 4 are formed in a separated pattern, and the pattern is not formed in the middle. The etching part 6 remains. Therefore,
It is necessary to form a flow path that connects the channel groove 3 and the ink reservoir 4.

FIG. 5 shows an example of a conventional thermal ink jet recording head. FIG. 5A is a sectional view taken perpendicularly to the axial direction of the channel groove, and FIG. 5B is a sectional view of FIG.
It is the top view cut by -B. In the figure, 1 is a channel substrate,
2 is a heater substrate, 3 is a channel groove, 4 is an ink reservoir, 5 is a nozzle, 6 is an unetched portion, 7 is a heater,
8 is an insulating layer, 9 is a thick film resin layer, 10 is a first concave portion, 11
Is a second concave portion, 12 is a partition wall, 13 is an ink droplet, and 14 is a recording medium. In this recording head, the flow path connecting the above-mentioned channel groove and the ink reservoir forms one elongated recess connected to all the channel grooves, thereby connecting the ink reservoir and each channel groove. .

A channel groove 3 and an ink reservoir 4 are formed in the channel substrate 1 by anisotropic etching, and the opening of the channel groove 3 serves as a nozzle 1. A heater 7 is formed on the heater substrate 2, and an electrode for supplying a drive current to the heater 7, a protective film, etc. are formed, but details of these are omitted. Further, an insulating layer 8 and a thick film resin layer 9 are formed on the heater substrate. These two substrates are joined and cut and separated into individual head chips to form a recording head.

The first recess 10 is called a pit and is formed by patterning the insulating layer 8 and the thick film resin layer 9 to suppress the lateral growth of bubbles generated on the heater 7, It is intended to prevent deviation of the nozzle from the nozzle 5 and suction of air. In addition, the second recess 11
Corresponds to the unetched portion 6 of the channel substrate 1 by leaving the insulating layer 8 at the bottom in order to protect the wiring, the driving circuit (not shown) and the like arranged under the insulating layer 8 from the invasion of the ink. The thick film resin layer 9 is formed at a position by patterning.

By the way, the ink used in the ink jet recording apparatus undergoes a filtration step in its manufacturing process. Further, since the ink filling operation into the ink cartridge is also performed in an extremely clean environment, dust or particles of a size of about several tens of microns, which clogging the channel portion of the recording head, are usually contained in the ink. Absent. But,
In the process of filling the recording apparatus with the ink cartridge, dust may mix into the ink from the joint portion that connects the ink cartridge and the recording head and enter the ink flow path of the recording head.

Also, dust or the like may remain in the ink reservoir during the process of cutting and separating the head chip or the process of assembling the separated head chip together with the printed circuit board, the heat sink, etc. as a recording head. In this case, since the opening of the ink reservoir is large enough to allow dust of about several tens of microns to pass therethrough, the second recess connecting the channel and the ink reservoir has a thickness of the thick film resin layer that forms the recess too much. Since the thickness cannot be increased, the flow path cross-sectional area of the portion corresponding to the unetched portion 6 of the channel substrate is small, which may cause dust to stagnate and hinder the ink supply to the channel.

As shown in FIG. 5, in a recording head having a structure in which a common second recess is connected to all channel grooves, even if dust enters the second recess and becomes stagnant, the second recess Since the concave portion is widened in the nozzle arrangement direction, the ink jet abnormality is reduced by the ink flowing around from the adjacent portion of the stagnant dust to be supplied. But,
Since dust can move in the nozzle arrangement direction in the second recess, there is a possibility that supply shortage will occur over a plurality of nozzles. Therefore, the nozzle causing the ejection abnormality may move, image deterioration may occur over the print width, or dust may be concentrated at a specific place, resulting in a large print omission.

As a head structure for preventing dust from entering the print head, a structure in which a filter is externally attached to the opening of the ink reservoir is considered. However, this structure adds a step of mounting the filter to the head chip, which increases the manufacturing cost. Further, it is not possible to remove dust remaining in the reservoir during the assembly process.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and prevents dust from being mixed in a flow path without increasing manufacturing cost, and prevents injection abnormality due to clogging of dust. It is an object of the present invention to provide an ink jet recording head that can be used.

[0012]

According to the present invention, there is provided a first substrate having a plurality of channel portions and an ink reservoir portion formed by anisotropic etching, and a substrate having a plurality of heaters corresponding to the channel portions. A second substrate having a thick film insulating layer on the thick film insulating layer, and having a first recess in which a heater is arranged and a second recess for connecting the channel part and the ink reservoir part to each other; In the invention according to claim 1, in the ink jet recording head formed by joining the parts, the channel side or the middle part of the second recess is connected to each other, and the ink reservoir side is divided respectively. In the invention according to claim 2, a part of the channel side or the intermediate part of the second concave portion corresponding to the plurality of heaters to which the voltage pulse is applied at the same timing is provided. Are connected to each other, it is characterized in that the ink reservoir side is divided respectively.

[0013]

According to the present invention, a part of the channel side or the middle part of the second concave portion connecting the channel groove and the ink reservoir is connected to each other, and the ink reservoir side is divided respectively. Even if dust enters from the ink reservoir due to the smaller flow passage cross-sectional area,
Dust can be trapped in this part. Even if dust is clogged here, ink is supplied from the adjacent individual recesses to the connected recesses on the channel side or in the middle part, and from this, ink is supplied to each channel groove in which the heater is arranged. It is possible to prevent abnormal injection due to insufficient supply. In addition, dust does not stay in each recess on the ink reservoir side, does not move to other portions, and dust does not concentrate at a specific place, resulting in large print omission.

Further, in order to improve the ink supply property from the commonly connected second concave portion to the heater portion, the distance from the first concave portion to the second concave portion is shortened and the flow path resistance is reduced. The structure is also conceivable. In this case, the generated pressure pulse may propagate to another flow path via the connected second recess. In an ink jet recording head in which a plurality of adjacent heaters are set as one block, voltage pulses are applied at the same timing with one block as one unit, and the blocks to be applied are sequentially shifted and ejected, the timing is different from this block. The propagation of the pressure pulse to the other blocks to be jetted can, in particular, affect the jetting state. In order to prevent this, the nozzle side or the central part is connected to each other and the ink reservoir side is divided for each adjacent second concave portion in the block to which the voltage pulse is applied at the same timing. Also in this structure, dust is trapped in the divided portion of the second recess on the ink reservoir side, and the dust does not concentrate at a specific place. Further, ink is connected from the adjacent individual recesses to the nozzle side. Since the ink is supplied through the formed portion, it is possible to prevent the ejection abnormality due to the insufficient supply of the ink.

[0015]

FIG. 1 shows a first embodiment of the ink jet recording head of the present invention. FIG. 1 (A) is a sectional view taken perpendicularly to the axial direction of the channel groove, and FIG. 1 (B) is Figure 1
FIG. 1C is a cross-sectional view taken along line BB in FIG.
It is sectional drawing cut | disconnected by CC of (B) figure. In the figure, the same parts as those in FIG. 15
Is a channel side portion of the second concave portion, and 16 is an ink reservoir side portion of the second concave portion.

In this embodiment, since the insulating layer 8 is formed of a thick film resin layer, the thick film resin layer forming the recess is composed of two layers. As for the thickness of the thick resin layer, the insulating layer 8 has a thickness of 0.5 to 30 μm, preferably 3 to 10 μm, and this thickness protects the wiring portion located under the insulating layer and the drive circuit from invasion of ink. It is thick enough to do. The thickness of the thick film resin layer 9 is 5 to 50 μm, preferably 1
5 to 30 μm, and the flatness of the resin layer is determined by the ejection state of ink droplets and the ink supply speed. In this embodiment, the insulating layer 8 has a thickness of 5 μm and the thick film resin layer 9 has a thickness of 22 μm.
μm. In addition, other dimensions of the bypass portion are shown in FIG.
Referring to (B), the first concave portion 10 to the second concave portion 11
Is 50 μm, the distance L2 from the end of the second recess 11 on the heater side to the unetched portion of the channel substrate is 80 μm, and the thickness d of the unetched portion 6 is 20 μm.
m, the channel-side portion 15 of the slit-shaped second recess 11
The length L3 of 80 μm, the second recess 1 which is individually separated
The length L4 of the ink reservoir side portion 16 of 1 is 60 μm,
The width W of the ink reservoir side portion 16 was set to 50 μm. Such an ink jet recording head is disclosed in JP-A-1-
It was prepared by the method described in Japanese Patent No. 148560. However, as shown in FIG. 1B, the channel-side portion 15 of the second recess is connected to all the channel grooves, and the ink-reservoir-side portion 16 individually corresponds to each channel groove. Is divided into

Such an ink jet recording head was assembled together with a printed circuit board and a heat sink so that it could actually operate on a printer. The assembled ink jet recording head was mounted on a printer, and images were repeatedly printed to evaluate image quality, particularly image defects such as missing dots and thin lines. As an evaluation method, after 20 images are continuously printed in a normal environment, maintenance operations such as wiping and priming are performed. Such a printing experiment was repeated 20 times, and after taking a total of 400 prints,
Replace the ink cartridge and repeat the printing experiment.
Replace the cartridge 10 times to finish, 4000 in total
The image quality defects were evaluated for the one print.

As a result, while printing 4000 sheets with some heads, there was a head in which dots corresponding to a certain number of nozzles were slightly smaller than those of the other nozzles, but it was not a defect that caused a problem. This is because dust remaining in the ink reservoir at the time of assembly or dust mixed when the ink cartridge is replaced is pulled toward the channel groove by the initial jetting, and is separated into the ink reservoir side portion 16 of the second recessed portion. Ink is supplied from the ink reservoir side portion 16 of the adjacent second concave portion to the channel side portion 15 of the connected second concave portion, and the channel corresponding to the ink reservoir side portion in which dust is stagnated from here. This is because the ink is supplied to the groove. That is, in the case of a thin image or line image in which printing is not performed from the nozzle adjacent to the nozzle corresponding to the ink reservoir side portion of the second concave portion in which dust is stagnant, ink is sufficiently supplied. Further, in the case of a high-density image in which adjacent nozzles are also printed, the ink supply is slightly reduced, but it is considered that due to the overlapping of adjacent dots, even if the dot diameter was slightly reduced, it did not cause a large printing defect. .

As a comparative experiment, a head having the same dimensions as those of the above-described recording head, in which all the second recesses were divided, was prepared, and the same printing experiment was conducted. However, the width W of each individual recess is 50 μm. As a result, there was a head in which dot omission and remarkable dot thinning were observed at several nozzles from the beginning of printing. This defect was not recovered by the maintenance operation. This is because dust is clogged in individual recesses,
This is because the ink supply path to the channel groove is completely blocked.

Further, as in the conventional recording head shown in FIG. 5, a recording head in which the second concave portion is not divided at all and all of which has a slit shape is prepared, and the same printing experiment is conducted. As a result, a large printing defect such as dots that are continuously missing from a specific nozzle, which is seen in the recording head when the second recess is divided, is not seen. However, in the print immediately after the maintenance operation, a printing defect was observed in which dots were missing over several adjacent nozzles. This defect may be recovered in the next maintenance operation or may be reproduced by moving the place. this is,
In the priming during the maintenance operation, if the negative pressure applied to all the nozzles is biased, the ink and the dust move in the nozzle arrangement direction in the second recess during the priming operation, and the dust is concentrated at a specific place, and the printing is performed. It is sometimes considered that the ink supply was hindered over several nozzles.

In the recording head having the same structure as that of the first embodiment, a recording head in which the distance between the first concave portion 10 and the second concave portion 11 was shortened was prototyped. That is, in the first embodiment, the distance L1 between the first concave portion 10 and the second concave portion 11 was 50 μm, but it was set to 20 μm in the prototype recording head. The other dimensions are the same as those in the first embodiment. Further, as shown in FIG. 3, the method of driving the recording head is such that the 144 heaters 7 are divided into two from the center, and the nozzle number 1 at the end and the nozzle number 7 at the center.
From 3 to 4, each 4 blocks are divided into 18 blocks of block numbers 1 to 18, and voltage pulses are applied to 8 heaters in the same block number at the same timing. The maximum frequency at which this recording head can repeatedly and stably eject ink droplets is about 1.5 times that of the head of the first embodiment.

When a printing experiment was carried out on this head as well, it was found that small dots were printed in places where there was no print signal. This is considered to be the effect of so-called crosstalk in which, when a voltage pulse is applied to a certain block, the generated pressure pulse propagates to another flow path through the commonly connected second recesses.

The second embodiment improves the effect of this crosstalk. FIG. 2 shows a second embodiment of the ink jet recording head of the present invention and is a plan view similar to FIG. 1 (B). In the figure, the same parts as those in FIG. In this embodiment, the channel-side portions 15 of the adjacent second recesses in the same block to which voltage pulses are simultaneously applied are connected to each other, and the ink-reservoir-side portion 16 is individually divided. The second recesses of the adjacent blocks are separated from each other by the partition wall 12. When a printing experiment was conducted on a recording head having such a structure, no small dots corresponding to the print signal were found. In addition, no printing omission due to dust was observed.

FIG. 4 shows a third embodiment of the ink jet recording head of the present invention and is a plan view similar to FIG. 1 (B). In the figure, the same parts as those in FIG. Reference numeral 17 is a central portion of the second recess. In this embodiment, rather than the recording head shown in FIG.
Furthermore, the effect of crosstalk is improved. In this embodiment, the channel-side portion 15 and the ink-reservoir-side portion 16 of the second concave portion are individually divided corresponding to the channel groove, and the lower portion of the unetched portion of the channel substrate, that is, the second concave portion. The central portions 17 of the are connected to each other. Since each channel-side portion 15 is individually divided, it is possible to prevent crosstalk that occurs through the connected channel-side portions as in the first and second embodiments. Further, since dust can be trapped in the ink reservoir side portion 16 of the second recess and ink can be supplied to the adjacent nozzles from the connected central portion 17, it is possible to prevent print omission due to dust. You can As in the second embodiment, the central portion 17 is connected to each of the same blocks to which voltage pulses are simultaneously applied,
It is also possible to adopt a configuration in which the blocks are divided by partition walls 12. In addition, the channel-side portion 15 of the second recess may be divided and provided for some channel grooves.

In the first to third embodiments described above, the ink reservoir side portions 16 of the divided second recesses are provided in the same number as the channel grooves and at intervals corresponding to the channel grooves. The size and number are not limited to those shown in this embodiment as long as they have an effect of trapping dust. For example, one ink reservoir side portion can be provided corresponding to two channel grooves. In that case, the length W may be appropriately determined in relation to the size of dust to be trapped.

Further, in the above-mentioned embodiment, the insulating layer 8 is
The thick film resin layer 9 is formed of the same material as the thick film resin layer 9 to form a multilayer structure.
A different material, for example, an inorganic material such as SiO ₂ or PSG, or another material can be used.

[0027]

As is apparent from the above description, according to the present invention, since the ink reservoir side of the second recess for supplying ink from the ink reservoir to the flow path is divided into a plurality of portions, dust or the like is generated. To prevent ink from concentrating in a certain area and causing a large printing defect, and because the channel side of the second recess is commonly connected, ink supply to the channel is prevented even if dust is trapped. Can be done. There is an effect.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a second embodiment of the inkjet recording head of the present invention.

FIG. 3 is a layout view of heaters according to a second embodiment.

FIG. 4 is an explanatory diagram of a third embodiment of the inkjet recording head of the present invention.

FIG. 5 is an explanatory diagram of an example of a conventional inkjet recording head.

FIG. 6 is a perspective view of a main part of a channel wafer.

[Explanation of symbols]

1 channel substrate, 2 heater substrate, 3 channel groove, 4 ink reservoir, 5 nozzles, 6 unetched portion, 7 heater, 8 insulating layer, 9 thick film resin layer, 1
0 first concave portion, 11 second concave portion, 12 partition wall, 13
Ink droplets, 14 recording medium, 15 channel-side portion of the second concave portion, 16 ink reservoir-side portion of the second concave portion, 17 central portion of the second concave portion.

Claims (2)

[Claims] 1. A first substrate having a plurality of channel portions and an ink reservoir portion formed by anisotropic etching,
A thick film insulating layer is provided on a substrate having a plurality of heaters corresponding to the channel portion, and a first concave portion in which a heater is disposed in the thick film insulating layer is connected to the channel portion and the ink reservoir portion. In an ink jet recording head formed by joining a second substrate having a second concave portion formed thereon,
An ink jet recording head, characterized in that a part of a channel side or an intermediate part of the concave part of is connected to each other and an ink reservoir side is divided. 2. A first substrate having a plurality of channel portions and an ink reservoir portion formed by anisotropic etching,
A thick film insulating layer is provided on a substrate having a plurality of heaters corresponding to the channel portion, and a first concave portion in which a heater is disposed in the thick film insulating layer is connected to the channel portion and the ink reservoir portion. In an ink jet recording head formed by joining a second substrate on which two concave portions are formed, one of a channel side or an intermediate portion of the second concave portion corresponding to a plurality of heaters to which voltage pulses are applied at the same timing. An ink jet recording head, wherein the parts are connected to each other and the ink reservoir side is divided.