JP2003341066A - Thermal inkjet head and its resistance value adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high performance thermal inkjet head capable of imaging clearly on a recording sheet while suppressing distortion in which a high recording speed can be dealt with while sustaining a simple arrangement. <P>SOLUTION: On a head substrate 1 formed by applying a large number of heating elements 3 made of a thin resistive film and power supply wiring 4 connected electrically with the heating elements onto the upper surface of a base plate 2, a top plate 7 having a large number of ink ejection holes 8 corresponding to the heating elements is placed to form a specified gap being filled with ink 9. In such a thermal inkjet head, electric resistance of the heating element 3 is set to increase as the distance to the surface of a protective film located directly under the ink ejection hole 8 becomes shorter. <P>COPYRIGHT: (C)2004,JPO

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 forming an image by adhering ink droplets on a recording paper in a predetermined pattern and a method for adjusting a resistance value of the thermal ink jet head.

[0002]

2. Description of the Related Art Conventionally, an inkjet head has been used as an apparatus for forming an image by depositing ink droplets on a recording paper in a predetermined pattern.

The ink jet head recording system uses a thermal energy generated by a heating element to eject ink droplets toward a recording sheet, a deformation of a piezoelectric element, and an electromagnetic wave irradiation. There are those that utilize the heat generated by, and among these, the thermal inkjet head type that utilizes the thermal energy of the heating element is easy to pattern the heating element,
Even a heat-generating element having a small area can generate a relatively large amount of heat energy, and thus is attracting attention as a material suitable for high-density recording.

In such a conventional thermal ink jet head, as shown in FIG. 7, a large number of heating elements 23 linearly arranged on the upper surface of a base plate 22 made of single crystal silicon, and electrically connected to the heating elements 23. A plurality of ink ejection holes 28 corresponding to the heating elements 23 in a one-to-one correspondence are formed on the head substrate 21 on which the power supply wirings 24 are attached.
There is known a structure in which a top plate 27 having a space is formed so as to form a predetermined gap therebetween, and the gap is filled with ink 29. While being conveyed, a large number of heating elements 23 are individually and selectively made to generate heat based on image data from the outside.
A bubble A is generated in the ink 29 on 3 and the ink 29 on the heating element 23 is pushed up to the ink ejection hole 28 side by the pressure of the generated bubble A, and this is made into an ink droplet i from the ink ejection hole 28. A predetermined image is recorded by ejecting the ink toward the outside and adhering it to the recording paper.

Incidentally, the heating element 23 and the power supply wiring 24.
Is a conventionally known thin film forming technique, specifically, a laminated body including a resistive thin film and a metallic thin film formed by sequentially depositing a resistive material such as TaSiO and a metallic material such as aluminum on the upper surface of the base plate 22 by conventional known sputtering. Was formed, and this was finely processed into a predetermined pattern by conventionally known photolithography and etching (photoetching) techniques.

The heating element 23 and the power supply wiring 2 are also provided.
The protective film 26 that covers 4 is, for example, a conventionally known sputtering, vacuum deposition method, or plasma CVD (Chemical Vap).
(or Deposition), etc.
3 and SiO ₂ (silicon oxide) or S on the surface of the power supply wiring 24, etc.
It was formed by depositing an inorganic material such as iON or Si ₃ N ₄ (silicon nitride) to a predetermined thickness.

[0007]

By the way, in the above-mentioned thermal ink jet head, the heating element 23 is used.
When forming the protective film 26, the top plate 27, and the like, the resistance thin film and the protective film 2 are caused by variations in film forming conditions and manufacturing conditions.
6. The thickness of the top plate 27 may vary along the arrangement direction of the heating elements 23.

However, the pressure from the bubbles generated in the ink due to the heat generation of the heating element 23 is more likely to be transmitted upward as the distance from the surface of the protective film 26 to the ink ejection hole 28 is smaller, and therefore, it is dealt with. The closer the ink ejection hole is to the surface of the protective film, the higher the ejection speed of the ink droplet i ejected from the ink ejection hole 28. Therefore, when all the heating elements 23 are heated under the same conditions, the ejection speeds of the ink droplets i individually vary, and the ink droplets i land on the recording paper at different timings. There is a risk that the landing position of i may be displaced and the image may be distorted.

Therefore, in order to solve the above-mentioned drawbacks, the distance between each ink ejection hole 28 and the surface of the protective film 26 is measured, and correction data is created based on the measured distance. It has been proposed that the timing of the ink droplets i that land is made uniform by adjusting the power applied to the heating element 23 using the same.

However, when adjusting the power applied to each heating element 23 using the correction data, a large memory for storing the correction data to be applied to all the heating elements 23, a complicated correction circuit, a power supply circuit, etc. Is required separately, and the configuration of the thermal inkjet head and the printer body in which it is incorporated is significantly complicated, and since such correction is performed for each printing line, the time required for recording operation is prolonged. A defect that causes a decrease in recording speed is induced.

The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is to form a clear image with little distortion on a recording paper, and to increase the recording speed while keeping the configuration simple. Another object of the present invention is to provide a high-performance thermal inkjet head that can also be used, and a method of adjusting the resistance value of the thermal inkjet head that can obtain such a thermal inkjet head.

[0012]

In a thermal ink jet head of the present invention, a large number of heating elements made of a resistive thin film and power supply wirings electrically connected to the heating elements are attached to the upper surface of a base plate, On the head substrate formed by covering the heating elements and the power supply wiring with a protective film, a top plate having a large number of ink ejection holes corresponding to the heating elements is arranged so as to form a predetermined gap therebetween, In the thermal inkjet head having the gap filled with ink, the electric resistance value of the heating element is larger as the corresponding ink ejection hole is closer to the surface of the protective film located immediately below the ink ejection hole. It is characterized by being set to a value.

The thermal ink jet head of the present invention is characterized in that the electric resistance value of the heating element is adjusted by a pulse trimming method.

Further, according to the method of adjusting the resistance value of the thermal ink jet head of the present invention, a large number of heating elements made of a resistive thin film and power supply wirings electrically connected to the heating elements are attached to the upper surface of the base plate. On the head substrate formed by covering the heating elements and the power supply wiring with a protective film, a top plate having a large number of ink ejection holes corresponding to the heating elements is arranged so as to form a predetermined gap therebetween, In a thermal inkjet head formed by filling the gap with ink, a step 1 of individually measuring a distance between the ink discharge hole and a surface of a protective film located immediately below the hole.
Step 2 of selecting a trimming pulse corresponding to the distance between the ink ejection hole and the surface of the protective film measured in step 1
Then, the trimming pulse selected in step 2 is applied to the corresponding heating element to adjust the electric resistance value of the heating element.

Furthermore, in the resistance value adjusting method of the thermal ink jet head of the present invention, the heating element to which the trimming pulse corresponds is provided in the middle of the power supply wiring and through the pad for trimming provided outside the ink filling area. It is characterized by being applied.

According to the present invention, the electrical resistance value of each heating element is individually corrected, and the thermal energy generated by each heating element is adjusted according to the distance between the ink ejection hole and the surface of the protective film located immediately below the ink ejection hole. Since all the ink droplets ejected from the ink ejection holes can be landed on the recording paper at substantially the same timing, a clear image with less distortion can be recorded. .

Further, according to the present invention, by adjusting the electric resistance value of the heating element, all the ink droplets are landed on the recording paper at substantially the same timing. Therefore, the correction power is used to apply the applied power. In comparison with the case of adjusting, the memory for storing the correction data, the complicated correction circuit, the power supply circuit, etc. are not required, and the configuration of the thermal inkjet head and the printer body in which the thermal inkjet head is incorporated can be simply maintained. It is possible to obtain a high-performance thermal ink jet head that can be used for speeding up the recording speed without any correction process during the recording operation.

Further, according to the present invention, the thermal ink jet head is assembled by applying a trimming pulse to the heating element via the trimming pad provided in the middle of the power supply wiring and outside the ink filling area. Even after the trimming, the probe (probe) of the probing device used for applying the trimming pulse can be surely and easily brought into contact with the pad for trimming, and the workability of trimming is improved. There is also the advantage of being good.

[0019]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. 1 is an exploded perspective view of a thermal inkjet head according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the thermal inkjet head of FIG. 1. The thermal inkjet head shown in FIG. Ink 9 is filled between the two members.

The head substrate 1 has a large number of heating elements 3 linearly arranged on an upper surface of a base plate 2 formed in a rectangular shape, and a power supply wiring 4 electrically connected to the heating elements 3. And is deposited and formed, and these are covered with a protective film 6.

The base plate 2 is made of a semiconductor material such as single crystal silicon or an electrically insulating material such as glaze alumina ceramics, and supports the heating element 3, the power supply wiring 4, the protective film 6 and the like on its upper surface. It functions as a supporting base material.

When the base plate 2 is made of, for example, single crystal silicon, a well-known Czochralski method (pulling method) or the like is used to form an ingot (lump) of single crystal silicon, and the ingot is formed to a predetermined thickness. It is manufactured by slicing into pieces and processing the outline. In this case, an insulating film (not shown) made of an electrically insulating material such as silicon oxide (SiO ₂ ) is provided on the entire surface of the base plate 2 in a thickness of, for example, 1 μm to 3 μm. The single crystal silicon forming 2 is electrically insulated from the heating element 3 and the like.

A large number of heating elements 3 provided on the upper surface of the base plate 2 are, for example, 600 dpi (do
are arranged linearly in the main scanning direction at a density of t per inch), each of which is TaN, TaSiO, TaSiNO,
Resistive thin film (thickness 0.01 μm to 0.2 μm) made of electric resistance material such as TiSiO, TiSiCO, NbSiO
It is formed by.

Since the heating element 3 itself is made of an electric resistance material, when power source power is supplied through the power supply wiring 4 and the like, Joule heat is generated and bubbles A are generated in the ink 9. Generates the required thermal energy required for

The heating elements 3 have their resistance values corrected by the pulse trimming method described later.
The electrical resistance value is set to a larger value as the corresponding ink ejection hole 8 described later is closer to the surface of the protective film 6 located immediately below the ink ejection hole 8.

Further, the power supply wiring 4 connected to the heat generating element 3 is for applying power source power to the heat generating element 3 described above, and one end of the power supply wiring 4 is led out to the outside of the ink 9 filling area described later. The lead-out portion is connected to a terminal such as a driver IC (not shown).

The power supply wiring 4 has a trimming pad 5 having a circular shape or a quadrangular shape larger than the line width of the power supply wiring 4 in the middle of each of the power supply wirings 4 and outside the filling area of the ink 9. The pads 5 are arranged in a line in the direction parallel to the arrangement direction of the heating elements 3 (main scanning direction).

The pad 5 is for contacting a probe (probe) 12 of a probing device for applying a trimming pulse when the electric resistance value of the heating element 3 is adjusted by a conventionally well-known pulse trimming method. It is positioned outside the edge of the top plate 7 so that the trimming work can be easily performed even after the thermal inkjet head is assembled.

The heating element 3 and the power supply wiring 4 are formed by a conventionally known thin film forming technique such as sputtering, photolithography, etching technique, or the like. Specifically, first, a resistive material such as TaSiO and a metallic material such as aluminum are sequentially deposited on the upper surface of the base plate 2 by the conventionally well-known sputtering to form a laminated body composed of a resistive thin film and a metallic thin film. The heating element 3 and the power supply wiring 4 are patterned into a predetermined shape by finely processing by known photolithography and etching (photoetching) techniques.
After the assembly process of the thermal inkjet head is completed, the electric resistance value of each heating element 3 is adjusted by the adjustment method described later.

The pad 5 of the power supply wiring 4 is applied to a predetermined portion of the power supply wiring 4 by nickel plating, gold plating or the like by a well-known electroless plating method or the like to have a thickness of, for example, 2 μm to 5 μm. It is formed.

The protective film 6 covering the heating element 3 and the power supply wiring 4 is corroded by the alkali ions and water contained in the ink 9 coming into contact with the heating element 3 and the power supply wiring 4. Alternatively, it is for effectively preventing the solidification of the dye contained in the ink 9 from adhering to the surface of the heating element 3, and for example, SiO ₂ (silicon oxide), SiON, Si ₃ N An inorganic material such as ₄ (silicon nitride) is formed to a thickness of 0.2 μm to 2.0 μm, for example.

The protective film 6 has its end located closer to the heating element 3 than the pad 5 so that the pad 5 is exposed.
It is formed by using plasma CVD (Chemical Vapor Deposition) or the like and depositing the above-mentioned inorganic material to a thickness of 0.2 μm to 20 μm on the surfaces of the heating element 3, the power supply wiring 4, and the like. When forming the protective film 6,
Alternatively, since it is difficult to keep the film forming conditions constant when forming the heating element 3 described above, the thicknesses of the protective film 6 and the resistance thin film vary depending on the location where the heating element 3 is formed.

On the other hand, on the above-mentioned head substrate 1,
The top plate 7 is arranged so as to form a predetermined gap therebetween.

The top plate 7 is for closing an ink flow path made of the ink 9 filled in the gap with the head substrate 1, and the outer shape of the top plate 7 has a dimension in the sub-scanning direction. Specifically, the top plate 7 should be smaller than the above.
Is arranged so that one end of the is located closer to the heating element 3 than the position of the pad 5.

The top plate 7 has a large number of ink ejection holes 8 that correspond to the heating elements 3 in a one-to-one correspondence, and is positioned so that the ink ejection holes 8 are located directly above the corresponding heating elements 3. Has been done.

The ink ejection hole 8 is for ejecting the ink as an ink droplet i toward the recording paper by the pressure from the bubble A generated in the ink during the recording operation of the ink jet head, and as described above. Since the thicknesses of the protective film 6 and the resistance thin film are varied depending on the location where the heating element 3 is formed, the distance between the ink ejection hole 8 and the surface of the protective film 6 located directly below the ink ejection hole 8 is different. There is.

On the other hand, as described above, regarding the electric resistance value of the heating element 3, the corresponding ink ejection hole 8 is
Since the value closer to the surface of the protective film 6 located directly below the surface of the protective film 6 is set to a larger value, the closer the ink ejection holes 8 are to the surface of the protective film, the smaller the thermal energy generated by the heating element 3, The ejection speed of the ejected ink droplet i becomes slow. Therefore, during the recording operation, the ink droplets i ejected from the ink ejection holes 8 land on the recording paper at substantially the same timing, and a clear image with less distortion can be recorded.

Further, in this case, since all the ink droplets i are made to land on the recording paper at substantially the same timing by adjusting the electric resistance value of the heating element 3, the correction data is used. Compared to the case of adjusting the applied power, a memory for storing correction data, a complicated correction circuit, a power supply circuit, etc. are not required, and the configuration of the thermal inkjet head and the printer body in which it is incorporated can be simply maintained. In addition, it is possible to obtain a high-performance thermal inkjet head that can be used for speeding up the recording speed without any correction process during the recording operation.

The top plate 7 is made of various materials such as a metal plate made of molybdenum or the like, a ceramic plate made of alumina ceramics, or a resin plate such as epoxy resin or polyimide resin. In the case of molybdenum, for example, a molybdenum ingot (lump) is formed into a plate shape by a conventionally known metal working method, and a well-known laser processing or photo etching is performed on a predetermined portion of the plate body. The top plate 7 is manufactured by adopting a technique or the like to form a large number of ink ejection holes 8 having a diameter of about 10 μm to 100 μm. By mounting it, the top plate 7 is fixed at a predetermined position on the head substrate 1.

As the ink 9 filled in the gap between the head substrate 1 and the top plate 7, for example, an aqueous dye ink is preferably used, and the viscosity thereof is, for example, 0.3 mPas.
-Adjusted to s-3.0 mPa-s (25 ° C).

The ink 9 as described above is supplied from an ink tank (not shown) to the gap between the head substrate 1 and the top plate 7, and bubbles are generated in the ink 9 by the thermal energy from the heating element 3 described above. When A occurs, a part of the ink 9 is partially ejected by the ink ejection holes 8 due to the pressure when the bubbles are generated.
As a result, ink droplets i are ejected to the outside, and a predetermined image is formed by attaching these ink droplets i to the surface of the recording paper conveyed along the outer surface of the top plate 7.

Next, a method of adjusting the resistance value of the thermal ink jet head described above will be described with reference to the flowchart of FIG.

(1) First, the head substrate 1 having the heating elements 3 and the like which are patterned by the conventionally well-known thin film forming technique.
And the top plate 7 having the ink ejection holes 8 are arranged so as to face each other so as to form a predetermined gap therebetween, and the gap 9 is filled with the ink 9 to assemble the thermal inkjet head.

(2) Next, the distance between the ink ejection hole 8 and the surface of the protective film 6 located immediately below the ink ejection hole 8 is measured.

The distance between the ink ejection hole 8 and the surface of the protective film is measured by using, for example, a laser. Specifically, a laser is irradiated from the opening of the ink ejection hole 8 toward the protective film 6 immediately below the opening, and the reflected laser on the surface of the protective film is detected using a photo sensor. After that, it is determined by calculating the distance between the ink ejection hole 8 and the surface of the protective film from the time required from laser irradiation to detection and the laser speed, and the accuracy thereof is ± 0. It is set to 1 μm.

(3) Next, the target resistance value corresponding to the distance between the ink ejection hole 8 and the surface of the protective film measured in the step (2) is determined from the conversion table shown in FIG.

This conversion table is based on the data obtained by actually ejecting the ink droplet i by slightly changing the distance between the ink ejection hole 8 and the surface of the protective film. Thus, for example, when the distance between the ink ejection holes 8 and the surface of the protective film is 16 μm, the target resistance value is 275Ω, and when the distance between the ink ejection holes 8 and the surface of the protective film is 20 μm, the target resistance value is Are set to 265Ω respectively.

(4) Next, the electric resistance value of the heating element 3 is
The resistance value correction width corresponding to the thermal head between the measured value and the target resistance value obtained in the step (2) is obtained by performing individual measurement using the probe (probe) 12 of the probing device and the like. From the diagram (Fig. 5) showing the relationship between the "resistance value correction width" and the "trimming pulse energy",
The energy of the trimming pulse to be applied to each heating element 3 is obtained, and the trimming pulse closest to this is selected from a plurality of types of trimming pulses prepared in advance.

When the electric resistance value obtained by the measurement is larger than the target resistance value, the resistance value is corrected in the direction of decreasing it. Therefore, the diagram of FIG. 5 (a) is used and the measurement is performed. When the electric resistance value obtained by is smaller than the target resistance value, the resistance value is corrected in the direction of increasing, and therefore the diagram of FIG. 5B is used.

(4) Finally, a conventionally known pulse trimming method, specifically, the trimming pulse selected in the step (3) is applied to the corresponding heating element 3 to change the electric resistance value of the heating element 3. The electric resistance value of the heating element 3 is adjusted by lowering or raising it.

The application of the trimming pulse to the heating element 3 is performed via the pad 5 of the power supply wiring 4 described above, and the probe 12 of the probing device is brought into contact with the surface of the pad 5 as shown in FIG. In this state, the heating element 3 is trimmed by applying the predetermined trimming pulse selected in the step (3) from the probing device, whereby the electric resistance value of the heating element 3 is adjusted.

At this time, the power supply wiring 4 is brought into contact with the probe 12 of the probing device when the trimming pulse is applied.
Pad 5 is provided outside the area filled with ink 9,
Even after assembling the thermal ink jet head, the probe 12 of the probing device can be surely brought into contact with the pad 5 for easy trimming, and the trimming workability can be improved. is there.

In this pulse trimming method, for example,
The pulse width (energization time) is relatively short for the heating element 3,
By applying a trimming pulse having a relatively large amplitude (voltage value), the resistance material forming the heating element 3 is crystallized. In this case, the heating element 3 is annealed and a decrease phenomenon of the resistance value occurs.

On the other hand, when increasing the resistance value of the heating element 3, for example, the head substrate 1 in which the heating element 3 is covered with the protective film 6 containing 2 wt% to 10 wt% of oxygen is used. On the other hand, by applying a trimming pulse having a relatively long pulse width and a relatively small amplitude, the resistive material forming the heating element 3 is combined with oxygen in the protective film 6, and a thin oxide film is formed on the surface of the resistive material. Increase the value.

At this time, the heating element 3 is made of a TaSiO type resistance material, and the Ta content is 50 atomic% to 60%.
If the atomic% is set, when adjusting the electric resistance value of the resistance material forming the heating element 3 by the pulse trimming method,
There is an advantage that the amount of resistance variation when a predetermined pulse is applied becomes an appropriate amount, and it becomes easier to finely adjust the resistance value by the pulse trimming method.

Here, the Ta content in the heating element 3 is 60.
When it is larger than atomic%, the resistance value variation of the heating element 3 when the trimming pulse is applied tends to be large and it becomes difficult to finely adjust the resistance value, while the Ta content rate in the heating element 3 is 50%. If it is less than atomic%, the resistance value variation of the heating element 3 when the trimming pulse is applied is small, so that when the electric resistance value of the heating element 3 is largely changed, it takes a long time to adjust the resistance value. . Therefore, it is preferable to set the Ta content rate in the heating element 3 to 50 atom% to 60 atom%.

After performing the above-mentioned trimming work, the resistance value of the trimmed heating element 3 is measured,
If the measured value is not sufficiently close to the target resistance value, the above trimming work is repeated until the resistance value falls within the allowable range.

In such a trimming operation, the resistance value may be adjusted only by lowering or raising the resistance value, or by both lowering and raising the resistance value. For example, only when the resistance value decreases, the heating element 3
When the resistance value adjustment is performed, the material and film thickness of the resistive thin film are selected so that the initial resistance value is set sufficiently higher than the target resistance value.

The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

For example, in the above embodiment, a partition member for separating the adjacent heating element 3 is interposed between the head substrate 1 and the top plate 7, or such a partition member is integrated with the top plate 7. You may make it form in.

In the above embodiment, the trimming pads 5 are arranged in a line in the main scanning direction, but instead, the trimming pads 5 are arranged in a staggered pattern in the main scanning direction. Alternatively, in this case, there is an advantage that a space can be provided between the adjacent pads and a short circuit between the adjacent power supply wirings 4 and pads 5 can be effectively prevented.

[0062]

According to the present invention, the electrical resistance value of each heating element is individually corrected so that the thermal energy generated by each heating element is separated from the ink ejection hole by the distance between the surface of the protective film located immediately below the ink ejection hole. Since all the ink droplets ejected from the ink ejection holes can be landed on the recording paper at almost the same timing, it is possible to record a clear image with little distortion. Becomes

Further, according to the present invention, the electric resistance value of the heating element is adjusted so that all the ink droplets land on the recording paper at substantially the same timing. In comparison with the case of adjusting, the memory for storing the correction data, the complicated correction circuit, the power supply circuit, etc. are not required, and the configuration of the thermal inkjet head and the printer body in which the thermal inkjet head is incorporated can be simply maintained. It is possible to obtain a high-performance thermal ink jet head that can be used for speeding up the recording speed without any correction process during the recording operation.

Further, according to the present invention, the thermal ink jet head is assembled by applying the trimming pulse to the heating element via the trimming pad provided on the way of the power supply wiring and outside the ink filling area. Even after the trimming, the probe (probe) of the probing device used for applying the trimming pulse can be surely and easily brought into contact with the pad for trimming, and the workability of trimming is improved. There is also the advantage of being good.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a thermal inkjet head according to an embodiment of the present invention.

2 is a cross-sectional view of the thermal inkjet head shown in FIG.

FIG. 3 is a flowchart illustrating an adjusting method according to an exemplary embodiment of the present invention.

[Fig. 4] "Distance between ink ejection hole 8-surface of protective film 6"
It is a diagram which shows the relationship between and "target resistance value."

FIG. 5A is a diagram showing a relationship between a “resistance value correction width” and a “trimming pulse energy” when the resistance value is decreased, and FIG. 5B is a “resistance value” when the resistance value is increased. It is a diagram which shows the relationship between "correction width" and "energy of a trimming pulse."

FIG. 6 is a sectional view for explaining a trimming operation.

FIG. 7 is a cross-sectional view of a conventional thermal inkjet head.

[Explanation of symbols]

1 ... Head substrate 2 ... Base plate 3 ... Heating element 4 power supply wiring 5 ... Pad 6 ... Protective film 7 ... top plate 8 ... Ink ejection hole 9 ... Ink 12 ... Probing device probe A ... bubbles i ... Ink drop

Claims (4)

[Claims] 1. A large number of heating elements made of a resistive thin film and power supply wirings electrically connected to the heating elements are attached to the upper surface of a base plate, and the heating elements and power supply wirings are covered with a protective film. A thermal ink jet head in which a top plate having a large number of ink ejection holes corresponding to the heating elements is arranged on a head substrate made of the above so as to form a predetermined gap between them, and the gap is filled with ink. In the above, the thermal resistance of the heating element is set to a larger value as the corresponding ink ejection hole is closer to the surface of the protective film located immediately below the ink ejection hole. Inkjet head. 2. The thermal ink jet head according to claim 1, wherein the electric resistance value of the heating element is adjusted by a pulse trimming method. 3. A large number of heating elements made of a resistive thin film and power supply wirings electrically connected to the heating elements are attached to the upper surface of the base plate, and the heating elements and power supply wirings are covered with a protective film. A thermal ink jet head in which a top plate having a large number of ink ejection holes corresponding to the heating elements is arranged on a head substrate formed of the above so as to form a predetermined gap therebetween, and the gap is filled with ink. 3. The method for adjusting the resistance value of a thermal inkjet head, wherein the electric resistance value of the heating element is adjusted through the following steps 1 to 3. Step 1: A step of individually measuring the distance between the ink ejection hole and the surface of the protective film located immediately below the ink ejection hole. Step 2: A step of selecting a trimming pulse corresponding to the distance between the ink ejection hole and the surface of the protective film measured in Step 1. Step 3: A step of applying the trimming pulse selected in Step 2 to the corresponding heating element to adjust the electric resistance value of the heating element. 4. A trimming pulse is applied to a corresponding heating element via a trimming pad provided in the middle of the power supply wiring and outside the ink filling area. Method for adjusting resistance value of thermal ink jet head.