JP2003246068A - Inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance inkjet head which can form good prints by uniforming a discharge amount and a discharge speed of ink by a simple constitution and a control mechanism. <P>SOLUTION: In the inkjet head, a top plate is set on a head board having many heating resistors arranged in a horizontal scanning direction to form a predetermined gap in-between. At the same time, the gap is sectioned to a plurality of segments arranged in an array in the horizontal scanning direction. Inks of different viscosities are filled for each segment. Prints are formed to a recording paper by selectively making the heating resistors heat to discharge the ink from ink discharge holes. An average resistance value of the heating resistors positioned in the segment is set in accordance with the viscosity of the ink filled in the segment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head which forms an image or the like by depositing ink drops on a recording paper in a predetermined pattern.

[0002]

2. Description of the Related Art Conventionally, an ink jet head has been widely used as a recording device for forming an image on recording paper.

The recording method of an ink jet head uses a thermal energy generated by a heating resistor to eject ink droplets toward a recording paper, uses a deformation of a piezoelectric element, and further irradiates an electromagnetic wave. There is a device that uses the heat generated along with it. Among these, the thermal jet type that uses the heat energy of the heating resistor is easy to pattern the heating resistor and also has a small area. However, since it is possible to generate a relatively large amount of heat energy, it is attracting attention as being suitable for high density recording.

As such a thermal jet type ink jet head, for example, as shown in FIG. 4, a head substrate 21 having a large number of heating resistors 23 attached and arranged in the main scanning direction on the upper surface of a base plate 22, and a plurality of inks. There is known a structure in which the top plate 24 having the ejection holes 25 is arranged so as to form a predetermined gap therebetween, and the gap formed between the two is filled with the ink 26. A large number of heating resistors 23 are selectively and selectively heated by Joules based on image data from the outside, bubbles are generated in the ink 26 by these thermal energies, and the ink 26 is generated by the pressure generated by the bubbles. Part of the ink is ejected from the ink ejection holes 25 toward the recording paper to form a predetermined image on the recording paper, thereby functioning as an inkjet head. .

Recently, it has been considered to form one ink jet head using a plurality of different kinds of ink. In this case, the gap formed between the head substrate 21 and the top plate 24 is the main scanning. It is divided into a plurality of sections arranged in a line in the direction, and the above-mentioned ink is filled in each section. For example, in the case of configuring an inkjet head for color printing, the gap is divided into three or more sections, and different color inks such as magenta, cyan, and yellow are filled in each section.

[0006]

However, when one ink jet head is constructed by using a plurality of inks 26 of different types, the characteristics of the inks 26 with respect to heat are different, so that all the heat generating resistors are formed. 23
When the ink is heated under the same conditions, the ejection speed and the ejection amount of the ink 26 are different for each section, and the ejection amount of the ink 26 is smaller in the section filled with the ink 26 having a particularly high viscosity,
Further, there is a disadvantage that the ejection speed of the ink 26 is also reduced.

Therefore, in order to eliminate the above-mentioned inconvenience, it is possible to make the discharge speed and discharge amount of the ink 26 uniform by adjusting the power applied to the heating resistor 23 according to the characteristics of the ink 26.

However, when the power applied to the heating resistor 23 is adjusted according to the characteristics of the ink 26, a special power supply circuit or the like for adjusting the power applied to the heating resistor 23 for each section is separately required. Therefore, the structure and the control mechanism of the inkjet head are complicated, which causes a defect that increases the cost of the inkjet head.

The present invention has been devised in view of the above-mentioned drawbacks, and an object thereof is a high performance capable of forming an excellent print by uniformizing the ink ejection amount and ejection speed with a simple structure and control mechanism. To provide an inkjet head.

[0010]

According to the ink jet head of the present invention, a top plate is arranged on a head substrate having a large number of heating resistors arranged in the main scanning direction so as to form a predetermined gap therebetween. At the same time, the gap is divided into a plurality of compartments arranged in a line in the main scanning direction, and ink is filled in these compartments. In an inkjet head that forms an image on a recording paper by ejecting from the ejection holes, the viscosity of the ink filled in the gap is different for each section, and the average resistance value of the heating resistors located inside the section is The larger the viscosity of the ink filled in the corresponding section, the smaller the value.

Further, the ink jet head of the present invention is characterized in that the resistance value of the heating resistor is adjusted by a pulse trimming method.

According to the present invention, there is provided an ink jet head in which the gap between the head substrate and the top plate is divided into a plurality of compartments, and a plurality of inks having different viscosities are filled in the compartments. By individually setting the average resistance value of the heating resistor located in the section according to the viscosity of the ink filled in the compartments, the ejection speed and the ejection amount of the ink filled in all the compartments can be made substantially constant. You can Moreover, in this case, there is no need to adjust the electric power applied to the heating resistor, and no special power supply circuit for adjusting the applied power is required. Therefore, the configuration and control mechanism of the inkjet head can be simply maintained. As a result, the inkjet head can be manufactured at low cost.

According to the ink jet head of the present invention, the resistance value of the heating resistor is adjusted by the pulse trimming method, so that the resistance value of the heating resistor can be adjusted accurately and easily. It is also possible to maintain high productivity of the inkjet head.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. 1 is a cross-sectional view of an inkjet head according to an embodiment of the present invention, and FIG. 2 is a plan view of the inkjet head of FIG. 1 as seen from the top plate side. The inkjet head shown in FIG. And top plate 6
And three types of ink 8 having different viscosities are filled between them.

The head substrate 1 has a structure in which a large number of heating resistors 3, a pair of power supply wirings 4, a protective film 5 and the like are adhered in a predetermined pattern on the upper surface of the base plate 2.

The base plate 2 is formed of single crystal silicon or the like in a rectangular shape, and functions as a support base material for supporting a large number of heating resistors 3 and a pair of power supply wirings 4 on the upper surface thereof. To do.

When such a base plate 2 is made of single crystal silicon, it is manufactured by slicing a single crystal ingot (lump) formed by the well-known Czochralski method (pulling method) or the like into a predetermined thickness. It In this case, on the surface of the base plate 2, an insulating film made of silicon oxide (SiO ₂ ) is formed on the surface of the base plate 2 for the purpose of electrically insulating the base plate 2 from a heating resistor 3 described later by a known thermal oxidation method or the like. 1 μm to 3 μ
It is formed to a thickness of m.

A large number of heating resistors 3 provided on the upper surface of the base plate 2 are, for example, 600 dpi (dot per dot) in the longitudinal direction (main scanning direction) of the base plate 2.
inch) and arranged in a straight line, each TaN
Or TaSiO, TaSiNO, TiSiO, TiSiC
It is formed of a resistance thin film made of a resistance material such as O and NbSiO.

Since the heating resistor 3 itself is made of an electric resistance material, when power source power is applied through the power supply wiring 4 and the like, Joule heat is generated and bubbles A are generated in the ink 8. Predetermined temperature (200 ℃ ~
400 ° C.).

The heating resistors 3 are divided into three heating resistor groups arranged in a line in the main scanning direction, and the electric resistance value thereof is substantially constant for each heating resistor group ( Within ± 1.2%), the average resistance value for each heating resistor group is set to a value according to the viscosity of the ink 8 described later.

The heating resistor 3 and the power supply wiring 4 are formed by adopting a conventionally known thin film forming technique. For example, the above resistance material and a metal material such as aluminum are sequentially deposited on the upper surface of the base plate 2 by a conventionally known sputtering method, and the obtained resistance thin film and metal thin film are predetermined by conventionally known photolithography and etching techniques. The heating resistor 3 and the power supply wiring 4 are formed by finely processing the pattern.

A protective film 5 made of silicon nitride or the like is deposited on the upper surfaces of the heat generating resistor 3 and the power supply wiring 4, and the heat generating resistor 3 and the power supply wiring 4 are corroded by the contact of the ink 8 by the protective film 5. Are protected from

On the other hand, the top plate 6 is arranged on the above-mentioned head substrate 1 so as to form a predetermined gap therebetween.

The top plate 6 has a large number of ink ejection holes 7 corresponding to the heating resistors 3 on the head substrate 1 in a one-to-one correspondence. The heating resistors 3 to which these ink ejection holes 7 correspond.
Attach it to the head substrate 1 so that it is located right above
It is fixed.

The diameter of each of the ink ejection holes 7 is set to 10 μm to 100 μm, and bubbles A are generated in the ink 8 as the heating resistor 3 heats during the recording operation of the ink jet head. Then, a part of the ink 8 is ejected from the ink ejection hole 7 toward the recording paper by the pressure caused by the generation of the bubble A.

The top plate 6 is made of a metal such as molybdenum, an electrically insulating material such as alumina ceramics, or a photosensitive resin. For example, when the top plate 6 is made of molybdenum, a molybdenum ingot (lump) is formed by a conventionally known metal working method. Is formed into a plate body having a predetermined thickness, and the obtained plate body is manufactured by forming ink ejection holes 7 in the thickness direction by a well-known laser processing, and the obtained top plate 6 is formed on the head substrate 1. It is fixed to the head substrate 1 by placing it via a spacer (not shown).

The gaps formed between the head substrate 1 and the top plate 6 are three sections arranged in a line in the main scanning direction, that is, three sections A corresponding to the above-mentioned heating resistor group. Each of the sections A, B, and C is filled with three types of color inks 8 having different viscosities.

As such a color ink 8, for example, three kinds of inks of magenta, cyan and yellow are used, and the viscosity thereof is, for example, 1.8 mPa of magenta ink.
.S, cyan ink is 1.6 mPa.s, and yellow ink is 1.4 mPa.s.

As described above, the average resistance value of the heating resistor group is set to a smaller value depending on the viscosity of these inks 8, specifically, the higher the viscosity of the ink 8, the smaller the magenta ink. The heating resistor group disposed inside the filled section A is 298.6Ω, and the heating resistor group disposed inside the section B filled with cyan ink is 300.
8Ω, and the heating resistor group disposed inside the section C filled with yellow ink is set to 301.6Ω.

In this way, the average resistance value of the heating resistor 5 located inside each section provided between the head substrate 1 and the top plate 6 is set to the viscosity of the ink 8 filled in the corresponding section. According to the individual setting, the ejection speed and the ejection amount of the ink 8 ejected from all the sections A, B, C can be made substantially constant, and a good print can be formed on the recording paper. Becomes

Further, in this case, since the discharge amount and the discharge speed of the ink 8 can be made substantially equal by adjusting the electric resistance value itself of the heating resistor 3, the applied power is adjusted by using the correction data and the like. Compared with other cases, a memory for storing correction data, a complicated correction circuit, a dedicated power supply circuit, etc. are not required, and the configuration of the inkjet head can be kept simple, and the inkjet head as a product can be made inexpensive. There is also.

As the ink 8, for example, pigment type water-based ink or water-based dye ink is used, and the ink 8 is supplied from the ink tank (not shown) between the head substrate 1 and the top plate 6 to generate heat. When a bubble A is generated in the ink 8 due to the heat energy generated by the heat generation of the resistor 3, a part of the ink 8 is ejected to the outside from the ink ejection hole 7 by the pressure caused by the generation of the bubble, and this is ejected from the top plate 6. A predetermined image is recorded by adhering it to the recording paper conveyed along the outer surface.

Next, a method for adjusting the resistance value of the heating resistor 3 of the above-mentioned ink jet head will be described by taking the case of using the conventionally well-known pulse trimming method as an example. (1) First, the head substrate 1 having a large number of heating resistors 3 on its upper surface is prepared, and the viscosity of the ink 8 filled in each compartment is measured.

(2) Next, the average resistance value corresponding to the viscosity of the ink 8 is obtained from the conversion table (see FIG. 3) showing the relationship between the ink viscosity and the average resistance value. This conversion table is based on data obtained by actually ejecting the ink 8 using an inkjet head filled with the ink 8 having various viscosities. According to FIG. 3, the viscosity of the ink 8 is 1. In the case of 8 mPa · s, the average resistance value (target resistance value) of the heating resistor 3 is 298.6Ω, and in the case where the viscosity of the ink 8 is 1.6 mPa · s, the target resistance value is 30.
It is set to 0.8Ω.

(3) Next, the electric resistance value of the heating resistor 3 formed on the head substrate 1 is individually measured using a prober or the like, and the measured value and the target resistance obtained in the step (2) are measured. The resistance value correction width corresponding to the difference from the value is obtained, and thereafter, a predetermined trimming pulse is applied to each heating resistor 3 to perform pulse trimming.

In such a pulse trimming method, a trimming pulse corresponding to the resistance value correction width is applied to the heating resistor 3 to lower or increase the electrical resistance value of the heating resistor 3 to thereby increase or decrease the electrical resistance value of the heating resistor 3. Is adjusted,
For example, when lowering the resistance value of the heating resistor 3, the pulse width (energization time) is relatively short with respect to the heating resistor 3,
A trimming pulse having a relatively large amplitude (voltage value) is used. By applying such a trimming pulse to the heating resistor 3, the resistance material is crystallized and the heating resistor 3 is annealed to lower the resistance value. The phenomenon occurs.

When the resistance value of the heating resistor 3 is increased, a trimming pulse having a relatively long pulse width and a relatively small amplitude is used for the heating resistor 3, and such a trimming pulse is used as the heating resistor. When applied to the body 3, the resistance material forming the heating resistor 3 is combined with oxygen in the atmosphere or oxygen in the protective film 5 disposed on the heating resistor 3 to form a thin oxide film on the surface. As a result, the phenomenon that the resistance value rises occurs.

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

In such trimming work, the resistance value may be adjusted only by decreasing or increasing the resistance value, or by both decreasing and increasing the resistance value. For example, when the resistance value of the heating resistor 3 is adjusted only by lowering the resistance value, the resistance material, the film thickness, etc. of the resistance thin film are set so that the initial resistance value is set sufficiently higher than the target resistance value. select.

When the resistance value is adjusted by the pulse trimming method as described above, the resistance value of the heating resistor 3 is accurately measured,
In addition, the adjustment can be easily performed, and thus the productivity of the inkjet head can be maintained high.

In this case, the heating resistor 3 is made of TaSiO.
It is made of a system resistance material and has a Ta content of 50 atom%.
If the electric resistance value of the heating resistor 3 is adjusted by the conventionally well-known pulse trimming method by setting it to ˜60 atomic%,
There is an advantage that the amount of change in resistance value when the trimming pulse is applied becomes an appropriate amount, and the resistance value can be more finely adjusted by the pulse trimming method.

Here, the Ta content in the heating resistor 3 is 6
If it is larger than 0 atom%, the resistance value variation of the heating resistor 3 when a trimming pulse is applied tends to be large and it becomes difficult to finely adjust the resistance value. On the other hand, Ta content in the heating resistor 3 is included. When the ratio is less than 50 atomic%, the resistance value variation of the heating resistor 3 when the trimming pulse is applied is small, and therefore, when the electric resistance value of the heating resistor 3 is largely changed, it takes a long time to adjust the resistance value. Will be required. Therefore, it is preferable to set the Ta content rate in the resistance material forming the heating resistor 3 to 50 atom% to 60 atom%.

The present invention is not limited to the above-mentioned embodiments, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the gap between the head substrate 1 and the top plate 6 is divided into three sections, and these sections are filled with three kinds of inks 8 of magenta, cyan, and yellow, respectively, and the ink jet is carried out. Although the head is configured, the number of sections is further increased and ink of black, photomagenta, photocyan, photoyellow, etc. 8
It may also be configured to discharge.

In the above embodiment, the ink discharge hole 7 is provided in the top plate 6, but instead of this,
In applying the present invention to an edge shooter type inkjet head that ejects ink droplets from the edge of the head substrate 3, the ink ejection holes are not provided in the top plate, and one end side of the head substrate is provided between the head substrate and the top plate. Ink ejection holes may be provided in the.

Further, in the above embodiment, it goes without saying that a driver IC for controlling the heat generation of the heat generating resistor 3 may be mounted on the head substrate 1.

[0047]

According to the present invention, in the ink jet head in which the gap between the head substrate and the top plate is divided into a plurality of compartments and a plurality of inks having different viscosities are respectively filled in the compartments, By individually setting the average resistance value of the positioned heating resistors according to the viscosity of the ink filled in the compartments, the ejection speed and the ejection amount of the ink filled in all the compartments can be made substantially constant. it can.
Moreover, in this case, there is no need to adjust the electric power applied to the heating resistor, and no special power supply circuit for adjusting the applied power is required. Therefore, the configuration and control mechanism of the inkjet head can be simply maintained. As a result, the inkjet head can be manufactured at low cost.

According to the ink jet head of the present invention, the resistance value of the heating resistor is adjusted by the pulse trimming method, so that the resistance value of the heating resistor can be adjusted accurately and easily. It is also possible to maintain high productivity of the inkjet head.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a plan view of the inkjet head of FIG. 1 viewed from a top plate 6 side.

FIG. 3 is a diagram showing a relationship between ink viscosity and a target resistance value.

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

[Explanation of symbols]

1 ... Head substrate 2 ... Base plate 3 ... Heating resistor 4 power supply wiring 5 ... Protective film 6 ... top plate 7 ... Ink ejection hole 8 ... Ink A, B, C ... Section

Claims (2)

[Claims] 1. A top plate is arranged on a head substrate having a large number of heating resistors arranged in the main scanning direction so as to form a predetermined gap therebetween, and the gaps are arranged in a line in the main scanning direction. Is divided into a plurality of compartments and ink is filled in these compartments, and the heating resistor is selectively heated to eject the ink from the ink ejection holes to print on the recording paper. In the ink jet head for forming the ink, the viscosity of the ink filled in the gap is different for each section, and the average resistance value of the heating resistors located inside the section is filled in the corresponding section. The ink jet head is characterized in that the larger the viscosity of, the smaller the value. 2. The ink jet head according to claim 1, wherein the heating resistor has a resistance value adjusted by a pulse trimming method.