JP2003237089A - Method for setting driving condition of printer and printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and surely set a driving condition by applying a setting method for the driving condition to particularly a printer which records to a recording object by heating of heating elements thereby ejecting ink liquid drops in relation to the setting method for the driving condition of the printer and the printer. <P>SOLUTION: A driving time interval in which a resistance value of the heating element changes by not smaller than a fixed rate by repetitive driving is obtained, and an upper limit value is set by the driving time interval to set a driving period. <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 a printer driving condition setting method and a printer, and in particular, can be applied to a printer that ejects ink droplets by heating a heating element to record on a recording target. The present invention obtains a driving period in which the resistance value of the heating element changes by a certain ratio or more by repeated driving, and sets the upper limit value by this driving period to set the driving period, thereby simplifying this type of driving condition. Make sure you can set it.

[0002]

2. Description of the Related Art In recent years, in the field of image processing and the like, there is an increasing need for colorization of hard copy. In response to this need, color copying methods such as a sublimation type thermal transfer method, a fusion thermal transfer method, an inkjet method, an electrophotographic method, and a heat development silver salt method have been conventionally proposed.

Among these methods, the ink jet method is one in which a small droplet of a recording liquid (ink) is ejected from a nozzle provided in a printer head and adheres to a recording object to form a dot, which has a simple structure. A high quality image can be output. This inkjet system is classified into an electrostatic attraction system, a continuous vibration generation system (piezo system), and a thermal system depending on the difference in the method of ejecting ink droplets from a nozzle.

Among these methods, the thermal method is a method in which air bubbles are generated by local heating of ink, and the ink is ejected from the nozzles by the air bubbles to fly to a print target, and a color image is printed with a simple structure. It is designed to be able to.

That is, this thermal printer is constructed by using a so-called printer head. In this printer head, a heating element for heating ink, a driving circuit by a logic integrated circuit for driving the heating element, etc. are mounted on a semiconductor substrate. To be done. As a result, in this type of printer head, the heating elements are arranged at a high density so that they can be reliably driven.

That is, in this thermal printer, it is necessary to arrange the heating elements at a high density in order to obtain a high quality printing result. Specifically, for example, 600
In order to obtain a print result equivalent to [DPI], it is necessary to dispose the heating elements at intervals of 42.333 [μm]. However, individual driving elements are arranged in the heating elements arranged at such a high density. It is extremely difficult to do. With this, in the printer head, switching transistors etc. are created on the semiconductor substrate, the corresponding heating elements are connected by the integrated circuit technology, and each switching transistor is driven by the drive circuit similarly created on the semiconductor substrate. The heating elements can be driven easily and reliably.

In a thermal printer, air bubbles are generated in the ink due to heating by the heating element.
When the ink is ejected from the nozzle, this bubble disappears.
This causes a mechanical shock due to cavitation due to repeated firing and extinguishing. Further, in the printer, the temperature rise and the temperature drop due to the heat generation of the heating element are repeated in a short time [several microseconds], which causes a great stress due to the temperature.

Therefore, in the printer head, a heating element is formed of tantalum, tantalum nitride, tantalum aluminum, or the like, and a protective layer of silicon nitride, silicon carbide, tantalum, or the like is formed on the heating element, and the protective layer is heat resistant. Insulation is improved, and direct contact between the heating element and the ink is prevented. In addition, a cavitation-resistant layer is formed on the protective layer so as to reduce the mechanical impact of cavitation.

FIG. 12 is a cross-sectional view showing the structure in the vicinity of the heating element in this type of printer head. In the printer head 1, an insulating layer (SiO ₂ ) or the like is laminated on a semiconductor substrate 2 on which semiconductor elements are formed, and then a heating element 3 is formed by a tantalum film or the like. Further, after the protective layer 4 made of silicon nitride (Si ₃ N ₄ ) is laminated, the wiring pattern (AI wiring) 5 is formed. Printer head 1
The heating element 3 is connected to a semiconductor or the like formed on the semiconductor substrate 2 by this wiring pattern, and a protective layer 6 made of silicon nitride (Si ₃ N ₄ ) is further laminated thereon. Layer 7 is formed. In the printer head 1, an ink liquid chamber, an ink flow path, and a nozzle are created by subsequently disposing a predetermined member. The printer head 1 drives the heating element 3 by a rectangular-wave drive signal after the ink is guided to the ink liquid chamber by the ink flow path thus created.

In the printer head 1 having such a structure, the power consumption can be reduced by reducing the heat generation amount of the heat generating element. However, if the heat generation amount of the heating element is insufficient, it becomes difficult to sufficiently heat the ink, which makes it difficult to eject ink droplets from the nozzle.

On the contrary, when the heating value of the heating element becomes excessively large, the content in the ink reacts with heat to deposit a carbide or oxide (hereinafter referred to as kogation) on the surface of the cavitation resistant layer 7. And then accumulated. This makes it difficult for the printer head 1 to eject ink droplets.

When the amount of heat generated is too large, a reaction due to heat occurs between the surface of the cavitation resistant layer 7 and the ink in the printer head 1, so that the cavitation resistant layer 7 is eroded. As a result, in the printer head 1, the cavitation resistant layer 7 does not function sufficiently, and the heat generating element 3 is disconnected due to a mechanical impact due to cavitation, and in this case also, it becomes difficult to eject ink droplets. .

Therefore, in the conventional printer head, the conditions under which the heating element can be driven under various conditions to stably eject the ink droplets, the conditions for erosion of the cavitation-resistant layer, and the occurrence of kogation are determined, The driving condition of the heating element is set within the range of these conditions.

On the other hand, for example, Japanese Patent Laid-Open No. 2001-800
77, Japanese Patent Application Laid-Open No. 2001-130005 proposes drive conditions for driving a heating element in a printer head having a specific configuration. Further, Japanese Patent Application Laid-Open No. 2001-171126 proposes a driving condition of a heating element based on an upper limit value of a heating value.

[0015]

By the way, in practice, in the printer head, the material of the heating element, the protective layer, etc.,
The film thickness and the size of the ink liquid chamber may differ depending on the model. In addition, the film structure itself from the heating element to the ink liquid chamber may differ depending on the model. In such a printer head, since the thermal conductivity from the heating element to the ink, the degree of heat radiation, etc. are different,
The appropriate conditions for driving the heating element will also vary.

As a result, in the printer head, Japanese Patent Laid-Open Nos. 2001-80077 and 2001-13000.
5, it is difficult to properly set the driving condition of the heating element depending on the conditions disclosed in Japanese Patent Application Laid-Open No. 2001-171126, etc., and eventually, the complicated operation is performed for each model to drive the heating element. There was a problem that conditions had to be set.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a printer setting method capable of easily and surely setting a driving condition of this kind, and a printer using this setting method. is there.

[0018]

In order to solve such a problem, in the invention of claim 1, a printer for printing a desired image by causing a heating element to generate heat for a predetermined drive period by a drive signal having a rectangular wave shape. It is applied to the setting method of the driving condition, the driving period in which the resistance value of the heating element changes by a certain ratio or more is obtained by the repeated driving, the upper limit value of the driving period is set by the driving period, and the upper limit value is not exceeded. , Set the drive period.

According to the second aspect of the invention, the invention is applied to a printer which prints a desired image by heating a heating element for a predetermined driving period by a rectangular wave driving signal, and the heating element is driven by repeated driving. A driving period in which the resistance value changes by a certain ratio or more is obtained, the upper limit of the driving period is set with reference to the driving period, and within a range not exceeding the upper limit,
The drive period is set.

According to the structure of claim 1, a driving period in which the resistance value of the heating element changes by a certain ratio or more is obtained by repeated driving, and the upper limit value of the driving period is set by the driving period, and the upper limit value is not exceeded. By setting the drive period within the range, it is possible to set the drive period within a range in which changes in the members forming the heating element can be effectively avoided by repeated driving. Also in this range,
This is a range in which kogation of ink and erosion of the cavitation resistant layer do not occur, and the driving conditions can be set easily and surely by these.

Thus, according to the second aspect of the invention, it is possible to provide a printer in which driving conditions are set easily and surely.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings as appropriate.

(1) Configuration of Embodiment FIG. 2 is a sectional view showing a printer head applied to a printer according to an embodiment of the present invention. The printer head 21 is configured by laminating protective layers 23 and 24 made of a silicon nitride film and a cavitation resistant layer 25 made of a tantalum film on a heating element 22.

That is, as shown in FIG. 3A, in the printer head 21, a silicon nitride film (Si ₃ N ₄ ) is deposited after the P-type silicon substrate 26 made of a wafer is cleaned. Then, the printer head 21 is processed by the lithography process and the reactive etching process to the silicon substrate 2
6 is processed so that the silicon nitride film is removed from the region other than the predetermined region where the transistor is formed. As a result, the silicon substrate 26 is attached to the printer head 21.
A silicon nitride film is formed in the region where the upper transistor will be formed.

Subsequently, in the printer head 21, a thermal silicon oxide film is formed in a region where the silicon nitride film is removed by a thermal oxidation process, and the thermal silicon oxide film isolates an element isolation region (LOCOS: LOCOS: Local
Oxidation Of Silicon) 27 is formed with a film thickness of 500 [nm]. Incidentally, this element isolation region is finally formed to have a film thickness of 260 [nm] by the subsequent processing. Further subsequently, in the printer head 21, after cleaning the silicon substrate 26, a gate having a tungsten silicide / polysilicon / thermal oxide film structure is formed in the transistor formation region. Further, the silicon substrate 26 is processed by an ion implantation process and an oxidation process for forming source / drain regions, and MOS (Metal-Oxide-Semiconductor) type transistors 28, 29 and the like are formed. The switching transistor 28 is a MOS type driver transistor having a withstand voltage of about 25 [V] and is used for driving the heating element. On the other hand, the switching transistor 29 is a transistor that constitutes an integrated circuit that controls this driver transistor, and
It operates by the voltage of [V]. In this embodiment, a low-concentration diffusion layer is formed between the gate and the drain, and the breakdown voltage is secured by relaxing the electrolysis of electrons accelerated in that portion, thereby ensuring the driver transistor 28.
Are formed.

When the transistors 28 and 29, which are semiconductor elements, are formed on the silicon substrate 26 in this way, the printer head 21 continues to undergo CVD (Chemical V).
PSG (Phosphorus Silicate Glass) which is a silicon oxide film to which phosphorus is added by the apor deposition method
B, which is a film, a silicon oxide film to which boron and phosphorus are added
A PSG (Boron Phosphorus Silicate Glass) film 30 is sequentially formed to have a film thickness of 100 [nm] and 500 [nm], whereby a first interlayer insulating film having a film thickness of 600 [nm] is formed as a whole.

Subsequently, after the photolithography process, C
_The contact hole 31 is formed on the silicon semiconductor diffusion layer (source / drain) by the reactive etching method using ₄ F ₈ / CO / O ₂ / Ar system gas.

Further, the printer head 21 is washed with dilute hydrofluoric acid, and then a film thickness of 30 is formed by a sputtering method.
Titanium with a thickness of [nm], titanium nitride barrier metal with a thickness of 70 nm, titanium with a thickness of 30 nm, aluminum with 1 [at%] of silicon, or 0.5 [at%] of copper. Made aluminum film thickness 5
00 [nm] is sequentially deposited. Subsequently, in the printer head 21, the titanium nitride film, which is an antireflection film, has a film thickness of 25
[Nm] to deposit the wiring pattern material. Then, the printer head 21
By the photolithography process and the dry etching process, the formed wiring pattern material is selectively removed,
The wiring pattern 32 of the first layer is created. In the printer head 21, the logic type integrated circuit is formed by connecting the MOS type transistors 29 forming the driving circuit by the wiring pattern 32 of the first layer thus created.

Subsequently, the printer head 21 is TEOS.
(Tetraethoxysilane: Si (OC ₂ H_Five )_Four ) Hara
Silicon as an interlayer insulating film formed by the CVD method using a raw material gas
The oxide film 33 is deposited. Then, the printer head 21
Is a coating type silicon acid containing SOG (Spin On Glass)
The silicon oxide film 3 is formed by applying the oxide film and etching back.
3 is flattened and these steps are repeated twice to form one layer
Between the second wiring pattern 32 and the second wiring pattern
The interlayer insulating film 33 is a silicon oxide film having a film thickness of 440 [nm].
Is formed by.

Subsequently, as shown in FIG. 3B, in the printer head 21, a tantalum film is deposited by a sputtering method, and thereby a resistor film is formed on the silicon substrate 26. Then, the photolithography process, B
A surplus tantalum film is removed by a dry etching process using Cl ₃ / Cl ₂ gas, and the heating element 22 having a folded shape is formed. In this embodiment, a tantalum film having a film thickness of 83 [nm] is deposited,
Further, the heating element 22 is formed in a folded shape so that the resistance value of the heating element 22 becomes 100 [Ω].

Subsequently, as shown in FIG. 4C, in the printer head 21, a silicon nitride film having a film thickness of 300 nm is deposited by the CVD method, and the protective layer 2 of the heating element 22 is formed.
3 is formed. Subsequently, as shown in FIG. 4D, a photolithography process and a dry etching process using CHF ₃ / CF ₄ / Ar gas are performed to remove the silicon nitride film at a predetermined position, thereby wiring the heating element 22. A portion connected to the pattern is exposed, and an opening is formed in the interlayer insulating film 33 to form a via hole 34.

Further, as shown in FIG. 5E, the printer head 21 has a film thickness of 200 by a sputtering method.
[Nm] titanium, film thickness 30 [nm] titanium, aluminum with 1 [at%] of silicon added,
Alternatively, aluminum to which 0.5 [at%] of copper is added is sequentially deposited to a film thickness of 600 [nm]. Subsequently, in the printer head 21, titanium nitride having a film thickness of 25 [nm] is deposited, thereby forming an antireflection film. Due to these, the printer head 21 has the wiring pattern material 35
Is formed.

Subsequently, as shown in FIG. 5F, the wiring pattern material 35 formed by the photolithography process and the dry etching process is selectively removed to form a second-layer wiring pattern 36. As a result, in the printer head 21, the wiring pattern for the power supply and the wiring pattern for the ground are created by the wiring pattern 36 of the second layer, and the wiring pattern for connecting the driver transistor 28 to the heating element 22 is created. The heating element 22
The silicon nitride film left over in the upper layer functions as a protective layer for the heating element 22 in the etching process for forming the wiring pattern.

Subsequently, as shown in FIG. 6G, in the printer head 21, a silicon nitride film 24 functioning as an ink protective layer is deposited to a thickness of 400 nm by the CVD method. Further, in a heat treatment furnace, heat treatment is performed at 400 ° C. for 60 minutes in a nitrogen gas atmosphere added with 4% hydrogen or in a 100% nitrogen gas atmosphere.
As a result, the printer head 21 has the transistor 28,
The operation of 29 is stabilized, the connection between the wiring pattern 32 of the first layer and the wiring pattern 36 of the second layer is stabilized, and the contact resistance is reduced.

Then, in the printer head 21, as shown in FIG. 2, a tantalum film having a thickness of 200 nm is deposited by a sputtering method, and the anti-cavitation layer 25 is formed by this tantalum film. Then the printer head 2
In No. 1, a dry film 41 and an orifice plate 42 are sequentially laminated. Here, for example, the dry film 41 is
After being made of organic resin and arranged by pressure bonding,
The parts corresponding to the ink chamber and the ink flow path are removed,
It is then cured. On the other hand, the orifice plate 4
Reference numeral 2 is a plate-like member that is processed into a predetermined shape so as to form a nozzle 44 that is a minute ink discharge port on the heating element 22, and is held on the dry film 41 by adhesion. As a result, the printer head 21 is formed by forming the nozzles 44, the ink liquid chamber 45, the ink flow path for guiding the ink to the ink liquid chamber, and the like.

As a result, the printer head 21 has a film thickness of 20 at the portion of the heating element 22 from the ink liquid chamber 45 side.
Anti-cavitation layer 25 made of a tantalum film having a thickness of 0 [nm], protective layers 23 and 24 made of a silicon nitride layer having a thickness of 500 [nm], a heating element 22 made of a tantalum film having a thickness of 83 [nm], and a thickness of 13000 [nm]. The layer structure of the silicon oxide film is formed on the silicon substrate 26.

In the printer head 21, such an ink liquid chamber 45 is formed so as to be continuous in the depth direction of the paper surface, whereby a line head is constituted.

FIG. 1 is a block diagram showing the heat generating element 22 of the printer head 21 together with the peripheral structure thereof in the printer according to the embodiment of the present invention. In FIG. 1, the drive circuit 52 is configured to drive the plurality of heating elements 22 formed in the printer head 21 via the corresponding switching transistors 28. In the configuration shown in FIG. Indicates only one heating element 22, and the description of the configuration relating to the other heating elements is omitted.

In this printer 51, a timing generator (TG) 53 generates and outputs timing signals of various operation references of the printer 51. The timing generator 53 generates, as one of these timing signals, a rectangular-wave-shaped timing signal TG1 that is a drive reference for the heating element 22 and outputs it to the printer head 21.

In the printer head 21, the drive circuit 5
2 drives each heating element 22 with print data DC output from a control circuit (not shown) with reference to the timing signal TG1.
During the period in which the signal level of 1 rises, the heating element 22 is connected to the power source 54 via the switching transistor 28.
The heating element 22 is caused to generate heat during this period (hereinafter, appropriately referred to as a driving period).
As a result, in the printer 51, the heating elements 22 are selectively heated by the print data DC during the driving period based on the pulse width of the timing signal TG1 to eject ink droplets from the corresponding nozzles to generate the print data DC. Corresponding images are printed.

Here, in this embodiment, the same printer head as the printer head 21 applied to the printer 51 is actually driven, and the timing signal TG1 for changing the resistance value of the heating element 22 by a certain ratio or more. The pulse width is obtained in advance, and the pulse width of the timing signal TG1 is set on the basis of the pulse width obtained in advance.

That is, as indicated by the symbol b in FIG. 7 (A), the printer head 21 is driven by a constant power, and heat is generated when the pulse width of the timing signal TG1 which is the driving period is a constant value or less. Due to insufficient heat generation of the element 22, it becomes difficult to eject ink droplets from the nozzle 44. Printer head 2
In No. 1, when the pulse width is gradually lengthened, the amount of heat generated by the heating element 22 gradually increases, and ink droplets come out of the nozzles 44 (hereinafter, ink droplet The pulse width at which the ejection starts is called the ejection start pulse width).

In the printer head 21, within a certain range from the ejection start pulse width, the ejection speed at which the ink droplets eject from the nozzles 44 rapidly increases due to the increase of the pulse width, and then the ejection with respect to the increase of the pulse width. The speed increases slowly. When the pulse width is further increased, the ejection speed of the printer head 21 decreases due to heat accumulation, and it becomes difficult to eject ink droplets at last (hereinafter, the pulse width at which this ink droplet does not eject is ejected). Called stop pulse width). This Figure 7
(A) is a measurement result when the heating element 22 of the printer head 21 described with reference to FIG. 2 is driven at a repetition frequency of 8.4 [kHz] with electric power of 0, 60 [W].

In the printer head 21, FIG.
9B to 9G, the driving power of the heating element 22 is 0.65 [W] (FIG. 7) under the same conditions.
(B)), 0.70 [W] (FIG. 7C), 0.75
[W] (FIG. 8D), 0.80 [W] (FIG. 8
(E)), 0.85 [W] (FIG. 8 (F)), 0.90
[W] (FIG. 9 (G)), when the power for driving the heating element 22 is increased,
As a result, the amount of heat generated per hour in the heating element 22 increases, so that the ejection start pulse width and the ejection stop pulse width become shorter. When the driving power is increased in this way, when the pulse width is increased from the ejection start pulse width, there is a range in which the ejection speed is almost constant with respect to the change in the pulse width.

When the resistance value of the heating element 22 is measured under such a driving condition, heat is generated by repeating driving with a certain pulse width or more at each power, as indicated by the symbol a in FIGS. 7 to 9. It was found that the resistance value of the element 22 changed. It has been found that the change in the resistance value increases as the pulse width increases, and decreases rapidly when the pulse width exceeds a predetermined value, and finally the heating element 22 is disconnected. Note that the measurement results of FIGS. 7 to 9 are results of driving the heating element 22 100,000 times at each power and pulse width, and the number of times of 100,000 times is about the upper end of the sheet size according to A4. It is the number of times ink droplets are continuously attached to the lower end.

Such a change in the resistance value of the heating element 22 is generated within a pulse width capable of stably ejecting ink droplets from the nozzle 44, and
If the driving condition of the heating element 22 is simply set by the pulse width that can stably eject the ink droplets from the nozzle 44, the driving of the heating element 22 is within the range in which the resistance value of the heating element 22 changes. There is also the possibility of setting a period.

Further, in such a change in the resistance value of the heating element 22, the pulse width is increased and the amount of heat generated by the heating element 22 is increased. It is presumed that the constituent material of 22 itself causes some reaction between the constituent materials of the upper and lower protective layers, etc., and further due to the alteration of the heating element 22 itself.
It is considered to be a factor that impairs the reliability of.

In practice, it has been found that the heating element 22 is driven by excessive electric power to break the bond at the crystal grain boundary of the heating element 22 and finally to break.

Thus, in this embodiment, by measuring the resistance value of the heating element 22 as described above, the resistance value of the heating element 22 is changed with respect to the pulse width at which the resistance value of the heating element 22 changes by 1%. The upper limit of the drivable pulse width in the actual printer head 21 is set by ensuring the margin due to the variation of the above.

FIG. 10 is a characteristic curve diagram showing the relationship between the pulse widths in FIGS. 7 to 9. This Figure 1
At 0, the discharge start pulse width is indicated by a black circle, such an upper limit value is indicated by a black filled triangle, and the pulse width at which the heating element 22 is broken is indicated by a black filled square mark.

Similarly, with respect to the ejection start pulse width, a margin due to variations in the resistance value of the heating element 22 is secured, and the lower limit value of the driving condition of the heating element 22 at each power is set. The range between the lower limit value and the upper limit value set in this way is the range shown by the arrows in FIGS. 7 to 10.

In practice, in the printer 51, the electric power for driving the heating element 22 is set by the voltage of the power supply 54, etc., and the upper limit value and the lower limit value are set for this electric power. Further, in the range of the lower limit value and the upper limit value set in this way, the upper limit value and the lower limit value are set so that the ink droplets can be ejected in a short repeating cycle, and in consideration of variations in the ejection speed. The driving condition of the heating element 22 is set on the side of the longer pulse width of the range, and the pulse width of the timing signal TG1 output from the timing generator 53 is set in the design process. The driving condition is that the pulse width is 1.5 [μsec] when driven with 0.8 [W] power, and 0.
When driving with a power of 9 [W], a pulse width of 1.3
It was [μsec].

(2) Operation of the Embodiment With the above-described configuration, in the printer head 21 of the printer 51 (FIGS. 2 to 6), the semiconductor substrate 26 is provided with the drive circuit 52, the switching transistor 28, and The heating element 22, the protective layers 23 and 24, the cavitation resistant layer 25, and the like are formed, and further, the ink liquid chamber 45, the nozzle 44, and the like are formed and formed.

In the printer 51, ink is introduced into the ink liquid chamber 45 of the printer head 21 thus formed, and the signal level of the timing signal TG1 output from the timing generator 53 rises (FIG. 1). ), The heating element 22 is selectively driven by the drive circuit 52 according to the print data DC. As a result, in the printer 51, the ink in the corresponding ink liquid chamber 45 is heated according to the print data DC, and the ink droplets are ejected from the nozzles 44. The ink droplets adhere to the print target and correspond to the print data DC. An image or the like is formed on the print target.

In this printer 51, the pulse width of the timing signal TG1 which is the reference for driving the heating element 22 in this way is set within a predetermined upper and lower limit range, and the upper limit value is repeatedly driven. By the heating element 22
It is set with reference to a pulse width whose resistance value does not change. As a result, in the printer 51, driving conditions can be set easily and reliably, and high reliability can be ensured.

That is, in the design process of the printer 51, the heating element 22 is driven a predetermined number of times with each pulse width by the electric power scheduled to drive the printer head 21, and the ink droplet starts to eject from the nozzle. The pulse width and the pulse width at which the resistance value of the heating element 22 has changed by a predetermined ratio from the start of driving are detected in advance. Further, the range is narrowed from the range of these two pulse widths in consideration of variations and the like, and the upper limit value and the lower limit value of the driving condition are set.

In the design process of the printer 51, the driving condition of the heating element 22 is set within the range of the upper limit value and the lower limit value, and the timing generator 53 outputs the driving element 22 so as to drive it. The pulse width of the timing signal TG1 is set. Thereby, in this embodiment, the driving condition of the heating element 22 can be easily set.

Under the driving conditions set in this way, the heating element 22 is in a range in which no heat load is applied, and the heating element 22 is in a range in which no change occurs.
Sufficient reliability can be secured for the heating element 22. In addition, this range is a range in which no kogation occurs in the ink liquid chamber 45, and a range in which cavitation resistant layer 25 does not corrode, so that driving conditions that can secure sufficient reliability are reliably set. be able to.

FIG. 11 shows a power of 0.8 [W], a pulse width of 1.5 [μsec] (indicated by reference symbol a), a power of 0.9 [W], and a pulse width of 1.3 [μsec] (reference b). , Power 0.9 [W], pulse width 1.5 [μs
ec] (indicated by symbol c), the heating element 2
It is a characteristic curve figure which shows the result at the time of driving 2 continuously. The heating element 22 was driven at a repetition frequency of 8.4 [kHz].

It should be noted that here, the power of 0.8 indicated by the symbol a
[W], pulse width 1.5 [μsec] driving condition, power 0.9 [W] indicated by symbol b, pulse width 1.3 [μs]
ec] is a condition of the range of the upper limit value and the lower limit value described above, and the driving condition of the electric power 0.9 [W] and the pulse width 1.5 [μsec] indicated by the symbol c is the upper limit value and the lower limit value. This is a drive condition that deviates from the range of the lower limit value to the upper limit value side.

According to this measurement result, the power is 0.8
In driving the heating element 22 under the driving conditions of [W], pulse width 1.5 [μsec], power 0.9 [W] and pulse width 1.3 [μsec], the driving is repeated 300 million times. However, no significant change was observed in the ink ejection speed, which revealed that the ink droplets can be ejected with sufficient reliability. On the other hand, the heating element 2 under the driving condition of electric power 0.9 [W] and pulse width 1.5 [μsec]
In the driving of No. 2, it was found that the driving speed of 200 million times or more drastically reduced the ink ejection speed, and as a result, sufficient reliability could not be secured.

The printer head 21 in this test was disassembled, observed by SEM, and analyzed by EDX. Power 0.9 [W], pulse width 1.5 [μsec]
In the heating element 22 under the driving condition of No. 2, it was confirmed that the ink and the cavitation resistant layer 25 reacted with each other by heat, and the cavitation resistant layer 25 of tantalum was transformed into tantalum oxide over the entire surface in the thickness direction.
It was also confirmed that the anti-cavitation layer 25 of tantalum was eroded along the grain boundaries. Note that tantalum oxide has a thermal conductivity of 1/10 that of tantalum, and when the cavitation resistant layer 25 is transformed into tantalum oxide by this, heat conduction from the heating element 22 to the ink liquid chamber is significantly hindered. It is considered that the ink ejection speed has decreased.

However, the heating element 2 under the driving conditions of power 0.8 [W] and pulse width 1.5 [μsec] and the driving conditions of power 0.9 [W] and pulse width 1.3 [μsec].
In the driving of No. 2, no alteration of the cavitation-resistant layer 25, erosion of the cavitation-resistant layer 25, adhesion of burns, etc. were observed.

(3) Effects of the Embodiments According to the above configuration, the driving period in which the resistance value of the heating element changes by a certain ratio or more is obtained by the repeated driving, the upper limit value is set by this driving period, and the driving period is set. By setting, the driving condition of this kind can be set easily and surely. Therefore, wasteful power consumption can be effectively avoided and the life of the printer head can be extended accordingly.

(4) Other Embodiments In the above-mentioned embodiments, the case where the upper limit of the driving condition is set on the basis of the pulse width at which the resistance value of the heating element changes by 1% is described. However, the present invention is not limited to this, and the point is that the drive condition can be easily set with sufficient reliability within the range where the resistance value of the heating element does not change. The value at which the resistance value of the element changes can be set in various ways.
That is, for example, when sufficient detection accuracy can be ensured, the upper limit value may be set based on the pulse width in which the resistance value of the heating element changes at 0.1% or less. When the drive condition is detected by reducing the change width of the resistance value, the number of times the heating element is driven for this detection can be reduced as compared with the number of times of drive according to the above-described embodiment. The driving condition can be set more easily.

In the above embodiment, the pulse width of the timing signal TG1 is set in the design process,
Thus, the case where the printer head is driven in the driving period obtained by the repeated driving has been described, but the present invention is not limited to this, and in the printer, a case where printer heads with different driving conditions are exchanged and used is also considered. As a result, the driving period obtained by the repeated driving is recorded in each printer head, and the driving condition is switched for each printer head by this recording, whereby the driving period obtained by the repeated driving of each printer head is changed. You may make it drive by. In recording such driving conditions, a recording means such as a memory is provided in the printer head, the driving conditions are recorded in the recording means, and a projection or the like is provided on the case of the printer head, and driving is performed by disposing the projection. A method of recording the conditions can be considered.

Further, in the above-mentioned embodiments, the case where the heating element is made of the tantalum film has been described, but the present invention is not limited to this, and the case where the heating element, the cavitation resistant layer, etc. are made of various laminated materials. Can be widely applied to.

[0068]

As described above, according to the present invention, the driving period in which the resistance value of the heating element changes by a certain ratio or more is obtained by the repeated driving, and the upper limit value is set by this driving period to set the driving period. As a result, this kind of drive condition can be set easily and surely.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a printer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a process of forming a printer head applied to the printer of FIG.

FIG. 3 is a cross-sectional view provided for explaining the continuation of FIG.

FIG. 4 is a cross-sectional view provided for explaining the continuation of FIG.

5 is a cross-sectional view provided for explaining the continuation of FIG.

FIG. 6 is a cross-sectional view provided for explaining the continuation of FIG.

7 is a characteristic curve diagram for explaining drive conditions of a printer head applied to the printer of FIG.

FIG. 8 is a characteristic curve diagram provided for the continuation of FIG. 7.

FIG. 9 is a characteristic curve diagram provided for the continuation of FIG.

FIG. 10 is a characteristic curve diagram showing the relationship between ejection start pulse width and the like and applied power.

FIG. 11 is a characteristic curve diagram showing reliability test results.

FIG. 12 is a sectional view showing a conventional printer head.

[Explanation of symbols]

1, 21 ... printer head, 3, 22 ... heating element,
7, 40 ... Anti-cavitation layer, 28 ... Driver transistor, 51 ... Printer, 53 ... Timing generator, 52 ... Driving circuit, 54 ... Power supply

Claims (2)

[Claims] 1. A method of setting driving conditions of a printer, wherein a heating element is heated by a rectangular wave driving signal for a predetermined driving period to print a desired image, wherein the resistance value of the heating element is changed by repeating driving. A drive condition of the printer is characterized in that the drive period that changes by a certain ratio or more is obtained, an upper limit value of the drive period is set by the drive period, and the drive period is set within a range not exceeding the upper limit value. Setting method. 2. A printer for printing a desired image by heating a heating element for a predetermined driving period by a rectangular wave driving signal, wherein the resistance value of the heating element changes by a certain ratio or more by repeated driving. A printer, wherein a driving period is obtained, an upper limit value of the driving period is set on the basis of the driving period, and the driving period is set within a range not exceeding the upper limit value.