JPH0651406B2 - Recording method of liquid jet recording head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording method for a liquid jet recording head that ejects recording liquid from an orifice to form flying droplets, and more particularly to a recording signal voltage of a heating resistor. The present invention relates to a recording method of a liquid ejecting recording head that ejects liquid by bubbles generated by heat generation due to application of the liquid.

[Prior Art] A liquid jet recording head of this type is disclosed in, for example, Japanese Patent Laid-Open No. 54-
The liquid jet recording method described in 51837 and German Published (DOLS) 2843064 is another liquid jet recording method in that thermal energy is applied to the liquid to obtain a driving force for droplet ejection. Has different characteristics.

That is, in the recording method disclosed in the above-mentioned publication, the liquid which is subjected to the action of thermal energy is overheated to generate bubbles, and the action force based on the generation of the bubbles causes the liquid to be ejected from the orifice at the tip of the recording head. As a result, flying droplets are formed, and the droplets adhere to the recording member to record information.

A recording head applied to this recording method generally includes an orifice provided for ejecting a liquid, and a heat acting portion that is a portion communicating with the orifice and causing thermal energy for ejecting a droplet to act on the liquid. And a heat generating resistor as a heat generating resistor that is means for generating thermal energy.

By the way, a shape as shown in FIG. 6 is currently proposed as the shape of the heating resistor. The requirements for defining such a shape are as follows. That is, a rectangular coordinate system XY is set on the surface of the heating resistor 1, φ (x, y) is the potential value at the point (x, y) on the surface of the resistor, and one of the peripheral boundaries of the resistor is A boundary value having a certain value is given to a portion in contact with the electrode 2, a boundary value different from the boundary value is given to a portion in contact with the other electrode 3, and the peripheral boundary method is given to a portion not in contact with either electrode. When the Laplace equation ∂ ² φ / ∂ x ² + ∂ ² φ / ∂y ² = 0 is solved for the heating resistor region by giving the boundary condition that the derivative of φ with respect to the line direction is 0, the slope of φ Size of The maximum value of It is specified by the ratio with.

For example, the shape shown in FIG. 6 has a ratio of 1.13. The value of the ratio in the conventional example shown in FIG. 7 is infinite. If this value is 1.8 or less, the current concentration at the four corners of the heater is less than in the conventional case (infinity), that is, the heat is less concentrated at the four corners, and therefore foaming does not occur first from the four corners and heat is generated. The entire surface of the resistor 1 is first foamed. Also,
Therefore, a stable foam is obtained. To express this concretely, the volume of the main bubbles (bubbles generated for ejecting the liquid) changes little with each ejection up to the ejection frequency of 10 kHz, and therefore the volume of the ejected droplets also fluctuates less. That is, stable ejection can be obtained and good printing can be obtained. In addition, the current concentration at the four corners is small and the durability of the heating resistor is improved as compared with the conventional case.

Further, the above-mentioned heating resistor has a pair of electrodes, and this electrode is generally composed of a selection electrode and a common electrode, and heat for ejecting droplets from the orifice described above by energizing between these electrodes. Energy is generated from the heating resistor. A major factor that determines the repeated use life (durability life) of such a liquid jet recording head is mechanical impact force called cavitation collapse. Cavitation collapse occurs when vapor bubbles self-contract and disappear. Specifically, the liquid near the heating resistor becomes overheated due to the abrupt heat generated by the heating resistor, the vapor temperature is reached when the liquid reaches the overheating limit temperature, and the liquid suddenly jumps out of the orifice due to the sharp volume increase. Cavitation collapse occurs as the bubbles (vapor bubbles) self-contract and disappear after the flying droplets are formed. The impact on the heating resistor due to this cavitation collapse has been a major factor in determining the durable life of the recording head.

There are several measures to avoid such a cause of failure and improve the durable life of the recording head. For example, the heating resistor is made of a material having good cavitation resistance. Alternatively, a protective layer having good cavitation resistance is provided at least between the heating resistor and the recording liquid. Furthermore, the liquid flow path is structured to reduce the impact force due to cavitation collapse. Conventionally, these measures have been taken to improve the durable life of the recording head.

[Problems to be Solved by the Invention] However, even in a liquid jet recording head having an improved durable life due to the above-mentioned measures, it is often the case that a sufficient durable life cannot be realized due to an electrical driving condition applied to the heating resistor. there were. The cause is, for example, when a vapor bubble is generated by applying an electric signal to the heating resistor and then the vapor bubble self-contracts. If there is, there is a phenomenon in which streaky secondary bubbles along the liquid flow direction remain at that position.

The main bubbles generated to eject the liquid are crushed by the force from the liquid flowing direction, that is, the liquid flow path direction, but the secondary bubbles described above that remain after the disappearance of the main bubbles are near the heat acting surface. Since the height of the bubbles is low, the bubbles do not receive the force in the flow direction of the liquid and therefore collapse in the direction perpendicular to the liquid flow path.

The cavitation of bubbles that collapse perpendicularly to the liquid flow path is very large and concentrated locally, and is several tens of times larger than the cavitation caused by the defoaming of the main bubbles. Therefore, due to the cavitation collapse of the bubbles, the upper protective layer of the heat-acting portion was destroyed, and the heating resistor was often destroyed, resulting in poor durability.

Conventionally, as shown in Japanese Patent Laid-Open No. 58-1571, the recording signal voltage Vop is 1.3 times higher than the boundary voltage Vth that determines whether or not vapor bubbles are generated to prevent secondary bubbles. It is proposed to: However, in the head having the heating resistor having the shape as shown in FIG. 6 that is currently proposed, there is no first foaming from the four corners as in the conventional case, so that the boundary voltage can be increased even with the same film structure. Vth will be different. Generally, the boundary voltage Vth rises. Therefore, the recording signal voltage Vo is based on the conventional boundary voltage Vth.
If p is set to 1.3 times or less of Vth, the durability may decrease due to the generation of secondary bubbles.

In view of the above-mentioned problems, the present invention changes the setting reference of the recording signal voltage of the recording head from the conventional boundary voltage Vth and uses the new reference to determine the most suitable recording signal voltage Vop in terms of durability life and practical use. An object of the present invention is to provide a recording method of a liquid jet recording head that can be set.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a heating resistor and a pair of electrodes electrically connected to the heating resistor, and between the pair of electrodes. By applying the recording signal voltage,
A liquid jet recording head for causing heat to be generated in a heating resistor between electrodes and ejecting a liquid by bubbles generated by the heat, wherein a rectangular coordinate system XY is set on the surface of the heating resistor, and φ
Let (x, y) be the potential value at the point (x, y) on the surface of the heating resistor, and among the peripheral boundaries of the heating resistor,
A boundary value of a certain value is given to a portion in contact with one electrode, a boundary value different from the above boundary value is given to a portion in contact with the other electrode, and a method of the peripheral boundary is given to a portion not in contact with either electrode. When the Laplace equation ∂ ² φ / ∂x ² + ∂ ² φ / ∂y ² = 0 is solved for the heating resistor region by giving the boundary condition that the derivative of φ with respect to the line direction is 0, the slope of φ Size of The maximum value of and in the center of the heating resistor In the recording method of the liquid jet recording head having a heating resistor with a ratio of 1.8 or less, bubbles (secondary bubbles) different from the bubbles (main bubbles) for ejecting liquid are generated. characterized in that the recording signal voltage V _OP satisfying 1.15 ≧ V _OP / V _R becomes relationship to the threshold voltage V _R to perform recording by applying to the liquid jet recording head.

[Operation] When a vapor bubble is generated in the thermal action portion filled with the recording liquid and the vapor bubble self-contracts after being pushed out from the droplet orifice, a secondary bubble of the vapor bubble is generated. Let V _{R be} the threshold voltage for this. The present invention is characterized in that the recording signal voltage Vop is determined on the basis of the threshold voltage V _R , and the recording signal voltage Vop is within a range satisfying the relationship of Vop ≦ 1.15 V _R. Therefore, according to the present invention, since the reference threshold voltage V _R is set from thermal problems, even in a head having a heating resistor shapes, such as FIG. 6, in view of heat resistance It is possible to set the optimum recording signal voltage Vop, and it is possible to perform recording in the most suitable state in terms of durability life and practical use, and it is possible to obtain high durability with improved durability life.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

First Embodiment FIGS. 1 to 3 show the steps of substrate preparation of the first embodiment of the present invention, and FIG. 4 shows an example of the configuration of the liquid jet recording head of the present embodiment. Here, 101 is a substrate, 102 is a heat generating part, 103,
104 is an electrode.

Explaining the substrate forming process of the heating resistor according to this embodiment, first, as shown in FIG. 2 (B), a SiO ₂ film having a thickness of 5 μm is formed by thermal oxidation of the Si wafer which is the substrate support 105. It is the lower layer 106 of the substrate 101. A heating resistance layer of HfB ₂ is formed on the lower layer 106 by sputtering.
Form 107 to a thickness of 1300Å.

Subsequently, the Ti layer 50Å and the Al layer 5000Å are successively deposited by electron beam evaporation to form the common electrode 103 and the selection electrode 104. At this time, a circuit pattern as shown in FIG. 1 is formed by a photolithography (photolithography) process, and the heat acting surface of the heat generating portion 102 of the heat generating portion 111 has a dimension of 30 μm.
The width is 150 μm, and the resistance of Al electrodes 103 and 104 is included.
Use a resistance value of 100 Ω.

Next, as shown in FIG. 2 (B), SiO ₂ is laminated as a first upper protective layer 108 to a thickness of 1.6 μm on the entire surface of the substrate 101 by a magnetron high rate sputtering method.

Then, as the second upper protective layer 110, as shown in FIGS. 2A and 2B, Ta is deposited to a thickness of 0.5 μm by the magnetron type high rate sputtering method. Next, the second upper protective layer
110 is formed by a photolithography process in a pattern covering the upper portion of the heat generating portion 102 as shown in FIGS. 2 (A) and 2 (B).

Further, as shown in FIGS. 3A and 3B, a photosensitive polyimide (trade name: Photo Nice) is applied as the third upper protective layer 109 on the first upper protective layer 108 of the substrate 101, A circuit pattern as shown in FIG. 3 is formed by a photolithography process.

As shown in FIG. 4, a photosensitive resin dry film 400 having a thickness of 50 μm is laminated on the substrate 101 prepared in this way, and exposure and phenomenon are performed by a predetermined pattern mask. 401 and a common liquid chamber 404 are formed, and a glass ceiling plate 405 is adhesively laminated on the film 400 via an epoxy adhesive to form a liquid jet recording head. In addition, 402 is an orifice, 403 is an ink flow path wall, and 406 is an ink supply port.

As an example, the liquid flow path 401 described above has a width of 50 μm and a height of 50 μm.
The size is m and the length is 750 μm. Also, the length from the front end of the heat generation part (heater) 111 to the orifice 402 is 15
Set to 0 μm.

In this way, the measured threshold voltage (minimum recording signal voltage) V _R of the above liquid jet recording head of the present embodiment that created was 22.0V. Also, the foaming boundary voltage Vth is
It was 20V. However, the pulse width of the recording signal is 7 μs and the frequency is 2 kHz. In addition, when recording was performed at a voltage shown in Table 1 below for the recording head of this example,
The durability as shown in the table was obtained. However, the recording conditions at that time were a pulse width of 7 μs, a frequency of 2 kHz, and an ink composition of water.
50%, NMP (N-methylpyrrolidone) 15%, DEG (diethylene glycol) 30%, dye 5%.

Second Embodiment FIG. 5 shows a cross section of a substrate 101 prepared in the second embodiment of the present invention. As shown in the figure, in this embodiment, a SiO ₂ film of 2.5 μm thickness is formed on a substrate support 105 of a Si wafer by thermal oxidation to form a lower layer 106, and HfB ₂ is sputtered on the lower layer 106. The heating resistance layer 107 was formed to a thickness of 1600Å. In addition, the resistance value of the heat acting surface of the heat generating part 111 is
The resistance was set to 80Ω including the resistance of Al electrodes 103 and 104. In addition,
As the upper protective layer 108 of No. 1, SiO ₂ was laminated in a thickness of 1.9 μm by a magnetron type high rate sputtering method.

Since the other substrate forming steps, the structure of the liquid jet recording head, and the like are the same as those in the above-described first embodiment, detailed description thereof will be omitted.

The threshold voltage V _R of the thus second embodiment the liquid jet recording head fabricated was measured, was 26.0V.
The foaming boundary voltage Vth was 23.5V. However, the pulse width of the recording signal is 7 μs and the frequency is 2 kHz. Further, when the recording head of this example was recorded at the voltages shown in Table 2 below, the durability shown in Table 2 was obtained.
However, the recording conditions at that time were pulse width 7 μs and frequency 2 kHz.
The ink composition is 50% water, 15% NMP, 30% DEG, and 5% dye.

Comparative Example FIG. 8 shows a substrate prepared in a comparative example of the present invention. As shown in this figure, the difference from the first embodiment is the shape of the heater (heat acting part). Since the other substrate forming steps, the structure of the liquid jet recording head, and the like are the same as those in the above-described first embodiment, detailed description thereof will be omitted.

The bubbling boundary voltage Vth of the liquid jet recording head of the third embodiment thus produced was 19.2V. However, the pulse width of the recording signal is 7 μs and the frequency is 2 kHz. When the recording head of this comparative example was recorded at the voltages shown in Table 3 below, the durability shown in Table 3 was obtained. However, the recording conditions at that time were a pulse width of 7 μs and a frequency of 2 kHz, and the ink composition was 50% water, 15% NMP, 30% DEG, and 5% dye.

Durability test result example Table 1 shows the durability test result of the first embodiment, and Table 2 shows the result.
2 shows the results of the durability test of Examples. Table 3 shows the durability test results of the comparative example (third example).

The foaming boundary voltage Vth of each of the first embodiment and the comparative example is 20.0.
It is V, 19.2V. The film configurations are the same, the dimensions are the same, but the boundary voltage Vth is different. In addition, the comparative example is 25V, which is 1.3 times Vth.
And has good durability.

Therefore, the boundary voltage disclosed in Japanese Patent Laid-Open No. 58-1571 is disclosed.
It can be adopted that the durability is good if it is driven by the recording signal voltage Vop which is 1.3 times or less of Vth. On the other hand, the first embodiment has poor durability when recorded at 26 V, which is 1.3 times the boundary voltage Vth. Therefore, the method of determining the recording signal voltage Vop with 1.3 times or less of the boundary voltage Vth, that is, Vth as a reference, which is disclosed in Japanese Patent Laid-Open No. 58-1571, has poor durability. Therefore, I thought as follows.

As can be seen from Tables 1 and 2, the durability deteriorates at a certain voltage or higher. For example, in the first embodiment, the durability deteriorates when the recording signal voltage Vop is 26 V or more as described above (
1 table). Taking the threshold voltage V _R of the secondary steam generated in the criteria, the threshold voltage V _R of the first embodiment 22V as described above, so, the Vop / V _{R =} 1.18. In the second embodiment, the durability deteriorates when the recording signal voltage Vop is 30 V or more as described above (Table 2). Taking the threshold voltage V _R to the reference, the threshold voltage V _R of the second embodiment since 26V as described above, Vop / V
_R = 1.15.

Therefore, by the Vop / V _{R =} 1.15, the durability of the recording head can be obtained what for practical use has been demonstrated.

EFFECTS OF THE INVENTION As described above, according to the present invention, with respect to the threshold voltage V _{R at which} bubbles (secondary bubbles) different from the bubbles (main bubbles) for ejecting liquid are generated. Since the recording signal voltage V _OP satisfying the relation of 1.15 ≧ V _OP / V _{R is} applied to the liquid jet recording head to perform recording, the liquid jet recording head can be recorded in the most suitable state in terms of durability life and practical use. It is possible to obtain high durability.

[Brief description of drawings]

FIGS. 1 to 3 show the steps of producing a substrate according to the first embodiment of the present invention, and FIGS. 1, 2 (A) and 3 (A) are plan views and FIG. 2 (B). ), Fig. 3 (B) is the XY of each corresponding diagram (A).
4 is a sectional view taken along the line, FIG. 4 is a perspective view showing the internal structure of the liquid jet recording head of the first embodiment when completed, and FIG. 5 is a sectional view showing the structure of the substrate of the second embodiment of the present invention. FIG. 6 is a plan view showing a shape example of a heating resistor according to the present invention, FIG. 7 is a plan view showing a shape example of a conventional general heating resistor, and FIG. 8 is for comparison with the present invention. It is a top view which shows the structure of the produced board. 101 ... substrate, 102 ... heating part, 103 ... common electrode, 104 ... selection electrode, 105 ... substrate support, 106 ... lower layer, 107 ... heating resistor layer, 108 ... first Upper protective layer, 109 ...... Third upper protective layer, 110 …… Second upper protective layer, 111 …… Heat generation part, 401 …… Liquid flow path, 402 …… Orifice, 403 …… Ink flow path wall , 404 ... common liquid chamber, 405 ... ceiling plate, 406 ... ink supply port.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirokazu Komuro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP 62-73588 (JP, A) JP SHO 60-159062 (JP, A) JP-A-59-194859 (JP, A)

Claims (1)

[Claims] 1. A heat generating resistor and a pair of electrodes electrically connected to the heat generating resistor, and by applying a recording signal voltage between the pair of electrodes, the heat generating resistor is provided between the electrodes. A liquid jet recording head for producing heat and ejecting liquid by bubbles generated by the heat, wherein a rectangular coordinate system XY is set on the surface of the heating resistor, and φ (x, y) is set to the surface of the heating resistor. The potential value at the upper point (x, y) is used, and a boundary value of a value at a portion in contact with one electrode of the peripheral boundary of the heating resistor is given, and the boundary value is defined as a portion in contact with the other electrode. Different boundary values are given, and φ for the normal direction of the surrounding boundary is applied to the part which is not in contact with either electrode.
When the Laplace equation ∂ ² φ / ∂x ² + ∂ ² φ / ∂y ² = 0 is solved for the heating resistor region by applying the boundary condition that the differential coefficient of 0 is 0, the magnitude of the slope of φ The maximum value of and in the center of the heating resistor In the recording method of the liquid jet recording head having a heating resistor with a ratio of less than 1.8, bubbles (secondary bubbles) different from the bubbles (main bubbles) for ejecting liquid are generated. 1.15 with respect to the threshold voltage V _R
A recording method for a liquid jet recording head, wherein recording is performed by applying a recording signal voltage V _OP satisfying a relation of ≧ V _OP / V _R to the liquid jet recording head.