JPH0292547A - Base for liquid jet recording head and liquid jet recording head equipped with such base - Google Patents

Abstract

PURPOSE:To improve quality of an image by improving reproducibility of boiling by a method wherein an electricity-heat converter of a shape of increasing a thickness is established in a part containing a position at which a bubble to be generated in recording liquid on a recording liquid contact surface corresponding to a heat generation part disappears, and a temperature difference between inside and outside the position at which the bubble disappears attains a specific value. CONSTITUTION:A bubble disappearing position is determined by a shape of a liquid path 1 to which a heating resistor is arranged, an arranged position, temperature, other ambient conditions, etc., is influenced by an inertia component Z of hydrodynamic impedance in a bubble peripheral drainage basin, and the bubble disappears near a position at which the heating resistor is proportionally allocated by an reverse ratio of Z. The bubble disappearing position is obtained by the formulas [I], [II] from the inertia component Z of impedance of the drainage basin. Herein, lengths of the drainage basin are l1, l2, sectional area of the liquid path is S, and density of liquid is rho. The bubble disappears near a position to be determined by those relation formulas. Then, by increasing a thickness of a heating resistor 107 layer at a part containing said position, heat flux transmitted to upper liquid decreased. Then, a difference in temperature between a peak value of surface temperature of the heating resistor and a peak value of surface temperature of an area in which the layer thickness is increased is 25 deg.C or higher up to and including 100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid jet recording head and a substrate used for the recording head, and in particular to a liquid jet recording head that boils the liquid by applying thermal energy to the recording liquid. The present invention relates to a liquid jet recording head that performs recording by jetting (discharging) droplets, and a substrate that includes an electrothermal transducer that generates the thermal energy in response to energization.

[Prior Art] Performances required of this type of liquid jet recording head or electrothermal converter include high responsiveness during high-speed driving, and the ability to heat the liquid sufficiently to boil it. , may be highly durable. For this purpose, we have traditionally used materials,
Various improvements have been made in terms of construction.

For example, JP-A-58-13471, which is filed by the applicant.
No. 6, No. 2003-11-112, discloses a recording head in which the electrothermal transducer has a resistance distribution that reduces the current density at the connection portion with the electrode, thereby improving electrical durability.

Furthermore, Japanese Patent Application Laid-Open No. 60-208246 discloses a recording head in which the electrothermal transducer is provided with a member for avoiding mechanical shock caused by liquid supply, thereby improving mechanical durability.

Furthermore, in JP-A No. 59-95155, an electrothermal converter (
A configuration is disclosed in which a conductive region is provided in the center of a resistor.

Furthermore, Japanese Patent Laid-Open No. 62-73588 filed by the applicant discloses a structure in which current concentration is eliminated by rounding the electrodes and the electrothermal converter (heating resistor).

[Problems to be Solved by the Invention] However, in a recording head having an electrothermal converter in the ejection energy generating means, in addition to the above conditions, high reproducibility of boiling is required.

According to the inventor of the present application, when repeatedly boiling a liquid, the drive signal (heating pulse) previously given to the electrothermal converter
When the bubbles generated in It has been confirmed that reproducibility is not guaranteed.

If the boiling phenomenon is not stabilized in this manner, the shape and size of the generated bubbles will not be constant, resulting in variations in droplet diameter and ejection speed, which will lead to problems such as deterioration of image quality.

An object of the present invention is to provide a recording head with high boiling reproducibility and a substrate thereof.

Another object of the present invention is to provide a liquid jet recording head with high image quality without variations in droplet diameter or ejection speed.

[Means for Solving the Problems] To this end, the substrate for a liquid jet recording head according to the present invention includes a support, a heating resistor layer disposed on the support and electrically connected to the heating resistor layer. It has a pair of electrodes,
An electrothermal transducer having a heat generating part formed between a pair of electrodes, which includes a position where bubbles generated in the recording liquid on the recording liquid contact surface corresponding to the heat generating part disappear. , and the electrothermal transducer having a dog-shaped thickness, and is characterized in that ΔTTH-TO is 20°C or more and 100°C or less.

Further, a liquid jet recording head according to another embodiment of the present invention includes a support and a pair of electrodes arranged on the support and electrically connected to a heating resistor layer and the heating resistor layer, An electrothermal transducer in which a heat generating part is formed between a pair of electrodes, and a portion including a position where air bubbles generated in the recording liquid on the recording liquid contact surface corresponding to the heat generating part disappear. and the electrothermal converter having a dog shape, and Δ
It is characterized by comprising a base body in which T - T I, -T O is 20° C. or more and 100° C. or less, and a member provided on the base body to form a liquid path for a recording liquid.

In these, TO is the peak value of the temperature of the electrothermal converter in the driving state when no recording liquid is present at the position where the bubble disappears, and TH is the peak value of the temperature in the driving state of the electrothermal converter when no recording liquid is present at a position other than that position. This is the peak value of temperature when the electrothermal converter is in operation.

[Function] According to the present invention, by making the layer thickness of the electrothermal transducer thicker in the portion where the current passes between the electrodes and including the position where bubbles disappear, The heat flux transferred from the electrothermal converter to the upper liquid becomes smaller in that region.

Therefore, this part has a lower temperature than other parts, and even if there is microscopic residual gas attached to that part after the bubbles disappear,
This will not become a foaming nucleus during subsequent driving.

In addition, by appropriately selecting and configuring the temperature difference, high ejection performance can be maintained, and combined with this effect, the reproducibility of boiling can be improved, and good recording quality can be obtained.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1(8) and 1(B) show an example of a liquid jet recording head to which the present invention can be applied, in which a plurality of ejection portions including a plurality of liquid paths, electrothermal transducers, and ejection ports (orifices) are integrated. FIG. 2 is a perspective view and a cross-sectional view taken along line X-X′ of the liquid jet recording head in an arranged form.

In these figures, a heating resistor 107 is placed on a substrate 103.
(107-1 to 107-6), and a common electrode 1061 and a selection electrode 105 are arranged as electrodes for energization, and the heating resistor 107 is just limited by the partition walls 101a to 101g formed on the groove cover plate 102. groove 101 (
101-1 to 101-6) to match the adhesive layer 10.
4 (104-1 to 104-7). A liquid (ink) is introduced into this, and when electricity is applied, the heating resistor 1
07, bubbles are generated in the liquid on the heating resistor 107 due to a sudden change in state, and droplets corresponding to the increase in volume are discharged from the orifice formed by the groove cover plate 102 and the substrate 103.

The heating resistor 107 according to this example has a structure in which the layer thickness is increased at the bubble extinguishing position, as will be described later.

Here, the bubble disappearance position (bubble extinction position) will be considered.

The point at which the bubble disappears is determined by the shape of the liquid path in which the heating resistor is installed, its location, temperature, and other environmental conditions, and is determined by the inertial component Z of the hydrodynamic impedance in the area around the bubble.
The inventor of the present application confirmed that foam disappears near the position where the heating resistors are proportionally distributed in accordance with the inverse ratio of Z.

Here, regarding the basin of interest, the position taken in the flow direction is X, the cross-sectional area at the position x of the basin is S lxl ,
The length of the basin is 1. If the density of the fluid (recording liquid) is ρ, then the inertial component Z of the impedance of the basin can be found as follows.

For example, as shown in FIG. 1, if the heating resistor 107 has a configuration in which the supply direction and discharge direction of the liquid are the same, the cross-sectional area S, x, -S・
Assuming constant, L-p Il, r/S, Z2-7) 12/S
(2) C1:C2:z, :Z+-12:Il
r (3). That is, bubbles disappear near the position determined by this relational expression.

Therefore, if the layer of the heat generating resistor 107 is made thicker in a region including that position, the heat flux transmitted to the liquid above becomes smaller in that region.

The above is a general relationship, but if the height of the nozzle ceiling at position
”El/h(x)dxl, +112-7[1/h(
x) ldx (4) as C,:C2@III,
:W, even if the bubbles disappeared at the position, it was sufficient.

Next, we will consider how much of a temperature difference the region including the defoaming position has from other regions to maintain good discharge performance.

FIG. 3 shows the peak value Tl+ of the surface temperature of the heating resistor and the peak value T of the surface temperature corresponding to the region where the layer thickness is increased. The average value 7 of the droplet ejection speed and the standard deviation Ov of the speed are plotted for the difference ΔT ("TH-TO) between It is the value in the state.

As is clear from the figure, when the temperature difference ΔT is 20° C. or more, Ov becomes almost constant and the discharging variation becomes stable, but it was confirmed that when the temperature difference ΔT exceeds 100° C., the average speed decreases. From this, it can be seen that in this case, the temperature difference ΔT is preferably 20° C. or more and 100° C. or less.

More preferably, when the standard deviation of the liquid ejection speed can be ignored to some extent, that is, when the liquid ejection speed is mainly considered, ΔT is 20° C. or more and 50° C. or less, and the liquid ejection speed can be ignored to some extent. In other words, when the above standard deviation is mainly considered, ΔT is 25°C.
The temperature was above 100°C. Furthermore, most preferably,
ΔT was 25°C or more and 60°C or less.

Furthermore, in this embodiment, the dimensions of the region including the defoaming position where the layer thickness of the heating resistor layer is increased are appropriately determined.

FIG. 4 shows the heat generating area area S of the region. and the total heat generating area Sll of the heat generating resistor. 7 and aV are plotted for /SH. As is clear from the figure, it was confirmed that when So/S++ was set to 1710 or more and 1/2 or less, the stem ■ and Ov value became stable and the discharge performance became good.

More preferably, it is S when the standard deviation of the liquid ejection speed can be ignored to some extent, that is, when the liquid ejection speed is mainly considered. /S□ is 1/10 or more 1/
4 or less, S if the liquid ejection speed can be ignored to some extent, that is, if the standard deviation above is mainly considered. /
SH was 1/8 or more and 1/2 or less. Furthermore, most preferably, So/S, 4 is 1/8 or more and 1/4 or less.

(Example 1) FIGS. 5A and 5B show a first example of the substrate according to the present invention, and FIG. -A' line sectional view.

Here, l is a substrate having a thickness of 525 μm, for example, and can be made of glass, St, or the like. , 2 is a surface oxidized 5i02 layer with a thickness of 2.5 μm, which is used as a heat storage layer. 3 is a heat generating resistor layer made of Hf82 with a thickness of 0.1 μm, a width of a heat generating part of 30 μm, a length of a heat generating part of 150 μm, formed by sputtering, for example, and the part 3-1 including the position where bubbles disappear (in equation (2) 11=, Q2, the layer thickness is 0.2 μm near the middle of the current path between the electrodes 4). Reference numeral 4 denotes an electrode such as A1 having a thickness of 0.5 μm formed by, for example, an EB evaporation method.

5 has a thickness of 1.5μ formed by sputtering, for example.
6 is a layer of Ta205 or the like with a thickness of 0.1 μm formed by sputtering method, 7 is a layer of SiO□, SiN, etc.;
is a layer of Ta or the like having a thickness of 0.5 μa formed by a sputtering method, and functions as a protective layer. Also, 8
is a liquid (ink) that is boiled.

In this embodiment, the layer thickness d of the portion 3-1 of the heating resistance layer 3 is
and when dry firing (when energizing without introducing ink)
The relationship between the temperature difference ΔT was as follows.

Therefore, the thickness of the portion 3-1 is 0.135 μm or more and 0.1
It is appropriate that it is 55 μm or less, and in this example, d=0.
It was set to 14 μm.

Also, the length of portion 3-1 is 25 μm, where 5o=
30x25(μm2), 5H=30x150(μm
2) and therefore S. Since /SH is 1/6, the condition explained in connection with FIG. 4 is also satisfied.

Note that the planar patterns of the heating resistor layer 3 and the electrodes 8i4 were formed by etching. Furthermore, as is clear from the figure, the corners at the connection between the electrode 4 and the heat generating resistor layer 3 are rounded to prevent deterioration in durability and local bubbling due to current concentration.

In such a configuration, when a voltage is applied between the electrodes 4,
A current flows through the heating resistor layer 3 and heat generation occurs. Since the amount of heat generated in the heating resistor layer 3 per unit time and unit area is inversely proportional to the thickness of the heating resistor layer, the heat transferred from the portion 3-1 to the liquid 8 through the upper layers 5.6 and 7 is: This amount is less than the heat transferred to the liquid from other parts of the three layers of heating resistors.

When bubbles were actually generated using the substrate according to this example, it was observed that the bubbles 10 disappeared at the location 9 in the upper part of the portion 3-1, as shown in FIG.
There is little heat transmitted to this part, and the temperature is lower than the rest of the part, so even if residual gas adheres, random nucleate boiling will not occur from there and disturb bubble generation, which is highly reproducible from the rest of the part. Highly sensitive film boiling was occurring. In this case, the shape and size of the bubbles were constant each time. Then, when this substrate was used in a recording head as shown in FIG. 1 to perform recording, the FL droplet diameter and ejection speed were uniform, and a good image was obtained.

The reason for the high reproducibility of boiling in parts other than the upper part of part 3-1 is that there is no residual gas attached and the liquid 8 is heated to the affected area, so the liquid 8 reaches near the superheating limit and the liquid This is because bubbles are formed by a spontaneous nucleation phenomenon based on internal molecular motion.

Comparative Example FIG. 7 (conventional example) shows a case where air bubbles are generated using an electrothermal converter having the same structure as the present example except that the multilayer heating resistor layer 3 is made uniform. , unlike the present example, random nucleate boiling occurs from the location where the bubbles 10 disappear, reducing the reproducibility of bubble generation.

In other words, in the case of (a) in the figure, the location where nucleate boiling occurs is 1.
Although it is a tube place, relatively good bubble generation has been achieved,
Such bubble formation does not always occur, as shown in (b) or (C) in the figure. ! Nucleate boiling may occur from several locations, in which case nucleate boiling heat transfer causes thermal energy to escape into the liquid, reducing the bubble volume. In such cases, it has been observed that because the shape and size of the bubbles are not constant, when the print head is configured to perform printing, variations occur in droplet diameter and ejection speed, resulting in a decrease in image quality. It was done.

(Example 2) FIG. 8 shows a second embodiment of the substrate according to the invention.

In the first embodiment, the portion 3-1 was formed at the same time as the heating resistor layer 3, whereas in this example, the portion 3'-1, which also constitutes an electrothermal transducer, was formed after the heating resistor layer 3' was formed. It has a multi-layered structure. This multilayer portion 3'-1 may be formed of the same material (for example, HfBz) as the heating resistor layer 3', or may be formed of a different material (for example, Ta and Ta).
AJ2) may also be used. In this example as well, the same effects as in (Example 1) were obtained.

In this way, the portion where the layer is thickened may be formed in any manner as long as the position where the bubbles disappear is completely included.

(Example 3) In the above example, a case was described in which the present invention was applied to a recording head in which the liquid path was linear. However, in the example shown in FIG. As shown, even if the discharge is perpendicular to the substrate 1', by increasing the thickness of the heating resistor layer 107' in the portion including the defoaming position 9 shown in the figure. , the same effect as described above can be obtained.

(Further other embodiments) Of course, the present invention can be applied regardless of the shape of the heating resistor. That is, even for the heating resistor employed in the conventional example described above, a thicker layer may be provided at the defoaming position.

It is also effective for recording heads that have electrothermal transducers shaped to be able to express gradation, which have been developed in recent years, such as the one disclosed in Japanese Patent Publication No. 31943/1983 proposed by the applicant. Applicable. In other words, the electrothermal converter has a structure (heat generation adjustment structure) that produces a controllable temperature distribution according to the level of the signal input in the heat generating part, and the bubbles are adjusted in multiple stages according to the signal level. The present invention can also be applied to a recording head having such a configuration.

For example, in the electrothermal converter as shown in Figures 1O (A) to (C), if the defoaming position is at the position indicated by the symbol 9'', the electrothermal conversion is performed at the part including that position (the part indicated by the broken line). body 1
The layer thickness of the heating resistor layer 3'' may be set to 0.07'' to 0.07''. Further, if the bubble extinguishing position differs depending on the size of bubbles generated, a plurality of such wide portions may be provided (see the portion indicated by the dotted chain line in FIG. 10(A)).

In addition, in order to adjust the bubbles in multiple stages, we have developed a structure in which the thickness of the heating resistor layer is changed along the direction of the current (Japanese Patent Application Laid-Open No.
31943), and a structure in which the thickness of the heating resistor layer is gradually increased toward the center line (Japanese Patent Laid-Open No. 62-20
1255).

That is, for example, in the former case, as shown in FIG. 11, the heating resistor layer 30 may be partially thickened in a portion 30-1 including the defoaming position. Of course, if the defoaming position changes depending on the size of the bubbles, a plurality of these can be provided.

In addition, the present invention is of course applicable to any device that uses an electrothermal converter as a discharge energy generating means without being limited to the integrated type shown in FIG. Needless to say, the present invention can also be applied to a scanning type recording head and a fully multi-type recording spatula in which the ejection ports are selected over the entire width of the recording medium.

[Effects of the Invention] As explained above, according to the present invention, the electrothermal converter (
By making the thickness of the heat-generating resistor layer (heat-generating resistor layer) uniform in the portion including the position where the bubbles disappear, the reproducibility of boiling was improved and the quality of the resulting image was improved.

[Brief explanation of the drawing]

1 (A> and (B) are respectively an exploded perspective view and a front view of a liquid jet recording head according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the defoaming position, Figure 3 is an explanatory diagram for explaining the range of temperature difference that is optimal for discharge, Figure 4 is an explanatory diagram for explaining the area ratio, and Figures 5 (A) and (B) are respectively 6 is an explanatory diagram showing the behavior of bubbles in the case of using the present invention, and FIG. 7 is a diagram showing the bubble behavior in the conventional example. FIG. 8 is a cross-sectional view of a substrate according to a second embodiment of the present invention; FIG. 9 is an explanatory diagram showing a recording head according to a third embodiment of the present invention; FIG. 10 (A) -(C) and FIG. 11 are plan views showing still other embodiments of the present invention. 1, 1'... Basic resistance, 2... Heat storage layer, 3.3'53''...・Heating resistor layer, 3-1.3'-
1, 30-1... Portion with the thickness of the heating resistor layer 3 as a dog, 4... Electrode, 5... Protective layer (Si(h), 6... Protective layer (Ta20s), 7 ...Protective layer (Ta), 8...Liquid, 9.9.9''...Bubble disappearance lid, 10...Bubble. Fig. 2 (T+-TO) = ΔT Fig. 3 01/10 1/2 o158 Fig. 4 Discharge port Fig. 9 Convex/convex C = Saebi =: Kiko) 2- and 22 ≧ Fig. 7 Fig. 1O

Claims (1)

[Scope of Claims] 1) A support, a heating resistor layer disposed on the support, and a pair of electrodes electrically connected to the heating resistor layer, and between the pair of electrodes. An electrothermal transducer in which a heat generating portion is formed, and the thickness is increased in a portion including a position where air bubbles generated in the recording liquid on the recording liquid contact surface corresponding to the heat generating portion disappear. and the electrothermal converter having a shape, ΔT=T_H−T_O is 20°C or more and 100°C
A substrate for a liquid jet recording head characterized by the following: T_O: Peak value of the temperature in the driving state of the electrothermal transducer when no recording liquid is present at the position. T_H: Peak value of temperature at a position other than the above position in the driving state of the electrothermal transducer when no recording liquid is present. 2) More preferably, the ΔT is 20° C. or more and 60° C. or less when mainly considering the ejection speed of the recording liquid, and 25° C. when mainly considering the standard deviation of the ejecting speed of the recording liquid. 2. The substrate for a liquid jet recording head according to claim 1, wherein the ΔT is greater than or equal to 25°C and less than or equal to 60°C, most preferably greater than or equal to 25°C and less than or equal to 60°C. 3) The length of the heat generating section along the liquid path of the recording liquid is proportionally distributed by the inverse ratio of the inertial component Z of the hydrodynamic impedance of the flow area on both sides of the heat generating section along the liquid path. 2. The substrate for a liquid jet recording head according to claim 1, wherein the position where the bubble disappears is set as the position where the bubble disappears. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [x: Position in the flow direction of the basin of interest, l
: Length of the basin of interest, S(x): Cross-sectional area of the liquid path at position x, ρ: Density of the recording liquid] 4) Position x of the basin in the flow direction of the recording liquid
Let h(x) be the height of the liquid path at 4. The substrate for a liquid jet recording head according to claim 3, wherein the substrate is located at a position where the liquid jet recording head disappears. 5) Ratio S_O/S_H of the area S_O on the heat generating part corresponding to the part and the total area S_H on the heat generating part
is preferably 1/10 or more and 1/2 or less, more preferably 1/1 when mainly considering the liquid ejection speed.
A claim characterized in that the ratio is 0 or more and 1/4 or less, and when the standard deviation of liquid ejection speed is mainly considered, 1/8 or more and 1/2 or less, most preferably 1/8 or more and 1/4 or less. 1. The substrate for a liquid jet recording head according to 1. 6) It has a support, a heating resistor layer disposed on the support, and a pair of electrodes electrically connected to the heating resistor layer, and a heat generating portion is formed between the pair of electrodes. The electrothermal transducer has a thicker shape at a portion including a position where bubbles generated in the recording liquid on the recording liquid contact surface corresponding to the heat generating part disappear. a converter, and a base body in which ΔT=T_H−T_O is 20°C or more and 100°C or less, and a member provided on the base body to form a liquid path for the recording liquid. A liquid jet recording head. T_O: Peak value of the temperature in the driving state of the electrothermal transducer when no recording liquid is present at the position. T_H: Peak value of temperature at a position other than the above position in the driving state of the electrothermal transducer when no recording liquid is present. 7) More preferably, the ΔT is 20° C. or more and 60° C. or less when mainly considering the ejection speed of the recording liquid, and 25° C. when mainly considering the standard deviation of the ejecting speed of the recording liquid. 7. The liquid jet recording head according to claim 6, wherein the ΔT is set to be at least 25 degrees Celsius and not more than 60 degrees Celsius, most preferably at least 25 degrees Celsius and not more than 60 degrees Celsius. 8) The length of the heat generating section along the liquid path of the recording liquid is proportionally distributed by the inverse ratio of the inertial component Z of the hydrodynamic impedance of the basin on both sides of the heat generating section along the liquid path. 7. The liquid jet recording head according to claim 6, wherein the position where the bubble disappears is determined as the position where the bubble disappears. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ 9) Position x of the basin in the flow direction of the recording liquid
Let h(x) be the height of the liquid path at 9. The liquid jet recording head according to claim 8, wherein the liquid jet recording head is at a position where the liquid jet recording head disappears. 10) Area S_O on the heat generating part corresponding to the part
and the total area S_H on the heat generating part S_O/S_
H is preferably 1/10 or more and 1/2 or less, more preferably 1/1 when mainly considering the liquid ejection speed.
A claim characterized in that the ratio is 10 or more and 1/4 or less, and when the standard deviation of liquid ejection speed is mainly considered, 1/8 or more and 1/2 or less, most preferably 1/8 or more and 1/4 or less. 6. The substrate for a liquid jet recording head according to 6.