JPH09216367A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat dissipation by forming an upper layer having specific thermal conductivity on a board, and providing thermal energy generating means for generating thermal energy on the upper layer. SOLUTION: An upper layer 11 having thermal conductivity of 350W/mK or more is formed on a board 1, a heating layer 2 for generating thermal energy is formed on the layer 11, an electrode 12 is formed on the layer 2, and the entirety is covered with a protective layer 13. As a result, the heat generated from the layer 2 is efficiently dissipated to the board 1 side, and when the conduction of the layer 2 is interrupted, the heat retaining in the layer 2 is rapidly fed to the board 1 side. Accordingly, even if the thermal conductivity of the board 1 is small, excellent recording can be conducted. Thus, the board having low thermal conductivity such as ceramic board can be used as the board for forming the heating layer, thereby facilitating to deal with the increase in the size of the head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head, and more particularly to an inkjet head which ejects ink droplets by the action of thermal energy.

[0002]

2. Description of the Related Art Since an ink jet recording apparatus has almost no vibration or noise during recording and can be easily colorized, it can be used not only in printers that output data from digital processing devices such as computers, but also in facsimiles and copiers. It is being used. As such an ink jet recording apparatus, for example, a thermal energy generating means such as a heating resistor is provided, and the ink subjected to the thermal energy is subjected to a pressure increase due to the rapid generation of bubbles to form an ink droplet from the orifice. High-speed, high-resolution, high-quality recording is achieved by using an inkjet head configured to eject ink as a recording head, and ejecting ink droplets from an orifice to a recording medium (the one to which ink droplets adhere) in accordance with a recording signal. There are some that are designed to do.

Such an ink jet head is a full line type in which the recording head has a length substantially equal to the width of the recording medium in the main scanning direction, and it is easy to realize a high density multi-orifice (multi nozzle), high resolution, There is an advantage that a high quality image can be recorded at high speed.

By the way, for example, in order to actually manufacture a multi-orifice recording head having a length of about A4 in the longitudinal direction, a portion forming the recording head, particularly a substrate on which a heating element for generating thermal energy is formed. Must be long.

Conventionally, a silicon substrate, a ceramics substrate, a glass substrate or the like has been used as the substrate. Among them, the silicon substrate exhibits excellent properties such as thermal conductivity and heat resistance, but it is difficult to obtain a large-sized substrate and it is difficult to cope with the lengthening of the head. Also,
A glass substrate with a large area can be easily obtained, but since the thermal conductivity is poor, if the drive frequency is increased,
Dissolved bubbles may be deposited from the ink, resulting in inability to eject ink drops. Furthermore, since a ceramic substrate has many defects due to the presence of surface defects in the manufacturing process, a glaze layer is provided on the entire surface of the ceramic substrate for use. However, because of the glaze layer, the glass substrate is used. Similarly, there is a disadvantage that the heat dissipation becomes poor.

Therefore, conventionally, for example, Japanese Patent Laid-Open Publication No. 64-155.
There is an ink jet head in which the surface of a ceramic substrate, excluding the heat generating portion, is covered with a grace layer (glass layer) as described in Japanese Patent No. This is because the glaze layer 52 having window-like holes in the substrate 51 as shown in FIG.
The heat storage layer 53 and the heat generation layer 54 are laminated on a portion of the substrate 51 where the glaze layer 52 is not formed, and the electrode 55 is formed thereon. According to this, in the heat generating portion X, the heat generated in the heat generating layer 54 is directly transmitted to the substrate 51 without passing through the glaze layer 52, and the heat dissipation is secured.

[0007]

However, the conventional ink jet head described above requires a step of forming window-like holes in the glaze layer, and such holes can be formed uniformly and efficiently. Is difficult to do. Moreover, when forming a film on the step of the hole, defects may occur in the heat generating layer, the electrode, the protective layer, and the like. Further, when a ceramic substrate is used, the thermal conductivity is higher than that of the glass substrate, but the thermal conductivity is one order of magnitude lower than that of the silicon substrate, and sufficient heat dissipation can be obtained when the driving frequency is increased. There is a problem of disappearing.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ink jet head capable of ensuring satisfactory heat dissipation and performing good recording.

[0009]

In order to solve the above problems, an ink jet head according to a first aspect of the present invention is an ink jet head which ejects ink droplets by the action of thermal energy, and has a thermal conductivity of 350 W / mK or more on a substrate. Was formed, and a thermal energy generating means for generating the thermal energy was provided on the upper layer.

According to a second aspect of the present invention, in the ink jet head according to the first aspect, the upper layer is composed of a diamond thin film.

According to a third aspect of the invention, there is provided the ink jet head according to the first or second aspect, wherein the thickness of the upper layer is within the range of 0.1 μm to 20 μm.

According to a fourth aspect of the present invention, there is provided an inkjet head according to any one of the first to third aspects, wherein the surface of the upper layer is smoothed.

According to a fifth aspect of the invention, there is provided an ink jet head according to any one of the first to third aspects, wherein a flat layer is formed on the upper layer.

An ink jet head according to a sixth aspect of the present invention is the ink jet head according to any one of the first to fifth aspects, wherein the heat generated by the thermal energy generating means is accumulated on at least one of the upper surface and the lower surface of the upper layer. The structure was provided with a heat layer.

An ink jet head according to a seventh aspect is the ink jet head according to the fifth aspect, wherein the flat layer also serves as the heat storage layer.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of an inkjet head according to an embodiment of the present invention, FIG. 2 is a plan view of a substrate portion of the head, and FIG. 3 is a schematic sectional view of FIG.

In this ink jet head, a wall member 3 is provided by using a photoresist on a substrate 1 having a heat generating layer 2 for generating heat energy, and a cover member 4 made of glass or the like is bonded onto the wall member 3. , Ink channel 5, liquid chamber 6
And the orifice 7, the heat energy of the heat generating layer 2 causes the ink to undergo a state change accompanied by a sharp volume increase, and the action force based on the state change causes the orifice 7 to move.
To eject ink droplets.

In this ink jet head, as shown in FIGS. 2 and 3, on the substrate 1 made of a ceramic substrate or a glass substrate, the heat dissipation property of the heat generated in the heat generating layer 2 is improved, so that the thermal conductivity is improved. An upper layer 11 having a power of 350 W / mK or more is formed, a heat generating layer 2 that generates the heat energy is formed on the upper layer portion 11, an electrode 12 is formed on the heat generating layer 2, and the entire protective layer 13 is formed. Covered with.

A specific material for the upper layer 11 is Be.
Examples thereof include O, SiC, BN, and diamond thin film. Diamond thin film is high frequency plasma CVD,
It can be formed by a method such as microwave plasma CVD or hot filament CVD.

As a specific material for the heat generating layer 2, any material can be used as long as it generates heat when energized. For example, metals such as tantalum, tungsten, molybdenum, niobium and chromium, alloys such as nichrome and silver-palladium, metal nitrides such as tantalum nitride, zirconium boride, lanthanum boride, tantalum boride, vanadium boride and boride. Metal borides such as niobium are mentioned as preferred materials.

As the protective layer 13, a material having excellent oxidation resistance is used. For example, inorganic oxides such as SiO ₂ , inorganic nitrogen compounds such as Si ₃ N ₄ , titanium oxide, vanadium oxide, niobium oxide, molybdenum oxide, tantalum oxide, tungsten oxide, chromium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, High resistance nitriding of transition metal oxides such as yttrium oxide and manganese oxide, metal oxides such as aluminum oxide, strontium oxide, calcium oxide, barium oxide and silicon oxide and their composites, silicon nitride, aluminum nitride, boron nitride, etc. And a complex of the above-mentioned oxide nitride, and a material such as amorphous silicon and amorphous selenium, which has a low resistance in the bulk, but has a high resistance through a manufacturing process such as vapor deposition, CVD, sputtering, etc. Can be mentioned.

The substrate 1 like this ink jet head
Between the heat generating layer 2 and the heat generating layer 2, the thermal conductivity formed on the substrate 1 is 3
By interposing the upper layer 11 of 50 W / mK or more, the heat generated in the heat generating layer 2 can be efficiently radiated to the substrate 1 side, and the heat generating layer 2 can be turned off when the power supply to the heat generating layer 2 is turned off. The heat remaining on the substrate 1 quickly flows to the substrate 1 side. As a result, even if the thermal conductivity of the substrate 1 is small, it is possible to efficiently radiate heat and obtain good recording.

When a diamond thin film is used as the upper layer 11, the diamond thin film has a very high thermal conductivity and the heat is quickly diffused in the thin film surface, so that the heat dissipation is further improved.

Here, a specific example in which a diamond thin film is formed as an upper layer on an alumina ceramic substrate will be described. To form a diamond thin film, a mixed gas of hydrocarbon (eg CH4) and hydrogen is used, and the base temperature is 60.
At about 0 to 1000 ° C., a hot filament, microwave plasma or the like is used for gas decomposition. When the hot filament is used, an example of its synthesis condition is shown in Table 1.
It is as follows.

[0025]

[Table 1]

Under these conditions, a diamond thin film was formed on the substrate, and the thin film had a very high thermal conductivity. In addition, the thermal conductivity can be adjusted to 2 by changing the film formation conditions.
It was possible to control in the range of 00 to 1500 W / mK.

The diamond thin film preferably has a practical thickness of 350 W / mK or more in order to secure heat dissipation. Among the thermal conductivity of the diamond thin film shown above, a diamond thin film having a low thermal conductivity can be obtained by increasing the methane gas concentration, but as the methane gas concentration is increased, secondary nucleation on the crystal plane occurs. The number of particles becomes dango-shaped particles, and defects may occur in the heating layer and electrodes formed on the particles, leading to a decrease in yield. Therefore, considering the upper limit of the methane gas concentration, the thermal conductivity of the diamond thin film is more preferably 400 W / mK or more. Further, in order to obtain a thin film having high thermal conductivity, the concentration of methane gas is lowered, but the film forming rate at that time is slowed down. Therefore, the thermal conductivity of the diamond thin film is more preferably 1200 W / mK or less in consideration of the film formation rate. Therefore, the thermal conductivity of the diamond thin film used for improving the heat dissipation of the substrate of the inkjet head is in the range of 350 to 1200 W / mK, preferably 400 to 1200 W / mK.

Further, in order to determine the optimum range of the film thickness of the diamond thin film used to improve the heat dissipation of the substrate of the ink jet head, an experiment was conducted using the film thickness as a parameter. Table 2 shows the results. In the table, “◎” is the best, “○” is good, “△” is slightly good, “x”.
Indicates a defect.

[0029]

[Table 2]

As can be seen from Table 2, the thickness of the diamond thin film is preferably in the range of 0.1 μm to 20 μm, and more preferably 0.3 μm to 10 μm.

Next, when the surface properties of the upper layer 11 in the above ink jet head are poor, various defects occur when the heating layer 2 and the electrodes 12 are formed on the upper layer 11, and the yield is increased. In such a case, the heat generating layer 2 and the like are formed after the surface of the upper layer 11 is smoothed by smoothing it.

When a diamond thin film is used as the upper layer 11, it is difficult to polish it by ordinary mechanical polishing because the hardness of the diamond thin film is high. Therefore, a method of heating an iron polishing plate to about 700 ° C. in a hydrogen atmosphere to perform polishing is used. In this method, polishing by a thermochemical reaction with a metal at a high temperature of diamond accelerates the polishing rate by adding hydrogen gas, and compared with ordinary mechanical polishing,
It is possible to polish efficiently and with a small polishing pressure.

In this way, the ratio of non-defective products of the heating layer and the electrode, and the heating element when the diamond thin film as the upper layer 11 is polished and smoothed and when it is not smoothed (untreated) The pulse durability of the device is shown in Table 3. In the table, “○” is 90% or more, and “△” is 70%.
% Or more and “x” means less than 70%.

[0034]

[Table 3]

As can be seen from Table 3, the heating layer 2 and the electrode 12 formed on the upper layer 11 obtained by polishing and smoothing the diamond thin film have almost no defects and the pulse durability of the heating element. The heat generation layer 2 and the electrode 12 formed on the upper layer 11 which is not smoothed
Has considerable defects, and the pulse durability of the heating element is also poor.

Next, FIG. 4 is a schematic sectional view of a substrate portion of an ink jet head according to another embodiment of the present invention.
In this embodiment, the flat layer 1 is formed on the upper layer 11 of the above embodiment.
4 is formed, and the heating layer 2 and the electrode 12 are formed on the flat layer 14.
Is formed. This flat layer 14 is
DLC by sputtering SiC film, plasma method using high frequency, microwave, etc., or ion deposition method
It can be formed of a film or the like.

In this way, the flat layer 14 is formed on the upper layer 11.
Table 3 shows the ratios of non-defective products of the heat generating layer and the electrodes and the pulse durability of the heat generating element in the case where the heat generating layer and the case where the flat layer 14 is not formed. In the table, “○” is 9
0% or more, “Δ” represents 70% or more, and “x” represents less than 70%.

[0038]

[Table 4]

As can be seen from Table 4, the flat layer 14 is formed on the upper layer 11, and the heating layer 2 and the electrode 12 formed on the flat layer 14 have almost no defects, and the heating element is The device has good pulse durability, while the flat layer 14
Heating layer 2 and electrode 1 formed on the upper layer 11 without forming
2 has a considerable defect, and the pulse durability of the heating element is also poor.

Next, FIGS. 5 and 6 are schematic sectional views showing different examples of the substrate portion of the ink jet head according to still another embodiment of the present invention. In these embodiments, the heat storage layer 15 for controlling the heat flow rate is formed between the substrate 1 and the upper layer 11 as shown in FIG. 5, or the upper layer 11 and the heat generating layer as shown in FIG. The heat storage layer 15 is formed between the two. The heat storage layer 15 can be formed by an inorganic oxide material such as silicon oxide, zirconium oxide, tantalum oxide, magnesium oxide, or aluminum oxide by a method such as sputtering.

In the heat storage layer 15, when the liquid is discharged, the heat generated in the heat generating layer 2 is transferred to the ink side as much as possible as compared to the heat transferred to the substrate 1 side. After the power supply to the heat generating layer 2 is turned off, the heat in the heat generating layer 2 is quickly released to the substrate 1 side, and the ink and the generated bubbles on the heat generating layer 2 are rapidly cooled. is there.

The heat storage layer 15 can be omitted by providing the flat layer 14 in the embodiment shown in FIG. 4 with the function of the heat storage layer. As a result, almost no defects are generated in the heat-generating layer 2 and the electrode 12 that have been formed, defects during film formation are extremely reduced, and the heat generated in the heat-generating layer 2 during liquid ejection is on the substrate 1 side. The rate of transfer to the ink side is as large as possible to the level of transfer to the ink side, and after the liquid is discharged, that is, after the power supply to the heat generating layer 2 is turned off, the heat in the heat generating layer 2 is quickly released to the substrate 1 side. As a result, it is possible to obtain the substrate of the inkjet head in which the ink and the generated bubbles on the heat generating layer 2 are rapidly cooled.

Further, according to the present invention, when a substrate having a low thermal conductivity such as a ceramics substrate or a glass substrate is used, heat dissipation is improved and good recording can be performed, but the present invention is not limited to this, and a Si substrate or the like is also possible. Even when it is applied to the case where a substrate having a higher thermal conductivity than that of the ceramics or glass is used, the heat dissipation is further improved and the driving frequency can be increased.

[0044]

As described above, according to the ink jet head of the first aspect, the thermal conductivity on the substrate is 350 W.
Since the upper layer having a thickness of / mK or more is formed and the thermal energy generating means for generating thermal energy is provided on the upper layer, the heat dissipation is improved and good recording can be performed. As a result, it becomes possible to use a substrate having a low thermal conductivity such as a ceramics substrate as a substrate for forming the heat generating layer, and it is possible to easily cope with an increase in the size of the head.

According to the ink jet head of the second aspect, in the ink jet head of the first aspect, since the upper layer is formed of the diamond thin film, high thermal conductivity can be easily obtained.

According to the ink-jet head of claim 3, in the ink-jet head according to claim 1 or 2, the thickness of the upper layer is within the range of 0.1 μm to 20 μm, and therefore the upper layer portion having good surface properties and not peeling off. Can be obtained.

According to the ink jet head of the fourth aspect, in the ink jet head according to any one of the first to third aspects, the surface of the upper layer is subjected to the smoothing treatment, so that the thermal energy generating means formed on the upper layer. The various defects of the heat generating layer and the electrodes, which become the same, are reduced and the yield is improved.

According to the ink jet head of the fifth aspect, in the ink jet head according to any one of the first to third aspects, since the flat layer is formed on the upper layer, various kinds of heat generating layers and electrodes serving as heat energy generating means. Defects are reduced and yield is improved.

According to a sixth aspect of the present invention, in the ink jet head according to any of the first to fifth aspects, the heat storage layer for accumulating heat generated by the heat energy generating means on at least one of the upper surface and the lower surface of the upper layer. The heat energy generated during liquid ejection can be efficiently transferred to the ink side, and the heat remaining after the liquid ejection can be promptly released to the substrate side. It can be performed.

In the ink jet head according to claim 7, in the ink jet head according to claim 5, since the flat layer also serves as the heat storage layer, it is not necessary to separately provide the heat storage layer, which causes an increase in the number of manufacturing steps. And the yield is improved.

[Brief description of drawings]

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

FIG. 2 is a schematic plan view of a substrate portion of the head.

FIG. 3 is a schematic cross-sectional view of FIG.

FIG. 4 is a schematic sectional view of a substrate portion of an inkjet head according to another embodiment of the present invention.

FIG. 5 is a schematic sectional view showing an example of a substrate portion of an inkjet head according to still another embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing another example of the substrate portion of the inkjet head according to still another embodiment of the present invention.

FIG. 7 is a schematic sectional view of a substrate portion of a conventional inkjet head.

[Explanation of symbols]

1 ... Substrate, 2 ... Heating layer, 3 ... Wall member, 4 ... Cover member, 5
... Ink flow path, 6 ... Liquid chamber, 7 ... Orifice, 11 ... Upper layer, 12 ... Electrode, 13 ... Protective layer, 14 ... Flat layer, 15 ...
Live heat layer.

Claims (7)

[Claims] 1. In an ink jet head for ejecting ink droplets by the action of thermal energy, an upper layer having a thermal conductivity of 350 W / mK or more is formed on a substrate, and heat for generating the thermal energy is formed on the upper layer. An ink jet head provided with an energy generating means. 2. The inkjet head according to claim 1, wherein the upper layer is a diamond thin film. 3. The ink jet head according to claim 1, wherein the upper layer has a thickness of 0.1 μm to 20 μm.
An ink jet head characterized by being in the range of μm. 4. The inkjet head according to any one of claims 1 to 3, wherein a smoothing treatment for smoothing the surface of the upper layer is performed. 5. The inkjet head according to claim 1, wherein a flat layer is formed on the upper layer. 6. The ink jet head according to any one of claims 1 to 5, wherein a heat storage layer for accumulating heat generated by the heat energy generating means is provided on at least one of an upper surface and a lower surface of the upper layer. An inkjet head characterized in that. 7. The ink jet head according to claim 5, wherein the flat layer also serves as the heat storage layer.