JPH0729436B2 - Liquid jet recording head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid jet recording head that performs recording by applying thermal energy to a recording liquid and ejecting and ejecting the liquid as flying droplets.

[Prior Art] The liquid jet recording method (inkjet recording method) is capable of high-speed recording because noise generation at the time of recording is negligibly small, and a special process of fixing on so-called plain paper is performed. Recently, there has been much interest in making recordings without the need for them.

Among them, for example, JP-A-54-51837 and German publication (D
The liquid jet recording method described in Japanese Patent Publication No. 2843064 is different from other liquid jet recording methods in that thermal energy is applied to a liquid to obtain a driving force for droplet ejection.
It has different characteristics.

That is, in the recording method disclosed in the above publication, the recording liquid that has been subjected to the action of thermal energy causes a state change accompanied by a rapid increase in volume, and the action force based on the state change causes the liquid at the tip of the recording head to change. The recording liquid is ejected from the ejection port (orifice) to form flying droplets, and the droplets adhere to a recording member such as paper to perform recording.

In particular, the liquid jet recording method disclosed in DOLS 2843064 discloses a so-called drop-on-demand (drop-on-demand) method.
d) Not only is it very effectively applied to recording law,
Since a recording head having a full line type and a high density multi-orifice can be easily embodied, it has a feature that an image with high resolution and high quality can be obtained at high speed.

The recording head characteristic of the recording apparatus used in the above recording method generally has an orifice provided for ejecting the recording liquid to form flying droplets, and communicates with the orifice.
A liquid discharge part having a liquid flow path having a heat acting part, which is a part where heat energy for discharging the droplet acts on the recording liquid, and heat energy for generating heat energy And generating means.

The thermal energy generating means comprises at least a pair of electrodes and a heating resistance layer having a region (heat generating portion) connected to these electrodes and generating heat between these electrodes. It is normal.

Typical examples showing the structure of such a liquid jet recording head are shown in FIGS. 2 (a) and 2 (b). Second
FIG. 2A is a front partial view seen from the orifice side of the liquid jet recording head, and FIG. 2B is a cut portion when cut at a portion indicated by a chain line XY in FIG. 2A. It is a figure.

The recording head 100 has thermal energy generating means 101 on its surface.
The surface of the substrate 102 provided with is bonded so as to be covered with a grooved plate 103 provided with a predetermined number of grooves having a predetermined width and depth with a predetermined linear density. 105 has a structure formed. In the case of the recording head shown in the figure, it is shown as having a plurality of orifices 104, but of course, the present invention is not limited to this, and a single-orifice recording head is also included in the present invention. It falls within the range of.

The liquid ejecting unit 105 has an orifice 104 for ejecting the liquid at the end thereof, and thermal energy generated by the thermal energy generating means 101 acts on the recording liquid to generate bubbles, which depend on the expansion and contraction of the volume. It has a heat acting portion 106 that is a portion that causes a rapid state change.

The heat acting portion 106 is the heat generating portion 10 of the heat energy generating means 101.
A heat acting surface 108, which is located above the heat generating portion 107 and is in contact with the recording liquid of the heat generating portion 107, is the bottom surface.

The heat generating portion 107 includes a lower layer 109 provided on the substrate 102, a heating resistance layer 110 provided on the lower layer 109, and a heating resistance layer.
First protective layer 111 and second protective layer 112 provided on 110
Composed of and.

The heating resistance layer 110 is provided with electrodes 113 and 114 on its surface for energizing the heating layer 110 to generate heat. The electrode 113 is an electrode common to the heat generating portion of each liquid ejecting portion, and the electrode 114 is a selection electrode for selecting and generating heat from the heat generating portion of each liquid ejecting portion. It is provided along the flow path.

The first protective layer 111 and the second protective layer 112 are provided in the heat generating unit 10.
In 7, the heat generating resistance layer 110 and the liquid discharge part 1 are provided to chemically and physically protect the heat generating resistance layer 110 from the recording liquid used.
In addition to isolating the recording liquid that has filled the liquid flow path of 05,
The heating resistor layer 110 has a protective function of preventing a short circuit between the electrodes 113 and 114 through the recording liquid. Also,
The first protective layer 111 serves to prevent electrical leakage between adjacent electrodes. In particular, prevention of electrical leakage between selected electrodes, or electrode contact between the recording liquid and the recording liquid due to some reason that the electrode under each liquid flow path, and the electric current of the electrode caused by energizing this It is important to prevent corrosion, and for this reason, the first protective layer 111 having such a protective layer function is provided at least on the electrode existing below the liquid flow path.

The upper layer including the first protective layer has different required properties depending on the place where it is provided. That is, for example, the heat generating portion 107 is required to have excellent heat resistance, liquid resistance, liquid permeation prevention property, thermal conductivity, antioxidant property, insulation property, and puncture resistance. Areas other than the portion 107 are relaxed by thermal conditions, but are required to have sufficiently excellent liquid permeation preventive property, liquid resistance and puncture resistance.

However, there is no material that constitutes the upper layer that satisfies all of the above-mentioned characteristics 1 to 10 sufficiently as desired.
It is the current situation that some of the characteristics of are used after being relaxed. That is, in the heat generating portion 107, the materials are selected by giving priority to and, and, on the other hand, in the electrodes other than the heat generating portion 107, for example, in the electrode portion, priority is given to and. A selection of materials has been made to form an upper layer with each corresponding material on each relevant area surface.

On the other hand, in addition to these, in the case of a multi-orifice type liquid jet recording head, in order to simultaneously form a large number of minute thermal energy generating means on the substrate, each layer is formed on the substrate during the manufacturing process. The step of forming the upper layer and the step of removing a part of the formed layer are repeated, and at the stage of forming the upper layer, the surface on which the upper layer is formed is a fine uneven shape having a step wedge portion (step portion). Therefore, the coverage of the upper layer (that is, step coverage) at the step portion is important.
That is, if the coverage of the step portion is poor, the recording liquid permeates at that portion, which causes an electric contact or an electric breakdown. Further, when the probability that the upper layer to be formed has a defective portion in the manufacturing method is not small, the penetration of the recording liquid through the defective portion occurs, which is a factor that significantly shortens the life of the thermal energy generating means. Has become.

For these reasons, the upper layer has good coverage at the stepped portion, the probability that defects such as pinholes will occur in the formed layer is low, and even if it occurs, it can be practically ignored. Or it is required to be less than that.

On the other hand, in the heat acting portion 106, the recording liquid is vaporized by heating, but it is immediately cooled and condensed because it is subcool boiling and the heating time is short. Therefore, foaming-condensation is repeated at a high frequency of several thousand times per second in the vicinity of the heat acting surface, and the pressure change (cavitation corrosion) at this time often breaks the substrate.

As described above, the liquid jet recording head is usually provided with various protective layers for the purpose of protecting the thermal energy generating means. For example, as shown in FIG. The durability of the recording head can be improved by providing a first protective layer having a function of isolating the recording liquid in the path, a second protective layer having a cavitation resistance function, and the like. Such a protective layer may be provided at a desired site capable of achieving the protective function, and may be provided with functional separation such as the above-mentioned first and second protective layers, and in particular, functional layers may be provided. It may be provided without being separated. It is of course possible to provide another protective layer in addition to the first and second protective layers described above. For example, in the case of the recording head illustrated in FIG. On the protective layer 111 under the liquid flow paths of the covered electrodes 113 and 114, a third protective layer made of an organic material or the like having excellent coverage is provided except for the heat acting surface. Of.

As a material for forming such a protective layer, a desired material is used depending on its protective function or the like. For example, in the case of the first protective layer 111 mainly for isolation from the recording liquid, SiO 2 is used.
Inorganic insulating materials such as inorganic oxides such as ₂ and inorganic nitrides such as Si ₃ N ₄ are used.
Of the protective layer 112 is viscous, has relatively excellent mechanical strength, and has adhesiveness and adhesiveness to the first protective layer.
For example, when the first protective layer is made of SiO ₂ , Ta
It is usually composed of a metal material such as. As described above, the second protective layer is made of an inorganic material such as a metal having a comparatively tenacity and a high mechanical strength, in order to prevent the cavitation effect generated at the time of liquid discharge, especially on the heat acting surface 108. The shock can be sufficiently absorbed, and the life of the thermal energy generation means 101 can be significantly extended.

Incidentally, as a material forming the constituent members of the common liquid chamber provided on the upstream side of the grooved plate 103 and the heat acting portion 106, fine precision machining can be easily applied, and the surface accuracy can be easily obtained as desired. In addition, a material that can be processed so that the recording liquid can smoothly flow through the flow path formed by them is generally used. Typical examples include ceramics and glass. , Metal, plastic, or silicon wafer. Among them, glass and silicon wafers are one of the commonly used materials because they are easy to process and have appropriate heat resistance, thermal expansion coefficient, and thermal conductivity. Further, on the outer surface around the orifice 104, in order to prevent the recording liquid from getting wet to the outside of the orifice 104 by the recording of the orifice 104, a water-repellent treatment is performed when the recording liquid is an aqueous system. When the recording liquid is a non-aqueous type, a device such as an oil repellent treatment is generally used.

Conventionally, the liquid jet recording head is configured in this way, but such a liquid jet recording head still has various problems to be improved.

One of them is due to the temperature characteristic of the liquid jet recording head. FIG. 3 shows the relationship between the size of the recording dots formed by the recording liquid adhering to the recording material, that is, the recording dot diameter and the temperature of the recording head. As is clear from this figure, the dot diameter greatly depends on the head temperature. this is,
This is because the viscosity of the recording liquid that forms flying droplets changes significantly due to changes in the head temperature. Particularly at low temperatures, the viscosity of the recording liquid is large, so stable flying droplets can be formed. Therefore, good image quality could not be obtained. Therefore, conventionally, an external heating type heater such as a Posistar is generally used to heat the entire recording head from the outside of the recording head, thereby addressing such a problem of image quality deterioration. However, this method has the drawbacks that the entire recording head is heated, so that the power consumption becomes large and the response speed of temperature rise is slow.

Also, in principle, the liquid jet recording head that uses thermal energy is accompanied by self-heating, and the recording liquid is flowing for recording on the substrate itself (the recording liquid is cooled by the substrate itself). , Shows a complicated temperature distribution. Therefore, in a liquid jet recording head having multi-noise, uniformization of temperature distribution and improvement of characteristics at low temperature are necessary conditions for obtaining good image quality.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and has low power consumption, and can immediately obtain good image quality even at low temperature, and is an inexpensive liquid. An object is to provide an ejection recording head.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a plurality of ejection ports for ejecting a liquid, a liquid channel communicating with the ejection ports, and a liquid channel. And a heat energy generating means for generating heat energy for discharging the liquid from the discharge port, and a plurality of the heat energy generating means are arranged continuously on the heat energy generating means.
A liquid jet recording head is proposed, which has a heating unit for directly heating the liquid without contributing to the ejection of the liquid, wherein the heating unit is provided on the thermal energy generating unit. It is provided that the heating means also functions as the second protection layer is provided on the provided first protection layer, the liquid is ink, and the heating means is a layer composed of tantalum. .

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary, but it goes without saying that the present invention is not limited to the following examples.

FIG. 1 shows an example of the liquid jet recording head of the present invention.
Incidentally, FIG. 1 shows a schematic view of the vicinity of the heating means of the head.

The liquid jet recording head of this example is basically a thermal energy for generating thermal energy used to form flying droplets on the protective layer of the conventional recording head illustrated in FIG. In addition to the generating means 2, the heating means 1 is provided that does not form the flying droplets, that is, generates thermal energy that does not directly contribute to the ejection of the liquid. In FIG. 1, in order to simplify the description, the configuration of each part of the head other than the thermal energy generating means 2 and the heating means 1 is omitted, but on the thermal energy generating means 2,
A first protective layer similar to that in FIG. 2 described above is laminated, and the heating means 1 serves as a second protective layer on the first protective layer and has a bar shape as illustrated in FIG. It is provided. In FIG. 1, reference numeral 2-2 is an electrode for applying a recording signal to the thermal energy generating means 2, and 2-1 is a heating resistor serving as a heat generating portion of the means 2. Further, 4 is an ink potential control electrode which is provided as necessary to control the potential of the recording liquid (ink), and 3 is the heating means 1
It is a control driver for energization control and ink potential control.

The liquid jet recording head according to the present invention is, for example, the first
As illustrated in the figure, the thermal energy generating means 2 for generating the thermal energy used to form the flying droplets.
And heating means 1 provided on the thermal energy generating means 2 for generating thermal energy that does not form the flying droplets.
And with. In the present invention,
Various configurations of the recording head other than the provision of the heating unit 1 are not particularly limited, and various contrivances similar to those in the liquid jet recording head of the conventional example may be made.

The heating means 1 is not particularly limited in its material and shape as long as it can heat the recording liquid.
For example, as the material, various heat generating resistors used for the heat energy generating means, a metal material such as Ta used as the second protective layer, and other electrically conductive materials can be specifically mentioned. . The shape may be, for example, a bar shape as illustrated in FIG. 1 so as to cover the entire surface of the heating resistor 2-1 of the heat generating portion of the heat energy generating means 2, or each heat energy generating means. Two
The heating resistors 2-1 may be provided so as to individually cover the heating resistors 2-1. Further, the installation site may be provided at a desired site on the thermal energy generation means, but preferably in the vicinity of the heat generation part of the thermal energy generation means, optimally the heat generation of the thermal energy generation means. It may be provided at a site corresponding to the section.

In addition, in this example, paying attention to the fact that the metal material such as Ta used for the second protective layer also functions as an electric resistor, and the heating means 1 also functions as the second protective layer. However, it is not always necessary to provide the heating means 1 separately from the protective layer, and when the protective layer is functionally separated as described in the first and second aspects, The heating means 1 may also be provided as having the function of a protective layer. By doing so, the thermal energy generating means 2 can be protected with a simple structure, and the object of the present invention can be achieved. Specific examples of the material suitable for the case where the heating means 1 also has the function of the protective layer are given below. In addition to ta described above, Au, Pd, Pt, Al, Ta, Ti, Zr, Hf, V, Nb ,
Examples thereof include various metals such as Mg, Si, Mo, W, Y and La, or their carbides, nitrides, borides and silicides. Of course, various layers similar to the protective layer laminated on the thermal energy generating means may be provided on the heating means 1 for the purpose of preventing oxidation of the means.

The ink potential control electrode 4 in FIG. 1 has an oxide film formed on the heating means 1 by the oxidation, for example, when the heating means 1 is made of a metal material that is easily anodized.
The potential of the recording liquid is kept higher than the potential of the heating means 1 in order to prevent deterioration of the cavitation resistance as the second protective layer due to this hard oxide film (for example, in FIG. 1). The potential of the heating means 1 indicated by the symbol A is
If it is 9 V, it is provided for the purpose of setting the potential of the ink potential control electrode 4 indicated by the symbol B to 10 V), and when a protective layer is also provided on the heating means 1, , It is not necessary to provide it. Of course, it is not necessary to provide the ink potential control electrode 4 especially when a metal material such as Au, Pd, or Pt that is not easily anodized is used. However, when using such a metal material that is not easily subjected to anodic oxidation, it is desirable to provide an adhesion improving layer such as Mo or W as the undercoat layer of the heating means 1. Such an ink potential control electrode 4 may be provided at a desired portion in contact with the recording liquid in the recording head, but in the present example, the recording liquid is supplied to the liquid flow path corresponding to each of the thermal energy generating means 2. The electrode 4 is provided in a common liquid chamber for supply so as to be in contact with the recording liquid.

[Operation] In the present invention, since the recording liquid that becomes flying droplets can be directly heated by the heating means as described above, it is possible to reduce the power consumption and to make the temperature distribution in the recording head substantially uniform. In particular, it is possible to provide a novel liquid jet recording head that can immediately obtain good image quality even at low temperatures.

[Examples] Examples of the present invention will be shown below.

Example 1 A liquid jet recording head of the present invention illustrated in FIG. 1 was prepared as follows.

First, a substrate having the cover-shaped heating means 112 as shown in FIG. 4 was prepared as follows. That is, a Si wafer having a thermally oxidized SiO ₂ layer with a thickness of 5 μm as a substrate is used as a substrate, and a heating resistor 110 made of HfB ₂ is deposited on the substrate to a thickness of 1500 Å by using RF magnetron sputtering, and then Al is continuously formed. The electrode layers 113 and 114 made of were formed into a film having a thickness of 5000 Å by using DC sputtering. After that, the electrode layers 113 and 114 and the heating resistor 110 are patterned by using photolithography technique to obtain a heat energy generating means composed of the heating resistor 110 and the electrodes 113 and 114 formed in a desired pattern on the substrate. It was On this heat energy generating means, a SiO ₂ film as a protective layer was formed by RF sputtering 1.
A film was formed to a thickness of 5 μm. After that, as the heating means 112
A Ta film was formed into a bar shape with a thickness of 1.0 μm by DC sputtering to obtain a substrate as shown in FIG. 4 in which the heating means 112 was formed into a bar shape.

To this substrate, a grooved plate (glass in this example) having a required groove serving as a liquid flow path and a common liquid chamber is aligned and then adhered to the liquid jet recording head of the present invention as illustrated in FIG. Got

When a recording test was carried out using this recording head, a high-quality image in which the reflection density of the printed matter was uniform could be obtained immediately even at low temperatures. In the recording test, the ink potential (point B) was set to 10 V and the heating means (point A) was set to 9 V in order to prevent oxidation of the heating means, and the pulse voltage as shown in FIG. 7 was applied. The recording liquid was preheated by being applied to the means, and immediately thereafter, a recording signal corresponding to the recording pattern was applied to the heating resistor 110. Even when the environmental temperature of the recording head was as low as 0 ° C., a conscientious image was obtained with a short preheating time of about 100 μS as shown in FIG.

Example 2 A liquid jet recording head of the present invention was obtained in the same manner as in Example 1 except that the ink potential control electrode was not provided and a protective layer made of SiO ₂ was provided on the heating means 112.

Using this recording head, recording was performed in the same manner as in Example 1 except that the ink potential was not controlled. As with Example 1, a high-quality image in which the reflection density of the printed matter was uniform was obtained at low temperature. I was able to get it immediately.

By the way, as described above, such a high quality image cannot be formed by the conventional liquid jet recording head having no heating means as described above. This is because the viscosity of the recording liquid (ink) changes with temperature. FIG. 5 is an example of such a viscosity change with respect to the temperature of the recording liquid. As is clear from FIG. 5, the ink viscosity rapidly increases at low temperatures. For example, the ink viscosity at 0 ° C. is twice as high as that at 25 ° C., and due to such thickening, the ejection speed of flying droplets at a low temperature is reduced. Therefore, in the conventional liquid jet recording head, It was difficult to form stable flying droplets, and it was difficult to obtain high-quality images. Therefore, conventionally, the recording head is heated by using an external heating type heater such as a posistor.

FIG. 6 shows an example of a temperature rising state when a conventional liquid ejecting head as illustrated in FIG. 2 is heated using a posistor (however, the environmental temperature of the recording head during heating is 26 ° C.). According to this, it takes about 30 seconds to raise the head temperature by 10 ° C. For example, when the environment temperature is 0 ° C, the decrease in the ejection speed of the flying droplets due to the increase in the viscosity of the ink does not cause a problem so much. If the recording is performed at the ink temperature of 10 ° C, it takes about 30 seconds to start the recording. Will need a waiting time. Moreover, in the external heating method, the temperature distribution of the recording head is not always uniform, and such non-uniformity of the temperature distribution also contributes to the deterioration of image quality.

However, since the present invention directly heats the recording liquid by the heating means provided on the thermal energy generating means, it does not require the long waiting time as described above, and can be preheated in a short time of about 100 μS as described above. The recording liquid can be heated uniformly, and stable flying droplets can be formed with low power consumption. Therefore, in the present invention, it is possible to immediately obtain a high-quality image even in a low temperature environment, and the density difference of the printed matter at the time of solid printing is about ± 3.5% in the prior art. ±
It could be reduced to about 1.%.

[Advantages of the Invention] As described above, according to the present invention, it is possible to reduce the power consumption and to make the temperature distribution in the recording head substantially uniform, and in particular, immediately obtain a good image quality even at a low temperature. It has become possible to provide a new liquid jet recording head capable of doing so.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an example of a liquid jet recording head of the present invention, FIG. 2 (a) is a schematic explanatory view of an example of a conventional liquid jet recording head, and FIG. 2 (b) is FIG. XY of (a)
FIG. 3 is a cutaway partial view of a cross section, FIG. 3 is a diagram showing an example of the relationship between the dot diameter and the head temperature during recording by a liquid jet recording head of a conventional example, and FIG. 4 is a substrate configuration relating to the liquid jet recording head of the present invention. FIG. 5 is a diagram illustrating an example of the relationship between ink viscosity and ink temperature, and FIG. 6 is a diagram illustrating an example of the relationship between heating time and head temperature of a conventional liquid jet recording head, FIG. 7 is a diagram showing an example of a pulse voltage applied to the heating means of the liquid jet recording head of the present invention. 1 ... Heating means 2 ... Thermal energy generating means

Claims (4)

[Claims] 1. A plurality of discharge ports for discharging a liquid, a liquid flow path communicating with the discharge ports, and heat provided for the liquid flow paths to discharge the liquid from the discharge ports. A heat energy generating means for generating energy, and a plurality of the heat energy generating means, which are continuously arranged on the heat energy generating means,
A liquid ejecting recording head, comprising: a heating unit that heats the liquid without directly contributing to the ejection of the liquid. 2. The heating means is provided as a heating means which also functions as a second protective layer on the first protective layer provided on the thermal energy generating means.
The liquid jet recording head according to the item. 3. The liquid jet recording head according to claim 1, wherein the liquid is ink. 4. The liquid jet recording head according to claim 1, wherein the heating means is a layer made of tantalum.