JPS62152866A - Liquid jet recording head - Google Patents

Abstract

PURPOSE:To improve the service durability of a liquid jet recording head by using a material having a specific temperature coefficient as a heating resistance layer which constitutes an electricity/heat exchanger. CONSTITUTION:A liquid jet recording head 1 consists of an orifice 5 and a liquid flow channel 6 which are formed by using a grooved board 4 with a prearranged number of grooves of prearranged width and depth arranged at a prearranged linear density to cover the surface of a substrate 3 where an electricity/heat exchanger is provided. A heating resistance layer 11 is a thin layer of a material having a temperature coefficient of 15 to 60%/ deg.C. Setting the lower limits to 15%/ deg.C produces an effect from this value. In the meantime, setting the upper limits to 60%/ deg.C causes the resistance value of the heating resistance layer to be influenced by a room temperature, provided said upper limits are exceeded. Even when the temperatures of the heating resistance layer have soared by the application time of voltages to the heating resistance layer becoming longer than a rated energization time, the layer does not reach a high temperature level because it has a high positive temperature coefficient.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid jet recording head that performs recording using flying droplets formed by ejecting liquid from an ejection port, and in particular to a liquid jet recording head that performs recording using flying droplets formed by ejecting liquid from an ejection port. This invention relates to a liquid jet recording head to be used.

[Conventional technology]

There are various types of liquid jet recording devices, and among them, for example, the liquid jet recording devices of the type disclosed in OLS No. 2843064, OLS No. 2944005, and USP 4335389 are capable of high-speed color recording. The recording head, which is the main part of the output unit, ejects recording liquid to form flying droplets.

Because the ejection ports (orifices) for printing can be arranged in high density, it is possible to obtain high resolution, and at the same time, the overall size of the recording head can be made compact, making it suitable for large-scale production. In the semiconductor field, there has been a lot of attention recently due to the fact that it is easy to increase the length by fully utilizing the advantages of IC technology and micro-processing technology, which are rapidly increasing in terms of technological progress and reliability. are collecting.

The characteristic recording head of the liquid jet recording device described above is equipped with an electrothermal transducer as a means for ejecting liquid from an orifice and generating thermal energy to form flying droplets. .

The basic operating principle of a liquid jet recording head provided with such an electrothermal converter will be explained with reference to FIGS. 2 and 3. Incidentally, FIG. 2 is a schematic diagram for explaining an electric circuit of a liquid jet recording head provided with a conventional electrothermal converter.
FIGS. 3A to 3D are schematic process diagrams for explaining the liquid ejection process of a liquid jet recording head provided with a conventional electrothermal converter.

In FIG. 2, 21 is a nozzle, and 22 is a heater as an electrothermal converter. A voltage is applied to the heater 22 from a power source 23, and the voltage application is controlled by a transistor 24 and a control device 25. That is,
When the transistor 24 is turned on by the control device 25, a current flows from the power supply 23 to the heater 22, the temperature of the heater 22 rises, and a sudden change in the state of the liquid 26 is caused. The situation will be explained using FIG.

In FIG. 3, when the temperature of the heater 22 rises, the liquid 26 undergoes a rapid state change including, for example, the generation of bubbles 27 (FIG. 3(a)).

Such bubbles 27 rapidly expand, causing rapid pressure changes in the liquid 26 (FIG. 3(b)).

Due to such pressure changes, the liquid 26 is discharged from the discharge port at the tip of the nozzle 21 as liquid 'a2.8 (see Fig. 3).
C)) After the liquid 26 is discharged, the bubble 27 disappears and returns to its original state (FIG. 3(d)).

The electrothermal converter is designed to be in direct contact with the liquid in order to efficiently apply the generated thermal energy to the liquid and increase the ON-OFF response speed of the thermal effect on the liquid.
It is said that it is desirable to have a structure in which the heat acting part of the liquid flow path communicates with the orifice.

However, the above-mentioned electrothermal converter basically consists of a heating resistor that generates heat when energized, and a pair of electrodes for energizing the heating resistor. If the body is in direct contact with the liquid, depending on the electrical resistance of the recording liquid, electricity may wave through the liquid, the liquid itself may electrolyze due to the flow of electricity through the liquid, or it may generate heat. When the resistor is energized, the heating resistor reacts with the liquid, causing a change in resistance value due to corrosion of the heating resistor itself, and even damage or destruction of the heating resistor, or even damage to the heating resistor. The surface of the heating resistor may be damaged or a portion of the heating resistor may be cracked due to mechanical shock due to a sudden change in the state of the liquid, preferably including the generation of vapor bubbles, due to the thermal action generated by the heating resistor. In some cases, it may occur or be destroyed.

For this reason, in the past, alloys such as NiCr and ZrB
2. The starting resistor is made of an inorganic material r1 having relatively excellent properties as a heating resistor material such as metal boride such as HfB2, and 5i is formed on the heating resistor made of the material 4.
By providing a protective layer (upper layer) made of a material with excellent oxidation resistance such as 02, the heating resistor is prevented from coming into direct contact with the liquid! Therefore, it has been proposed to solve the above-mentioned problems and improve reliability and durability in use of edge-turning.

[Problem that the invention seeks to solve]

However, a liquid jet recording head having an electrothermal converter having a configuration like h4 also has the following problems. In other words, since the temperature coefficient of the material of the heat-generating resistive layer constituting the conventional electrothermal converter is low, if the time when the current is applied to the heat-generating resistive layer exceeds the rated current-carrying time even by a small amount, it will overheat, resulting in deterioration or disconnection. Sometimes it caused. Specifically, for example, when a carbon-based conductive material such as carbon, silica, or resin is used as the material of the heating resistance layer, the temperature coefficient thereof is about 500 PPM/'0. It should be noted that the temperature coefficient herein refers to the hid portion of the resistance value of the material of the heating resistance layer when the temperature increases by 1° CL, expressed as a percentage.

If the heat-generating resistive layer constituting the '1π gas converter is overheated as described above and causes deterioration or disconnection, the liquid jet recording head having the electrothermal converter becomes unable to print.

Therefore, the main object of the present invention is to solve the problems regarding the durability of such a liquid jet recording head.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention includes a liquid flow path, a discharge port communicating with the liquid flow path and discharging the liquid as droplets, and a discharge port disposed along the liquid distribution flow path. A liquid jet recording head comprising: an electrothermal converter for generating thermal energy for forming the droplets;
The heating resistance layer constituting the electrothermal converter is 15 to 60%
A liquid jet recording head characterized in that it is made of a material having a temperature coefficient of /°C.

The temperature coefficient herein refers to a percentage of the resistance value of the material of the heating resistor layer outside L when the temperature increases by 1''O.

[Effect]

The present invention will be explained in more detail below with reference to the drawings.

FIG. 1(a) is a partial front view of the liquid jet recording head of the present invention seen from the orifice side, and FIG. 1(b) is a partial front view of the liquid jet recording head of the present invention.
FIG. 3 is a partial cross-sectional view taken along a portion indicated by a dashed-dotted line xy in a).

The liquid jet recording head 1 shown in the figure has a predetermined number of grooves of a predetermined width and depth at a predetermined linear density on the surface of a substrate 3 on which an electrothermal transducer 2 is provided. In the case of the liquid jet recording head l shown in FIG. 0, which has a structure in which an orifice 5 and a liquid flow path 6 are formed by joining and covering it with a grooved plate 4, it is shown as having a plurality of orifices 5. However, the present invention is, of course, not limited to this, and application to a recording head in the case of an orifice also falls within the scope of the present invention.

The liquid flow path 6 communicates at its end with an orifice 5 for discharging the liquid to form flying droplets, and the thermal energy generated by the electrothermal converter 2 acts on the liquid to generate vapor bubbles. However, it has a heat acting part 7 which causes a rapid state change due to expansion and contraction of its volume.

The heat acting part 7 is located above the heat generating part 8 of the electrothermal converter 2, and has a heat acting surface 9 that contacts the liquid of the heat generating part 8 as its bottom surface.

The heat generating section 8 includes a lower layer 10 provided on the substrate 3 and a heating resistor layer (heating resistor) 11 provided on the lower layer 10.
．． It is composed of an upper layer 12 provided on the heating resistance layer 11 as necessary. The heating resistor layer 11 is provided with electrodes 13 and 14 on its surface for supplying electricity to the layer 11 in order to generate heat. The electrode 13 is a common electrode for the heat generating section of each liquid discharging section, and the electrode 14 is a selection electrode for selectively generating heat in the heat generating section of each liquid discharging section. It is located along the road.

The L portion layer 12 has a heat generating resistor layer 11 and a liquid flow path 6 in order to chemically and physically protect the heat generating resistor layer 11 from the liquid used.
The electrode 13 is separated from the liquid in the
．． The heating resistor layer 11 has a protective function of preventing a short circuit between the heat generating resistor layer 11 and the heat generating resistor layer 11.

The upper layer 12 has the above-mentioned functions, but
If there is no risk of electrical short-circuiting between the electrodes 13 and 14 through the liquid, it is not necessarily necessary to provide it.

The upper layer 10 mainly has a heat flow control function. That is, when forming flying droplets, the proportion of heat generated in the heat generating resistor layer 11 being conducted toward the heat acting part 7 side is as high as possible than being conducted toward the substrate 3 side, and the flying droplets are After the droplets are formed and the power to the clogging heat generating resistor layer 11 is turned off, the heat in the heat acting part 7 and the heat generating part 8 is quickly released to the substrate 3 side, and the heat in the heat acting part 7 is released. It is provided to rapidly cool the liquid and generated bubbles.

The liquid jet recording device of the present invention can be made more excellent by designing the lower layer 1O in such a manner that it can fully exhibit the above-mentioned functions in relation to the heating resistor layer 11 and the plate 3.

That is, when the flying droplets are formed, the proportion of the heat flow toward the heat acting section 7 is as large as possible, and when the power to the heating resistor layer 11 is turned off.

By increasing the proportion of the heat flow toward the substrate 3 side as much as possible, we can improve the efficiency of droplet ejection energy, high thermal response, and continuous repeatable droplet ejection, improve the droplet formation frequency, and improve the droplet formation frequency. It is possible to more effectively achieve uniformity of the amount of droplets, stabilization of the flight direction of the droplets, uniformity of the initial flight speed of the droplets, and improvement of the fidelity and reliability of response to recording signals.

As described above, the heat generating resistance layer 11 in the liquid jet recording head of the present invention is provided as a thin layer of a material having a temperature coefficient of 15 to 60%/°C, more preferably 50 to 60%/°C. .

The lower limit of the temperature coefficient according to the present invention is set to 15%/°C because this value is effective in achieving the main purpose of the present invention, which is to prevent deterioration and disconnection due to overheating of the 2-heating resistance layer. Yes.

The reason why the lower limit is more preferably 50%°C is because it is even more effective.

Further, the reason why the upper limit value of the temperature coefficient according to the present invention is set to 60%/° C. is because if this upper limit value is exceeded, the resistance value of the heat generating resistive layer becomes influenced by room temperature.

The heating resistance layer of the liquid jet recording head according to the uninvented invention has a low temperature and therefore a low resistance value at the initial stage after voltage is applied.

Therefore, a large current flows through the heating resistance layer. Therefore, the temperature of the heating resistor layer rises rapidly, and the state of the liquid also changes rapidly. The ejection force of the ejected liquid also increases rapidly.

(H) Even if the temperature of the heating resistive layer increases due to, for example, the voltage application time exceeding the rated energization time, the heating resistive layer has a high positive temperature coefficient of 15 to 60%/°C. Therefore, the temperature will not rise to an extremely high temperature. Therefore, deterioration and disconnection of the heat generating resistor layer due to overheating are prevented.

Furthermore, since the temperature of the heat generating resistive layer can be known from its resistance value, temperature control such as temperature correction of the liquid jet recording head can be easily performed.

Examples of the material having a temperature coefficient of 15 to 60%/°C, more preferably 50 to 60%/°C, according to the present invention include barium titanate-based materials. is a material whose main component is barium titanate, with additives such as lanthanum, cerium, and their compounds added as necessary.

In the present invention, the thickness of the heating resistance layer 11 is determined based on the characteristics of the constituent materials so that appropriate thermal energy can be effectively generated.
The number of participants is determined as appropriate depending on the type, content rate, flying droplet formation characteristics required for the device itself, etc., but preferably 500 or more people.
It is preferable that the size is about 8, and optimally 1.6p to 1.
．． It is desirable to have 9 pots.

In the present invention, one heating resistance layer is formed by a thin film forming method such as a CVD method, an electron beam evaporation method, and a sputtering method.

〔Example〕

Next, examples of the present invention will be described.

First, an electrothermal converter mounting board was created based on the following requests.

After forming the heating resistance layer 11 made of a material containing barium titanate as a main component and the aluminum electrode layer on the lower layer 10 of the alumina substrate 3, selective etching
Heating resistance layers 11-1 to 1l-3- with m and 200 pm
-- formed one. In addition, the selective electrode 14 is etched.
and a common electrode 13 was formed. Furthermore, a protective layer (upper layer) 12 was laminated on the surface of each electrode and each heating resistance layer as needed, and an electrothermal converter 2 was formed on the plate 3-1.

In addition, apart from these, multiple grooves (for example, width 40ILm, depth 40gm) and a common ink chamber (not shown) are provided on the glass plate.
A grooved plate 4 was also created by cutting and forming grooves using a micro cutter.

The electrothermal converter head throwing board and grooved plate created in this way are joined together after aligning the electrothermal converter with the grooves, and then connected to a common ink chamber from an ink supply section (not shown). An ink introduction tube (not shown) for introducing liquid ink was also connected to complete the recording head as one unit.

Further, this recording head was attached with a lead substrate having lead electrodes (a common lead electrode and a selection lead electrode) connected to the selection electrode and common electrode mentioned above.

When a liquid ejection test was conducted using the liquid ejecting recording head of this example prepared in this way, it showed about 2.5 times the durability compared to the conventional one.

Furthermore, by knowing the temperature of the first heating resistor layer from its resistance value, it was possible to easily correct the temperature of the liquid jet recording head.

In addition, a similar liquid ejection test was conducted using a silicon wafer as the substrate 3 instead of the alumina substrate described above, and as the lower layer 10, using 2 to 5 tiles of 5i02 layer formed by heat treating the surface of the silicon wafer. I did it and got similar good results.

Further, as the non-plate 3, in addition to those used in the above embodiments, glass, ceramics, heat-resistant plastic, etc. can also be used.

In addition to A-ai, A-Cu is used as an electrode material.

A1-5t etc. can be used, but when using these materials, in order to isolate the electrode and the liquid, for example, the heat-active surface should be covered with a coating made of hardened photosensitive heat-resistant resin. It is preferable to cover the electrode and the area around the electrode except for the electrode.

In this embodiment, a liquid jet recording head is shown in which the direction in which the liquid flows in the liquid flow path and the direction in which the liquid is ejected as droplets from the ejection ports are the same, but the present invention is not limited to this. For example, if there is an angle in both directions, for example, 90
It also includes cases where ' is formed.

〔effect〕

The liquid jet recording head of the present invention described in detail above has the following effects.

(1) Even if the voltage application time to the heating resistance layer exceeds the rated energization time and the temperature rises, the heating resistance layer has a high positive temperature coefficient of 15 to 60%/'0. Therefore, the temperature will not rise to an extremely high temperature. Therefore, deterioration and disconnection of the heating resistance layer due to overheating are prevented.

(2) Since the temperature of the heat generating resistive layer can be known from its resistance value, temperature control such as temperature correction of the liquid jet recording head can be easily performed.

(3) Due to the effects of (1) and (2) above, it is possible to obtain a liquid jet recording head with excellent durability in use and good print quality.

[Brief explanation of drawings]

FIG. 1(a) is a partial front view from one orifice side of a preferred embodiment of a liquid jet recording head to which the present invention is applied, and FIG. 1(b) is a point in FIG. 1(&). FIG. 3 is a partial cross-sectional view taken along a portion indicated by a chain line XY. FIG. 2 is a schematic diagram for explaining an electric circuit of a liquid jet recording head provided with a conventional electrothermal converter. FIGS. 3(a) to 3(d) are schematic process diagrams for explaining the liquid ejection process of a liquid jet recording head provided with a conventional electrothermal converter. 1 ----------One liquid jet recording head. 2 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
---One board, 4--
----------Plate with one groove, 5 ----------------
−−−−−−−− Orifice, 6 −−−−−−−−
−−−−−−−−−−−−−−One liquid flow path. 7 −−−−−−−−−−−−−−−−−−−−− One heat acting part. 8 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
1--Heat action surface. 10---------------
Lower layer, ti −−−−−−−−−−−−−−
-1---Heating resistance layer, 12------------
−1−−−−−−−−−− Upper layer, 13 −−−−−
----------1---------Common electrode, 14-
−−−−−−−−−−−−−−−−−−−−One selection electrode, 21−−−−−−−−−−−−−−−−1−−−−
--Nozzle. 22 −−−−−−−−−−−−−−−−−1−−−−
Heater, 23 −−−−−−−−−−−−−−1−−
−−−−−−−−−Power supply, 24 −−−−−−−−−−
−−−−−−−−) Transistor, 25 −−−−−−
------11-----Control device. 26---------1------------
--One liquid, 27 ---------One---------
---------One bubble, 28----
−−−−−−−−−−−−−−−One droplet.

Claims (2)

[Claims] (1) A liquid flow path, an ejection port communicating with the liquid flow path and discharging the liquid as droplets, and a discharge port disposed along the liquid flow path to generate heat for forming the droplets. In a liquid jet recording head equipped with an electrothermal transducer for generating energy, the heat generating resistive layer constituting the electrothermal transducer has one
A liquid jet recording head characterized in that it is made of a material having a temperature coefficient of 5 to 60%/°C. (2) The liquid jet recording head according to claim (1), wherein the material having a temperature coefficient of 15 to 60%/°C is a barium titanate-based material.