JP2006224601A - Liquid discharge head and recording apparatus using its head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an energy saving type discharge head which simultaneously foams from the surface and the back surface and is hardly destroyed. <P>SOLUTION: The head for inkjet recording in which a liquid is foamed by heating, and the liquid is discharged by utilizing the generated air bubbles, is equipped with a liquid droplet discharge port, a flow path 15 disposed in communication with the liquid droplet discharge port and filled with the liquid, and a heating body 1 supported under a condition that it is made to be floated from the inner wall face of the flow path 15, and the heating body 1 has a laminated structure whose surface and back surface are symmetrical. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid ejection head that heats and foams a liquid in a flow path, and ejects the liquid using generated bubbles, and a recording apparatus.

  Conventionally, liquid ejecting apparatuses have been applied in various fields such as microfabrication, experimental analysis, and image formation. Here, an ink jet recording method will be described as an example.

  An ink jet recording method that forms an image by ejecting ink droplets and depositing them on a recording medium has the advantages of being capable of high-speed recording, high recording quality, and low noise. Further, this method has many excellent advantages such as easy color image recording, recording on plain paper, and the like, and further facilitating miniaturization of the apparatus.

  A recording apparatus using such an ink jet recording method is generally provided with an ejection port for ejecting ink as flying ink droplets, an ink path communicating with the ejection port, and a part of the ink path. There is provided a recording head having energy generating means for giving ejection energy to the ink inside. For example, JP-B 61-59911, JP-B 61-59912, JP-B 61-59913, and JP-B 61-59914 use an electrothermal converter as an energy generating means, and by applying an electric pulse. A method for ejecting ink by applying thermal energy generated by the ink to the ink is disclosed.

  In the recording methods disclosed in the above publications, bubbles are generated in the ink subjected to the action of thermal energy, and the ink is discharged from the discharge port at the tip of the recording head by an action force based on the rapid expansion of the bubbles. The ejected ink droplets adhere to the recording medium to form an image. According to this method, since the discharge ports in the recording head can be arranged with high density, it is possible to record a high-resolution, high-quality image at high speed. A recording apparatus using this method is a copying machine, It can be used as information output means in printers, facsimiles and the like.

  In this ink jet recording method, an electrothermal transducer, that is, a heating element for heating a liquid as described above is required. Conventionally, a thin film resistor is disposed on a wall surface in a flow path, and the thin film resistor What connected the electrode for applying an electric pulse to 2 sides was used.

However, when the thin film resistor is installed on the wall surface as described above, the thermal energy generated by the thin film resistor may be dissipated to the wall surface at a considerable rate. Thereby, the efficiency which converts a thermal energy into the energy of foaming falls, and power consumption may become large. In order to solve this problem, Japanese Patent Application Laid-Open No. 55-57477 and Japanese Patent Application Laid-Open No. 62-94347 provide heating element elements that are partially extended into the space in the flow path. An apparatus that reduces power consumption by preventing heat dissipation from the heat generating element to the print head body or substrate as much as possible and efficiently converting the electric energy input to the heat generating element into foaming energy is disclosed. ing.
JP-A-55-57477 JP 62-94347 A

  However, in the above-described conventional technology in which the efficiency of converting the input electric energy into foaming energy is improved, the temperature of the front and back surfaces of the heater arranged in the air may not necessarily be the same. There is a possibility that the heater may be damaged because a gap occurs in the foaming time and a large force is applied only from one side of the heater surface.

  The present invention has been made in view of the above problems. SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid discharge head that is less likely to break and that can prevent the deviation of foaming between the front and back surfaces arranged in the air and can efficiently convert the energy input to the heating element into discharge energy. Furthermore, it is to provide a recording apparatus with low power consumption.

  The present invention relates to a liquid droplet ejection port and a liquid placed in communication with the liquid droplet ejection port in an ink jet recording head that heats and foams the liquid and uses the generated bubbles to eject the liquid. And a heating element supported in a state of being floated from the inner wall surface of the channel, and the heating element has a laminated structure in which the front and back are symmetrical.

  In addition, the recording apparatus of the present invention is arranged to communicate with a droplet discharge port and a droplet discharge port in an inkjet recording head that heats and foams the liquid and uses the generated bubbles to discharge the liquid. A recording medium having a liquid discharge head, comprising: a flow path for filling a liquid; and a heating element supported in a state of being floated from an inner wall surface of the flow path, wherein the heating element has a symmetric laminated structure. Device.

(Operation of the invention)
By using a heating element supported in a state of being floated from the inner wall surface of the flow path, it is possible to efficiently convert the input energy into discharge energy, and the heating element has a laminated structure that is symmetrical on the front and back sides. By using this, the temperature distribution of the heating element can be made symmetrical, and foaming can occur simultaneously on the front and back of the heating element. When heat generation occurs simultaneously on the front and back surfaces, the force acting on the surface of the heating element and the force acting on the back surface cancel each other, thereby preventing the generation of enormous stress that causes destruction and preventing the heating element from being destroyed.

  As described above, in the liquid discharge apparatus type discharge head of the present invention, the heat generating element is supported in a state of being floated from the inner wall of the flow path, thereby preventing the heat generated in the heat generating element from being dissipated to the substrate, By using an air-generating element having a symmetrical front and back laminated structure, the temperature distribution on the front and back sides becomes symmetrical, and foaming occurs at the same time on the front and back sides, thereby preventing damage to the heating element. In addition, this makes it possible to provide a discharge device that can perform high-resolution and high-speed printing, has lower power consumption than conventional ones, and suppresses damage to the heating element.

  In the liquid discharge head of the present invention, by disposing the heating element in a state where it is floated from the inner wall surface of the flow path filled with liquid, heat dissipation to the head body and the substrate can be prevented, Electric energy input to the heating element can be efficiently converted into foaming energy. The support structure of the heating element may be a doubly-supported beam shape or a cantilever beam shape so long as the liquid discharge port direction is not blocked. The shape of the heating element is particularly small when the plate shape is used, but may be other shapes. In the case of a flat plate-shaped heating element, the foamed surface is often the surface having the largest area. Even when the foamed surface is another surface of the flat plate or when a heating element other than the flat plate shape is used, the foamed surface may be substantially parallel to the ejection direction.

  In the liquid discharge head according to the present invention, when a flat plate-like heating element is used, the surface having the largest area of the heating element is set as a foamed surface, and bubbles are generated on both surfaces, thereby being installed on the wall surface of the prior art. Compared with the generated heating element, the volume of bubbles is approximately doubled, and the liquid ejection energy can be improved. Alternatively, it is possible to obtain the same ejection energy with less power consumption compared to the prior art.

  In the liquid discharge head of the present invention, when a flat plate-shaped heating element is used, the surface having the largest area of the heating element is the foamed surface, and bubbles are generated on both surfaces, thereby stabilizing the discharge characteristics. Can do. In order to simultaneously generate bubbles on both sides of the heating element, for example, the heating element may be rapidly heated to a temperature at which film boiling occurs. Thereby, since the temperature of the heating element uniformly rises above the foaming temperature in a short time, the variation in foaming time on both sides of the heating element is reduced, and bubbles can be generated simultaneously on both sides of the heating element.

  In the liquid discharge head of the present invention, the generated bubbles are communicated with the outside air in the vicinity of the droplet discharge port, so that the volume of the liquid to be discharged becomes constant and the liquid discharge characteristics can be stabilized. In order to make the bubbles communicate with the outside air, for example, a method of shortening the distance between the heat generating element and the droplet discharge port, or increasing the volume of the bubbles by increasing the driving voltage can be used.

  In addition, the recording apparatus of the present invention is capable of high-speed recording by providing a plurality of the recording heads described above, and is stable by providing means for supplying an electrical signal that causes film boiling to each heating element of the recording head. Recording is possible.

  Further, in the recording apparatus of the present invention, it is possible to realize high-quality recording with high resolution and high-speed printing by discharging liquid using the above-described liquid discharge method.

  Specific examples are shown below, but the dimensions, shapes, materials, driving conditions, etc. of the substrate, top plate, flow path, heating element, droplet discharge port, etc. are examples, and can be arbitrarily changed as design matters. It is.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(First embodiment)
FIG. 1 is a diagram showing the characteristics of the liquid ejection apparatus of the present invention. The figure shows the characteristics of the cross section of the present invention. The droplet discharge port 10, the flow channel 15 for filling the liquid arranged in communication with the droplet discharge port 10, and the inner wall surface of the flow channel are floated. A heating element 1 having a symmetrical laminated structure supported in a state and a heat generation driving means 2 for generating heat by Δt for a certain period of time are provided. In the figure, reference numeral 21 denotes a liquid chamber, 22 denotes ejected liquid droplets, 23 denotes bubbles generated by heating the liquid by the heating element 1, and 24 to 25 denote substrates constituting the flow path and the liquid chamber.

  As shown in FIG. 2, the discharge head of Example 1 is particularly symmetric with the heating element having a protective layer on both sides of the thin film resistor, more specifically, an anti-cavitation layer on the insulating protective layer. A tantalum thin film having a thickness of 0.26 μm is used as the anti-cavitation layer, and a silicon nitride thin film having a thickness of, for example, 0.8 μm is used as the insulating layer as a thin film resistor. For example, a tantalum nitride thin film having a thickness of 0.05 μm is used.

  Specifically, the heat generation has a symmetrical structure in which a groove to be the flow path 11 is formed on the single crystal silicon substrate 24 by etching and a tantalum nitride thin film is provided with protective layers made of tantalum and a silicon nitride thin film on both sides. The body element 1 is arranged so as to be doubly supported with respect to the groove, electrodes (not shown) are formed at both ends of the heating element, and a top made of single crystal silicon in which a groove to be the flow path 11 is formed. The plate 25 is bonded to the substrate to form the droplet discharge port 10. Bubbles are mainly generated on the surface having the largest area among the surfaces of the heating element 1. As shown in FIG. 1, the surface having the largest area among the surfaces of the heating element 1, that is, the surface in which bubbles are mainly generated (hereinafter referred to as a bubble surface) is parallel to the liquid ejection direction. Are arranged as follows.

3 shows a case where the resistor layer of the element shown in FIG. 2 is heated at a power of 0.4 [GW / m ² ] to 1.995 [GW / m ² ] per unit time unit area. It is a figure which shows temperature distribution. As shown in FIG. 3, the temperature distribution of the front and back symmetrical heating element 1 provided with the protective layer is symmetrical, and foaming occurs simultaneously on the surface of the heating element 1.

  Next, the liquid discharge principle of the discharge head of this embodiment will be described. In the state where the flow path 11 is filled with liquid, the driving device 2 applies a pulse voltage to the heating element 1 to rapidly increase the temperature of the heating element to a temperature at which film boiling occurs (300 ° C. or more). . As a result, bubbles 23 are simultaneously generated on both sides of the foaming surface of the heating element and start to expand rapidly. Further, the bubbles continue to expand, pushing the droplets toward the droplet discharge port 10 side. When the bubbles further expand, independent droplets 22 are formed and discharged from the droplet discharge port. Thereafter, the liquid remaining in the flow path without being taken in by the liquid droplets is combined with the liquid on the liquid supply port 207 side to return to the initial state.

  For example, C.I. I. Each compounding component consisting of 23.0% by weight of food black, 15.0% by weight of diethylene glycol, 5.0% by weight of N-methyl-2-pyrrolidone, and 77.0% by weight of ion-exchanged water is stirred in a container to be uniform. After mixing and dissolving, an ink having a viscosity of 2.0 cps (20 ° C.) obtained by filtering through a polyfluorinated ethylene fiber filter having a pore diameter of 0.45 μm is supplied to the flow path and discharged.

(Second embodiment)
FIG. 4 is a diagram showing the characteristics of the air heating element according to the second embodiment. In the second embodiment, in particular, the heating element has a front and back symmetrical laminated structure having thin film resistance layers on both sides of the thin film insulator. Features.

Here, the insulating layer is a SiO ₂ thin film having a thickness of 50 to 500 nm, and the resistance thin film layer is a tantalum nitride thin film having a thickness of 0.05 μm.

FIG. 5 is a diagram showing a temperature distribution during foaming in the case where the resistor layer of the element shown in FIG. 4 is heated with electric power of 1.995 [GW / m ² ] per unit time unit area. As shown in FIG. 3, the temperature distribution of the front and back symmetrical heating elements 1 having resistance heating elements on both sides of the insulating layer is symmetric, and foaming occurs simultaneously on the surface of the heating element 1.

1 is a diagram illustrating an inkjet discharge head according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating characteristics of the first embodiment. FIG. 3 is a diagram showing a temperature distribution of Example 1. FIG. 6 is a diagram illustrating characteristics of the second embodiment. FIG. 6 is a diagram showing a temperature distribution of Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating body 2 Drive apparatus 10 Discharge hole 12 Protective layer 13 Resistance heating element layer 14 Insulating layer 15 Flow path 21 Liquid chamber 22 Droplet 23 Bubble 24, 25 Substrate

Claims (5)

  In an inkjet recording head that heats and foams a liquid and uses the generated bubbles to discharge the liquid, a droplet discharge port, and a flow path for filling the liquid that is arranged in communication with the droplet discharge port A liquid discharge head comprising a heating element supported in a state of being floated from the inner wall surface of the flow path, and the heating element has a laminated structure that is symmetrical between the front and the back.   2. The liquid discharge head according to claim 1, wherein the heating element has a symmetrical structure in which a protective layer is provided on both sides of the thin film resistor.   3. The liquid discharge head according to claim 1, wherein the heating element has a symmetrical structure in which a thin film resistance layer is provided on both sides of a thin film insulator.   In an inkjet recording head that heats and foams a liquid and uses the generated bubbles to discharge the liquid, a droplet discharge port, and a flow path for filling the liquid disposed in communication with the droplet discharge port A recording apparatus having a liquid discharge head, comprising: a heating element supported in a state of being floated from an inner wall surface of the flow path, wherein the heating element has a laminated structure that is symmetrical between the front and the back.   The recording apparatus according to claim 4, comprising a plurality of liquid discharge heads, and means for supplying an electric signal to each heating element.

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