JP2007331319A - Inkjet head unit and ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head unit which has a high reliability, and to provide an ink jet recorder. <P>SOLUTION: The inkjet head unit comprises an inkjet head substrate 1, a sealing member, and a hydrophilic liquid 9. The inkjet head substrate 1 includes both a head body part equipped with pressure chambers which eject supplied ink from openings by a pressure change, and piezoelectric vibrators which are set at one face side of the pressure chambers in the head body part and apply a pressure to the pressure chambers. The sealing member seals together with the inkjet head substrate 1 a space which includes the piezoelectric vibrators, thereby forming a sealed space. The hydrophilic liquid 9 is arranged in a state in touch with the piezoelectric vibrators in the sealed space. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet head unit and an ink jet recording apparatus, and in particular, an ink jet head unit that discharges ink by deforming a pressure chamber using a piezoelectric vibrator, and an ink jet recording that includes the ink jet head unit as a printing unit. It relates to the device.

  The ink jet recording apparatus performs printing by discharging several tens of picoliters of ink toward a recording medium such as paper through a large number of nozzle holes having a diameter of several tens of microns. The ink discharge section is formed from a nozzle plate having a large number of nozzle holes, a pressure chamber communicating with each nozzle hole, a common liquid chamber for supplying ink to the pressure chamber, and a means for generating pressure in the pressure chamber. Yes.

  There are two types of methods for generating pressure in the pressure chamber, one is a method for generating bubbles in the pressure chamber by using Joule heat, and the other is a method for deforming the pressure chamber by a piezoelectric vibrator. Yes, these methods are used according to the required performance and application.

Piezoelectric vibrators have the ability to convert mechanical energy into electrical energy, or convert electrical energy into mechanical energy. This basic structure has a piezoelectric body sandwiched between two electrodes in the thickness direction. It is a laminated body. Typical examples of the piezoelectric material used for this piezoelectric vibrator include lead zirconate titanate (Pb (Zr, Ti) O ₃ ) (PZT), which is an oxide having a perovskite crystal structure, and magnesium, There are those added with manganese, nickel, niobium and the like. In particular, a large piezoelectric displacement is obtained in the <001> axis direction (C-axis direction) in the case of tetragonal PZT having a perovskite crystal structure and in the <111> axis direction in the case of rhombohedral PZT.

  However, many piezoelectric materials are polycrystalline bodies composed of aggregates of crystal grains, and each crystal axis faces a random direction. For this reason, spontaneous polarization Ps is also randomly arranged, and a large amount of mutation cannot be obtained as it is.

  In the case of a piezoelectric element, the crystal structure is controlled so that the sum of these vectors is parallel to the electric field. In a piezoelectric actuator (a laminate is provided with a diaphragm) as one form of this piezoelectric element, when a voltage is applied between both electrodes, a mechanical displacement proportional to the magnitude of the voltage is obtained.

  By the way, with recent miniaturization of electronic devices, miniaturization of piezoelectric elements has been strongly demanded. At the same time, higher definition is required for higher print quality. It is possible to satisfy these requirements by using a thin film piezoelectric vibrator that can significantly reduce the volume compared to a sintered body, rather than using a sintered body that has been widely used in the past as a piezoelectric vibrator. It becomes.

  This is because the thickness of a piezoelectric element made of a sintered body is several tens of μm, which is thicker than about 3 μm of a thin film piezoelectric element, and therefore there is a limit to the accuracy of etching using a photolithography technique. . In order to perform predetermined etching with high accuracy, the line width must be equal to or less than the film thickness, and by using a thin film piezoelectric element having a thin film thickness, highly accurate fine processing is possible. As a method of forming a thin film piezoelectric element, for example, a PZT film, there are a sputtering method, a CVD method, a sol-gel method, and the like, and a high performance thin film piezoelectric element can be obtained by adjusting the film forming conditions and devising heat treatment conditions. I came.

  However, when a high voltage is applied in a state where the piezoelectric vibrator is exposed to a humid atmosphere for a long time, the electrical insulation of the piezoelectric vibrator is lowered and dielectric breakdown occurs. Such a phenomenon has been regarded as one of the major problems in reliability in piezoelectric vibrators. In particular, the use of a thin film piezoelectric vibrator that is easily affected by foreign substances because of its thin film thickness is more likely to cause dielectric breakdown than when a thick sintered body is used for the piezoelectric vibrator.

Therefore, various methods have been proposed as a method for suppressing the influence of moisture as much as possible and ensuring high reliability. For example, a method of enclosing a dried fluid in a space formed in a sealing cap and a flow path substrate on which a piezoelectric vibrator is formed (see, for example, Patent Document 1), and a sealed space including a piezoelectric element by using heat generation means in combination. For example, a method of encapsulating a desiccant in the substrate (for example, see Patent Document 2), a method of covering the piezoelectric vibrator with a protective member impregnated with an insulating liquid (for example, see Patent Document 3), and the like have been proposed.
JP-A-10-305578 JP-A-11-300957 JP 2000-43258 A

  However, it is difficult to say that the conventional sealing method can provide a sufficient inkjet head with respect to long-term reliability. It is said that a thin film piezoelectric vibrator cannot completely suppress the occurrence of dielectric breakdown unless it is operated in a low humidity state with a dew point of -40 ° C. or lower. In the conventional sealing method described above, this dew point −40 The environment below ℃ cannot be maintained for a long time, and eventually dielectric breakdown occurs. Therefore, a recording apparatus equipped with this inkjet head has a short product life and poor reliability.

  In a sealing method for enclosing a dry fluid (Patent Document 1), the influence of moisture can be completely removed at the initial stage of sealing, but the state cannot be maintained for a long time. Since moisture enters from the adhesive resin connecting the sealing cap over time, the initial low humidity state cannot be maintained. By adopting a resin with low moisture permeability, it is possible to reduce the amount of moisture permeation, but it is difficult to completely suppress the moisture permeability of the resin, and eventually it will be affected by moisture, resulting in dielectric breakdown. Wake up and leak current flows.

Compared with the method disclosed in (Patent Document 1), the method disclosed in (Patent Document 2) can remove the moisture that has entered by using a hygroscopic agent, and accordingly can ensure long-term reliability. . However, since the desiccant and the heat generating means are used in combination, the structure becomes complicated and it is impossible to cope with downsizing. In addition, the hygroscopic agents such as silica gel, slaked lime, and MgF ₂ mentioned as examples have low performance in both drying performance and drying capacity, so that the environment with a dew point of −40 ° C. that can completely suppress the leakage current of the piezoelectric vibrator. Difficult to hold for a long time.

  The method disclosed in (Patent Document 3) prevents moisture entering from the outside from deteriorating the piezoelectric vibrator by covering the piezoelectric vibrator with a protective member impregnated with an insulating liquid, and insulating the piezoelectric vibrator. Examples of hydrophobic liquids include hydrophobic silicone oil and fluorine-based inert liquids. However, in this structure, the entering water is hydrophobic and therefore separates from the insulating liquid. The separated moisture may collect at the interface between the piezoelectric vibrator and the liquid, and the moisture concentration becomes high.

  In addition, when the liquid to be impregnated is heavier than water, the water that has entered will accumulate on the upper surface of the liquid surface away from the piezoelectric vibrator, but the separated water may be in direct contact with the piezoelectric vibrator due to vibration. . In such a case, dielectric breakdown occurs and leak current occurs.

  Thus, it has been difficult to realize an ink jet head that can satisfy high reliability by the methods proposed so far.

  The present invention has been made in view of the above, and an object thereof is to provide an ink jet head unit having high reliability and a recording apparatus using the same.

  In order to solve the above problems, an ink jet head unit according to the present invention is provided on a side of a pressure body in a head main body portion including a pressure chamber for discharging supplied ink from an opening portion by pressure change. An inkjet head substrate including a piezoelectric vibrator that applies pressure to the pressure chamber; a sealing member that seals a space including the piezoelectric vibrator to form a sealed space together with the inkjet head substrate; And a hydrophilic liquid disposed in contact with the piezoelectric vibrator.

  An ink jet head unit according to the present invention includes a head main body having a pressure chamber that discharges supplied ink from an opening due to a pressure change, and a pressure chamber that is provided on one side of the pressure chamber in the head main body. An ink jet head substrate including the piezoelectric vibrator, a first sealing member that seals a space including the piezoelectric vibrator to form a first sealed space together with the ink jet head substrate, and a first sealing member. A space between the first sealed space and the second sealed space, and a second sealing member that forms a second sealed space by sealing the space including the piezoelectric vibrator in the sealed space. And a hydrophilic liquid disposed on the surface.

  An ink jet recording apparatus according to the present invention is equipped with the above ink jet head unit.

  According to the present invention, it is possible to reduce the concentration of moisture that has entered the sealed space to such an extent that dielectric breakdown does not occur by disposing a hydrophilic liquid inside the sealed space surrounding the piezoelectric vibrator. it can. In addition, by disposing a hydrophilic liquid, the water vapor that has entered the sealed space surrounding the piezoelectric vibrator can be changed to a liquid state, so that damage to the piezoelectric vibrator can be reduced. Become. Furthermore, in the case of conventional hydrophobic liquids such as silicon oil and fluorine-based inert liquid, the infiltrated water is separated from the hydrophobic liquid, and the moisture concentration is present at the interface between the piezoelectric vibrator and the hydrophobic liquid. However, this problem can also be improved. As a result, the influence of moisture on the piezoelectric vibrator can be suppressed for a long time, and the dielectric breakdown of the piezoelectric vibrator due to voltage application can be prevented, and an ink jet head unit having high reliability can be obtained.

  Further, according to the present invention, the first sealed space is formed by sealing the space including the piezoelectric vibrator, and the space including the piezoelectric vibrator is sealed inside the first sealed space. 2 is formed, and a hydrophilic liquid is disposed in the space between the first sealed space and the second sealed space, so that moisture entering from the outside becomes gaseous water vapor as a piezoelectric vibrator. In order to enter in a liquid state that is converted from gas to liquid and dissolved in a hydrophilic liquid, instead of directly entering the inside of the second closed space containing Can be suppressed. As a result, the influence of moisture on the piezoelectric vibrator can be suppressed for a long time, and the dielectric breakdown of the piezoelectric vibrator due to voltage application can be prevented, and an ink jet head unit having high reliability can be obtained.

  Further, according to the present invention, an ink jet recording apparatus having high reliability can be obtained by providing the ink jet head unit.

  An ink jet head unit according to a first aspect of the present invention includes a head main body including a pressure chamber that discharges supplied ink from an opening by pressure change, and a pressure chamber provided on one side of the pressure chamber in the head main body. An inkjet head substrate including a piezoelectric vibrator that applies pressure to the substrate, a sealing member that seals a space including the piezoelectric vibrator to form a sealed space together with the inkjet head substrate, and a piezoelectric member in the sealed space. A hydrophilic liquid arranged in contact with the vibrator, and the moisture concentration entering the sealed space is diluted by the hydrophilic liquid, and a voltage is applied. It has the effect | action that the dielectric breakdown of a piezoelectric vibrator is prevented.

  The ink jet head unit of the second invention is characterized in that, in the first invention, a protective film is formed on the surface of the piezoelectric vibrator, and the moisture concentration entering the sealed space is made hydrophilic. Further, since the influence of moisture is suppressed by the protective liquid, the dielectric breakdown of the piezoelectric vibrator due to the application of voltage is prevented for a long time.

  An ink jet head unit according to a third invention is characterized in that, in the first invention, the surface of the piezoelectric vibrator is subjected to a water repellent treatment, and the moisture concentration entering the inside of the sealed space is Since it is diluted with a hydrophilic liquid and the water repellent treatment repels the liquid water and the influence of moisture is suppressed, it has the effect of preventing the dielectric breakdown of the piezoelectric vibrator by applying voltage over a long period of time. .

  The inkjet head unit of the fourth invention is characterized in that, in the third invention, the water-repellent treatment is performed by a fluorine-based material, and the fluorine-based water-repellent material has high performance, Since the influence of moisture due to the water repellent treatment can be suppressed for a long time, the dielectric breakdown of the piezoelectric vibrator by applying a voltage is prevented for a long time.

  An ink jet head unit of a fifth invention is characterized in that, in the first invention or the second invention, the hydrophilic liquid is an alcohol liquid, and the alcohol solution has a high water solubility. Therefore, even if a large amount of moisture permeates, the amount of moisture contained in the liquid can be reduced for a long period of time, and the dielectric breakdown of the piezoelectric vibrator due to the application of voltage can be prevented for a long period of time.

  An ink jet head unit according to a sixth aspect of the present invention is the ink jet head unit according to the third or fourth aspect, wherein the hydrophilic liquid contains at least one of water and alcohol-based liquid. Since the surface of the vibrator is treated with water repellency, the effect of moisture is suppressed by repelling liquid water, and the alcoholic solution is highly soluble in water, so even if a large amount of moisture enters, it is included in the liquid. Since the amount of moisture is reduced for a long period of time, dielectric breakdown of the piezoelectric vibrator due to application of voltage is prevented for a long period of time.

  An ink jet head unit of a seventh invention is characterized in that, in the first to sixth inventions, a powdery desiccant is dispersed in a hydrophilic liquid. The moisture contained in the initial stage is removed by the powdery desiccant, and the moisture that has penetrated later is also removed by the powdery desiccant, so the amount of moisture contained in the liquid is reduced for a long period of time, and the piezoelectric is applied by applying voltage. The dielectric breakdown of the vibrator is prevented for a long period of time.

  An ink jet head unit according to an eighth invention is the ink jet head unit according to the seventh invention, wherein the powdery desiccant is a molecular sieve, and the molecular sieve has little state change due to adsorption of moisture. Suitable as a desiccant that adsorbs moisture in the liquid and can efficiently remove moisture contained in the hydrophilic liquid, preventing dielectric breakdown of the piezoelectric vibrator by applying voltage over a long period of time. It has the action.

  An ink jet head unit according to a ninth aspect of the present invention is a head main body having a pressure chamber that discharges supplied ink from an opening by pressure change, and is provided on one side of the pressure chamber in the head main body to apply pressure to the pressure chamber. An inkjet head substrate including a piezoelectric vibrator to be added; a first sealing member that seals a space including the piezoelectric vibrator to form a first sealed space together with the inkjet head substrate; In a space between the first sealed space and the second sealed space, a second sealing member that seals a space including the piezoelectric vibrator to form a second sealed space inside the sealed space. A hydrophilic liquid disposed, and moisture entering from the outside does not directly enter the second sealed space including the piezoelectric vibrator as water vapor in a gaseous state, From gas to liquid Since the liquid enters the liquid state after being converted into a hydrophilic liquid, the amount of moisture entering the second sealed space is suppressed, and dielectric breakdown of the piezoelectric vibrator due to application of voltage is prevented for a long time. Has the effect of

  An ink jet head unit of a tenth invention is characterized in that, in the ninth invention, the hydrophilic liquid contains at least one kind of water or an alcohol-based liquid, and moisture entering from the outside is Rather than directly entering the second sealed space including the piezoelectric vibrator as the vapor in the gaseous state, the second sealed is because the gas is converted from the liquid into the liquid and is dissolved into the hydrophilic liquid. The amount of moisture entering the space is suppressed, and the alcoholic solution has a high water solubility, so that dielectric breakdown of the piezoelectric vibrator due to application of voltage is prevented for a long period of time.

  An ink jet head unit according to an eleventh aspect is characterized in that, in the ninth aspect or the tenth aspect, the second sealed space is provided with a desiccant, and the second sealed space including a piezoelectric vibrator. Even if moisture enters the surface, the moisture is removed by the desiccant, so that the dielectric breakdown of the piezoelectric vibrator due to application of voltage is prevented for a long time.

  An ink jet head unit according to a twelfth aspect is characterized in that the ink jet head unit according to any one of claims 1 to 11 is mounted, and has an effect that the print quality is stable for a long time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In these drawings, the same members are denoted by the same reference numerals, and redundant description is omitted. Further, the present invention is not limited to the following description, and can be appropriately changed without departing from the gist of the present invention.

(Embodiment 1)
FIG. 1 is a perspective view showing the overall configuration of the inkjet head substrate according to the first embodiment of the present invention, and FIG. 2 is a perspective view showing the main parts of the piezoelectric actuator section and the pressure chamber member according to the first embodiment of the present invention. FIG. Hereinafter, each component will be briefly described. A is a pressure chamber member, and a pressure chamber opening 101 penetrating in the thickness direction (vertical direction) is formed in the pressure chamber member A. B is a piezoelectric actuator part arranged so as to cover the opening of one end (the upper end in FIG. 2) of the pressure chamber opening 101, and C is the other end (the lower end in FIG. 2) of the pressure chamber opening 101. It is an ink flow path member arranged so as to cover the opening. The pressure chamber opening 101 of the pressure chamber member A is closed to the pressure actuator 102 by the piezoelectric actuator portion B and the ink flow path member C located above and below the pressure chamber opening A, respectively.

  The piezoelectric actuator portion B has a first electrode layer 103 (individual electrode) positioned almost directly above the pressure chambers 102, and the pressure chambers 102 and the first electrode layers 103 are arranged in a staggered manner. Has been.

  The structure of this piezoelectric actuator part B is demonstrated based on FIG. FIG. 3 is a cross-sectional view of the main part of the inkjet head substrate in a direction orthogonal to the ink supply direction (arrow X) shown in FIG. In FIG. 3, the pressure chamber member A and the piezoelectric actuator portion B having the four pressure chambers 102 arranged in the orthogonal direction are drawn for reference.

  In FIG. 3, reference numeral 103 denotes a first electrode layer positioned substantially directly above each pressure chamber 102 as described above. Reference numeral 110 denotes a piezoelectric layer provided on one surface (lower side in FIG. 3) of the first electrode layer 103. Reference numeral 112 denotes a second electrode layer (common electrode) which is provided on one surface (lower side in FIG. 3) of the piezoelectric layer 110 and is common to all the piezoelectric layers 110.

  Reference numeral 111 denotes a vibration layer which is provided on one surface (lower side in FIG. 3) of the second electrode layer 112 and which is displaced in the layer thickness direction due to the piezoelectric effect of the piezoelectric layer 110 and vibrates. Reference numeral 113 denotes an intermediate layer (vertical wall) provided on one surface (lower side in FIG. 3) of the vibration layer 111 and positioned above the partition wall 102a that partitions the pressure chambers 102 from each other.

  And the 1st electrode layer 103, the piezoelectric material layer 110, and the 2nd electrode layer 112 comprise the piezoelectric element by which these are laminated | stacked in order. In addition, the vibration layer 111 is provided on the surface on the second electrode layer 112 side. And the protective film 10 is formed so that the whole of these component elements may be covered.

  In FIG. 3, reference numeral 114 denotes an adhesive that bonds the pressure chamber member A and the piezoelectric actuator portion B, and each of the intermediate layers 113 is part of the adhesive 114 when bonded using the adhesive 114. Even if it protrudes outward from the partition wall 102a, the adhesive layer 114 does not adhere to the vibration layer 111, and the vibration layer 111 causes the desired displacement and vibration. It has the role of expanding the distance from the lower surface of the.

  As described above, the pressure chamber member A is preferably bonded to the side surface of the vibration layer 111 of the piezoelectric actuator portion B opposite to the second electrode layer 112 via the intermediate layer 113, but the second electrode layer of the vibration layer 111 The pressure chamber member A may be directly joined to the side surface opposite to 112.

  The ink flow path member C is used for the common liquid chamber 104 shared between the pressure chambers 102 arranged in the ink supply direction (the arrow X direction in FIG. 1), and for supplying the ink in the common liquid chamber 104 to the pressure chamber 102. Supply port 105 and an ink flow path 106 for discharging the ink in the pressure chamber 102.

  D is a nozzle plate, and a nozzle hole 107 communicating with the ink flow path 106 is formed in the nozzle plate D. Further, E is an IC chip, and a voltage is supplied from the IC chip E to each of the first electrode layers (individual electrodes) 103 via bonding wires BW.

  The inkjet head unit according to the first embodiment was configured using the inkjet head substrate having such a configuration. Hereinafter, it demonstrates in detail based on drawing.

  4 is a cross-sectional view of the inkjet head unit according to the first embodiment of the present invention as viewed from the front side, and FIG. 5 is a cross-sectional view of the inkjet head unit according to the first embodiment of the present invention as viewed from the side. .

  4 and 5, reference numeral 1 denotes an inkjet head substrate on which a number of nozzles, pressure chambers, and piezoelectric actuators described above are formed, and 2 denotes a head that is bonded to the inkjet head substrate 1 to support the inkjet head substrate 1. The base 3 is connected to the inkjet head substrate 1 and is a flexible printed circuit board for driving the piezoelectric actuator, 4 is a drive IC connected to the flexible printed circuit board 3, 5 is an ink chamber to which ink for printing is supplied, 6 Is an ink tube for supplying ink for printing to the ink chamber 5. 7 is a sealing cap, and 8 is an adhesive resin for bonding the head base 2 and the sealing cap 7 together. Reference numeral 9 denotes a hydrophilic liquid for adsorbing moisture in the sealed space.

  In FIG. 4, the head base 2 is disposed on the inkjet head substrate 1. In FIG. 5, the head base 2 is disposed on the side surface of the inkjet head substrate 1.

  The inkjet head substrate 1 and the flexible printed circuit board 3 are electrically connected by, for example, an anisotropic conductive film. Ink for printing is supplied by the ink chamber 5 and the ink tube 6. Then, the flexible printed circuit board 3 connected to the inkjet head substrate 1 transmits the signal of the drive IC 4 to the inkjet head substrate 1, and the piezoelectric actuator vibrates and prints according to the signal.

  In order to protect the piezoelectric actuator arranged on the inkjet head substrate 1 from moisture, the head base 2 and the sealing cap 7 are sealed and sealed by bonding with an adhesive resin 8, and the sealed space is hydrophilic. The liquid 9 is filled. The periphery of the piezoelectric vibrator is covered with a hydrophilic liquid 9.

  The adhesive resin 8 used here is not particularly limited, and may be either a type that is cured / adhered by ultraviolet rays (UV) or a type that is cured / adhered by heating or standing at room temperature. The lower the wetness, the better.

  For the head base 2 and the sealing cap 7, it is preferable to use a material exhibiting low moisture permeability. The head base 2 is generally made of a polymer resin having excellent wettability and processability, for example, a modified polyethylene oxide resin, but a polymer resin having a lower moisture wettability such as a cycloolefin polymer. May be used.

Furthermore, nickel (Ni) film, titanium (Ti) film, etc. excellent in liquid contact property with ink, alloy films thereof, silicon oxide film (SiO ₂ film), silicon nitride (SiN) film, alumina (Al A head base having improved moisture permeability can be used by coating an oxide such as a ₂ O ₃ ) film on the surface of a polymer resin with a thickness of several μm to several tens of μm by sputtering or plating. Absent. Further, since there is little possibility that the sealing cap 7 is in direct contact with the ink, it is not necessary to consider liquid contact properties, and it is preferable to use a material that completely blocks moisture such as metal and glass.

  As a method of filling the hydrophilic liquid 9, after filling the hydrophilic liquid 9, the sealing cap 7 is fixed and sealed with the adhesive resin 8. For example, a part of the sealing cap 7 is hydrophilic. A hole for filling the liquid 9 is made, the sealing cap 7 is fixed with the adhesive resin 8, the hydrophilic liquid 9 is filled into the sealed interior using this hole, and finally the hole is bonded. It may be occluded with an agent.

  FIG. 4 shows a case where gas remains in the sealed space, but it has been confirmed that the same effect can be obtained even when the entire sealed space is filled with a hydrophilic liquid.

  In the inkjet head unit according to the present embodiment configured as described above, the moisture concentration entering the sealed space can be diluted with a hydrophilic liquid. It becomes possible to prevent dielectric breakdown.

  Even if the periphery of the piezoelectric vibrator is sealed so as to be a sealed space, it is impossible to completely suppress the ingress of moisture from the outside air, and there is a certain amount of moisture in the sealed space over time. . The piezoelectric vibrator used in the ink jet head causes dielectric breakdown even with a very small amount of moisture. Therefore, in the ink jet head unit according to the present embodiment, by filling the inside of this sealed space with the hydrophilic liquid 9, the concentration of the moisture that has entered is reduced to such an extent that dielectric breakdown of the piezoelectric vibrator does not occur. Can do.

  In addition, the moisture that enters the sealed space is not liquid but enters water vapor, that is, in the form of gas, but the water vapor is likely to enter from a fine gap and has a higher entry speed than the liquid moisture. For this reason, the damage to the piezoelectric vibrator is also great. However, by filling the inside of the sealed space with the hydrophilic liquid 9, it is possible to change the water vapor that has entered into a liquid state, thereby reducing damage to the piezoelectric vibrator.

  Furthermore, in the case of conventional hydrophobic liquids such as silicon oil and fluorine-based inert liquid, the infiltrated water is separated from the hydrophobic liquid, and the moisture concentration is present at the interface between the piezoelectric vibrator and the hydrophobic liquid. However, this problem can also be improved.

  Therefore, according to the ink jet head unit according to the present embodiment, the sealing configuration according to the present embodiment in which the periphery of the piezoelectric vibrator is covered with a hydrophilic liquid, the influence of moisture on the piezoelectric vibrator compared to the conventional case. Therefore, it is possible to realize a highly reliable inkjet head unit that does not cause dielectric breakdown of the piezoelectric vibrator. By installing this inkjet head, stable print quality can be maintained for a long time. It is possible to realize an ink jet recording apparatus capable of performing the above.

Example 1
In Example 1, an inkjet head unit having the above-described sealing configuration according to the present invention is manufactured, and the reliability of the inkjet head unit having a conventional configuration (comparative example) and the head unit according to the present invention (example) is improved. Compared. A characteristic diagram showing the relationship between the voltage application time and the leakage current is shown in FIG. Reliability was evaluated in an environment where the temperature and humidity were 40 ° C. and 60%, and the current flowing while applying a voltage of 30 V was measured.

  In the ink jet head unit (example) according to the present invention, a modified polyethylene oxide resin seal is used for the head base 2, and an aluminum (Al) metal is used for the sealing cap 7, and an adhesive resin 8 for fixing them. For this, a thermosetting fluorine resin was used. In addition, glycerin was used for the hydrophilic liquid 9 filled in the sealed space. As a method for filling glycerin, the sealing cap 7 with a hole was fixed to the head base 2, and then the glycerin was filled into the sealed space through this hole, and finally the hole was closed with ultraviolet (UV) resin.

  As a conventional inkjet head unit (comparative example) produced for comparison, a comparative example 1 in which nothing is filled in the sealed space and a structure in which silicon oil having a dimethylpolysiloxane structure is filled in the sealed space Comparative Example 2 was prepared. The other components and manufacturing methods in these comparative examples were the same as those of the inkjet head unit (example) according to the present invention described above.

  In FIG. 6, when comparing the reliability evaluation results between the example and the comparative example 1 and the comparative example 2, the inkjet head unit (example) of the configuration of the present invention has an increase in leakage current over a long period of time. It turns out that it is not observed. On the other hand, the reliability of the inkjet head unit of Comparative Example 2 filled with silicone oil is improved as compared with the inkjet head unit of Comparative Example 1 that is not filled with anything, but the reliability is considerably inferior to the Example. It has become a thing. In other words, the ink jet head unit (example) manufactured by the configuration of the present invention eliminates the influence of moisture on the piezoelectric vibrator and maintains good print quality for a long time even in a high temperature and high humidity environment. It can be said that this is possible.

  In the present embodiment, only glycerin, which is an alcoholic liquid, is described as the hydrophilic liquid 9 filled in the sealed space, but other alcoholic liquids such as ethanol, methanol, isopropyl alcohol, and the like are also equivalent to glycerin. Performance was obtained. In the present invention, the hydrophilic liquid 9 filled in the sealed space may use a solvent such as acetone or dichlorobenzene as a hydrophilic liquid other than alcohol. In the present invention, the liquid required to fill the inside of the sealed space may be a hydrophilic liquid, and the polar solvent having a polar group can exert the effects of the present invention as described above. .

  In the above, the reliability during continuous energization in an environment where the temperature and humidity are 40 ° C. and 60% was evaluated, but also in a storage test for evaluating leakage current after storing for a long time in a worse environment. It has been confirmed that the inkjet head unit of the present invention can obtain high reliability as compared with the conventional configuration.

  Specifically, when stored in an environment where the temperature and humidity are 60 ° C. and 90%, in a conventional inkjet head unit (Comparative Example 1) in which nothing is filled, silicon oil is filled after about 10 hours. In the conventional inkjet head unit (Comparative Example 2), current leakage occurred after about 200 hours. On the other hand, in the ink jet head unit (Example) produced by the configuration of the present invention and filled with glycerin, no increase in leakage current was observed even after evaluation after storage for 500 hours.

(Example 2)
In Example 2, an example in which a desiccant powder is added to a hydrophilic liquid will be described. In Example 2, an ink jet head unit was prepared by adding molecular sieve 3A powder to glycerin, which is a hydrophilic liquid 9, and filling a sealed space containing a piezoelectric vibrator. The other components and the manufacturing method were the same as those of the inkjet head unit (Example) according to the present invention described in (Example 1). The reliability of the ink jet head unit configured as described above was evaluated. The ink jet head unit according to the second example has the same or higher reliability than the ink jet head unit according to the first example, and there is no problem even if a powder desiccant is added to the hydrophilic liquid 9. It was confirmed that the effects of the invention can be obtained.

  The type of desiccant added to the hydrophilic liquid is not particularly limited, but it is preferable that the state does not change due to the adsorption of moisture. In that sense, a desiccant that physically adsorbs moisture is preferable to a desiccant that adsorbs moisture by a chemical action that causes deliquescence and volume expansion due to moisture adsorption. Molecular sieve is a typical desiccant that absorbs moisture by physical action, and naturally gas drying is also suitable for liquid drying.

  The size of the desiccant added to the hydrophilic liquid is preferably fine. The reason is that the piezoelectric vibrator and the desiccant may be in direct contact with each other because they are directly added to the hydrophilic liquid filled in the sealed space. When the size of the desiccant added to the hydrophilic liquid is increased, the displacement of the piezoelectric vibrator is hindered, which adversely affects ink ejection. Although the size of the piezoelectric vibrator varies depending on the piezoelectric performance and recording density, it is about several tens of μm to several hundreds of μm. is doing.

(Embodiment 2)
FIG. 7 is a cross-sectional view of the ink jet head unit according to the second embodiment of the present invention as seen from the side surface side. In the present embodiment, unlike the case of the first embodiment, the flexible printed circuit board 3 is electrically connected to the ink jet head substrate 1 outside the sealed head of the ink jet head substrate 1 on which the piezoelectric actuator is formed. Has been. This electrical connection is performed by, for example, thermocompression bonding using an anisotropic conductive film.

  The inkjet head unit according to the present embodiment has the same configuration as that of the first embodiment described above except that the flexible printed circuit board 3 and the sealed space are completely separated. A hydrophilic liquid 9 covers the piezoelectric vibrator.

  Also in the ink jet head unit according to the present embodiment configured as described above, the same effect as that of the ink jet head unit according to the first embodiment described above can be obtained, and the ink jet head unit subjected to the main sealing is highly reliable. Have sex. That is, in the ink jet head unit according to the present embodiment, since the influence of moisture on the piezoelectric vibrator can be reduced as compared with the conventional case, the piezoelectric vibrator has high reliability without causing dielectric breakdown. An ink jet head unit can be realized. By mounting this ink jet head, it is possible to realize an ink jet recording apparatus capable of maintaining a stable print quality for a long time.

  Further, since the ink-jet head unit according to the present embodiment has less intrusion of moisture from the flexible printed circuit board 3 and the interface including the ink-jet head unit as compared with the configuration shown in the first embodiment, the hydrophilic liquid 9 The water concentration contained in is kept low. Therefore, the inkjet head unit according to the present embodiment has an effect that long-term reliability is further improved as compared with the sealing configuration shown in the first embodiment.

(Embodiment 3)
The ink jet head unit described in the third embodiment is different from the ink jet head unit according to the first embodiment only in forming a protective film on the surface of the piezoelectric vibrator. This configuration will be described with reference to FIG. FIG. 8 is a cross-sectional view of the main part of the inkjet head substrate in a direction orthogonal to the ink supply direction shown in FIG. In FIG. 8, the pressure chamber member A and the piezoelectric actuator portion B having the four pressure chambers 102 arranged in the orthogonal direction are drawn for reference.

  In FIG. 8, reference numeral 103 denotes a first electrode layer positioned almost directly above each pressure chamber 102 as described above. Reference numeral 110 denotes a piezoelectric layer provided on one surface (lower side in FIG. 8) of the first electrode layer 103. Reference numeral 112 denotes a second electrode layer (common electrode) which is provided on one surface (lower side in FIG. 8) of the piezoelectric layer 110 and is common to all the piezoelectric layers 110.

  Reference numeral 111 denotes a vibration layer that is provided on one surface (lower side in FIG. 8) of the second electrode layer 112 and that is displaced in the layer thickness direction and vibrates due to the piezoelectric effect of the piezoelectric layer 110. Reference numeral 113 denotes an intermediate layer (vertical wall) provided on one surface (lower side in FIG. 8) of the vibration layer 111 and positioned above the partition wall 102a that partitions the pressure chambers 102 from each other.

  And the 1st electrode layer 103, the piezoelectric material layer 110, and the 2nd electrode layer 112 comprise the piezoelectric element by which these are laminated | stacked in order. In addition, the vibration layer 111 is provided on the surface on the second electrode layer 112 side. And the protective film 10 is formed so that the whole of these component elements may be covered.

  In FIG. 8, reference numeral 114 denotes an adhesive that bonds the pressure chamber member A and the piezoelectric actuator portion B, and each of the intermediate layers 113 is part of the adhesive 114 when bonded using the adhesive 114. Even if it protrudes outward from the partition wall 102a, the adhesive layer 114 does not adhere to the vibration layer 111, and the vibration layer 111 causes the desired displacement and vibration. It has the role of expanding the distance from the lower surface of the.

  As described above, the pressure chamber member A is preferably bonded to the side surface of the vibration layer 111 of the piezoelectric actuator portion B opposite to the second electrode layer 112 via the intermediate layer 113, but the second electrode layer of the vibration layer 111 The pressure chamber member A may be directly joined to the side surface opposite to 112.

  Using such an ink jet head substrate, an ink jet head unit having the sealing configuration described in FIG. 1 was produced.

The material of the protective film 10 is preferably a soft material having a low Young's modulus so as not to hinder the movement of the piezoelectric vibrator. However, depending on the characteristics of the piezoelectric vibrator and the film thickness of the protective film 10, oxides, nitrides, etc. A material having a high Young's modulus can also be used. In this case, the film thickness is about 1 μm at most. For example, magnesium oxide (MgO), germanium monoxide (GeO), alumina (Al ₂ O ₃ ), nickel oxide (NiO), calcium oxide (CaO), monoxide Examples thereof include silicon (SiO), silicon dioxide (SiO ₂ ), aluminum nitride (AlN), boron nitride (BN), and silicon nitride (Si ₃ N ₄ ).

  These protective films 10 can be produced by sputtering, electron beam vapor deposition, resistance heating vapor deposition, ion plating, or the like.

  As the soft material, an elastomer material such as rubber is suitable, and examples thereof include silicone resin, fluororesin, and butyl rubber, which can be cured by heat or UV irradiation. In these elastomer materials, depending on the Young's modulus of the material, even if it is formed about several hundred μm, the movement of the piezoelectric vibrator may not be affected. In addition, there is no problem with the two-layer structure in which a material having a high Young's modulus such as an oxide or nitride is formed after forming an elastomer material on the piezoelectric vibrator, and there is a similar effect.

  Also in the ink jet head unit according to the present embodiment configured as described above, the same effect as that of the ink jet head unit according to the first embodiment described above can be obtained, and the ink jet head unit subjected to the main sealing is highly reliable. Have sex. That is, in the ink jet head unit according to the present embodiment, since the influence of moisture on the piezoelectric vibrator can be reduced as compared with the conventional case, the piezoelectric vibrator has high reliability without causing dielectric breakdown. An ink jet head unit can be realized. By mounting this ink jet head, it is possible to realize an ink jet recording apparatus capable of maintaining a stable print quality for a long time.

  In the present embodiment, since the protective film 10 covers the surface of the piezoelectric vibrator, the synergistic effect of the hydrophilic liquid 9 and the protective film 10 affects the influence of moisture on the piezoelectric vibrator. Can be reduced more effectively. Therefore, in the ink jet head having the configuration according to the present embodiment, current leakage due to dielectric breakdown of the piezoelectric vibrator does not occur, so that good print quality can be maintained for a long time.

  Further, as described above, a powdery desiccant may be dispersed in the hydrophilic liquid 9. Even in this case, the effect according to the present embodiment described above can be obtained. In this case, as the powdery desiccant, those described in Example 2 can be used. In addition, as the hydrophilic liquid 9 in this case, the liquid described in Example 1 can be used.

  Even if the surface of the piezoelectric vibrator is subjected to water repellent treatment instead of the protective film 10, the influence of moisture on the piezoelectric vibrator is more effectively reduced by the synergistic effect of the hydrophilic liquid 9 and the water repellent treatment. can do. Therefore, current leakage due to dielectric breakdown of the piezoelectric vibrator does not occur, and good print quality can be maintained for a long time.

  In this case, for example, a solution containing water and hydrochloric acid is added to a raw material solvent in which an alkoxysilane compound that forms the main skeleton of the water-repellent film and a fluoroalkylalkoxysilane that imparts a high water-repellent function are mixed in an optimal ratio. Then, stirring and polymerization were performed to prepare a sol coating solution. A water-repellent thin film can be formed by applying this coating solution so as to cover the head component by spin coating and then baking at about 200 ° C.

  Further, the surface of the piezoelectric vibrator may be subjected to water repellent treatment using a fluorine-based material. Since the fluorine-based water-repellent treatment material has high performance and can maintain the water-repellent effect for a long period of time, it is possible to prevent dielectric breakdown of the piezoelectric vibrator by applying a voltage for a long period of time.

  At this time, a powdery desiccant may be dispersed in the hydrophilic liquid 9 as described above. Even in this case, the effect according to the present embodiment described above can be obtained. In this case, as the powdery desiccant, those described in Example 2 can be used. In addition, as the hydrophilic liquid 9 in this case, the liquid described in Example 1 can be used.

(Embodiment 4)
FIG. 9 is a cross-sectional view of the ink jet head unit according to the fourth embodiment of the present invention as seen from the side surface side. Unlike the case of Embodiment 1 and Embodiment 2, this embodiment has a double-sealed structure. The piezoelectric vibrator is sealed with an internal sealing cap 11, and a sealing structure is provided on the outside thereof. Then, the hydrophilic liquid is not filled in the interface including the piezoelectric vibrator, but the hydrophilic space is filled in the sealed space between the inner sealing cap 11 and the sealing structure on the outer side. Yes. A desiccant 12 is sealed in the space where the piezoelectric vibrator is sealed.

  The hydrophilic liquid 9 to be filled, the desiccant 12, the adhesive for sealing, and the members of the internal sealing cap 11 can be the same as those described in the first embodiment.

  According to the configuration of the ink jet head unit according to the present embodiment, moisture entering from the outside is first diluted with the hydrophilic liquid 9 and is difficult to reach the space including the piezoelectric vibrator by being in a liquid state. Become. Even if the space including the piezoelectric vibrator is reached, the moisture is removed by the desiccant 12, so that the dielectric breakdown of the piezoelectric vibrator does not occur, and no leakage current occurs.

  Since the inner sealing cap 11 is surrounded by a hydrophilic liquid, it is difficult for moisture to enter in a gaseous state. Therefore, the constituent material of the inner sealing cap 11 is low in moisture permeability such as metal. It is not limited to.

  Also in the ink jet head unit according to the present embodiment configured as described above, the same effect as that of the ink jet head unit according to the first embodiment described above can be obtained, and the ink jet head unit subjected to the main sealing is highly reliable. Have sex. That is, in the ink jet head unit according to the present embodiment, since the influence of moisture on the piezoelectric vibrator can be reduced as compared with the conventional case, the piezoelectric vibrator has high reliability without causing dielectric breakdown. An ink jet head unit can be realized. By mounting this ink jet head, it is possible to realize an ink jet recording apparatus capable of maintaining a stable print quality for a long time.

  In the present embodiment, since the double sealing structure is used as described above, moisture entering from the outside does not directly enter the sealed space including the piezoelectric vibrator as vapor in the gaseous state. In addition, since the liquid enters the liquid state after being converted from gas to liquid and dissolved into a hydrophilic liquid, the amount of moisture entering the sealed space including the piezoelectric vibrator can be suppressed, and piezoelectricity is generated by applying a voltage. The dielectric breakdown of the vibrator can be effectively prevented for a long time.

  As described above, the ink jet head unit according to the present invention is useful in the field of an ink jet recording apparatus that forms an image by ejecting ink using the displacement of a piezoelectric vibrator.

1 is a perspective view showing an overall configuration of an inkjet head substrate according to a first embodiment of the present invention. The perspective view which shows the principal part of the piezoelectric actuator part and pressure chamber member concerning Embodiment 1 of this invention. Cross-sectional view of main parts of inkjet head substrate Sectional drawing which looked at the inkjet head unit concerning Embodiment 1 of this invention from the front side Sectional drawing which looked at the inkjet head unit concerning Embodiment 1 of this invention from the side surface side FIG. 3 is a characteristic diagram showing reliability of the inkjet head unit according to the first embodiment of the present invention and the conventional inkjet head unit. Sectional drawing which looked at the inkjet head unit concerning Embodiment 2 of this invention from the side surface side Sectional drawing of the principal part which looked at the inkjet head board | substrate concerning Embodiment 3 of this invention from the direction orthogonal to an ink supply direction. Sectional drawing which looked at the inkjet head unit concerning Embodiment 4 of this invention from the side surface side

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head board 2 Head base 3 Flexible printed circuit board 4 Drive IC
DESCRIPTION OF SYMBOLS 5 Ink chamber 6 Ink tube 7 Sealing cap 8 Adhesive resin 9 Hydrophilic liquid 10 Protective film 11 Internal sealing cap 12 Desiccant 101 Pressure chamber opening 102 Pressure chamber 102a Partition wall 103 First electrode layer 104 Common liquid chamber 105 Supply Port 106 Ink Flow Channel 107 Nozzle Hole 110 Piezoelectric Layer 111 Vibration Layer 112 Second Electrode Layer 113 Intermediate Layer 114 Adhesive A Pressure Chamber Member B Piezoelectric Actuator Section C Ink Flow Channel Member D Nozzle Plate E IC Chip

Claims (12)

A head main body having a pressure chamber that discharges the supplied ink from the opening by pressure change; a piezoelectric vibrator that is provided on one side of the pressure chamber in the head main body and applies pressure to the pressure chamber; An inkjet head substrate comprising:
A sealing member that forms a sealed space by sealing the space including the piezoelectric vibrator together with the inkjet head substrate;
A hydrophilic liquid disposed in contact with the piezoelectric vibrator in the sealed space; and
An inkjet head unit comprising: The inkjet head unit according to claim 1, wherein a protective film is formed on a surface of the piezoelectric vibrator. 2. The ink jet head unit according to claim 1, wherein a surface of the piezoelectric vibrator is subjected to water repellent treatment. 4. The ink jet head unit according to claim 3, wherein the water repellent treatment is performed with a fluorine-based material. The inkjet head unit according to claim 1, wherein the hydrophilic liquid is an alcohol liquid. The inkjet head unit according to claim 3 or 4, wherein the hydrophilic liquid includes at least one of water and alcohol-based liquids. The inkjet head unit according to claim 1, wherein a powdery desiccant is dispersed in the hydrophilic liquid. 8. The ink jet head unit according to claim 7, wherein the powdery desiccant is a molecular sieve. A head main body having a pressure chamber that discharges the supplied ink from the opening by pressure change; a piezoelectric vibrator that is provided on one side of the pressure chamber in the head main body and applies pressure to the pressure chamber; An inkjet head substrate comprising:
A first sealing member that seals a space including the piezoelectric vibrator together with the inkjet head substrate to form a first sealed space;
A second sealing member that seals a space including the piezoelectric vibrator to form a second sealed space inside the first sealed space;
A hydrophilic liquid disposed in a space between the first sealed space and the second sealed space;
An inkjet head unit comprising: The inkjet head unit according to claim 9, wherein the hydrophilic liquid includes at least one of water and an alcohol-based liquid. The inkjet head unit according to claim 9 or 10, wherein a desiccant is provided in the second sealed space. An ink jet recording apparatus comprising the ink jet head unit according to claim 1.

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