JP2005131973A - Inkjet recording head and inkjet printer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording head having a high heat-radiating characteristic achieved by optimizing the heat-transferring direction, thereby increasing the printing speed in the inkjet recording head using thermal energy. <P>SOLUTION: In this inkjet recording head having a pressurizing mechanism using the thermal energy, a metal plated layer with a film thickness of 50-150 μm is formed on a surface of at least an ink supply hole and a protection layer with a film thickness of 0.5-5 μm is formed thereon. The head has a support member made of a ceramic in which the heat conductivity of the protection layer is higher than that of the metal plated layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inkjet recording head and an inkjet printer that are mounted on a high-precision inkjet recording apparatus used for recording characters and images.

  Conventionally, an ink jet recording apparatus has been used as a means for printing color characters and images on recording paper. However, in recent years, printing density has been increased and printing speed has been increased along with higher accuracy of image output. Is now required.

  By the way, an ink jet recording head mounted on an ink jet type ink jet printer uses a thermal energy generated by a heating resistor as a pressurizing mechanism for ejecting and flying ink droplets toward a recording paper, or irradiation of electromagnetic waves. Some of them use the heat generated along with this.

  For example, FIG. 5 shows a cross-sectional view of an ink jet recording head. As shown in the figure, the ink jet recording head 21 using the heat energy of the heat generating resistor as a pressurizing mechanism has a plurality of ink chambers 24, and the heat generating resistors 25 for pressurizing ink in each ink chamber 24. A head body 22 including a flow path member 23 provided thereon and a nozzle plate 29 provided thereon with an ink discharge hole 28 communicating with each ink chamber 24; and supporting the head main body 22; The support member 30 is made of ceramic and has an ink supply hole 31 communicating with the ink chamber 24 of the member 23. The ink supply hole 31 includes an inclined bottom surface 33 that opens toward the head main body and deepens toward the center. In addition, there is a structure composed of a long hole 32 and a small-diameter hole 34 communicating therewith. Although not shown, the ink supply hole 31 is supplied with ink from an ink tank that accumulates ink.

  In order to print on the recording paper using the ink jet recording head 21, with the ink supplied from the ink supply hole 31 to the ink chamber 24, the heating resistor 25 is heated to generate bubbles A in the ink chamber 24. By generating the ink, the ink in the ink chamber 24 is pressurized, and ink droplets B are ejected from the ink ejection holes 28 to print on the recording paper (see Patent Document 1).

  By the way, the recent development trend of ink jet printers is to increase the printing speed at the same time as the high image quality of printing. Accordingly, the density of ink discharge holes is increased and the printing cycle is shortened. In particular, in the ink jet recording head 21 using the heat energy of the heating resistor as shown in FIG. 5, the heating resistors 25 are also arranged at a high density corresponding to the increase in the density of the ink discharge holes 28, so the printing cycle is short. When time has elapsed, the heat energy from the heating resistor 25 increases, and the temperature in the ink chamber 24 rises. As a result, there is a problem in that the ink foaming action changes, resulting in variations in printing. Therefore, there has been a problem of shortening the printing cycle by improving the heat dissipation near the ink chamber 24.

  However, as a material of the support member 30 as shown in FIG. 5, an alumina sintered body having a relative density of 90% to 94% has been used in consideration of cost, although the heat dissipation is generally low.

On the other hand, Patent Document 2 discloses a technique in which an alumina sintered body is used as the support member 30 and the above-described heat problem is taken into consideration. That is, an intermediate layer made of a material having high thermal conductivity such as C, Mg, Al, Cu, Ag, Au, and W (not shown) on the surface of the support member 30 using any one of silicon, glass, and ceramic. And a lower layer made of a material having low thermal conductivity made of an inorganic material made of silicon oxide, zirconium oxide, tantalum oxide, magnesium oxide, or the like on the intermediate layer, and the thermal conductivity of the intermediate layer being the thermal conductivity of the lower layer. By using a material that is twice or more of the rate, the heat dissipation and heat storage properties are well-balanced, and the ink temperature change effect due to heat generated by the heating resistor 25 is achieved.
JP 2001-130004 A Japanese Patent Laid-Open No. 03-205155

  The ink jet recording head of Patent Document 2 has a structure in which an intermediate layer and a lower layer are laminated on the surface of the support member 30 and a nearby ink liquid dissipates heat to the ink through the lower layer having a low thermal conductivity. The ink supply hole 31 is thermally divided, the ink liquid in the vicinity of the ink chamber 24 accumulates heat, and the effect of dissipating heat to the support member 30 is reduced, so that the printing cycle is not accelerated.

  For this reason, since the heat dissipation effect to the support member 30 through the ink liquid is insufficient, the temperature of the ink in the ink chamber 24 rises, the viscosity of the ink changes, the ink flow is inhibited, and continuous operation is performed at high speed for a long time. It was not possible, and it was necessary to stop printing halfway for cooling, which hindered speeding up.

  On the other hand, it is generally known that when the ink temperature rises, the ink viscosity changes, and thus appears as uneven density in the image, so that the ink temperature does not rise above 60 ° C. where the ink viscosity change starts. The print cycle time is controlled.

  That is, in the case of the ink jet recording head 21 using the heat energy of the heating resistor as in Patent Document 1 and Patent Document 2, if the temperature of the heating resistor 25 is instantaneously raised to several hundred degrees, the ink component There has been a problem of kogation in which pyrolyzate or the like is deposited on the surface of the heating resistor 25.

  Further, since the surface of the ink supply hole 31 is exposed to the ink, glass components (Si, Mg, Ca components) in the alumina sintered body that is the material of the support member 30 are largely eluted into the ink. Glass deposits are likely to be generated on the surface of the heating resistor 25, and this deposit hinders heat conduction from the heating resistor 25 to the ink. In some cases, defects occurred in printing. Therefore, in order to improve the durability of the ink jet recording head 21, there has been a problem of reducing the deposits on the surface of the heating resistor 25.

  Furthermore, as the image quality is improved, the one provided with the ink discharge hole 28 having a small hole diameter is used. However, the pores and the recesses that open in the ink supply hole 31 of the support member 30 are used. Processing scraps and debris have entered, and these processing scraps and debris cannot be removed sufficiently even after washing. If they are used as they are, they are exposed to ink when ink is supplied to the ink supply holes 31. Further, there is a possibility that processing holes, dust, and the like that have entered the pores and the recesses that are opened on the surface are discharged into the ink and the ink discharge holes 28 having a small hole diameter are clogged.

  In view of the above problems, the present invention provides a flow path member having a plurality of ink chambers and having a pressurizing mechanism that pressurizes ink in each of the ink chambers using thermal energy, and a surface of the flow path member. A head body composed of a nozzle plate having an ink discharge hole arranged and communicated with each of the ink chambers, and a ceramic made with an ink supply hole that supports the head body and communicates with the ink chambers of the flow path member. In the ink jet recording head comprising the support member, at least the surface of the ink supply hole exposed to the ink has a metal plating layer having a film thickness of 50 to 150 μm and a film thickness of 0 that has a higher thermal conductivity than the metal plating layer. A protective layer of 5 to 5 μm is laminated.

  Moreover, it is preferable that the ceramic which forms a supporting member is a ceramic which has any one of alumina, aluminum nitride, or silicon carbide as a main component.

  And when using the ceramic which has an alumina as a main component, it is preferable that the relative density is 95% or more.

  Further, the metal plating layer is preferably formed using either Ni or Mo. The protective layer is preferably a ceramic film of any one of a DLC film, a SiC film, and an AlN film.

  Thus, according to the ink jet recording head of the present invention, at least the surface of the ink supply hole exposed to the ink has a metal plating layer having a high thermal conductivity of 50 to 150 μm and a thickness of 0.5 to 5 μm. Since the protective layer is laminated and the thermal conductivity of the protective layer is larger than that of the metal plating layer, the heat stored in the ink in the ink supply hole is efficiently released to the support member through the protective layer and the metal plating layer. be able to. As a result, it is possible to prevent the heat generated in the heating resistor from accumulating in the ink chamber and the ink supply hole to increase the ink temperature, to extend the continuous printing time, and to shorten the printing cycle.

  Furthermore, by preventing the ink temperature from rising, it is possible to suppress changes in ink viscosity and maintain the freshness of the print image quality.

  In addition, by forming the support member using ceramics with a low coefficient of linear expansion and high rigidity, which is any one of alumina, aluminum nitride, and silicon carbide, the deformation of the ink jet recording head is small and accurate even when heat is applied. Can be produced well. These ceramics have high thermal conductivity, and can quickly dissipate the heat of the ink transmitted through the protective layer and the metal plating layer into the atmosphere.

  Furthermore, by using any one of Ni and Mo whose thermal conductivity is higher than the thermal conductivity of the material used for the support member for the metal plating layer, the heat stored in the metal plating layer can be efficiently released to the support member. it can. Similarly, by using a ceramic film of a DLC film, SiC film, or AlN film having a thermal conductivity higher than that of the material used for the metal plating layer for the protective layer, the heat stored in the protective layer is stored. Efficient escape to the metal plating layer.

  Furthermore, the protective layer is formed of a ceramic film that is one of a DLC film, a SiC film, and an AlN film, thereby suppressing the degranulation (particles) of the ceramic particles forming the support member, even when the ink is strongly alkaline. The metal component does not elute into the ink, and it is possible to prevent deterioration in print quality due to clogging of the ink ejection holes due to the eluted particles.

  By using the ink jet recording head of the present invention for an ink jet printer, it is possible to provide a high speed printer that does not pause printing for cooling.

  1A and 1B are diagrams showing an example of an ink jet recording head of the present invention. FIG. 1A is a perspective view thereof, and FIG. 1B is a perspective view with a part broken away. 2A to 2C are exploded perspective views showing an example of the ink jet recording head of the present invention. 3 is a cross-sectional view taken along the line XX of FIG. 1A, FIG. 3B is a cross-sectional view taken along the line YY of FIG. 1A, and FIG. It is the figure which showed the structure of the protective layer.

  The ink jet recording head 1 includes a head body 2 and a support member 10.

  The head main body 2 has a plurality of ink chambers 4, and is provided on the flow path member 3 including the heat generating resistors 5 for pressurizing the ink in the ink chambers 4. And a nozzle plate 9 having ink discharge holes 8 communicating with the chamber 4. The support member 10 is formed with an ink supply hole 11 that supports the head body 2 and communicates with the ink chamber 4 formed in the flow path member 3 of the head body 2.

  The flow path member 3 that forms the head body 2 is formed by, for example, arranging a plurality of stepped grooves 6 in parallel on a silicon substrate, and a plurality of heating resistors 5 at predetermined intervals in the stepped portion 7 of the stepped groove 6. The nozzle plate 9 is arranged on the flow path member 3 so that the ink discharge holes 8 are positioned in parallel to each other and facing the heat generating resistors 5. The diameter of the ink discharge hole 8 may be about 30 μm if the number of pixels to be printed is 300 dpi, but the ink discharge hole 8 is preferably 11 to 25 μm for use in high-quality printing.

  The support member 10 is a rectangular parallelepiped with a plane, and a plurality of ink supply holes 11 formed in the width direction are formed in the longitudinal direction, and each ink of the head main body 2 is formed from the ink supply holes 11. It is configured to communicate with the chamber 4. Each ink supply hole 11 has an elongated hole 12 having an inclined bottom surface 13 that opens toward the head body 2 and deepens toward the center, and a small diameter that opens to the opposite side of the head body 2 and communicates with the elongated hole 12. It consists of a hole 14.

  The small diameter hole 14 is configured to be able to supply ink from an ink tank (not shown), and the surface of the ink supply hole 11 is exposed to the supplied ink.

  In order to print on the recording paper using the ink jet recording head 1, bubbles are generated in the ink chamber 4 by causing the heating resistor 5 to generate heat while ink is supplied from the ink supply hole 11 to the ink chamber 4. As a result, the ink in the ink chamber 4 is pressurized and ink droplets are ejected from the ink ejection holes 8.

  Here, the inkjet recording head 1 of the present invention has a metal plating layer 15 having a film thickness of 50 to 150 μm on the surface of at least the ink supply hole 11 of the support member 10 that is exposed to the ink, and more heat than the metal plating layer 15. It is important that a protective layer 16 having a high conductivity and a film thickness of 0.5 to 5 μm is laminated.

Here, as shown in Table 1, examples of the material of the metal plating layer 15 include Cu, Al, Ag, Au, Ni, Mg, and Mo. In particular, Ni and Mo have a linear expansion coefficient of 12 × 10 ⁻⁶ (/ ° C.) or less and are relatively close to ceramics, so that they have good adhesion to ceramics and are preferable from the viewpoint of economy.

Examples of the ceramic film of the protective layer 16 include a DLC film (diamond-like carbon), a SiC film, and an AlN film as shown in Table 2. In particular, the DLC film is most preferable because it has high thermal conductivity and low internal stress.

  Here, the film thickness of the metal plating layer 15 is set to 50 μm or more in the case of the inkjet recording head 1 in which the nozzle density of the ink discharge holes to be printed is 300 dpi or more, the heat dissipation effect is low and the ink temperature is less than 50 μm. The situation is that the situation continues to rise and printing must be paused. In particular, in order to be able to print without stopping the printing run of the inkjet recording head 1 for one A4 size sheet, it is desirable that the film thickness be formed to be greater than 100 μm. In addition, the thickness of the metal plating layer 15 is set to 150 μm or less. When the thickness is greater than 150 μm, the generation of bubbles in the ink chamber becomes unstable, and the metal plating layer 15 is in close contact with the support member 10 due to internal strain. This is because the property decreases.

  The reason why the protective layer 16 is formed on the metal plating layer 15 is that the metal plating layer 15 has insufficient corrosion resistance against strongly alkaline ink and cannot be in liquid contact with the ink.

  If the thickness of the protective layer 16 is smaller than 0.5 μm, the function of protecting the metal plating layer cannot be achieved. If the thickness is larger than 5 μm, film peeling is likely to occur due to a difference in thermal expansion coefficient from the metal plating layer. Because it becomes.

  Then, since the thermal conductivity of the protective layer 16 that is in direct contact with the ink liquid is higher than the thermal conductivity of the metal plating layer 15, heat is quickly radiated to the ceramics of the support member 10 without insulating the heat propagation at the boundary between the layers. can do. The heat generated in the heating resistor 5 can be efficiently radiated to the support member 10 via the ink liquid in the ink supply hole, and the temperature rise of the ink in the flow path member 3 can be suppressed. .

  In the inkjet recording head 1 of the present invention, the ceramic forming the support member 10 is preferably any one of alumina, aluminum nitride, and silicon carbide.

In particular, when using ceramics whose main component is alumina, which is an inexpensive and easy-to-use material, the relative density is preferably 95% or more, optimally 98% to 99.9%. The relative density of ceramics is related to the pore state of the material. As the relative density increases, the amount of pores decreases and the thermal conductivity increases. As shown in Table 3, these ceramics are materials having a high thermal conductivity, a linear expansion coefficient of 10 (× 10 ⁻⁶ / ° C.) or less, which is similar to the flow path member 3, and a rigidity having a Young's modulus of 300 GPa or more. Therefore, the material is suitable for use in the support member 10 of the inkjet recording head 1.

  In particular, alumina can produce a complicated shape (the shape of the inclined bottom surface 13 of the ink supply hole 11) at a low cost by press-molding the shape of the ink supply hole 11, and the base treatment ( The metal plating layer 15 can be firmly adhered by a metallization method by Mo-Mn paste printing. Further, the metal plating layer 15 does not peel off the side surface and the inclined bottom surface 13 of the small-diameter hole 14 of the ink supply hole 12 having a lower adhesion strength than the flat surface of the support member 10 and can withstand long-term use. It is an optimal material for forming a film to be formed.

  Next, a method for manufacturing the support member 10 of the head body 2 of the present invention will be described.

  First, a ceramic sintered body of the support member 10 according to the present invention is manufactured. In the case of alumina, an appropriate amount of alumina raw material powder and a sintering aid such as silica and magnesia are prepared, the mixed raw material is wet pulverized, a binder as a forming aid is added and mixed to create a slurry, and a spray dryer is used. The slurry is spray-dried in the form of a mist to obtain uniform powder granules. The powder granule is shaped by powder press molding and fired at a firing temperature of 1500 to 1800 ° C. in an oxidizing atmosphere to obtain an alumina sintered body.

  In the case of aluminum nitride, an appropriate amount of aluminum nitride raw material powder and a sintering aid composed of rare earth oxides such as yttrium oxide, erbium oxide, and cerium oxide are prepared, the mixed raw material is wet-ground, and a binder that serves as a molding aid is added. A slurry is prepared by mixing, and the slurry is spray-dried in the form of a mist with a spray dryer to obtain a uniform powder downstream. The powder granule is shaped by powder press molding and fired at a firing temperature of 1600 to 2100 ° C. in an inert gas or nitriding gas atmosphere to obtain an aluminum nitride sintered body.

  In the case of silicon carbide, use silicon carbide raw material powder and raw material powder containing sintering aids such as alumina, yttria, cerium oxide, or silicon carbide raw material powder and raw material powder containing boron and carbon as sintering aids. After forming this, it is fired at 2000 to 2100 ° C. in an inert atmosphere to obtain a silicon carbide sintered body.

  Moreover, a relative density can be raised to 98% or more by carrying out a hot isostatic pressing (HIP) process to the ceramic sintered compact.

  Next, after firing, the surface of the support member 10 to be combined with the head main body 2 and the surface to be combined with the ink tank are ground to produce the support member 10 having a flatness maintained within 2.0 μm.

  Then, after removing oil stains, grinding fluid, and grinding debris by ultrasonic cleaning, screen printing is performed to form a Mo—Mn base film on the entire surface of the support member 10 including the inclined bottom surface 13 of the ink supply hole 11. Then, a Mo—Mn paste was applied at 1400 ° C. and fired at 1400 ° C. in an atmosphere of hydrogen or hydrogen and nitrogen to form a film having a high adhesion strength of about 10 μm. After forming a manganese alumina spinel compound on the entire surface and forming a base film strongly bonded to molybdenum metal, a metal plating layer 15 is formed by electroplating. Since the electroplated portion is a metal crystal film of about 99.5 wt%, the heat conductivity inherent to the metal can be maintained.

  Next, a ceramic film is formed as the protective layer 16. As the film forming method, the film is formed by a vacuum vapor deposition method or a low temperature plasma CVD method.

  For example, in order to form a film by the plasma CVD method, the support member 10 is disposed on a cathode electrode plate disposed in the chamber, and source gas and carrier gas are supplied into the chamber in accordance with the ceramic film to be formed. To do. Then, by applying a voltage between the anode (anode) electrode board and the previous cathode (cathode) electrode board, the electrons extracted from the cathode (cathode) electrode board collide with the source gas to generate plasma. The film-forming component in the plasma can be deposited on the surface of the support member 10 at a reaction temperature of 100 to 800 ° C. along the electric field. The film thickness can be adjusted by adjusting the film formation time. However, if the film thickness is too thin, the corrosion resistance with the ink does not function. Conversely, if the film thickness is too thick, the film thickness varies. Since it arises, it is preferable to coat the ceramic film of the protective layer 16 in the range of 0.5 to 5 μm.

  As mentioned above, although the best mode for carrying out the present invention has been shown, the present invention is not limited to the above-described mode, and is applied to an improved or modified version without departing from the gist of the present invention. Needless to say, you can.

(Example 1)
Here, the support member 10 provided in the ink jet recording head 1 is formed of alumina having a relative density of 98%, and the metal plating layer 15 having a film thickness of 100 μm is formed of Cu on the surface of the ink supply hole 11 to form the metal plating layer. A protective layer 16 made of a DLC film having a thickness of 1 μm was formed on 15 and the head body 2 was joined with a Teflon (R) adhesive to produce an inkjet recording head 1. Ink temperature was measured at the center of the ink chamber of the flow path member when ink was supplied to the ink jet recording head 1 and the heating resistor was energized to continuously give a 50 W thermal energy output.

  As a comparative example, the protective layer 16 is made of a SiO2 film having a thermal conductivity of 1.4 (W / m · K) instead of the DLC film (Comparative Example 1), the protective layer 16 and the metal plating layer 15. Were prepared and evaluated simultaneously (Comparative Example 2).

  FIG. 6 is a graph showing the measurement results of the ink temperature change in Example 1 and Comparative Examples 1 and 2.

  From this result, it was confirmed that the DLC film was formed on the protective layer of Example 1 to significantly suppress the temperature rise of the ink.

(Example 2)
Next, the support member 10 is formed of alumina having a relative density of 98%, and Cu, Ni, Al, and Au are used as the material of the metal plating layer on the surface of the ink supply hole 11, and the film thicknesses are 20 μm and 50 μm, respectively. Samples of 100 μm and 150 μm were prepared, a DLC film of 1 μm was formed thereon as a protective layer, and an ink jet recording head 1 was prepared in which the head body 2 was bonded with a Teflon (R) adhesive.

Then, the output of the heating resistor was set to 5 W and heat energy was continuously applied, and the ink temperature at the center of the ink chamber of the flow path member was measured. In the measurement, the diode sensor was built in the silicon substrate forming the flow path member, and the experiment was stopped when the ink liquid temperature reached 80 ° C., and the time until the stop was compared.

  When the thickness of the metal plating layer was smaller than 50 μm, the ink liquid temperature reached 80 ° C. within 6 seconds. Further, the evaluation result with the support member using alumina without the metal plating layer and the protective layer under the same conditions showed that the ink liquid temperature was 80 ° C. in 2 seconds.

  From this experimental result, it can be seen that if the thickness of the metal plating layer is less than 50 μm, the heat dissipation effect is slightly improved, but it is insufficient for increasing the speed, and continuous operation is possible if it is about 100 μm. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the inkjet recording head of this invention, (a) is the perspective view (b) is the perspective view which fractured | ruptured partially. FIG. 2 is an exploded perspective view showing an example of an ink jet recording head of the present invention. (A) is the XX sectional view taken on the line of Fig.1 (a), (b) is the YY sectional view taken on the line of Fig.1 (a). It is the figure which showed the structure of the metal plating layer and protective layer of this invention. It is sectional drawing which shows an example of the conventional inkjet recording head. It is a figure which shows the measurement result of the ink temperature change of Example 1 and Comparative Examples 1 and 2.

Explanation of symbols

1: Inkjet recording head 2: Head body 3: Channel member 4: Ink chamber 5: Heating resistor 6: Stepped groove 7: Stepped portion 8: Ink ejection hole 9: Nozzle plate 10: Support member 11: Ink supply hole 12: long hole 13: inclined bottom surface 14: small diameter hole 15: metal plating layer 16: protective layer

Claims (6)

A flow path member having a plurality of ink chambers and having a pressurizing mechanism that pressurizes the ink in each of the ink chambers using thermal energy, and is disposed on the surface of the flow path member and communicates with the ink chambers. An ink jet recording head comprising: a head main body comprising a nozzle plate having ink ejection holes; and a ceramic support member having an ink supply hole for supporting the head main body and communicating with the ink chamber of the flow path member. In this case, a metal plating layer having a film thickness of 50 to 150 μm and a protective layer having a film thickness of 0.5 to 5 μm having a higher thermal conductivity than the metal plating layer are formed on at least the surface of the ink supply hole exposed to the ink. An ink jet recording head characterized by being laminated. 2. The ink jet recording head according to claim 1, wherein the ceramic forming the support member is a ceramic mainly composed of any one of alumina, aluminum nitride, and silicon carbide. 3. The ink jet recording head according to claim 1, wherein the ceramic forming the support member is a ceramic mainly composed of alumina having a relative density of 95% or more. The ink jet recording head according to claim 1, wherein the metal plating layer is formed using any one of Ni and Mo. The inkjet recording head according to claim 1, wherein the protective layer is formed using a ceramic film of any one of a DLC film, a SiC film, and an AlN film. An ink jet printer using the ink jet recording head according to claim 1.

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