JP2006247922A - Protective film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a protective film having a uniform film thickness on the internal surface of a thin channel of a droplet discharging head such as one which is used for inkjet recording. <P>SOLUTION: The protective film is formed on the internal surface of the tunnel-like channel having an opening section which is formed on a head tip used for the droplet discharging head in a film making chamber which is equipped with a film making gas introducing means by this protective film forming method. The protective film forming method includes a process for decompressing the film making chamber, a process for introducing a film making gas into the film making chamber, and a process for forming the protective film on the internal surface of the channel by swinging the head chip in the length direction of the channel under an atmosphere of the film making gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a protective film forming method, and more particularly to a protective film forming method for forming a protective film on the inner surface of a channel of a head chip used in a droplet discharge head.

  In recent years, methods for recording an image or forming a fine pattern or structure by ejecting fine droplets such as an ink jet head for an ink jet printer have been well known. A typical example of such a droplet discharge head is one that discharges a droplet by utilizing deformation of a piezoelectric ceramic material by voltage, and one that generates bubbles in the liquid by heating to cause volume expansion. Thus, it is known that liquid droplets are discharged. As an example of this type of element, a fine groove having a groove depth of about 0.5 mm, a groove width, and a wall thickness between grooves of 0.18 mm is formed on a substrate made of a ceramic material and having a thickness of about 1 to 2 mm. Some have a structure in which a large number of fine tunnel-like spaces are formed by joining a cover material on the side where the grooves are formed. The liquid to be discharged is held in this tunnel-shaped space, and the liquid is discharged by the method described above. Such a space is called a channel in the following description.

  In order to obtain a function of discharging a liquid based on an electric signal, an electrode made of a metal material is often formed on the inner surface of the channel. In the case of discharging liquid by generating bubbles by heating, a heater as a heating means is often formed inside the channel as a metal, ceramic, or a composite thereof. Accordingly, the inner surface of the channel of the droplet discharge head is usually formed of a metal material, a ceramic material, or a composite material thereof.

  On the other hand, various types of discharged liquids are used. Oily liquids such as oil-based inks are generally less corrosive to metals and ceramics, but water-soluble liquids such as water-based inks are applied to metals and ceramics. On the other hand, it may be corrosive. In particular, when a voltage is applied to the electrode, corrosion is accelerated by an electrochemical reaction. Depending on the purpose of droplet ejection, a highly corrosive liquid may be used.

  In order to prevent the corrosion of the ceramic material and the metal material caused by such a cause and to improve the durability of the droplet discharge head, a protective film is formed on the inner surface of the channel. As a material for such a protective film, polyparaxylylene, which is a polymer of paraxylene, or a derivative thereof is well known, and is generally protected on the inner surface of the channel by chemical vapor deposition (hereinafter referred to as CVD). A film is formed. In addition, various devices have been made to improve the performance and durability of the polyparaxylylene protective film (see, for example, Patent Document 1 and Patent Document 2).

  Patent Document 1 discloses a method for improving the protective performance by improving the adhesion and heat resistance of a protective film by using a combination of multiple types of polyparaxylylene having different properties and derivatives thereof.

Patent Document 2 discloses a method for improving the adhesion and durability of a protective film to be formed by incorporating a silane coupling agent into polyparaxylylene.
JP 2000-71451 A Japanese Patent Laid-Open No. 2003-19797

  The methods disclosed in Patent Documents 1 and 2 are intended to improve the performance as a protective film mainly focusing on the adhesion of the polyparaxylylene film and the properties of the film itself. It is an effective method for improvement. However, when a polyparaxylylene film is formed on the inner surface of the channel of the droplet discharge head, there are the following technical problems.

For example, in the case of an ink jet head which is a typical example of a droplet discharge head, the channel usually has a very small cross-sectional shape, and the cross-sectional area may be 0.1 mm ² or less and the length may be about 10 mm. It is a very narrow space. In addition, when manufacturing an inkjet head, the protective film is formed by forming a groove in order to sufficiently bond the substrate having the groove for forming the channel and the cover material bonded to the substrate. It is desirable to perform the process after bonding the cover material to the substrate thus formed, and therefore it is required to form a film in the tunnel-like space. In addition, the channel does not necessarily have openings at both ends, and one end may be closed and only the other end may have an opening.

  When a protective film is formed on the inner surface of such a long and narrow channel by CVD, the film-forming gas is easily distributed near the opening of the channel or a film having a required thickness is easily formed, but the film is separated from the opening. The film-forming gas does not sufficiently reach the back part of the channel, and the thickness of the film tends to be thinner than the vicinity of the opening. When it is difficult to form a protective film with a uniform thickness, in order to obtain the required film thickness in the part where the film thickness tends to be thin, it is more than necessary near the opening of the channel. This narrows the channel space. If film formation is continued until the film thickness of the protective film reaches 1 μm or more at the center of the channel, the film thickness often exceeds 10 μm near the opening of the channel.

  If the film thickness is thin, pinholes and cracks existing in the film tend to penetrate the film, and the performance as a protective film may not be sufficient. Corrosion begins when ink comes into contact with the ceramic or electrode at the pinholes or cracks, and the corrosion expands, leading to a decrease in the durability of the inkjet head. On the other hand, if the film thickness is too thick, adhesion to the substrate and durability may be reduced.

  In general, the thickness of the protective film made of polyparaxylylene is desirably 1 μm or more and 8 μm or less. By forming the thickness of the protective film in this range, the performance as the protective film is exhibited and the adhesion and durability of the film are maintained, while the protective film is prevented from narrowing the channel.

  The present invention has been made in view of the above circumstances, and the object thereof is to form a portion of a tunnel-like channel having a small opening area with respect to the length, such as a channel of an inkjet head, from the opening. A protective film with a uniform thickness is formed on the distant part to prevent the part where the film thickness is insufficient, and conversely, the part where the film thickness is excessively thick. It is to provide a protective film forming method that realizes a protective film having a necessary and sufficient thickness.

  The above object can be achieved by the following method and configuration.

(Claim 1)
In a film forming chamber provided with a film forming gas introducing means, a protective film forming method for forming a protective film on the inner surface of a tunnel-shaped channel having an opening formed in a head chip used for a droplet discharge head,
Depressurizing the film forming chamber;
Introducing a film forming gas into the film forming chamber;
Forming a protective film on the inner surface of the channel by swinging the head chip in the length direction of the channel in an atmosphere of the film-forming gas;
A method for forming a protective film, comprising:

(Claim 2)
The inner surface of the channel is at least partly formed as an electrode,
The method for forming a protective film according to claim 1, wherein the film forming gas is introduced into the film forming chamber in a state where the electrode is cooled.

  According to the first aspect of the present invention, the head chip is swung in the channel length direction in the film forming gas atmosphere, so that the head chip is efficiently introduced not only into the channel opening but also into the central portion inside the channel. A protective film having a uniform film thickness can be formed.

  According to the second aspect of the present invention, when at least a part of the inner surface of the channel is formed as an electrode, the head chip is swung in the length direction of the channel while the electrode is cooled, thereby opening the channel. Is efficiently introduced not only into the central portion of the channel but also into the central portion of the channel, and the efficiency of deposition and adhesion of the film-forming gas to the cooled electrode portion increases, and the importance of the protective film is particularly high on the inner surface of the channel. A protective film having a sufficient thickness is formed on the electrode portion.

  Hereinafter, although an embodiment of the present invention is described based on a drawing, the present invention is not limited to this embodiment. This embodiment is an example of a method using a CVD film forming apparatus conventionally known as a film forming apparatus in order to form a protective film on the inner surface of a channel of an ink jet head which is a typical example of a droplet discharge head. First, the devices and components used, and their functions and operations will be described with reference to FIGS.

  FIG. 1 is an external view showing a CVD film forming apparatus 1 for carrying out a method for forming a protective film according to the present invention. In the vaporization chamber 2, the polyparaxylylene, which is a raw material for the film forming gas, is converted into diparaxylylene, which is a dimer, by thermal decomposition and sublimation. The monomer is decomposed into radical intermediates, and this monomer is introduced into the film forming chamber 4 by the film forming gas introducing means 5 as a film forming gas. The monomer adheres to the film formation body in the film forming chamber 4 and forms a protective film of polyparaxylylene having a molecular weight of several hundreds of thousands by a polymerization reaction.

  In the detoxification cooling device 6, the film forming gas remaining in the film forming process and its decomposition product are cooled, and the harmful decomposition product is adsorbed by an adsorbent to prevent discharge to the outside. Before the film forming process, the exhaust device 7 exhausts the air in the film forming apparatus 1 including the film forming chamber 4 to decompress the film forming chamber 4 to a substantially vacuum, and among the generated film forming gas, The gas remaining without contributing to film formation is exhausted, and the inside of the film formation chamber 4 is maintained at a gas pressure suitable for film formation during the film formation process.

  In addition to the above-described components, the CVD film forming apparatus 1 is provided with a flow rate adjusting valve (not shown) for adjusting the gas pressure in the film forming chamber 4 by adjusting pipes connecting the respective components and adjusting the gas flow rate. ing.

  After exhausting the air in the film forming apparatus 1 sufficiently by the exhaust apparatus 7 to 4000 Pa or less, generation of the film forming gas is started as described above, the generation speed, the exhaust speed of the exhaust apparatus 7 and the above-mentioned The gas pressure in the film forming chamber 4 can be adjusted by adjusting the flow rate adjusting valve. That is, the partial pressure of the film forming gas in the film forming chamber 4 is approximately equal to the amount of the film forming gas introduced by the film forming gas introduction means 5 and the amount of the film forming gas exhausted by the exhaust device 7. The flow rate adjustment valve is adjusted so as to be maintained at 4000 Pa, and a protective film is formed in that state.

  FIG. 2 is a schematic view of the inside of the film forming chamber 4 of the CVD film forming apparatus 1 as viewed from the horizontal direction. In FIG. 2, the same components as those in FIG. In addition, as described above, the dimensions of the head chip and the channel are extremely small. In FIG. 2, the dimensional ratio of each component in the drawing is drawn differently from the actual dimensional ratio for easy understanding. There is a case.

  A holding means 12 is provided in the film forming chamber 4 and holds the swinging means 20. A head chip 10 that is a film forming body is held on the swinging means 20 via a cooling means 30. The gantry 14 fixes the holding means 12.

Next, the head chip 10 will be described with reference to FIG. The head chip 10 shown in FIG. 3 is a head chip used for an ink jet head that discharges droplets by utilizing shear mode deformation of a piezoelectric ceramic, and its structure is well known and will be described briefly.

  A thick plate 17-a and a thin plate 17-b of lead zirconate titanate (generally called PZT, hereinafter referred to as PZT) well known as a piezoelectric ceramic as the substrate 17 are bonded with an adhesive layer (not shown). The combined material is used as the substrate 17, and the cover material 18 is also made of PZT in order to match the thermal and mechanical characteristics. The polarization direction indicated by the symbol A of the thick plate 17-a and the polarization direction indicated by the symbol B of the thin plate 17-b are the thickness direction of the plate and are opposite to each other. The cover material 18 is not polarized. The thickness of the thin plate 17-b is approximately half of the depth of a groove to be described later. The reason why the substrate 17 has such a structure is to cause shear mode deformation efficiently, and since it is well known in this field, detailed description thereof is omitted.

  In FIG. 3, a groove for forming the channel 15 is formed on the substrate 17 by a method such as grooving with a precision dicing saw, but the method of forming the groove is not limited to this. The electrode 16 is formed by vapor deposition of aluminum after forming the groove. However, the electrode formation method is not limited to vapor deposition, and the electrode 16 may be formed by, for example, nickel electroless plating.

  In some inkjet heads, every other channel is used, and the channel between them is called an air channel and does not contain liquid. In general, it is not necessary to form a protective film on the air channel, and in this case, the interval between the plurality of nozzles is preferably twice or an integral multiple of the interval between the channels 15 of the head chip 10. A head chip 10 shown in FIG. 3 is a head chip for an ink jet head of a type having no air channel.

  The head chip 10 has 80 channels 15 each having a channel width and a wall thickness between the channels of 0.18 mm (that is, a channel interval of 0.36 mm), a height of 0.5 mm, and a length of 5 mm. However, only a part thereof is shown in the figure. Of the 80 channels 15, 72 channels 15 excluding 4 on both sides are used for droplet ejection. Out of the four on each side, three on the outside are used as a space for releasing excess adhesive when bonding is performed for bonding. Each of the inner channels has a structure in which the channels 15 at both ends of the 72 channels 15 used for ejecting droplets are sandwiched between 0.18 mm thick walls in the same manner as the other channels 15, and the outside of the walls. This is a space necessary for forming the electrode 16. It is necessary to form a protective film for the central 72 channels used for droplet ejection.

  As shown in FIG. 5, the electrode 16 of the head chip 10 of the present embodiment is on the surface having both the side surface and the bottom surface indicated by reference numeral 16-a and the opening indicated by 16-b among the inner surface of the channel 15. No electrode is formed on the surface formed by the cover material 18 and the portion formed on the bottom surface of the substrate 17a indicated by 16-c. Normally, the portion indicated by 16-c is electrically connected to the drive circuit by a method such as wire bonding.

  The protective film 19 is formed on the inner surface of the channel 15 to protect the surface formed by the electrode 16-a and the cover material 18 on the upper portion of the channel 15.

  At the stage completed as a droplet discharge head, a minute discharge port (not shown) through which droplets are discharged is provided at one end of the channel 15. Usually, a thin plate called a nozzle plate in which a number of minute holes as ejection ports are formed is joined to the end face of the head chip 10, or a minute hole is formed after the thin plate is joined to form the ejection port of the droplet ejection head Is provided. The size of the discharge port is usually sufficiently smaller than the cross section of the channel 15.

  Next, an example of the rocking means, its structure and operation will be described with reference to FIG. 4 shows the holding means 12, the swinging means 20 fixedly held on the holding means 12, the Peltier element 30 fixedly held on the swinging means 20, and the head chip 10 held on the Peltier element 30. . In FIG. 4, the dimensional ratios of the constituent elements and the vertical and horizontal dimensional ratios are drawn differently from the actual dimensional ratios for easy understanding.

  The holding means 12 of the present embodiment includes the horizontal direction (X, Y) and the vertical direction (Z) in order to hold the held swinging means 12 and the head chip 10 in a position and direction suitable for handling and operation. Although a movable mechanism in the rotational direction having a straight line parallel to the vertical direction as a rotational axis is provided, in carrying out the protective film forming method of this method, the operation of the swinging means 20 and the handling of the head chip 10 If there is no problem, all or a part of these movable mechanisms may be omitted.

  Although the channel 15 of the head chip 10 is not shown in FIG. 4, the head chip 10 has the length direction of the channel 15 substantially coincided with the swinging direction of the swinging means 20, that is, the left-right direction in the drawing. It is necessary to hold. Further, it is necessary to securely fix the head chip 10 with respect to the Peltier element 30 and the Peltier element 30 with respect to the swinging means 20 so that the relative position does not shift due to the swing.

  The Peltier element 30 is provided for cooling the electrode 16. The cooling means is preferable because it has no mechanical moving part and can be cooled only by energization. However, the cooling means is not limited to this, and a small refrigerator or the like can also be used. Although wiring, a power supply device, and a control device and a sensor for controlling temperature and current for energizing the Peltier element 30 are also necessary, illustration is omitted.

  The swinging means 20 is intended to swing the head chip 10 in the length direction of the channel 15.

  Regarding the frequency and amplitude of the oscillation, it is considered that the higher the frequency, the higher the effect of introducing the film-forming gas into the channel 15. It is necessary that the fixing member 29 described later for fixing the head chip 10 as a part has a sturdy structure and the head chip 10 is firmly fixed. On the other hand, it is difficult to strongly fix a PZT material having a small fracture stress among ceramic materials. The same applies to the amplitude of the oscillation, and it is considered that the larger the amplitude, the higher the effect of introducing the film-forming gas into the channel 15, but the oscillation means 20 and the fixing member 29 should be made robust. I need it. The length of the channel 15 of the head chip 10 is about 10 mm even if it is large.

  Therefore, the frequency for swinging the head chip is preferably 1 to 10 Hz, and the amplitude is preferably 5 to 10 mm. Here, the amplitude is indicated by the distance from one end to the other end of the displacement caused by oscillation, and in the following description, pp is added after the unit.

  As the swinging method, there is a method of converting the rotation of the motor into a linear reciprocating motion with a cam, switching the rotational direction of the motor itself and switching the rotational motion to a linear motion with a rack and pinion gear, etc. Although it is possible to use the resulting method even in the decompressed film forming chamber, in this embodiment, it is possible to increase the ease of use in the space containing the film forming gas and the speed of oscillation. From the viewpoint of easiness, a configuration having almost no sliding portion as shown in FIG. 4 was adopted. This is because, when there are members that slide with each other in a decompressed space, the friction coefficient may be different from that under normal pressure, which may affect sliding, and in a space containing a film-forming gas, This is to avoid influences such as the possibility that a film is formed on the sliding portion with the passage of time to affect the sliding and that the sliding portion may generate heat due to high-speed swinging.

  The swinging means 20 of the present embodiment includes a lower plate 21 fixed to the holding means 12, two plate springs 23 attached to the lower plate 21, an upper plate 22 held by the plate spring 23, and an upper plate 22. The fixed swing member 25, the solenoid holding member 28 fixed to the lower plate 21, the solenoid 27 held by the solenoid holding member 28, one of the solenoids 27 is fixed to the swing member and the opposite side has a gap. The actuator 26 is inserted into the internal space. A lead wire for supplying current to the solenoid 27 is also provided, but the illustration is omitted. A power supply for supplying current and a control device for the power supply are also provided inside or outside the film forming chamber 4, but illustration thereof is omitted.

  The structure in which the two plate springs 23 are combined in this way is well known, and there is almost no change in the angle with respect to the lower plate 21 of the upper plate 22, and the displacement in the direction perpendicular to the swinging direction is also the plate spring 23. If the length is sufficiently large relative to the amount of displacement in the swing direction, the structure can be kept sufficiently small. As the material of the leaf spring 23, phosphor bronze, stainless steel, spring steel containing silicon or manganese can be used, and when corrosive gas is used inside the film forming chamber 4, stainless steel is preferable.

  The actuator 26 may be structured to slide with respect to the inner surface of the solenoid 27. However, as described above, the actuator 26 is used under a reduced pressure, used in an environment containing a film-forming gas, and the swinging member 25 is provided. For reasons such as being slightly displaced in a direction perpendicular to the swinging direction and preferably swinging at a high speed, it is preferable that the space inside the solenoid 27 is inserted with a gap.

  Although the solenoid holding member 28 is fixed to the lower plate 21 in this embodiment, the solenoid 27 can stably hold the relative position with respect to the actuator 26 inserted with a gap in the space inside the solenoid 27. If it is a method, you may attach and hold | maintain in the other location in the film forming chamber 4. FIG.

  The fixing member 29 is a member for fixing the head chip 10 to the Peltier element 30. The head chip 11 is manufactured in a structure capable of mounting a plurality of head chips 10 as much as possible depending on the dimensions of the head chip 11.

  In the configuration as described above, by exciting the solenoid 27 with an alternating current, the actuator 26 can be attracted, and each component held on the upper plate 22 can be swung in the direction indicated by the arrow A. It is. When the actuator 26 is made of a soft magnetic material, only the attraction force is used, and the actuator 26 is displaced on the opposite side to the attraction direction by the reaction of attraction. When a permanent magnet made of a hard magnetic material is used as the actuator 26, both attractive force and repulsive force can be used.

  Further, the system composed of the swinging means 20 and the head chip 10 and the Peltier element 30 which are the swinging members has a resonance frequency, and the frequency includes the shape of the leaf spring 23, the elastic coefficient of the material, the upper plate 23 and its It depends on the mass of the member mounted on it. If the frequency of the alternating current that excites the solenoid 27 matches the resonance frequency, a large oscillation amplitude can be obtained with a small current value.

  Next, a method of cooling the head chip 10 by the Peltier element 30 will be described with reference to FIG. The Peltier element 30 is used when the protective film forming method according to claim 2 of the present invention is carried out, and aims to increase the efficiency with which the film forming gas adheres by cooling the electrode 16 of the head chip 10. . This utilizes the fact that in the CVD film forming apparatus, the film forming gas adheres to the film forming body and the film forming gas has a high efficiency when the temperature of the film forming body is low.

  FIG. 5A is a perspective view showing a state where the electrode 16 of the head chip 10 is extended to the outside of the channel 15. The same components as those in FIG. 3 are given the same numbers. The portion 16-a inside the channel 15 of the electrode 16 is cooled by heat conduction through the portion 16-b by cooling the bottom portion 16-c of the substrate 17 by the Peltier element 30. The Peltier element 30 is well known and will be described briefly. As shown in FIG. 5B, the positive electrode 30-1, the N-type semiconductor 30-2, a heat absorbing plate 30-3 made of a metal material, When the P-type semiconductor 30-4 and the negative electrode 30-5 are connected in this order and are energized in the direction indicated by the symbol I, the temperature of the heat absorbing plate 30-3 decreases, and the positive electrode 30-1 and the negative electrode 30- The temperature of 5 rises. The positive electrode 30-1 and the negative electrode 30-5 are brought into close contact with the swinging member 25, so that the swinging member 25 and the upper plate 22 serve as a heat sink, and the heat radiated from the positive electrode 30-1 and the negative electrode 30-5 is absorbed. Absorption increases the temperature rise. The substrate 17 side of the head chip 10 is placed on the heat absorbing plate 30-3 so as to be in contact with the heat absorbing plate 30-3 of the Peltier element 30. The upper surface of the heat-absorbing plate 30-3 is fixed with the bottom surface having the electrode 16-c of the head chip 10 in close contact with the direction of the channel 15 substantially parallel to the swinging direction. For this purpose, a step or protrusion may be provided in an appropriate shape on the upper surface of the heat absorbing plate 30-3.

  The electrode 16 is formed of a metal material and usually includes a material having a particularly high thermal conductivity among metal materials such as aluminum, copper or gold. In the head chip 10 shown in FIG. 5, the electrode 16 is formed of aluminum. ing. The thermal conductivity of aluminum is about 240 W / (m · K), the thermal conductivity of PZT is about 2 W / (m · K), and there is a difference of about two digits. As described above, since the thermal conductivity is greatly different, when the portion of the electrode 16-c is cooled, the temperature of the portion of the electrode 16-a on the inner surface of the channel 15 becomes lower than the temperature of the portion without the electrode. . In FIG. 5B, the channel 15 and the electrode 16 are drawn larger than the actual size ratio for easy understanding.

  The apparatus and components used in the protective film forming method of the present invention and the functions and operations thereof have been described above. Next, the method for forming the protective film of the present invention using these devices and components will be described in detail. .

(First embodiment)
Hereinafter, although 1st Embodiment which concerns on Claim 1 of this invention is described, this invention is not limited to this embodiment.

  As described with reference to FIG. 1, in the vaporization chamber 2 of the CVD film forming apparatus 1, polyparaxylylene, which is a raw material for the film forming gas, is decomposed into diparaxylylene, which is a dimer, by thermal decomposition and sublimation. This dimer is heated to about 690 ° C. in the thermal decomposition chamber 3 to be decomposed into a paraxylylene radical intermediate which is a monomer, and this monomer is used as a film-forming gas in the film-forming chamber 4 by the film-forming gas introducing means 5. Introduce. The monomer adheres to the film forming body inside the film forming chamber 4 and forms a protective film of polyparaxylylene having a molecular weight of several hundreds of thousands by a polymerization reaction.

  After exhausting the air in the film forming apparatus 1 sufficiently by the exhaust apparatus 7 to 4000 Pa or less, generation of the film forming gas is started as described above, the generation speed, the exhaust speed of the exhaust apparatus 7 and the above-mentioned By adjusting the flow rate adjusting valve, the gas pressure in the film forming chamber 4 is maintained at about 4000 Pa, while the head chip 10 is swung in the length direction of the channel 15 by the swinging means shown in FIG. As a result, the film-forming gas is efficiently introduced into the channel 15 as compared with the case where it is not swung.

  If the material, thickness and length of the two leaf springs 23 are appropriately determined with respect to the mass of the upper plate 22 of the swinging means 20 and the members mounted thereon, the upper plate 22 of the swinging means 20 and The resonance frequency at which the member mounted thereon swings can be 1 Hz or more. Although the resonance frequency varies depending on the number of head chips 10 mounted, the mass of the head chip is smaller than the mass of the Peltier element 30 and the swing member 25, and the change in the resonance frequency is slight.

  When the rocking means is configured so that the resonance frequency is 5 Hz, and the protective film is formed for about 25 minutes while the head chip 10 is rocked by energizing the solenoid 27 so that the amplitude is 8 mmp-p. In addition, the film thickness of the head chip 10 was about 3 μm at the approximate center in the length direction of the channel 15, and the film thickness was about 7 μm near the opening of the channel 15.

(Second Embodiment)
A second embodiment according to claim 2 of the present invention will be described with reference to FIG. The second embodiment is a method of forming the protective film 21 in the protective film forming method described in the first embodiment by cooling the electrode 16 of the head chip 10 to increase the efficiency of deposition of the film forming gas.

  As the Peltier element 30, an FPH1-12702 Peltier module (30 mm × 30 mm × 4.8 mm (thickness)) manufactured by Fujitaka Co., Ltd. can be used. When a direct current of about 1.6 A was applied in the direction shown in FIG. 5, the temperature of the head chip 10 could be lowered by about 8 ° C. compared to the case where the direct current was not applied.

  With the electrode 16 thus cooled, the protective film 19 is formed by the same method as in the first embodiment except that the protective film is formed for about 20 minutes while the head chip 10 is swung. As a result, a film thickness of about 3 μm is obtained at the approximate center in the length direction of the channel 15 of the head chip 10, and a film thickness of about 7 μm is obtained in the vicinity of the opening of the channel 15. It was the above film thickness.

  According to the embodiment of the present invention described above, a protective film of polyparaxylylene can be formed on the inner surface of the channel of the head chip for the inkjet head, and the film thickness can be set to 7 μm at the maximum and 3 μm at the minimum. A protective film forming method for forming a protective film having a necessary and sufficient thickness over the entire length direction of the channel was realized, and the object of the present invention was achieved. In addition, a protective film having a sufficient thickness could be formed on the surface of the electrode portion where the necessity of a protective film was particularly high even inside the channel. The maximum film thickness of the protective film of 7 μm is 14 μm or less in total on both sides, and the channel width can be reduced within 8% with respect to the channel width of 0.18 mm (180 μm).

  As for the swinging means 20, in addition to the one shown in FIG. 4, a combination of rotation of the motor and a cam mechanism, a method of reversing the rotation direction of the motor repeatedly, and realizing a reciprocating motion by a rack and pinion mechanism, a linear motor A known method such as one that realizes reciprocation can be used. Further, a mechanism for reciprocating the film forming chamber may be provided, and a mechanism for transmitting the mechanism to the inside of the film forming chamber may be provided.

  If the channel 15 of the head chip 10 does not have an opening in both of them, and one of them is closed, the opening side moves to the head of the reciprocation by swinging than when the closed side moves to the head. If the speed is increased, the effect of introducing the deposition gas into the channel 15 is high.

  The method for cooling the electrodes is not limited to the Peltier element shown in FIG. 5B, and a small refrigerator may be used. Instead of providing the cooling means directly on the rocking member 25, a member cooled by heat conduction from the cooling means arranged other than on the rocking member 25 may be arranged on the rocking member 25.

  When cooling is not performed, the head chip 10 may be disposed directly on the swing member 25 without providing the Peltier element 30. In the case where a plurality of head chips 10 are collectively formed to form a protective film, the head chips 10 may be arranged or stacked on the swing member 25 within a range in which reliable fixing is possible. In the case of cooling, it is preferable to arrange the head chips 10 on the Peltier element 30 in order to form a protective film together for a plurality of head chips 10.

  Whether or not cooling is performed, it is preferable that the plurality of head chips 10 be arranged so as not to block the opening of the channel 15.

  By applying the protective film forming method of the present invention to the protective film formation of the head chip of the inkjet head, it is possible to realize an inkjet head having durability of tens of thousands of hours or more in operation time.

  Although the case where polyparaxylylene is used as the protective film has been described, tetrachloropolyparaxylylene, difluoropolyparaxylylene, etc., which are derivatives thereof, may be used depending on the characteristics required for the protective film. In addition, if a material other than polyparaxylylene or a derivative thereof can be ejected as a gas, the protective film should be formed using a material suitable for the droplet discharge head on which the protective film is formed. Are also within the scope of the present invention.

It is a figure which shows the whole film forming apparatus which implements this invention. It is a figure which shows the film forming chamber inside of the film forming apparatus which implements this invention. It is a figure which shows the head chip in which a protective film is formed with the method of forming the protective film of this invention. It is a figure which shows the means to rock | fluctuate a head chip by the method of forming the protective film of this invention. It is a figure which shows an example of the method of cooling a head chip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Film forming apparatus 4 Film forming room 5 Film forming gas introduction means 10 Head chip 12 Holding means 15 Channel 16 Electrode 17 Substrate 18 Cover material 19 Protective film 20 Oscillating means 30 Peltier element

Claims (2)

In a film forming chamber provided with a film forming gas introducing means, a protective film forming method for forming a protective film on the inner surface of a tunnel-shaped channel having an opening formed in a head chip used for a droplet discharge head,
Depressurizing the film forming chamber;
Introducing a film forming gas into the film forming chamber;
Forming a protective film on the inner surface of the channel by swinging the head chip in the length direction of the channel in an atmosphere of the film-forming gas;
A method for forming a protective film, comprising: The inner surface of the channel is at least partly formed as an electrode,
The method for forming a protective film according to claim 1, wherein the film forming gas is introduced into the film forming chamber in a state where the electrode is cooled.

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