JP4838056B2 - Droplet discharge apparatus and image forming apparatus - Google Patents

Description

The present invention relates to a droplet ejection apparatus and image forming equipment comprising an ink jet head having an improved ejection port surface can achieve discharge state of stable ink.

  When recording is performed by the ink jet recording method, there is a case where minute ink flying from the ejection port is generated with a delay of the main ink droplet accompanying the main ink droplet ejected in response to the recording signal. Such fine ink (hereinafter referred to as ink mist) may rapidly decelerate immediately after flying from the ejection port, and may float near the nozzle without reaching the recording paper. Such floating ink mist often adheres to the ejection port surface of the ink jet head and often causes ink accumulation. It is known that the occurrence of such a liquid pool leads to the occurrence of problems such as unstable ejection of ink droplets from the ejection port and non-ejection of ink.

  Conventionally, in order to solve such a problem of liquid accumulation, a water repellent treatment has been performed on a discharge port surface provided with a discharge port (see, for example, Patent Document 1). When the water-repellent film is formed on almost the entire surface of the ejection port in this way, the ink stays in the peripheral portion of the ejection port, and the above-described problems such as unstable ejection of ink are improved to some extent. However, when recording at high printing speed and high duty with continuous high-frequency driving for a long period of time, a large amount of ink mist is generated, and ink droplets gradually accumulate on the ejection port surface.

  The following briefly describes how ink mist adhering to the ejection port surface changes the ink ejection state.

  In a configuration in which water repellent treatment is applied to almost the entire surface of the nozzle, ink mist floating near the nozzle plate adheres randomly, but gradually gathers in the vicinity of the attached mist or overlaps with the attached mist. Grows into the body. Since the water repellent nozzle plate surface has a large contact angle with water (ink), the ink mist aggregate having a diameter of about 300 μm to 500 μm has high fluidity, and when the contact angle with water exceeds 80 degrees, Its fluidity becomes even more remarkable. In particular, in the case of a device configuration in which the recording head itself is reciprocally scanned in the recording area, the ink mist assembly starts to move easily due to inertial force resulting from the reciprocating motion or by its own weight, and the adjacent ink mist assembly And coalesce, and grow into even larger ink droplets. Then, the movement of the ink mist aggregate becomes easy and finally reaches the discharge port, and the ink mist thus grown is partially drawn into the discharge ports of the corresponding one or two nozzles, and even non-discharge It will create the phenomenon that occurs.

  As a technique for solving such a phenomenon, at a central water-repellent region including a region having a plurality of discharge ports, and at a predetermined distance away from the plurality of discharge ports, on at least one side of the central water-repellent region, An invention of an ink jet head including a partial hydrophilic region having a hydrophilic portion that is intermittently arranged in plural so as to capture the increased ink droplets attached to the discharge port surface is known (see Patent Document 2). . This invention shows that when the entire nozzle surface is made water-repellent, ink mist accumulates during continuous printing or the like and becomes ink droplets that are drawn into the discharge port to cause non-discharge. Further, it is shown that when a hydrophilic portion is partially provided on the nozzle surface, ink mist gathers in the hydrophilic portion and growth of ink droplets in the vicinity of the nozzle is prevented.

  In addition, an ink jet head has been proposed in which a recess is formed around the nozzle and the surface of the cover plate excluding the side surface of the recess and the surface of the nozzle plate are subjected to ink repellent treatment (see Patent Document 3). The technique of storing in the hydrophilic part of is described.

  Further, the ink repellent treated surface is formed by using an ink jet printer in which the periphery of the ink discharge port on the surface of the nozzle plate of the head is subjected to ink repellent treatment, and the peripheral edge thereof is further subjected to parent ink treatment, and ink having a viscosity at 25 ° C. of 4 cp or more. Ink jet method for forming an image by setting the forward contact angle of the ink to 80 to 110 °, the backward contact angle to 40 ° or more, and the forward contact angle and backward contact angle of the ink to the parent ink processing surface to 30 ° or less. An image forming method has been proposed (see Patent Document 4). Here, when the ink repellent treatment part around the nozzle has a high contact angle with the ink, the ink tends to move, and the ink movement to the hydrophilic part is promoted to remove the ink around the nozzle. Has been.

In recent years, in order to achieve high-speed printing on plain paper and high image quality, highly penetrable ink has been increasingly used for plain paper. These highly permeable inks developed by the present applicant are designed to increase the permeability to sized plain paper, and are therefore more oleophilic, with respect to the water-repellent treatment film on the nozzle plate surface. The contact angle is often small (80 ° or less). When such an ink is used, the ink once adhered to the nozzle plate surface is less likely to move to the hydrophilic portion by moving the nozzle surface, and the nozzle having a partially hydrophilic portion as described above. Even if a plate is used, the effect is small, and as with the case where water repellent treatment is applied to the entire surface, ink mist adhering to the vicinity of the nozzle grows and enters the nozzle, thereby destroying the meniscus and causing ink non-ejection. is there.
Japanese Patent No. 2763410 Japanese Patent No. 3332503 Japanese Patent Laid-Open No. 2005-7789 JP-A-11-268248

In view of the above problems, the present invention includes a water repellent treatment portion that is water repellent treated and a non-water repellent treatment portion that is not water repellent treated on the nozzle surface of the nozzle plate. and its object is to provide a droplet ejection apparatus and image forming equipment to provide a potential difference between the parts.

In order to achieve the above object, the invention described in claim 1 is a droplet discharge device having a nozzle plate of a discharge port member in which nozzles that are discharge ports for discharging a droplet are arranged, wherein the nozzle plate The nozzle surface includes a region in which the nozzles are arranged, and includes a water repellent treatment portion that is water repellent treated with an electrically insulating water repellent material, a region in which the nozzles are arranged, and a peripheral portion of the nozzle plate. And a non-water-repellent treatment part that is formed in a region between them and not subjected to water-repellent treatment with the water-repellent material, and the region where the nozzles are arranged is repelled with the water-repellent material between adjacent nozzles. The non-water-repellent treatment portion is grounded, and is configured to have a potential difference from the water-repellent treatment portion by the grounding .

  According to a second aspect of the present invention, in the liquid droplet ejection device according to the first aspect, the non-water-repellent treatment part is provided on both sides of the region spaced from the region where the nozzles are arranged. Features.

According to a third aspect of the present invention, there is provided an image forming apparatus equipped with the liquid droplet ejection apparatus according to the first or second aspect.

As described above, according to the present invention, the nozzle surface of the nozzle plate is provided with the water repellent treatment portion subjected to the water repellent treatment and the non-water repellent treatment portion not subjected to the water repellent treatment. part and it is possible to provide a droplet ejection apparatus and image forming equipment to have a potential difference.

In the droplet ejection apparatus and an image forming equipment of this embodiment, adhesion of the ink mist floating in the vicinity of the nozzle plate surface even with a high permeability of the ink is prevented, the droplet discharge device and does not occur with nozzle clogging and its object is to provide an image forming equipment.

Hereinafter, with the droplet ejection apparatus and an image forming equipment of the present embodiment will be described with reference to the accompanying drawings. In addition, this embodiment is not limited to what is described below, A various change is possible in the range which does not deviate from the meaning.

  A first embodiment of a droplet discharge apparatus according to this embodiment will be described with reference to FIGS. FIG. 1 is an exploded perspective view of the ink head of the droplet discharge device. FIG. 2 is a cross-sectional explanatory view along the longitudinal direction of the liquid chamber of the ink head of the droplet discharge device. FIG. 3 is an enlarged view of a main part of the droplet discharge device shown in FIG. Further, FIGS. 4 and 5 are cross-sectional explanatory views showing different examples of the ink head of the droplet discharge device in the lateral direction of the liquid chamber.

  As shown in FIGS. 1 to 3, the droplet discharge device includes, for example, a channel plate 1 formed of a single crystal silicon substrate, a vibration plate 2 bonded to the lower surface of the channel plate 1, and an upper surface of the channel plate 1. And a nozzle plate 3 (hereinafter also referred to as a nozzle plate) 3, and a nozzle 4 for ejecting ink droplets by means of a pressurized liquid chamber 6 communicated via a communication path 5 and a fluid resistance portion 7. A communication portion 9 communicating with the pressure fluid chamber 6 is formed, and a recording liquid (for example, ink) is supplied from a common liquid chamber 8 formed in a frame member 17 described later through a supply port 10 formed in the diaphragm 2 to the communication portion 9. Supply.

  Then, as shown in FIG. 3, each pressurizing liquid chamber is provided on the outer side of the diaphragm 2 forming the wall surface of the pressurizing liquid chamber 6 (on the side opposite to the pressurizing liquid chamber 6 (surface opposite to the nozzle surface)). 6, the upper end portion of the multilayer piezoelectric element 12 that is a pressure generating means is joined via the connecting portion 11 formed on the diaphragm 2, and the lower end portion of the multilayer piezoelectric element 12 is joined to the support substrate 13. And fixed. Note that the support substrate 13 may be divided for each row of the piezoelectric elements 12.

  The piezoelectric element 12 is formed by alternately stacking piezoelectric material layers 14 and internal electrodes 15a and 15b. In this case, the ink in the pressurized liquid chamber 6 can be pressurized using the displacement in the d33 direction as the piezoelectric direction of the piezoelectric element 12, and the displacement in the d31 direction is used as the piezoelectric direction of the piezoelectric element 12. Thus, the ink in the pressurized liquid chamber 6 may be pressurized.

  The periphery of the flow path plate 1 and the diaphragm 2 is bonded (adhered) to a frame member 17 formed by injection molding, for example, with epoxy resin or polyphenylene sulfide, and the frame member 17 and the support substrate 13 are not illustrated. Fix the parts to each other with adhesive. The frame member 17 is formed with the above-described common liquid chamber 8 and a supply path (communication pipe) (not shown) for supplying recording liquid from the outside to the common liquid chamber 8. Further, it is connected to a recording liquid supply source such as a cartridge (not shown).

  Further, an FPC cable 18 is connected to the piezoelectric element 12 by solder bonding, ACF (anisotropic conductive film) bonding or wire bonding in order to give a drive signal. The FPC cable 18 is selectively connected to each piezoelectric element 12. A drive circuit (driver IC) 19 for applying a drive waveform is mounted.

  The flow path plate 1 is formed by, for example, anisotropically etching a single crystal silicon substrate having a crystal plane orientation (110) with an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH), so that the communication path 5, the pressurized liquid chamber 6, a through-hole, a fluid resistance portion 7 and a communication portion 9 are formed.

  For example, as shown in FIG. 3, the diaphragm 2 can be formed of a nickel metal plate and is manufactured by, for example, an electroforming method. The diaphragm 2 has a thin wall portion for facilitating deformation of the portion corresponding to the pressurized liquid chamber 6, and the first layer 11 a on the diaphragm 2 side and the piezoelectric element 12 side in order to connect the piezoelectric element 12 to the center portion. A connecting portion 11 having a two-layer structure including the second layer 11b is provided.

  In the lateral direction of the liquid chamber (the direction in which the nozzles 4 are arranged), as shown in FIG. 4, a bi-pitch structure in which the piezoelectric elements 12 and the column portions 22 are alternately arranged can be adopted, or FIG. As shown in FIG. 4, a normal pitch structure without the support 22 can be adopted.

  When the droplet discharge device configured as described above is driven by, for example, a pushing method, a drive pulse voltage of 20 to 50 V is selectively applied to the plurality of piezoelectric elements 2 according to an image recorded from a control unit (not shown). Apply. As a result, the piezoelectric element 12 is displaced by applying a pulse voltage to deform the vibration plate 2 in the direction of the nozzle plate 3, and the liquid in the pressurized liquid chamber 6 is added by the change in volume (volume) of the pressurized liquid chamber 6. Press. By doing so, droplets are ejected from the nozzle 4 of the nozzle plate 3. As the liquid droplets are discharged, the pressure in the pressurized liquid chamber 6 decreases, and a negative pressure is generated in the pressurized liquid chamber 6 due to the inertia of the liquid flow at this time. Under this state, the application of voltage to the piezoelectric element 12 is turned off, so that the diaphragm 2 returns to its original position and the pressurized liquid chamber 6 has its original shape, and further negative pressure is generated. . As a result, the liquid entered from the liquid supply pipe leading to the liquid tank (not shown) is filled in the pressurized liquid chamber 6 and droplets are ejected from the nozzle 4 in response to the applied pulse to which the next drive pulse is applied.

  In order to solve the above-described problem, this embodiment has water repellency by first performing water repellency treatment with an electrically insulating water repellant material on the nozzle surface of the nozzle plate in the droplet discharge device as described above. A head including a water-repellent portion and a non-water-repellent portion in which a part of the nozzle surface is not subjected to the water-repellent treatment with the water-repellent material.

  There is a potential difference between the water repellent portion and the non-water repellent portion of the nozzle plate surface, and an electric field is generated by this potential difference. On the other hand, since the ink mist is charged due to the polarity of the ink, the peeling action from the nozzle liquid chamber, etc., the ink mist floating near the nozzle plate surface has a force acting in a direction in contact with the electric lines of force on the nozzle plate surface. Induced by.

  In the present embodiment, a voltage is applied to or grounded to at least one of the portions that are not subjected to the water repellent treatment with the water repellent material and a portion that is subjected to the water repellent treatment so as to have a higher potential difference. As a result, the electric lines of force further increase, and the charged ink mist floating near the nozzle plate adheres to the nozzle surface. The attached ink mist forms an aggregate and at the same time has a more hydrophilic non-water-repellent treatment portion. Therefore, the ink droplet generated from the ink mist is not drawn into the nozzle.

FIG. 8 is an explanatory view for explaining the inducing action of the ink mist by the electric lines of force on the nozzle plate surface described above.
In FIG. 8A, 31 is a flow path plate member formed of, for example, Si, 32 is an adhesive, 33 is a nozzle plate member formed of resin, and 34 is, for example, SiO _2. This is a bonding layer for improving the adhesion between the water repellent layer and the nozzle forming member 33, and 35 is a water repellent layer.

  Further, as shown in FIG. 8B, when a positive potential is applied to the nozzle plate member 33, the nozzle plate member 33 having a relatively high electrical conductivity is charged with a positive charge, and the water repellent surface having high electrical insulation. Produces a potential difference that is relatively negative, and generates lines of electric force as shown in the figure. Then, as shown in FIG. 8C, the ink ejected from the nozzles becomes droplets having a negative charge relative to the nozzle plate member 33 when leaving the nozzle wall or the water repellent layer. .

  Then, as shown in FIG. 8 (d), the main droplets in the discharged droplets are immediately separated from the nozzle surface by the discharge energy and subjected to printing, but the satellite droplets having a small volume are stalled by the air resistance, It floats near the nozzle surface. At that time, the relatively negatively charged ink droplets are attracted and adhered to the relatively positively charged portion of the nozzle surface where the water repellent agent is not attached by electrostatic force. Therefore, ink mist does not adhere to the peripheral portion of the nozzle outlet where the water repellent treatment agent is adhered, and the meniscus is not destroyed.

  Further, in the present embodiment, a portion that is not water-repellent treated with the water-repellent material when ink is ejected from a nozzle using an ink having a contact angle of 80 ° or less with respect to the portion that has been water-repellent-treated with the water-repellent material. However, printing is performed by applying to a portion that is not water-repellent treated with the water-repellent material, that is, a portion that is relatively conductive, so as to have a potential opposite to the electric charge of the ink droplet.

  Highly permeable ink with a fast drying speed is relatively oleophilic, and even if the nozzle forming member (nozzle plate) is subjected to water repellent treatment, the contact angle with the treated portion is low. In such a case, conventionally, nozzle clogging due to ink mist could not be resolved. Further, when ink is ejected from the nozzles, charging occurs according to the frictional charging series between the ink and the nozzle material, and the ink mist having a small gravity has a high mobility due to the influence of charging. Here, the charging polarity of the ink depends on the material, but by applying a charge opposite to the charging polarity to the non-water-repellent part accordingly, the floating ink mist is electrostatically applied. It is possible to attract a portion far from the water repellent treated nozzle.

  Next, the nozzle plate 3 of the droplet discharge device and the manufacturing method thereof will be described with reference to FIGS. FIG. 6 is an enlarged cross-sectional view of a nozzle portion of a nozzle plate to which this embodiment is applied. FIG. 7 is a diagram showing an example of the manufacturing process of the nozzle plate according to the present embodiment.

As shown in FIG. 6, the nozzle plate 3 is usually formed by bonding a resin member (nozzle plate member) 33 made of a resin film such as a polyimide film on a highly rigid member 31 such as a silicon wafer via an adhesive 32. A nozzle forming member 30 is formed, and a bonding layer 34 formed of a SiO ₂ thin film is formed on the surface of the nozzle plate member 33 constituting the nozzle forming member 30 (surface on the droplet discharge surface side). A water repellent layer 35 is formed. At this time, the bonding layer 34 formed of the SiO ₂ thin film layer bonds the nozzle plate member 33 and the first water-repellent treatment layer 35, and also connects the water-repellent layer 35 and the next water-repellent layer treatment 35. Join. The entire structural portion of the bonding layer (here, SiO ₂ thin film layer) 34 and the water repellent layer (here, one or more fluorine-based water repellent layers) 35 is referred to as a “water repellent treatment layer 40”.

  A nozzle hole 4 having a required diameter is formed by excimer laser processing in the nozzle plate member 33 formed of a resin member constituting the nozzle forming member 30, and the nozzle hole 4 is formed in the highly rigid flow path plate member 31. A nozzle communication port 44 that communicates is formed.

The nozzle plate manufacturing method of the present embodiment is a non-water-repellent treatment in which the surface of the nozzle plate member 33 of the nozzle forming member 30 is not water-repellent with a water-repellent material after the nozzle forming member 30 is manufactured as shown in FIG. A mask 51 for forming a portion is formed (FIG. 7A). Next, after forming this mask 51, a water repellent layer 35 subjected to a water repellent treatment with an insulating water repellent material is formed through a bonding layer (SiO ₂ thin film layer) 34 (FIG. 7B). Next, an excimer laser is irradiated from the direction opposite to the surface that has been subjected to the water repellent treatment with the water repellent material to form a nozzle (FIG. 7C). Next, the mask 51 is removed, and a nozzle plate having a non-water-repellent treatment portion that is not partially water-repellent-treated with a water-repellent material is formed (FIG. 7D).

  Further, when the water repellent layer is formed by the water repellent treatment, the mask 51 is not formed, the water repellent treatment is uniformly performed on the entire surface, the nozzle processing is performed by the excimer laser, and then the excimer laser is irradiated from the water repellent treated surface. Then, a nozzle plate having a non-water-repellent treatment portion that is not partially water-repellent-treated may be formed by removing the surface water-repellent treatment agent.

Here, the formation of the bonding layer 34 in the SiO ₂ thin film layer is preferably performed at a temperature that is relatively not heated, that is, does not cause thermal influence on the nozzle plate member 33. It is preferable to form by a possible method. As specific methods, it can be said that sputtering, ion beam evaporation, ion plating, CVD (chemical vapor deposition), P-CVD (plasma vapor deposition) and the like are suitable.

Further, if the thickness of the bonding layer 34 formed of the SiO ₂ thin film layer is set to a necessary minimum thickness within a range in which adhesion can be secured, the process time can be shortened and the material cost can be reduced. If the thickness of the bonding layer (SiO ₂ thin film layer) 34 becomes too thick, there is a risk of hindering nozzle hole processing with an excimer laser. In other words, even if the nozzle plate member (resin member) 33 is cleanly processed into a nozzle hole shape, a part of the bonding layer (SiO ₂ thin film layer) 34 is not sufficiently processed, and a processing residue may occur.

Therefore, specifically, the adhesive layer can secure an adhesive force, and the film thickness of the bonding layer 34 is 1 to 300 mm (0.1 to 30 nm (1 mm = 1 mm = 1 mm = 10 mm) so that the bonding layer (SiO ₂ thin film layer) 34 does not remain during excimer laser processing. 0.1 nm)) is preferable, and more preferably within a range of 10 to 100 mm (1 to 10 nm). As a result of the experiment, the adhesiveness was sufficient even when the thickness of the bonding layer (SiO ₂ thin film layer) 34 was about 30 mm (3 nm), and there was no problem with the workability by the excimer laser. In addition, a slight machining residue was observed at 300 mm, but it was within the usable range, and when it exceeded 5000 mm, a considerably large machining residue was generated, and it was confirmed that an unusable nozzle profile was generated.

  Various materials are known as the water repellent material used for the fluorine-based water repellent layer 35. For example, an organic compound having a fluorine atom, particularly an organic substance having a fluoroalkyl group, and an organic silicon having a dimethylsiloxane skeleton. A compound etc. can be used.

  As the organic compound having a fluorine atom, fluoroalkylsilane, alkane having a fluoroalkyl group, cambonic acid, alcohol, amine and the like are desirable. Specifically, as fluoroalkylsilane, heptadecafluoro-1,1,2,2-tetrahydrodecyltrimethoxysilane, heptadecafluoro-1,1,2,2-tetrahydrotrichlorosilane; fluoroalkyl As the alkane having a group, octafluorocyclobutane, perfluoromethylcyclohexane, perfluoro-n-hexane, perfluoro-n-heptane, tetradecafluoro-2-methylpentane, perfluorododecane, perfluoroeucosan; fluoro Examples of the carboxylic acid having an oalkyl group include perfluorodecanoic acid and perfluorooctanoic acid; and examples of the alcohol having a fluoroalkyl group include 3,3,4,4,5,5,5-heptafluoro-2-pentanol. A having a fluoroalkyl group The emissions, heptadecafluoro-1,1,2,2-tetrahydro-decyl amine. Examples of organosilicon compounds having a dimethylsiloxane skeleton include α, ω-bis (3-aminopropyl) polydimethylsiloxane, α, ω-bis (3-glycidoxypropyl) polydimethylsiloxane, α, ω-bis (vinyl). ) Polydimethylsiloxane and the like.

  As another water repellent material, an organic compound having a silicon atom, particularly an organic compound having an alkylsiloxane group can be used.

  Examples of the organic compound having an alkylsiloxane group include alkylsiloxane groups having two or more alkylsiloxane groups and cycloaliphatic epoxy groups in the molecule constituting the alkylsiloxane epoxy resin composition. Examples thereof include a polymer compound (A) containing the structural units represented by the general formulas (a) and (b).

  The compound having the above structure also functions as a binder when used in combination with other water-repellent compounds. That is, it improves the workability of the ink-repellent composition and improves the workability as a dry coating film that improves the drying property after evaporation of the solvent.

  The most preferable water repellent in this embodiment is a mixture of perfluoropolyoxetane and modified perfluoropolyoxetane (manufactured by Daikin Industries, trade name: OPTOOL DSX), which has a thickness of 10 to 300 mm (1 to 30 nm). The necessary water repellency is obtained by vapor deposition. As a result of the experiment, there was no difference in water repellency and wiping durability performance even when the thickness of the OPTOOL DSX was 10 mm, 100 mm (10 nm), or 300 mm (30 nm). Therefore, considering cost etc., 10-100cm (1-10nm) is more suitable.

  As described above, in the nozzle plate used in the present embodiment, the water repellent layer 35 and the nozzle forming member 30 are strengthened by interposing the bonding layer 34 between the nozzle forming member 30 and the water repellent layer 35. Adhesion and liquid resistance and wiping resistance are greatly improved, high water repellency (ink repellency) can be maintained and can be sustained, and stable without causing any bending in the droplet ejection direction Drop ejection characteristics (ejection characteristics) can be obtained.

  In this case, by forming the nozzle forming member 30 using a resinous film, the nozzle hole processing selection range is widened, and the accuracy in ultraviolet laser processing (including excimer laser processing) as will be described later. High nozzle hole processing can be performed efficiently and at low cost. By using a polyimide resin film as this resin film, the selection range of nozzle hole processing is widened, and the toughness, chemical resistance, and heat resistance are excellent, depending on thermal and mechanical stress during processing such as adhesive curing. Deformation is reduced, and highly accurate nozzle hole processing can be performed.

  Further, by forming the water repellent layer 35 with a fluorine-based water repellent and setting the film thickness of the water repellent layer to 10 to 100 mm (1 nm to 10 nm), high water repellency can be obtained. And then. The fluorine-based water repellent film can be made very thin, so that necessary materials can be reduced and the cost can be reduced. By using perfluoropolyoxetane or modified perfluoropolyoxetane or a mixture of both as the fluorine-based water repellent, it becomes possible to form a water-repellent film by a vacuum deposition method. It is possible to easily form a very thin film, and the water repellency is extremely high, and it is possible to simultaneously improve the wiping durability of the water repellent film and the workability by an ultraviolet laser.

Furthermore, the nozzle formation member and the water-repellent layer, using the SiO ₂ film as a bonding layer to bond the water-repellent layers to each other, the thickness of the SiO ₂ film, by a 10Å or 100Å or less, adhesion of the water repellent layer In particular, since the SiO ₂ film and the fluorine-based water repellent are in close contact with each other by chemical bonding, it is possible to make the fluorine-based water-repellent film very thin, reducing the necessary materials and processing. Since the time can be shortened, the cost can be reduced.

  As described above, according to the droplet discharge device, the image forming apparatus, the image forming method, and the method for manufacturing the droplet discharge device of the present embodiment, when ink is discharged by an example of an inkjet printer, that is, an image forming apparatus, the speed The main droplet with energy immediately lands on the recording paper and an image is formed, but the minute ink droplet generated as a satellite rapidly decreases in flying speed and does not reach the recording paper, but near the nozzle plate surface. Floating. A part of it adheres to the nozzle plate surface. At that time, there is a potential difference between the water repellent treated portion and the non-water repellent treated portion of the nozzle plate surface, and an electric field as indicated by the lines of electric force in FIG. 8 is generated. On the other hand, the ink mist is charged due to the influence of the polarity of the ink, the peeling action from the nozzle liquid chamber (friction when the ink is pulled away from the inner wall of the nozzle), and the like. Therefore, the ink mist floating near the nozzle plate surface is induced by the electric lines of force on the nozzle plate surface. In the present embodiment, the ink mist is subjected to water repellent treatment because a voltage is appropriately applied so as to be guided to a hydrophilic portion that is not water repellent treated with the water repellent material on the nozzle plate surface according to the charge polarity of the ink. The nozzle does not adhere to the vicinity of the nozzle, and nozzle clogging due to meniscus destruction by the adhered ink mist is avoided. The ink mist adhering to the hydrophilic portion of the nozzle plate surface is removed by a periodic cleaning operation using a wiper.

  According to the image forming apparatus of the present embodiment, at least a portion of the nozzle plate surface that is not water-repellent treated with the electrically insulating water-repellent material has a potential difference from a portion that is not water-repellently treated with the water-repellent material. Since a voltage is applied to one side or one side is grounded, lines of electric force are generated, and the relatively negatively charged ink mist floating near the nozzle plate is relatively positively charged on the nozzle surface. Ink droplets generated from the ink mist are attracted to the nozzles that are attracted by the electrostatic force to the part that is not water-repellent treated with the water-repellent material, and the ink mist does not adhere to the periphery of the nozzle that is water-repellent treated with the water-repellent material. It is not drawn in.

  Further, according to the image forming apparatus of this embodiment, when ejecting ink from a nozzle using a droplet having a contact angle of 80 ° or less with respect to a portion that is water repellent treated with an electrically insulating water repellent material, The portion that is not water-repellent treated with the water-repellent material, that is, the portion that is not water-repellent treated with the water-repellent material, that is, is relatively conductive so that the portion that is not water-repellent treated with the water-repellent material has a potential opposite to the electric charge of the droplet. Since printing is performed by applying to the portion having the ink, the floating ink mist can be attracted by electrostatic force, and the ink mist is attracted to the conductive portion away from the nozzle, thereby preventing nozzle clogging. An image forming apparatus can be obtained.

  Further, according to the image forming method of this embodiment, when ejecting ink from a nozzle using a droplet having a contact angle of 80 ° or less with respect to a portion that is water repellent treated with an electrically insulating water repellent material, The portion that is not water-repellent treated with the water-repellent material, that is, the portion that is not water-repellent treated with the water-repellent material, that is, is relatively conductive so that the portion that is not water-repellent treated with the water-repellent material has a potential opposite to the electric charge of the droplet. By printing on the part that has it, it becomes possible to attract the floating ink mist with electrostatic force, attract the ink mist to the conductive part away from the nozzle, and prevent nozzle clogging. Can do.

  Furthermore, according to the manufacturing method of the droplet discharge device in the present embodiment, the conductive nozzle plate material is used, and the water-repellent treatment is performed with the electrically insulating water-repellent material. When the nozzle plate is grounded or a voltage is applied, the lines of electric force are strengthened, the force to attract ink mist is strengthened, and the ink mist is attracted to the part away from the nozzle to eliminate nozzle clogging. It is effective to manufacture.

  Hereinafter, the droplet discharge device, the image forming apparatus, the image forming method, and the method for manufacturing the droplet discharge device of the present embodiment will be described more specifically with reference to examples. However, the present embodiment is not construed as being limited by the examples described below.

[Example 1]
-Preparation of nozzle plate An adhesive 32 was applied to a Si high-rigidity member 31 forming an ink flow path, and a polyimide film (Upylex manufactured by Ube Industries, Ltd .; thickness: 25 μm) 33 was bonded thereto. Further, a mask as shown by 51 in FIG. 7A was formed on the polyimide film, and Si was sputtered in a vacuum chamber, followed by O ₂ ion treatment to form a SiO ₂ layer 34. Thereafter, a fluorine-based water repellent treatment agent (manufactured by Daikin; Optool DSX) was deposited to form a water repellent treatment portion 35, which was taken out of the vacuum chamber to complete the water repellent treatment (FIG. 7B).

In this vacuum chamber, the rigid member 31 by sputtering, by irradiating O ₂ ions in the high-rigidity member 31 surface to form a SiO ₂ thin film 34, deposition of the water-repellent layer 35 onto the SiO ₂ film 34 These were performed using a film forming apparatus as shown in FIG. Reference numerals 302 to 304 in the figure denote stations arranged around the drum 301.

  Next, nozzle processing was performed from the surface opposite to the water repellent treated surface by excimer laser to form nozzle holes (FIG. 7C). The mask 51 was removed, and a nozzle plate was produced leaving a non-water-repellent part that was not partly water-repellent (FIG. 7D).

  Using this nozzle plate, a recording head was assembled as shown in FIG. 1, and a head for IPSiO G-707 (Ricoh inkjet recording apparatus) was produced.

Using the produced head, it was mounted on IPSiO G-707, and a positive charge was applied to the nozzle plate to perform a print test.
In the implemented print test, solid printing that continuously ejects ink from all ejection ports on A4 size recording paper is continuously performed, and whether ink droplets generated from ink mist are drawn into the nozzles and non-ejection occurs. Observed. The non-ejection was observed by visually confirming white lines (non-ejection) of solid printing.

[Example 2]
In the print test of Example 1, a print test was performed in the same manner with negative application to the nozzle plate, and the occurrence of white streaks was evaluated. This print evaluation was performed under the condition that excessive ink mist was generated.

  In this embodiment, mist adheres to the vicinity of the nozzle on the 20th sheet and ink is not ejected, and some white streaks are observed. However, in normal 5% duty printing, before ink non-ejection occurs. Since the nozzle surface was wiped by automatic cleaning, it was confirmed that white streaks do not occur in continuous printing.

In addition, compared with Example 1, the mist was likely to adhere to the vicinity of the nozzle because the ink mist used in this experiment was negatively charged, so that the water repellent portion and the non-water repellent portion of the nozzle plate Therefore, it is considered that the ink mist was easily attracted electrostatically because the vicinity of the water repellent treated nozzle was relatively positively charged.
In addition, the attached mist grows and grows, and at the same time, it becomes easy to move on the water-repellent surface and gradually moves to the more hydrophilic non-water-repellent surface, so it does not immediately hit the nozzle edge. .

[Example 3]
In the print test of Example 1, a print test was similarly performed with the nozzle plate grounded, and the occurrence of white streaks was evaluated.

[Comparative Example 1]
In the print test of Example 1, a print test was similarly performed with the nozzle plate electrically insulated, and the occurrence of white streaks was evaluated.

[Comparative Example 2]
In the production of the nozzle plate of Example 1, a mask was not used at the time of water repellent treatment, and a nozzle that was uniformly water repellent treated was used on the entire surface, and the nozzle was processed in the same manner to produce a head.
Using the head, a print test was performed in the same manner as in Example 1 to evaluate the occurrence of white streaks.

[Comparative Example 3]
In the production of the nozzle plate of Example 1, a mask was not used at the time of water repellent treatment, and a nozzle that was uniformly water repellent treated was used on the entire surface, and the nozzle was processed in the same manner to produce a head.
A print test was conducted in the same manner as in Example 1 with the nozzle plate electrically insulated using this head, and the occurrence of white streaks was evaluated.

[Example 4]
In the production of the nozzle plate of Example 1, the mask 51 is not formed at the time of the water repellent treatment, the water repellent treatment is uniformly performed on the entire surface, and after the nozzle processing, the excimer laser is irradiated from the water repellent treatment surface side to repel the surface. The water treatment agent was removed, and a nozzle plate having a non-water repellent treatment portion was produced.
Using this nozzle plate, a head was assembled in the same manner as in Example 1, and a print test was performed to evaluate the occurrence of white stripes.

  Table 1 shows the evaluation results in Examples 1 to 4 and Comparative Examples 1 to 3.

It is a disassembled perspective view which shows an example of the droplet discharge apparatus of this embodiment. It is a cross-sectional explanatory drawing along the liquid chamber longitudinal direction of the head part of the droplet discharge device of this embodiment. It is a principal part enlarged view of the head part of the droplet discharge apparatus of this embodiment. FIG. 5 is a cross-sectional explanatory view of a bi-pitch structure along the liquid chamber short direction of the head portion of the droplet discharge device of the present embodiment. FIG. 4 is a cross-sectional explanatory diagram of a normal pitch structure along the lateral direction of the liquid chamber of the head portion of the droplet discharge device of the present embodiment. It is an expanded sectional explanatory view of the nozzle plate of the droplet discharge device of this embodiment. It is process drawing which shows an example of the manufacturing process of the nozzle plate of this embodiment. It is a figure for demonstrating the effect which prevented the recursion to the nozzle of the ink liquid splash in this embodiment. It is a configuration diagram of a film forming apparatus of the SiO ₂ film and the water-repellent film used in Examples.

Explanation of symbols

1 flow-path plate 2 diaphragm 3 the nozzle plate or the nozzle plate 4 nozzles 6 pressurized liquid chamber 12 piezoelectric element 30 nozzle member 31 flow-path plate member 32 adhesive 33 nozzle plate member 34 coupled layer (SiO ₂ film)
35 Water repellent layer 40 Water repellent treatment layer 51 Mask 301 Drum 302 Si sputter 303 O ₂ ion gas 304 Vapor deposition of OPTOOL DSX (fluorine resin manufactured by Daikin Industries, Ltd.)

Claims (3)

A droplet discharge device having a nozzle plate of a discharge port member in which nozzles that are discharge ports for discharging droplets are arranged,
The nozzle surface of the nozzle plate is
A water repellent treatment portion including a region in which the nozzles are arranged and being water repellent treated with an electrically insulating water repellent material;
A non-water-repellent treatment part that is formed in a region between the nozzle array region and the peripheral edge of the nozzle plate and is not water-repellent with the water-repellent material,
The area where the nozzles are arranged is water-repellent with the water-repellent material between adjacent nozzles,
The non-water-repellent treatment part is grounded and configured to have a potential difference from the water-repellent treatment part by the grounding .   2. The droplet discharge device according to claim 1, wherein the non-water-repellent treatment part is provided on both sides of the region spaced from the region where the nozzles are arranged. 3. Image forming apparatus equipped with the liquid droplet ejection apparatus according to claim 1 or 2.

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