JP2000127385A - Ink jet recording head and ink jet recorder employing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging of nozzle by providing means for ejecting ink depending on an image signal and sustaining an unsealed state, means for shielding a seal liquid and an opening for passing ink thereby sustaining the state of the seal liquid and the size of an ink drop being ejected constantly. SOLUTION: An ink jet recording head comprises a face 11 provided with an ink ejection opening 13, an ink chamber 12 continuous to an ejection opening 13 and provided with an ink ejecting means 14 on the circumferential side wall face, a holding means 20 disposed at the outer fringe part of the ejection opening 13, a seal liquid 2 for preventing the ink 1 in the ejection opening 13 from touching the air, an opening 52 for passing ink, and a sealing means 51 covering the seal liquid 2. The ink ejecting means 14 ejects ink depending on an image signal and the ejection opening 13 is unsealed when ink 1 is ejected. The liquid 2 is arranged in a gap defined by the sealing means 51 and the face 11 by injecting it using a liquid filler or a tube or by applying it using a brush, a cloth or a blade.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus which performs printing by discharging droplets such as ink drops on a surface to be printed.

[0002]

2. Description of the Related Art A typical example of an ink jet recording system for performing printing by ejecting droplets, particularly ink drops, onto a surface to be printed is a system using a nozzle. There are on-demand type and continuous flow type. The on-demand type is a system in which ink is intermittently ejected from nozzles in accordance with recording information to perform printing, and typical examples include a piezoelectric element system and a thermal system. The piezoelectric element method is to apply a pulse voltage to the piezoelectric element attached to the ink chamber to deform the piezoelectric element,
By changing the ink liquid pressure in the ink chamber and ejecting ink drops from nozzles, dots are recorded on recording paper. In the thermal method, ink is heated by a heating element provided in an ink chamber, and an ink drop is ejected from a nozzle by a bubble generated thereby to record dots on recording paper. On the other hand, in the continuous flow type, ink is continuously ejected from a nozzle by applying pressure to the ink, and at the same time, vibration is applied by a piezo vibrator or the like to form a protruding ink column into a droplet, which is further selectively applied to the droplet. The recording is performed by charging and deflecting the image.

In these ink jet recording apparatuses, it is a major problem to prevent nozzle clogging due to drying and thickening of ink during non-operation, and various ink materials have been developed for that purpose. However, it is still difficult to reduce the evaporation of the ink solvent. In a commercially available ink jet recording apparatus, at the time of non-printing or during a long period of non-operation, the nozzle and the outside air are shielded by a capping means made of resin or the like to delay the drying. However, in order to more effectively increase the airtightness by this capping means, complicated procedures and equipment are required, and since the nozzles cannot be completely shielded from the air, the ink of the nozzles during storage can be removed. Drying and thickening gradually progress, and nozzle clogging occurs. After all, currently available inkjet recording apparatuses require various maintenance operations in order to recover nozzle clogging due to long-term suspension.

Japanese Patent Application Laid-Open No. 52-104130 discloses a means for avoiding the problem related to clogging after a long-term suspension of a printing apparatus.
Japanese Patent Application Laid-Open Publication No. H11-163555 discloses a method of sealing ink and air with a relatively simple method of sealing an ink discharge port by means of a film of sealing liquid insoluble in ink and sealing liquid on the surface of the ink to prevent drying of the ink. Means are shown. But,
This method has been found to have the following disadvantages. That is, in the above method, the ejected ink is
Although the seal liquid penetrates the seal liquid film covering the ink surface, the state of the seal liquid changes variously and does not maintain a constant state, so that the resistance at the time of ejection is not constant. For example, a state in which the seal liquid is opened by the first discharge and the discharge port is not covered with the seal liquid (a state in which the seal is broken) occurs. Immediately after that, the droplet is discharged in that state. When the discharge is stopped, the seal liquid around the discharge port gradually starts to form a film on the ink surface. further,
Even after the ink discharge ports are covered with the seal liquid, the thickness of the seal liquid film is not constant until a sufficient time has elapsed and the initial state is completely restored. As described above, when ink is selectively ejected on demand in accordance with an image signal, the state of the seal film is not constant depending on the elapsed time since the last ink droplet passage. Since the ink droplets are ejected through the seal film, the resistance at the time of ejection differs depending on the thickness of the seal liquid and the presence or absence of the seal liquid. As a result, in continuous ejection or intermittent ejection in accordance with image information, the ejection speed of ink droplets and the diameter of ink droplets change, causing defects such as dot disorder and a decrease in density in a printed image. Is low.

Japanese Patent Application Laid-Open No. Sho 63-242644 discloses a method in which a magnetic fluid is used as a seal liquid, and printing is performed by droplets from nozzles penetrating a film of the magnetic fluid. However, since magnets are required to hold the magnetic fluid and high-precision magnetic field control means are required, there are drawbacks such as the complexity of the print head and the increase in the number of parts, which makes the equipment expensive. are doing.
On the other hand, JP-A-49-115548 and JP-A-54-69436 disclose a method of supplying a seal liquid in order to improve the ejection stability of ink droplets in a liquid seal method. A method has been proposed in which the path is opened and closed to maintain a state in which the seal liquid does not cover the ink surface during the ejection operation and to maintain a state in which the seal liquid is covered by the seal liquid when the ejection is stopped. However, this method requires a switch or the like to switch between the above two states, resulting in a complicated head and an increase in the size of the printing apparatus.

Japanese Patent Application Laid-Open No. Hei 5-177841 discloses a method in which nozzle capping by a magnetic fluid is performed in conjunction with carriage movement. But,
This method also inevitably increases the complexity of the head and the size of the printing device. As described above, the conventional method of sealing a nozzle with a sealing liquid has a problem that the quality of a printed image is low due to a problem in the stability of ink ejection, and this problem is avoided. Therefore, in order to maintain the state where the nozzle is not covered with the seal liquid only at the time of ink ejection, a switch for opening and closing the seal liquid supply path and an external force for interlocking the carriage with the nozzle capping and the carriage are required. There is a major drawback that the printing device becomes large and complicated, for example, it becomes necessary. However, there has not yet been a technique for achieving both the prevention of nozzle clogging and the ejection performance of ink, or the stabilization of ejection performance without using a switch or external force as described above.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for sealing a nozzle with a sealing liquid, such as an external force or a switch. Inkjet that can prevent nozzle clogging while maintaining the size of the ejected ink droplets by keeping the state of the seal liquid at the time of ink ejection constant without using an additional device It is an object of the present invention to provide a recording head and to provide an ink jet recording apparatus having such an ink jet recording head.

[0008]

The above object can be attained by providing the following ink jet recording head and an ink jet recording apparatus provided with the ink jet recording head. (1) an ink discharge port, a seal liquid for sealing the ink discharge port, ink discharge means for discharging ink in accordance with an image signal and releasing the seal of the ink discharge port at the time of ink discharge, and a seal for the ink discharge port An ink jet recording head, comprising: holding means for holding a released state; and shielding means having an opening through which ink passes and covering the sealing liquid. (2) an ink ejection port, an ink ejection means for ejecting ink in accordance with an image signal, and releasing the seal of the ink ejection port with a sealing liquid at the time of ink ejection, and a predetermined gap from the ink ejection port; An ink jet recording head comprising: a shielding unit having an opening through which ink passes; and a holding unit for holding a state in which the seal of the ink ejection port is released. (3) Conveying means for conveying the image recording medium, an ink jet recording head for ejecting ink to the image recording medium conveyed by the conveying means to record an image, and an image signal input for inputting an image signal to the ink jet recording apparatus Means, wherein the ink jet recording head is the ink jet recording head according to (1) or (2).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have observed the discharge phenomenon in a state where the seal liquid is arranged in the ink discharge port, and as a result, have found that the discharge liquid opens the seal liquid. The present invention is based on finding a means capable of maintaining the state of the sealing liquid once opened. When ink is ejected while the ink ejection port is covered with a seal liquid (for example, Japanese Patent Application Laid-Open No. 52-10413).
No. 0), the ejected ink droplets open a seal liquid film covering the ink surface. When the ejection of the ink droplet is stopped, the seal liquid around the ejection port gradually starts forming a seal film on the ink surface. When selectively ejecting ink on demand according to an image signal, depending on the elapsed time from the previous ink ejection, the seal liquid is not re-supplied as a film over the ink ejection port,
It may be closing due to resupply from the surroundings. Further, even when the ink discharge ports are covered with the sealing liquid, the thickness of the sealing film is not constant. That is, the state of the seal film varies and is not constant. Since the ink droplets are ejected through the seal film, the state of the seal film, for example, whether or not the seal liquid exists on the ink ejection port, or if it exists, the ejection resistance of the ink droplet depends on the thickness of the seal film. It will be different. When continuous ejection or intermittent ejection is performed in accordance with image information, the ejection resistance during that time is not constant, so the ejection speed of ink droplets and the diameter of ink droplets change and become unstable, resulting in dot disturbance and density fluctuation in the printed image. Defects such as deterioration will occur.

In the ink jet recording head of the present invention, an ink discharge port (hereinafter, may be simply referred to as "discharge port") and a seal liquid for sealing the ink discharge port (hereinafter, may be simply referred to as "seal liquid"). ), An ink discharge means for discharging ink in accordance with an image signal and releasing the seal of the ink discharge port at the time of ink discharge (hereinafter, may be simply referred to as “discharge means”), and a seal for the ink discharge port. Holding means for holding the state where
It may be simply referred to as “holding means”. ) And shielding means (hereinafter, sometimes simply referred to as “shielding means”) having an opening through which ink passes and covering the sealing liquid. In the present invention, by providing the holding means, the ink can be continuously discharged without a change in the discharge resistance in a state where the seal with the seal liquid is released, and the ink discharge according to the image signal is performed. No matter what time interval occurs, maintaining the unsealed state will reduce the quality of the printed image due to the ejection resistance of the ink droplets caused by the change in the state of the seal liquid as described above. Can be avoided. Further, in the present invention, the provision of the shielding means makes it possible to easily control the thickness of the seal liquid and to prevent foreign substances from entering the ink discharge ports.

According to the present invention, as a result of observing the discharge phenomenon in a state where the seal liquid is arranged in the ink discharge port, the inventors have found that the seal by the seal liquid is released by the discharge of the ink. In this state, means for enabling continuous discharge in the state described above has been found. This means, once the seal liquid is unsealed,
This state is maintained by the surface tension, wetting, etc. of the sealing liquid. The unsealed sealing liquid tends to close by wetting, but the wetting is delayed by the holding means. A printed image formed by ink ejected while the state in which the seal is released is maintained is free from dot disturbance, density reduction, and the like, and a clear printed image can be output. After printing, the seal liquid, whose seal has been released, gradually wets the holding means, forms a seal film again on the ink surface, and suppresses the drying of the ink in the ink discharge port for a long period of time to prevent clogging. That is,
In the present invention, a state in which the sealing liquid can be stably discharged while the seal is released can be ensured by the holding means for a sufficiently long time in practical use. As a result, it is possible to supply an inkjet printhead that prevents nozzle clogging and achieves ink ejection performance without using additional devices such as external force and switches, and does not cause any problems due to long-term suspension of the printing device. Became.

Further, according to the present invention, there is provided a shielding means having an opening corresponding to the ink discharge port. Since the shielding means regulates the surface of the sealing liquid, a certain amount of the sealing liquid can be supplied. This also has the effect that the film thickness can be easily controlled. Further, since the shielding means is located outside the ink discharge port and the seal liquid layer,
It also has the effect of preventing the sealing liquid layer from being broken by foreign matter / paper jam from the outside and the foreign matter from entering the ink ejection port. Further, by providing the openings of the shielding means so as to correspond to the individual ink discharge ports, the seal liquid level is separated from the other nozzles. It also has the effect of not receiving any. Further, by making the opening of the shielding means correspond to a plurality of ink ejection ports, there is an advantage that an in-line high-density ink ejection port can be provided.

Next, the ink jet recording head of the present invention will be described in detail with reference to the drawings. In the following embodiments, for convenience, a diagram in which the ink ejection ports 13 are arranged on the upper side is shown. However, the ink ejection direction, that is, the arrangement direction of the recording heads can be appropriately selected as desired. Is ejected in the direction of gravity (downward).
First, referring to FIGS. 1A and 1B, an embodiment in which a holding unit is provided on a surface provided with ink ejection ports, which is one of the basic structures of the ink jet recording head of the present invention, will be described. FIG. 1A is a cross-sectional view thereof, and FIG.
FIG. 2A is a plan view viewed from a direction A. FIG.
(A), the ink jet recording head shown in FIG. 1 (B) has an ink discharge port 13, a surface 11 provided with the ink discharge port 13, an ink chamber 12 connected to the ink discharge port 13, and a peripheral wall surface of the ink chamber. The provided ink ejection means 14 and the holding means 20 provided at the outer edge of the ink ejection port (the holding means here does not indicate a holding means having a specific structure, but may be an individual one as described below. The holding means is conceptually shown.), And the ink ejection port 13
A seal liquid 2 for sealing the ink 1 inside the container so as not to contact the air, and an opening 5 through which the ink passes.
2 and a shielding means 51 for covering the sealing liquid. Although the ink discharging means shown in FIG. 1A is provided on the peripheral wall surface of the ink chamber, it is not always necessary to provide the ink discharging means on the peripheral wall surface, and may be provided on a part of the bottom surface. The same applies to other inkjet recording heads described below.

FIGS. 2A and 2B are views showing another embodiment of the ink jet recording head of the present invention, in which a holding means is provided in a shielding means.
2A is a cross-sectional view thereof, and FIG. 2B is a sectional view of FIG.
2 are plan views as seen from the direction of FIG. FIGS. 3A and 3B show another basic configuration of the ink jet recording head of the present invention, in which the holding means is provided on both the surface provided with the ink discharge ports and the shielding means. FIG. FIG. 3A is a cross-sectional view thereof, and FIG.
(A) is a plan view as seen from the direction of C. FIG.
Are provided with a plurality of ink discharge ports, each discharge port is sealed with a seal liquid, and as a shielding means placed on the seal liquid, openings 52 are individually provided corresponding to each ink discharge port.
An example of an ink jet recording head using the shielding means provided with is shown as a perspective view with the shielding means removed.

The ink discharging means 14 which can be used in the present invention can be used without limitation among various types of ink discharging means used in a conventional ink jet recording head, such as a thermal method and a piezoelectric element method. it can. In the ink jet recording head, the ink chamber 1 is supplied by a capillary force or a pressure difference from supply means (not shown).
2 is supplied with ink 1. In the thermal method, ink is heated by a heater in the ink chamber 12 or in an ink flow path leading to the ink chamber in accordance with an image signal, and volatile components contained in the ink evaporate instantaneously to generate bubbles and eject ink. I do. In the piezoelectric element method, an ink chamber or a wall constituting an ink flow path communicating with the ink chamber is formed of a member through which deformation of the piezoelectric element can be propagated, and an electric field is applied to the piezoelectric element in accordance with an image signal. Discharges ink by distortion.

As the sealing liquid 2 usable in the present invention, since the sealing liquid performance is maintained, the sealing liquid and the ink are not compatible with each other, and the sealing liquid does not spontaneously emulsify with the ink. is necessary. In order for the sealing liquid to be incompatible with the ink,
Specifically, the solubility of the sealing liquid in the ink at room temperature (25 ° C.) may be 0.1 wt% or less. further,
It is necessary that the sealing liquid is non-volatile at room temperature so that the sealing liquid does not evaporate while the head is at rest. Non-volatile at normal temperature means that the vapor pressure at 25 ° C. is 0.1 mmHg or less. The kinematic viscosity of the sealing liquid which can be used in the present invention is in the range of 1 to 100 mm ² / s, it is desirable to reduce the resistance for discharge or less 50 mm ² / s. The surface tension of the sealing liquid that can be used in the present invention can be used as long as it is in the range of 15 to 70 mN / m.
mN / m or less, and desirably less than the surface tension of the ink used. It is needless to say that any liquid suitable for these properties can be used, but a plurality of materials can be mixed to adjust the viscosity and the surface tension before use. An organic solvent or oil that is liquid at room temperature can be used as the sealing liquid when using aqueous ink. For example, hydrocarbons such as octane, nonane, tetradecane and dodecane, higher fatty acids such as oleic acid and linoleic acid, water-insoluble alcohols such as n-decanol and dimethylbutanol, plasticizers such as dibutyl phthalate and dibutyl maleate And vegetable oils,
Mineral oil, silicone oil, fluorine oil and the like can also be used. These may be used alone or in combination of two or more as long as they can be mixed uniformly.

In the present invention, as shown in FIG. 4, the seal liquid is arranged so that the ink 1 inside the ink discharge port 13 does not contact the outside air. The sealing liquid is injected into a gap formed by the surface 11 provided with the ink discharge ports and the shielding means 51 from a dropper or a pipe, a brush, a cloth,
It is arranged by means such as coating with a blade. Alternatively, it may be arranged by a capillary force, a surface tension, or a pressure difference from a surface 11 on which the ink ejection ports are arranged or a tube or a porous member arranged near the surface of the head. The seal liquid supplied to the surface 11 of the head by these methods comes into contact with the ink 1 in the ink discharge port 13 to form a film of the seal liquid on the ink surface. The film thickness of the sealing liquid can be appropriately selected depending on the surface tension and viscosity of the ink, the discharging means, the nozzle diameter, the storage period for preventing clogging, and the like.
It is preferably not less than μm and not more than 100 μm. The film thickness of the sealing liquid can be adjusted by regulating the supply amount or the holding amount depending on the shape around the head.

The shielding means 51 in the ink jet recording head of the present invention may have any thickness and material as long as it has an opening through which ink droplets pass. The opening of the shielding means should preferably have a small opening area in order to effectively prevent foreign substances from entering from the outside. Further, in order to prevent the liquid level from being affected by the adjacent ejection ports, the openings 52 may be individually opened corresponding to the individual ink ejection ports as shown in FIG. As shown in FIG. 5, slit-shaped openings may be provided so as to correspond to a plurality of discharge ports as shown in FIG. In order to correspond to the ejection port for each ink color, FIG.
A slit-shaped opening 52 is provided for each block as shown in FIG. Alternatively, when corresponding to ejection ports arranged in high density in-line according to the recording pixel density, as shown in FIG. 7, it is configured with slit-shaped openings 52 corresponding to a plurality of in-line ejection ports. Further, as another embodiment, as shown in FIG. 8, an opening may be formed by arranging two divided shielding means on both sides of a row of a plurality of discharge ports.

The shielding means in the present invention is not particularly limited in shape and the like, and has an opening through which ink passes.
Any material that covers the sealing liquid can be used. Further, as one aspect of the shielding means in the present invention, the shielding means has an opposing surface opposing the surface provided with the ink discharge ports. In this case, the holding means is provided on the facing surface. An example of such a shielding means is a plate. FIGS. 1 to 18 show a case where a plate is used as the shielding means, but the shielding means of the present invention is not limited to this. The shielding means in the ink jet recording head of the present invention may be of any thickness and material as long as it has an opening through which ink droplets pass. For example,
Various metal materials such as gold, platinum, cobalt, iron, copper, nickel, aluminum, stainless steel, titanium, glass,
Ceramic materials such as alumina, polyethylene resin, polypropylene resin, polyester resin,
A plastic material such as a polyimide resin, an acrylic resin, and a polycarbonate resin can be used alone or in combination. Further, the surface may be covered with a thin film of metal, resin, or the like for the purpose of protecting the surface in contact with the ink or the sealing liquid. In the present invention, the opening of the shielding means can be formed by laser processing, various types of etching, various types of mechanical processing such as punching and drilling, electric discharge machining, electroforming (electroforming), and the like. As the processing conditions, an optimum combination may be selected in consideration of the material of the ink ejection surface, processing accuracy, processing cost, and the like.

In the present invention, in order to break the seal by the seal liquid by the ink discharge means 14, the discharge of ink droplets is used as it is. In this case, the ink surface can be opened by pushing and spreading the liquid surface of the sealing liquid by the ejection of the ink droplet, or by skipping the sealing liquid together with the ejection of the ink. As a method of releasing the seal by the seal liquid, the ink discharge means 14 repeats a plurality of discharges under normal printing conditions, or the momentum of the discharged ink droplet so that the seal state is completely released by one discharge. Can also be increased. In the latter case, the ejection unit 14 can increase the speed of the ejected ink droplet by appropriately combining the application time of the pulse for driving the ejection unit, the applied voltage, the number of applications, the application period, and the like.

The ink ejection for releasing the seal by the seal liquid is to use the first ejection at the start of the printing operation or a plurality of ejections from the beginning as a so-called idle ejection for collecting the ink at the start of the printing to the absorber or the like. It is also possible to start printing after all seals of the seal liquid covering all the ink ejection ports on the head or the ink ejection ports of each block are released. According to this method, when a few to several tens of ejected ink droplets at the start of printing contain the sealing liquid, these ink droplets are not used for printing, so printing with stable recording dots from the start of printing can be performed. It becomes possible.

According to the observations made by the inventors, when the ink discharge port is sealed with a seal liquid, the seal liquid can be sealed by the ink discharge means as shown in FIG. It was observed that the end portion was spread and opened (the seal was broken) at the peripheral portion of the ink discharge port 13. If there is no holding means, the sealing liquid immediately starts to wet toward the center of the discharge port from this state (FIGS. 19A to 19B). Then, the ink surface inside the ejection port 13 wets (C),
Closed by the supply of the sealing liquid from the surroundings (FIG. 19)
(D)) After that, the state returns to the initial state while the thickness of the seal film increases (FIGS. 19E to 19F). As described above, when the holding means is not provided, the state in which the seal is released is not maintained.

In the present invention, the state where the seal of the ink discharge port is released means that the end of the seal liquid is maintained around the ink discharge port. That is, the end of the seal liquid is in contact with the solid wall surface outside the discharge port, and the seal liquid will spread from the wall surface toward the ink surface as shown in FIG. 19A or 19B. It is in the state that it is.

It is known that the phenomenon of wetting spread proceeds as the liquid passes over the energy barrier between the metastable state of wetting and the next metastable state (for example, Ono: surface tension, By providing a portion that resists wetting, it is possible to delay the advance of wetting at the end of the sealing liquid. That is, in order to maintain the state in which the sealing liquid has been released, a portion that is resistant to wet progress on the solid surface may be provided.

Hereinafter, the holding means in the present invention will be described in detail. The holding means in the present invention can be provided on the surface provided with the ink discharge ports, on the shielding means, or on both of them. In addition, when provided on the shielding means, in addition to an opposing surface (hereinafter, this opposing surface is referred to as a “shielding device seal side surface”) facing the surface of the shielding device on which the ink ejection ports are provided, and also inside the shielding device opening. It can also be provided on the peripheral side wall surface which is a wall surface. In the present invention, these holding means are formed in the form of slits provided with ink discharge ports or shielding means openings (openings are individually provided corresponding to the discharge ports, or provided corresponding to a plurality of discharge ports). ), And the state in which the seal is released for each discharge port or each opening of the shielding means may be maintained. Further, a common or integrated holding means may be provided at a plurality of discharge ports or shielding means openings arranged in a row or in a staggered manner to collectively hold a state where a plurality of discharge ports are unsealed. it can. For example, when a plurality of discharge ports are arranged in a line, an integrated (for example, band-shaped) holding means surrounding the line can be provided, and a plurality of openings are arranged in a line in the shielding means. In this case, an integrated (for example, band-shaped) holding means surrounding the row can be used. In the present invention, it is possible to provide the holding means both on the surface provided with the ink discharge ports and on the side surface of the shielding means seal, or on the peripheral side wall surface of the shielding means opening.

First, the holding means is shown in FIGS.
As shown in (B), a basic configuration formed on the surface on which the ink ejection ports are provided will be described. One embodiment is a holding means provided around the discharge port. In the inkjet recording head of the present invention, when the holding unit is provided around the ink ejection port, the holding unit needs to be present at least in a region where the seal is released by the ink ejection on the surface where the ink ejection port is provided. . The area where the seal is released is changed by the thickness of the seal liquid, the kinematic viscosity of the seal liquid, the discharge energy, etc., and is not uniquely determined, but as an example,
When the diameter of the ink discharge port is 50 μm, the kinematic viscosity of the seal liquid is 30 mm ² / s, the film thickness of the seal liquid is 50 μm, the applied voltage to the heater serving as the discharge means is 12 V, and the application time is 8 μs, about 225 μm from the center of the discharge port Area.
That is, the sealing state with the sealing liquid has been broken up to a region of about 200 μm from the periphery of the discharge port. Further, even in the case of an inkjet recording head having a triangular (circumscribed circle diameter of 50 μm) ejection port, the area where the seal has been released is
It was approximately 225 μm from the center of the circumcircle of the discharge port. Further, the position where the holding means is provided may be provided also in a region outside the region where the seal is released by the ink discharge, and further, the holding means may be provided in a portion connecting the ink discharge port to the ink chamber or a peripheral side wall surface of the ink chamber. For example, a wetting resistance region may be provided.

Next, a specific embodiment of the holding means itself will be described. In order to form a portion that becomes resistant to wetting around the ink ejection port, as shown in FIG.
In the surface provided with the ink ejection port, the ink ejection port 1
Steps such that the height of the surface 3 and the outer edge thereof are lower than those of the other surfaces, or as shown in FIG.
On the surface where the ink discharge port 13 is provided, a step is provided such that the height of the surface of the ink discharge port 13 and the outer edge thereof is higher than the other surfaces, or the ink is formed as shown in FIG. On the surface provided with the discharge port 13, a groove is provided at a position slightly away from the periphery at the outer edge of the ink discharge port 13, and further, on the surface provided with the ink discharge port as shown in FIG. It is possible to use a method of designing a shape having a concave or convex portion on the surface where the ink ejection port is provided, such as providing a projection at a position slightly away from the peripheral edge at the outer edge of the ejection port 13. The unevenness may be triangular, and the groove may be V-shaped. However, in the case where a convex step is provided as shown in FIG. 9B with respect to the surface on which the ink discharge ports are provided, or in the case where a convex protrusion is provided as shown in FIG. In order for the seal to close on its own, the height of the step from the head surface or the height of the projection must be lower than the film thickness of the seal liquid.

Further, as the holding means provided around each ink ejection port, a plurality of grooves or projections may be continuously provided on the outer edge of the ink ejection port as shown in FIG. 10 or FIG. When a plurality of grooves and projections are provided, the time required to return to the sealed state can be further lengthened. In the case of the holding means using the uneven shape of the surface provided with the ink discharge ports as shown in FIGS. 9A to 11 described above, the microscopic contact state of the seal liquid end is discontinuous. , The resistance to the spread of wetness is generated, and the state in which the seal is released can be maintained for a certain period of time. Further, when viewed from the direction A in FIG. 1 (A), the portion which becomes resistant to the above-mentioned wetting, for example, as viewed in the direction A, has a resistance to the advance of the whole as a whole even though it is partially missing like a letter C. Although it has, the one that is formed in a perfect annular shape,
The effect of wetting resistance is great. In the present invention, examples of a method for forming the uneven shape as the holding means include laser processing, various types of etching, and mechanical processing. As the processing conditions, an optimum combination may be selected in consideration of the material of the ink ejection surface, processing accuracy, processing cost, and the like.

Next, a case will be described in which the holding means is a holding means formed of a region having low wettability with respect to the seal liquid, formed on the surface provided with the ink discharge ports. FIG. 12 shows an example of the ink ejection port 1 as an example.
3 shows an ink jet recording head in which a holding means comprising a wetting resistance region 21 is arranged at the outer edge of the ink jet recording head. As shown in FIG. 13, in the wetting resistance region 21, the contact angle θe between the sealing liquid 2 and the wetting resistance region 21 is increased to prevent the wetting of the sealing liquid 2, so that the sealing liquid 2 as shown in FIG. Is delayed on the surface of the wetting resistance region 21, and the state in which the sealing liquid is released is maintained for a certain period of time. The wetting resistance region 21 may be formed by coating a film having low wettability with the seal liquid on the outer edge of the ink discharge port 13 or may be made of a material having low wettability of the seal liquid only in the peripheral portion of the ink discharge port. . From the results of the inventors observing the wetting of the sealing liquid,
Surface 1 provided with ink ejection ports as shown in FIG.
1, a wetting resistance region 2 around the ink ejection port 13
By setting the contact angle θe between 1 and the sealing liquid 2 to be large, it was confirmed that the wetting resistance region became resistant to the spreading of the sealing liquid. The greater the contact angle θe, the greater the delay effect on the wetting advance. However, it is preferable that the contact angle θe be 10 degrees or more. The advance of the wetting of the sealing liquid depends on the kinematic viscosity of the sealing liquid (the larger the wetting speed is slower), the surface tension (the larger the wetting speed is slower), the film thickness (the thinner wetting speed is slower), etc. Can be adjusted, but within the range of the seal liquid that can be used in the present invention, the larger the θe, the slower the wetting speed (the longer the time required for wetting), and as a result, the sealing liquid is released. The time during which the state can be maintained increases. In order to keep the unsealed state long enough for practical use so that several sheets can be printed with the unsealed state, it is more preferable to set the contact angle θe to 30 °.
It is sufficient to delay the wetting advance to a degree or more.

The wetting resistance region may be formed around the ink discharge port at a predetermined distance from the edge of the ink discharge port as shown in FIG. Alternatively, a plurality of wetting resistance regions may be provided as shown in FIG. When a plurality of wetting resistance regions are provided, each of the wetting resistance regions has resistance to the progress of the wetting of the sealing liquid. . Further, the above-mentioned wetting resistance region has a C
Although there is a resistance to the wetting progress as a whole, even if a part is missing like a letter "", the effect of the wetting resistance is greater if it is formed in a complete annular shape.

Although several examples of the holding means in the ink jet recording head of the present invention have been described, in the above-mentioned holding means, when a step is used, the higher (or deeper) the step is, the longer the time required for wetting advance. (The result is a long time to keep the seal unsealed)
In addition, it takes more time to advance the wetting when there are a plurality of grooves and projections than one, and when the number of the plurality of grooves and projections is larger, it takes more time to advance the wetting when the groove is deeper and when the projection is higher. Is long. In addition, the lower the wettability of the wetting resistance region, the longer it takes to advance the wetting. Therefore, in order to keep the state in which the seal is released for a long time, it is preferable to adopt the mode of the holding means as described above.

Next, a case where the holding means is provided as an integrated holding means on the surface on which the ink ejection ports are provided and around the row of the plurality of ink ejection ports will be described. An example of providing an integrated holding means is shown in FIGS. As a specific configuration of the holding means,
For example, taking FIG. 5 as an example, the AA cross section in FIG. 5 can be the same as the cross section shown in FIGS. 9A to 9D. That is, in the case of a step,
It is formed as a step that surrounds the row of ink ejection ports, and in the case of a groove or projection, it can be formed as a groove or projection that surrounds the row of ink ejection ports. Further, as described in FIG. 12, a band-shaped portion surrounding the row of ink ejection ports may be a wetting resistance region having low wettability to the seal liquid.
Further, similarly to the case of surrounding the outer edge of each ink ejection port (see FIGS. 10 and 11), a plurality of grooves or projections are formed.
It may surround a row of discharge ports. 5 and 7 are examples in which an integrated holding means is provided so as to surround a row in which a plurality of ink ejection ports are arranged, and the recording head in FIG. 6 is provided for each block having a plurality of ejection ports. This is an example in which an integrated holding means is provided. FIG. 7 shows an example in which integrated holding means surrounding discharge ports arranged in an inline manner is provided. Here, the term “surrounding” means not only a continuous band-shaped box, but also a discontinuous band-shaped box that is partially interrupted, and, as a whole, a box-shaped box. I do. Even in the case of a band having a cut in several places, it has an effect of maintaining the state in which the sealing liquid is released.

Next, the case where the holding means is provided on the side face of the shielding means seal will be described. One mode of the holding means provided in the shielding means includes a holding means provided at least around the opening of the shielding means. When the holding means is provided around the end of the opening on the side face of the shielding means seal (hereinafter referred to as "opening end"), the holding means is present at least in the area where the seal is released by ink discharge on the side face of the shielding means seal It is necessary to. The area where the seal is released is changed depending on the thickness of the seal liquid, the kinematic viscosity of the seal liquid, the discharge energy, and the like, and is not uniquely determined. For example, the diameter of the ink discharge port is 50 μm. The diameter of the opening is 70 μm, the kinematic viscosity of the sealing liquid is 30 mm ² / s, and the film thickness of the sealing liquid is 50 μm.
When the voltage was 12 μm, the applied voltage to the heater as the ejection means was 12 V, and the application time was 8 μs, the area was about 235 μm from the center of the opening. That is, about 200 μm from the periphery of the opening.
The sealing state by the sealing liquid was released up to the area of m. Although the basic configuration is shown in FIGS. 2A and 2B, FIGS. 15A and 15B show cases where the shielding means openings are individually provided corresponding to the ink ejection ports. (B)
As shown in (1), a mode in which the holding means is formed on the outer edge of each opening end can be adopted. FIG. 15A is a view of the shielding means viewed from the side surface of the seal. As a specific holding means, for example, as shown in FIG. 16A, a step is provided on the side face of the shielding means so that the height of the outer edge surface of each opening end is lower than the other surfaces. Figure 16
As shown in FIG. 16B, a step is formed so that the surface of the outer edge of each opening end is higher than the other surfaces, or each opening end is provided as shown in FIG. In the outer edge portion of FIG.
As shown in (D), a shielding means is provided so that the shape of the periphery of each opening end and the shape of the other portion are different, such as by providing a projection at a position slightly away from the periphery at the outer edge of each opening end. A method of designing the shape of the seal side surface so as to have an uneven shape can be used. Further, as shown in FIG. 16E, the outer edge of the end of the opening may be a wetting resistance region having low wettability to the sealing liquid. Further, as the holding means provided at the outer edge of each opening end, as described in the case where the holding means is formed on the surface provided with the ink discharge port (see FIGS. 10 and 11), the outer edge has grooves or grooves. A plurality of projections may be continuously provided. When a plurality of grooves or projections are provided, it is possible to further increase the time until the sealing state is released. Further, similarly to the case where the integrated holding means surrounding the plurality of rows of the ink discharge ports is formed, the integrated holding means surrounding the plurality of the rows of the openings can be formed.

In the holding means provided in the shielding means, when the opening of the shielding means is provided corresponding to a plurality of ink discharge ports, an integrated holding means is provided on the outer edge of the end of the opening. Can be provided. FIG. 17 shows a view of the shielding means in which the holding means is formed at the outer edge of the opening end as viewed from the side of the shielding means seal. The holding means in this case is the same as the case where the openings are individually provided corresponding to the ink discharge ports, and the holding means is formed at the outer edge of each opening end. Configuration holding means can be used. That is, in the case of a step, the outer edge of the opening end is formed as a step surrounding the opening, and in the case of a groove or projection, as the groove or projection surrounding the opening at the outer edge of the opening end. Can be formed. Further, on the side face of the shielding means seal, the outer edge of the opening end may be a wet resistance region having low wettability to the seal liquid. Further, similarly to the case where the holding means is provided at the outer edge of each opening end, a plurality of grooves or projections may surround the opening end.

Further, as a method of providing the holding means on the side of the shielding means, whether the openings are individually provided corresponding to the ink discharge ports or provided corresponding to the plurality of ink discharge ports Regardless, as shown in FIG. 18, it is also possible to adopt a method in which the peripheral wall surface of the opening of the shielding means has a peripheral wall surface having low wettability to the seal liquid. In this case, by setting the contact angle θe of the sealing liquid to the peripheral wall surface of the opening of the shielding means at 10 °, preferably 30 ° or more, a favorable wet spreading resistance region is formed.

Further, in the present invention, as a basic configuration, as shown in FIGS. 3A and 3B, the holding means can be provided on both the surface on which the ink discharge ports are provided and the shielding means side. The holding means formed on the surface on which the ink ejection port is provided and the shielding means side can be used by appropriately combining the above-described holding means. When the holding means is formed on both the surface on which the ink discharge ports are provided and the shielding means side,
With both holding means, the time during which the sealed state is released can be made longer, and the time can be controlled more finely. Holding means formed on the surface on which the ink discharge ports are provided and holding means provided on the shielding means side,
Although the above-described holding means can be appropriately selected, in the case where the openings are individually provided corresponding to the ink ejection ports, when the holding means is provided at the outer edge of each ink ejection port Preferably, the holding means provided on the surface of the shielding means is preferably provided at the outer edge of each end of the opening, and when the holding means integrated around a row in which a plurality of discharge ports are arranged is provided, It is preferable that the holding means on the side is also a correspondingly integrated holding means.

In the present invention, after the printing operation is completed, the seal liquid forms a seal film again by the surface tension, and the effect of preventing drying of the ink is maintained. The seal liquid held in a state where the seal is released is changed from a metastable state against wetting, that is, a state in which an end of the seal liquid is held in a part that is resistant to wetting, to an energy barrier of a wetting resistance part. The surface tension of the seal liquid overcomes and spreads in the direction of the ink liquid surface of the ink discharge port. The inventors have also observed through observation that the seal liquid held in a state where the seal has been released is wetted and spreads over the ink surface after a certain period of time. In the case where a step is provided as shown in FIG. 9A, the seal liquid is held at the corner of the step, and after a while, the film of the seal liquid has covered the ink ejection port. This phenomenon was repeatedly observed. When no holding means was used, the sealing liquid was immediately closed as shown in FIG. 19, whereas when the holding means was used, the sealing liquid was again released from the state where the seal was released. The time required to seal the ink ejection port was sufficiently long, and it was possible to stably perform ink ejection within this time. 9 (B) and 9
When a convex step or projection is provided as in (D), the end of the sealing liquid is held at the corner of the step, and the height of the step or projection from the surface where the ink ejection port is provided is reduced. It has been observed that higher values increase the time to reseal by the sealing liquid. In the case where the periphery of the ink discharge port is constituted by the wetting resistance region 21 as shown in FIG. 12, the end of the seal liquid 2 wets the surface of the wetting resistance region 21 over a certain period of time, and Sealing the outlet was observed. It was also observed that the larger the surface tension of the sealing liquid, the longer the time during which the seal was broken, for all holding means.

As described above, the time during which the seal is maintained in the released state depends on the height of the step or the protrusion, the magnitude of the resistance to the wetting of the sealing liquid such as the contact angle of the sealing liquid in the wetting resistance area, or By properly selecting the surface tension of the sealing liquid, the film thickness of the sealing liquid, and the like, it is possible to adjust from several seconds to several tens of minutes. In addition, it was confirmed that the sealing liquid was closed without using any external force in any of the holding means. That is, the sealing liquid is released from the sealing state by the discharging means, and the time until the sealing film is formed again by the surface tension of the sealing liquid while being held in the metastable state by the holding means is delayed. By setting the delay time longer than the series of printing operation times, it is possible to stably maintain the ink ejection while keeping the seal liquid unsealed. Also,
If the delay time is set to several tens of seconds to several minutes, it is possible to print one or a plurality of recording papers during this time. If the time required for one printing is longer than the time during which the unsealed state is maintained, the first ink ejection is performed for each printable sheet during the time when the unsealed state is maintained. If the operation is set so as to perform the above-described idle discharge and the operation of collecting the ink is performed, the stable ink discharge can be similarly performed.

In the conventional means, an external force is required to maintain the state where the seal is released by the seal liquid at the time of discharge, or a switch or the like is required. Although it was possible to discharge ink and print by passing the seal liquid without using these external forces or switches, printing was possible, but the state of the seal was not constant, and the state of the seal liquid was not constant. The printed image was disturbed even during the printing of one sheet. ADVANTAGE OF THE INVENTION According to this invention, it can hold | maintain the state which the seal | sticker by the sealing liquid was released, without using external force, and can perform stable printing during this period. In addition, the ink ejection port can be sealed with the sealing liquid without using an external force, and clogging can be prevented for a long time.

As described above, in the ink jet recording head of the present invention, an example in which the sealing liquid is previously arranged on the ink jet recording head has been described. However, in the present invention, in addition to the above-described ink jet recording head, It is also possible for the user to supply the sealing liquid during use. The sealing liquid is supplied to the surface 11 of the head where the ink discharge ports are arranged in advance by a means such as liquid injection from a dropper or a pipe or application by a brush, cloth, or a blade. Alternatively, from the surface 11 of the head where the ink discharge ports are arranged, or the gap between the shielding means 51 and the head surface 11, or a tube or a porous member disposed near the surface of the head, the capillary force, the surface tension, or the pressure difference May be supplied. Of course, the same effects as described above can be obtained even when the user supplies the sealing liquid during use.

According to the present invention, there is also provided a conveying means for conveying an image recording medium, an ink jet recording head for recording an image by discharging ink onto the image recording medium conveyed by the conveying means, and an image recording method for the recording head. The present invention also relates to an ink jet recording apparatus including an image signal input unit for inputting a signal, and an ink jet recording apparatus using the ink jet recording head described in detail above. The ink jet recording apparatus according to the present invention has an effect that by incorporating the ink jet recording head according to the present invention, a maintenance step such as a vacuum which is conventionally essential can be reduced or omitted.

[0042]

The present invention will be described in more detail with reference to the following examples.
However, the present invention is not limited thereto.
Absent. Example 1 In this example, the tag shown in FIGS. 1A and 1B is used.
Ip ink jet recording head and this head
The evaluation of the printing performance in the case of using and printing is shown. Discharge hand
As the step, use a thermal type by heating.
Was. Several types of silicone oils are used as the sealing liquid
(Kinematic viscosity 30 mm) ^Two/ S, surface
A tension of 20 mN / m and a specific gravity of 1.0) were used. This seal
Vapor pressure of liquid at 25 ℃ is less than 0.1mmHg and non-volatile
Gender. Also, it does not dissolve in the ink,
Was not compatible. In this embodiment, the seal has been released
As holding means for holding the state, FIG.
Make the outer edge of the ink ejection port wettable with the seal liquid.
Employ means to lower. Recording head body (ink chamber,
This refers to a portion provided with ink ejection means and the like. )
It is made of nickel and has an ink ejection port 13 having a diameter of 35 μm.
Holds an annular wetting resistance area 21 with a width of 5 μm in contact with the periphery
It is formed as a means. This wetting resistance region 21 is
This is the part where the wettability to the liquid is reduced. C
Ink ejection port to reduce wettability with
13 around the ink ejection port 13 on the surface provided with
Made of a fluororesin dissolved in a solvent in a predetermined part
After applying the coating material, it was dried to form a film.
In the present embodiment, before forming the resin film of the fluororesin
While the contact angle of the seal liquid of
In the area where the nitrogen-based resin film is formed (wet resistance area),
The antenna was 30 degrees or more. (Actually the wet progress is slow
Was. )

Next, a plate in which an opening having a diameter of 45 μm is formed by laser processing on stainless steel having a thickness of 30 μm so as to form a gap of 50 μm opposite to the surface on which the ink discharge ports are formed is used as shielding means. Arranged and supported. Thereafter, the sealing liquid is placed in the gap, and the thickness is set to 50.
A μm seal film was formed. In this state, a voltage was applied to the heater serving as the ink discharge means 14, and the state of ink discharge was observed under magnification. The ink used consisted of 60% by weight of water, 38% by weight of diethylene glycol and 2% by weight of a dye, and had a viscosity (viscosity coefficient) of 2.0 mPa · s and a surface tension of 40%.
This is an aqueous ink having a mN / m of 1.06 and a specific gravity of 1.06. First 4
When 10 shots of ink are ejected at kHz, the seal with the seal liquid is released, and the seal liquid is held in a state of partially covering the wetting resistance region 21 as shown in FIG. The state was observed to be maintained (for 60 seconds). When ink droplets were ejected in this state, stable ejection was possible. Thereafter, when the ejection was completed, the sealing liquid began to wet onto the ink ejection port 60 seconds after the first ejection, and the sealing liquid completely sealed the ink ejection port 61 seconds after the first ejection. While the sealing by the sealing liquid was released, even if the ejection frequency was changed from 2 Hz to 4 kHz, little variation was observed in the ejection speed of the ink droplets and the diameter of the ink droplets.

For comparison, ejection was performed under the same conditions using a head having the same configuration except that the holding means 20 (wetting resistance region 21) was not formed, and the state was observed. The seal was broken, but remained there for a short time. Observation was made of the time from when the discharge was actually stopped to when the liquid state began to return to the sealed state (the liquid level began to move), but the time was within 1 second.
In addition, when the ejection was performed while changing the ejection frequency from 2 Hz to 4 kHz, and the ejection speed of the ink droplet and the diameter of the ink droplet were measured, it was observed that the ejection speed and the diameter of the ink droplet varied greatly.

<Print Test 1> Using this head, an image signal was applied to print an image on A4 recording paper. When the printed image was enlarged and observed with a microscope,
Only a few dots from the recording dot corresponding to the first ejection of the ink ejection port, the dot diameter was smaller than the other parts,
This change was limited to a very small area of the whole and was not clearly recognized by the naked eye, so that there was almost no problem as to the overall image quality. After that, there was no change in the recorded dot diameter, and a clear image was recorded. further,
50 images were printed continuously for 10 minutes at a rate of 5 sheets for 60 seconds. When the images were observed,
Although the dot diameter was slightly small at the start of recording of the first ejection hole of every five recording papers, the other recording papers showed no variation in dot diameter and no decrease in density. A clear image was printed over the entire surface. In addition, there was concern about the impact on image quality due to the impact of a small amount of seal liquid with ink.However, there is a problem with the image quality, probably because the silicone oil used is colorless and transparent, or because the amount of flight is very small. There was no.

<Print Test 2> Using the head of this embodiment, the idle discharge of all the ink discharge ports was performed 10 times (4
10 discharges at 1 kHz), output one A4 image within 60 seconds from the first idle discharge, wait 2 seconds without printing (until 62 seconds after the first idle discharge), and then repeat Printing was repeated in a cycle. That is, the image was printed on the recording paper while performing the idle discharge of all the ink discharge ports at a rate of once every 62 seconds. When the printed image was enlarged and observed with a microscope, the dot diameter did not change even at the start of recording, and a clear image was recorded over the entire recording paper. It was also possible to print 10 sheets of A4 recording paper in 60 seconds. When the image was observed, no variation in dot diameter and no reduction in density was observed on all recording papers, and a clear image was printed over the entire surface.

<Printing Test 3> After leaving the head of this embodiment without capping for 10 days in an environment of a temperature of 25 ° C. and a relative humidity of 30% RH, the above (printing test As a result of performing the recording operation 2), clogging did not occur in all the ink discharge ports, and a clear image was recorded without any disturbance of the dots of the printed image. <Comparative print test> A print test under the same conditions as the above <Print test 3> was performed using a head having the same configuration except that the holding means 20 was not formed. Variations in diameter were seen. On all of the recording papers, unclear images were printed with some noticeable roughness.

Example 2 In this example, an ink jet recording head having a plurality of ink discharge ports and shielding means having openings corresponding to the plurality of ink discharge ports, and printing was performed using this recording head The evaluation of the printing performance in the case is shown. The recording head body is made of nickel and has ten ink ejection ports 13 each having a diameter of 35 μm and formed in a row at a pitch of 64 μm. Around the row of the ten discharge ports, a width of 2
A band-shaped integrated holding means (wetting resistance area) of 0 μm was provided. The center line of the band is located at 40 μm from the center row of the discharge ports. Other conditions are the same as in the first embodiment. In order to form a wetting resistance region, a coating material made of a fluorine-based resin dissolved in a solvent is applied to a predetermined portion around the ink ejection port 13 on the surface where the ink ejection port 13 is provided, and then dried. To form a film. In this embodiment, the contact angle of the sealing liquid before forming the resin film of the fluorine-based resin was 10 degrees or less, whereas the contact angle of the portion where the fluorine-based resin film was formed (wetting resistance region) was 3
It was 0 degrees or more. (The wetting actually slowed down.)
The thickness of the sealing liquid 2 is 50 μm on the surface 11 of the ink head thus prepared, on which the ink ejection ports 13 are arranged.
A shielding means having a width of 55 μm and an opening formed so as to surround the ten discharge ports was formed by laser processing on stainless steel having a thickness of 30 μm.

In this state, a voltage was applied to the heater serving as the ink discharge means 14, and the state of ink discharge was observed under magnification. First, when 10 inks are ejected at 4 kHz, the seal with the seal liquid is released, and the seal liquid is held in a state of partially covering the wetting resistance region 21 as shown in FIG. It was observed that the condition was maintained (60 seconds). When ink droplets were ejected in this state, stable ejection was possible. After that, when the ejection was completed, 6
After 0 seconds, the seal liquid began to wet onto the ink discharge port, and the seal liquid completely sealed the ink discharge port 61 seconds after the first discharge. While the seal was released, no variation was observed in the ink droplet ejection speed or the ink droplet diameter even when the ejection frequency was changed from 2 Hz to 4 kHz.

For comparison, ejection was performed under the same conditions using a head having the same configuration except that the holding means 20 was not formed, and the state of the ejection was observed. For a short period of time. Observation was made of the time from when the discharge was actually stopped to when the liquid state began to return to the sealed state (the liquid level began to move), but the time was within 1 second. In addition, when the ejection was performed while changing the ejection frequency from 2 Hz to 4 kHz, and the ejection speed of the ink droplet and the diameter of the ink droplet were measured, it was observed that the ejection speed and the diameter of the ink droplet varied greatly.

<Print Test 1> Using this head, an image signal was applied to print an image on A4 recording paper. When the printed image was enlarged and observed with a microscope,
Only a few dots from the recording dot corresponding to the first ejection of each ink ejection port had a smaller dot diameter than the other parts, but this change was limited to a very small area of the whole and it was not clearly recognized by the naked eye There was almost no problem with the overall image quality. After that, there was no change in the recorded dot diameter, and a clear image was recorded. Further, 50 images were continuously printed at a rate of 5 sheets for 60 seconds over a period of 10 minutes. At the time when the images were observed, the discharge holes of the first one sheet of the recording paper of every five sheets were printed. Although the dot diameter was slightly small at the start of recording,
Until the sheet, no variation in dot diameter and no decrease in density were observed, and a clear image was printed over the entire surface.

<Print Test 2> Using the head of this embodiment, the idle discharge of all the ink discharge ports was performed 10 times (4
10 discharges at 1 kHz), output one A4 image within 60 seconds from the first idle discharge, wait 2 seconds without printing (until 62 seconds after the first idle discharge), and then repeat Printing was repeated in a cycle. That is, the image was printed on the recording paper while performing the idle discharge of all the ink discharge ports at a rate of once every 62 seconds. When the printed image was enlarged and observed with a microscope, the dot diameter did not change even at the start of recording, and a clear image was recorded over the entire recording paper. It was also possible to print 10 sheets of A4 recording paper in 60 seconds. When the image was observed, no variation in dot diameter and no reduction in density was observed on all recording papers, and a clear image was printed over the entire surface.

<Printing Test 3> After leaving the head of this embodiment in an environment of an air temperature of 25 ° C. and a relative humidity of 30% RH for 10 days without capping, the above-mentioned printing test was performed without maintenance. As a result of performing the recording operation 2), clogging did not occur in all the ink discharge ports, and a clear image was recorded without any disturbance of the dots of the printed image.

<Comparative print test> A print test was performed under the same conditions as in <Print test 2> using a head having the same configuration except that the holding means 20 was not formed. The variation in dot diameter was observed.
On all of the recording papers, unclear images were printed with some noticeable roughness.

Embodiment 3 In this embodiment, the holding means in the embodiment 1 is replaced with the one shown in FIG.
The head was manufactured in the same manner as in Example 1 except that the groove was changed as shown in FIG. That is, an annular groove having a width of 3 μm and a depth of 2 μm was formed in a portion surrounded by concentric circles 5 μm and 8 μm apart from the periphery of the ink ejection port having a diameter of 35 μm. This groove can be formed by providing a protective film of a photoresist other than the portion where the groove on the head surface is provided, processing the whole by etching, and then removing the protective film. In the case of this embodiment, the etching treatment was performed so that the head material in the annular portion exposed to the etching was eroded by 2 μm. When the sealing liquid was applied to the head surface subjected to this treatment and the degree of wetting progress was observed, it was confirmed that the wetting of the end of the sealing liquid was again delayed after the wetting was temporarily delayed in this groove portion. . A seal liquid film of 50 μm was formed by supplying a seal liquid to the head, and a voltage was applied to a heater serving as an ink discharge means to observe the state of ink discharge in an enlarged manner. First 10 at 4kHz
When the ejected ink was ejected, the seal was broken, and it was observed that the seal liquid was retained in the groove portion. When ejection of ink droplets was continued in this state, it was confirmed that the ink droplets were maintained in a released state. Thereafter, when printing was completed, the seal liquid began to wet onto the ink discharge port 20 seconds after the first discharge, and the seal liquid completely sealed the ink discharge port 21 seconds after the first discharge. During that time, even if the ejection frequency was changed from 2 Hz to 4 kHz, no variation was observed in the ejection speed of the ink droplets and the diameter of the ink droplets.

Using the head of this embodiment, the idle discharge is performed once at the start of printing, an image is output within 20 seconds from the first idle discharge, and after 1 second without printing (the first empty Printing was repeated in the same cycle again (until 21 seconds after ejection). That is, the image was printed on the recording paper while performing the idle discharge of all the ink discharge ports at a rate of once every 21 seconds.
When the printed image was enlarged and observed with a microscope, the recorded dot diameter did not change, and a clear image was recorded over the entire recorded image. In the first 20 seconds of this cycle, printing of one sheet of A4 recording paper was completed, and after waiting for one second, idle ejection was performed, and the next recording paper could be printed. That is, in the present embodiment, the idle discharge is performed while the recording paper is fed, the sealing liquid is opened, and while the holding unit holds the state where the sealing state is released, the recording paper is discharged for one sheet. It was possible to repeat the completion of printing. Further, after the head was left in an environment of a temperature of 25 ° C. and a relative humidity of 30% RH for 10 days without capping, the above image was recorded. As a result, clogging occurred in all the ink discharge ports. As a result, a clear image was recorded without disturbing the dots of the printed image.

Embodiment 4 In this embodiment, in the same manner as in Embodiment 1, except that the holding means is provided on the sealing liquid side of the plate serving as the shielding means, instead of providing the holding means on the surface provided with the ink discharge ports,
An ink jet recording head was manufactured. That is, an annular wetting resistance region having a width of 20 μm was formed in contact with the periphery of the opening having a diameter of 45 μm. The method for forming the wetting resistance region was the same as in Example 1. A printing test was performed in the same manner as in Example 1, and similar results were obtained.

[0058]

As described above, according to the present invention, the seal by the sealing liquid is released by the discharge means, and the seal is released regardless of the time interval at which the discharge in accordance with the image signal occurs. , It is possible to eliminate fluctuations in the ejection resistance of ink droplets due to changes in the state of the sealing liquid. The seal liquid in the state where the seal is released starts to flow so as to cover the ink discharge port by the advance of the wetting, but the advance of the wet is delayed by the holding means, and the state where the seal is released can be maintained for a long time. Therefore, the holding means of the present invention can secure a practically sufficient time for outputting a clear printed image without causing dot disorder or density reduction in the printed image formed by the ejected ink. After printing, the sealing liquid, which has been released from the sealing state, wets the ink surface to form a sealing film again, and has an effect of continuously preventing drying of the ink. That is, it is possible to supply an ink jet recording head which prevents both clogging and ink ejection performance without using an additional device such as an external force or a switch, and which does not cause various problems due to long-term suspension of the ink jet recording apparatus. . Further, in the present invention, a shielding means having an opening corresponding to the ink ejection port is provided, and the shielding means regulates the surface of the sealing liquid, so that a fixed amount of the sealing liquid can be supplied. Is easily controlled. Further, since the shielding means is located outside the ink discharge port and the seal liquid layer,
It also has the effect of preventing the sealing liquid layer from being broken by foreign matter / paper jam from the outside and the foreign matter from entering the ink ejection port. Further, by providing the openings of the shielding means so as to correspond to the individual ink discharge ports, the seal liquid level is separated from the other nozzles. It also has the effect of not receiving any. Further, by making the opening of the shielding means correspond to a plurality of ink ejection ports, there is an advantage that an in-line ink ejection port can be provided. Further, the ink jet recording apparatus of the present invention incorporating the above ink jet recording head also has an effect that a maintenance step such as a vacuum which is conventionally required can be reduced or omitted.

[Brief description of the drawings]

FIG. 1 is a diagram showing one of the basic configurations of an ink jet recording head of the present invention, and FIG.
(B) is a plan view as seen from the A direction.

FIG. 2 is a diagram showing another basic configuration of the ink jet recording head of the present invention, and FIG.
FIG. 2B is a plan view seen from the B direction.

FIG. 3 is a diagram showing another basic configuration of the ink jet recording head of the present invention, and FIG.
FIG. 3B is a plan view seen from the C direction.

FIG. 4 is a diagram illustrating an example of an ink jet recording head of the present invention.

FIG. 5 is a diagram showing another example of the ink jet recording head of the present invention.

FIG. 6 is a diagram illustrating another example of the inkjet recording head of the present invention.

FIG. 7 is a diagram illustrating another example of the inkjet recording head of the present invention.

FIG. 8 is a diagram illustrating another example of the inkjet recording head of the present invention.

FIG. 9 is a diagram illustrating an example of a holding unit according to the present invention.

FIG. 10 is a view showing another example of the holding means in the present invention.

FIG. 11 is a view showing another example of the holding means in the present invention.

FIG. 12 is a view showing another example of the holding means in the present invention.

FIG. 13 is a diagram illustrating a contact angle between a seal liquid and a surface on which an ink discharge port is provided.

FIG. 14 is a view showing another example of the holding means in the present invention.

FIG. 15 is a view showing another example of the holding means in the present invention.

FIG. 16 is a view showing another example of the holding means in the present invention.

FIG. 17 is a view showing another example of the holding means in the present invention.

FIG. 18 is a view showing another example of the holding means in the present invention.

FIG. 19 is a diagram illustrating a state of the seal liquid when the holding unit is not used in the sealing of the ink discharge port with the seal liquid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink 2 Seal liquid 11 Surface on which ink ejection port is provided 12 Ink chamber 13 Ink ejection port 14 Ink ejection means 20 Seal liquid holding means 21 Wet resistance area 51 Shielding means 52 Opening

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Suwabe 430 Green Tech Nakai-cho, Nakai-machi Sakaigami-gun, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Yasushi Oki Yasushi 430 Green Tech Nakai-cho, Nakai-cho, Ashigara-Kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Term (reference) 2C056 EA17 JA24 2C057 AF74 AG14

Claims (30)

[Claims] 1. An ink discharge port, a seal liquid for sealing the ink discharge port, an ink discharge means for discharging ink in accordance with an image signal and releasing the seal of the ink discharge port at the time of ink discharge, and the ink discharge port An ink jet recording head comprising: a holding unit for holding a state in which the seal is released; and a shielding unit having an opening through which ink passes and covering the seal liquid. 2. An ink jet recording head according to claim 1, wherein said holding means is means for delaying advance of the wetting of the sealing liquid. 3. The ink jet recording head according to claim 1, wherein said holding means is provided on a surface provided with an ink discharge port. 4. The ink jet recording head according to claim 1, wherein said holding means is provided in said shielding means. 5. The ink jet recording head according to claim 1, wherein the holding unit is provided on a surface on which the ink discharge ports are provided and on a shielding unit. 6. The ink jet recording head according to claim 3, wherein the holding unit is provided at least around an ink ejection port. 7. An ink jet recording head according to claim 3, wherein said holding means is an integrated holding means surrounding a row of a plurality of ink ejection ports. 8. The ink jet recording head according to claim 4, wherein the holding unit is provided at least around an opening of the shielding unit. 9. An ink jet recording head according to claim 4, wherein said holding means is an integrated holding means surrounding a row of openings of a plurality of shielding means. 10. A method according to claim 1, wherein the holding means is formed by a step such that the height of the surface of the outer edge portion of the ink discharge port is lower than the other surface on the surface provided with the ink discharge port. The ink jet recording head according to claim 6, wherein: 11. The ink jet recording apparatus according to claim 11, wherein the holding means has a step in which the surface of the ink discharge port is provided such that the surface of the outer edge portion of the ink discharge port is higher than the other surfaces. The ink jet recording head according to claim 6, wherein: 12. The ink jet recording head according to claim 10, wherein the height of the step is equal to or less than the thickness of the sealing liquid. 13. An ink jet recording head according to claim 6, wherein said holding means is constituted by a groove provided at an outer edge portion of an ink discharge port. 14. An ink jet recording head according to claim 13, wherein a plurality of said grooves are provided. 15. An ink jet recording head according to claim 6, wherein said holding means is constituted by a projection provided on an outer edge portion of an ink discharge port. 16. The ink jet recording head according to claim 15, wherein a plurality of said projections are provided. 17. The method according to claim 15, wherein the height of the projection is equal to or less than the thickness of the sealing liquid.
7. The ink jet recording head according to 6. 18. The ink jet recording head according to claim 6, wherein said holding means is formed by a region formed on the surface provided with the ink discharge ports and having low wettability to a seal liquid. 19. An ink jet recording head according to claim 7, wherein said holding means is constituted by a band-like portion surrounding the row of the plurality of ink ejection ports, which has low wettability with respect to a seal liquid. 20. The ink jet recording head according to claim 1, wherein said shielding means has an opposing surface opposing a surface on which the ink ejection ports are provided. 21. The ink jet recording head according to claim 20, wherein said shielding means is a plate. 22. The device according to claim 20, wherein the holding means is formed by a step such that the height of the outer edge of the end of the opening in the facing surface is lower than that of the other surface. Or the inkjet recording head according to claim 21. 23. The apparatus according to claim 20, wherein said holding means is formed by a step such that a height of a surface of an outer edge at an end of said opening in said facing surface is higher than other surfaces. Or the inkjet recording head according to claim 21. 24. The ink jet recording head according to claim 20, wherein said holding means is constituted by a groove provided in an outer edge portion of an end of said opening on said facing surface. 25. The ink jet recording head according to claim 20, wherein said holding means is constituted by a projection provided on an outer edge of an opening end of said facing surface. 26. The ink jet recording head according to claim 20, wherein said holding means is constituted by said facing surface having low wettability with respect to a seal liquid. 27. The ink jet recording head according to claim 1, wherein the openings are individually provided corresponding to the ink discharge ports. 28. The ink jet recording head according to claim 1, wherein the opening is provided corresponding to a plurality of ink ejection ports. 29. An ink ejection port, an ink ejection means for ejecting ink in accordance with an image signal, and unsealing the ink ejection port with a sealing liquid at the time of ink ejection, and a predetermined gap from the ink ejection port. An ink jet recording head, comprising: a shielding unit having an opening through which ink passes; and a holding unit for holding a state in which the seal of the ink discharge port is released. 30. A conveying means for conveying an image recording medium,
An ink jet recording head that records an image by discharging ink onto an image recording medium conveyed by a conveying unit,
In an inkjet recording apparatus comprising: an image signal input unit that inputs an image signal to the inkjet recording apparatus;
30. An ink jet recording head according to claim 1, wherein
An ink jet recording apparatus according to any one of the preceding claims.