JP2005212133A - Liquid ejection recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high definition printing by suppressing generation of rebound drops and suppressing contamination in a printer even in case of high speed printing while preventing the image quality from lowering due to satellite drops. <P>SOLUTION: The liquid ejection recording head is arranged such that the central axis of a nozzle part 6 (denoted as the center line of the nozzle on the drawing) and the central axis of a compression chamber 7 (denoted as the center line of the compression chamber on the drawing) are inclined against the direction normal to the opening face of an ejection port 3, and the inclining direction of the central axis of the nozzle part 6 is reversed from that of the central axis of the compression chamber 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermal ink jet type liquid jet recording head that records an image on a recording medium by causing a liquid (ink) to fly by thermal energy, and more particularly to the shape of a flow path of a liquid jet nozzle.

  Thermal inkjet ink jet recording devices that record ink on a recording medium by ejecting ink droplets from nozzles with the pressure of bubbles generated by the heat generated by the heating elements are smaller, less expensive, and more colored than other methods. It is easy to use and has features such as recording noise, low power consumption and low running cost, so it is widely used in homes and offices. On the other hand, the inkjet recording method has a drawback that the printing speed is slower than the xerographic method widely used in offices. For this reason, in recent years, printing is performed by moving the carriage on which the head is mounted at a higher speed while improving image quality in batch printing with a larger number of nozzles arranged at higher density.

  By the way, in the thermal ink jet method, when a droplet is ejected, a minute droplet called a rebound drop is ejected at a low speed after ejecting a recording droplet. The rebound drop flew up in the air stream agitated by the high-speed carriage, contaminated the inside of the printer, and scattered on the recording paper, thus degrading the print quality.

  On the other hand, in JP-A-4-279352 and JP-A-5-69546, a flow path in which the central axis of the pressurizing chamber is within the tolerance of the inner wall of the nozzle using a nozzle obtained by processing a resin material by injection molding. A structure that forms a structure and prevents the rebound drop from jumping out of the nozzle has been proposed.

  However, in the method of injection molding of a resin material, fine nozzles are formed at a high density and a large number of nozzles are arranged on a long head because of the difference in manufacturing accuracy and the thermal expansion coefficient between the heating element substrate and the resin material. It was difficult.

On the other hand, in Japanese Patent Laid-Open No. 11-227208, a liquid flow path is formed in a silicon substrate made of the same material as the heating element substrate by an etching process, and the thermal expansion coefficient of the heating element substrate and the nozzle substrate is the same. A manufacturing method has been proposed.
JP-A-4-279352 JP-A-5-69546 JP 11-227208 A

  However, as a further problem, in the structure where the flow path is tilted so that the center axis of the pressurizing chamber is in tolerance with the inner wall of the nozzle, the satellite drop bends and flies, but the mist (rebound drop) problem can be improved. However, the current situation is that image quality degradation is newly caused by satellite drops.

  Therefore, the present invention suppresses the occurrence of rebound drop, suppresses contamination in the printer even in high-speed printing, prevents image quality deterioration due to bending of the flying direction of the satellite drop, and realizes high-quality printing. Let it be an issue.

In order to achieve the above object, the invention described in claim 1 includes a discharge port that discharges a liquid, a nozzle portion that communicates with the discharge port, a pressurization chamber that communicates with the nozzle portion, and a pressurization chamber. On the other hand, a liquid supply path that communicates with the nozzle portion from the opposite direction, a common liquid chamber that communicates with the liquid supply path and supplies a liquid, and a pressurization chamber is provided corresponding to the thermal action of the pressurization chamber. In a liquid discharge recording head having a thermal resistance portion that causes a foaming phenomenon to occur in the liquid by applying heat to the liquid in the portion, and discharges the liquid from the discharge port.
The central axis of the nozzle part and the central axis of the pressurizing chamber are respectively inclined with respect to the normal direction of the opening surface of the discharge port, and the central axis of the nozzle part and the central axis of the pressurizing chamber are The liquid jet recording head is characterized in that the inclination directions are opposite to each other.

  With the configuration of the above invention, the liquid channel 9 configured by the nozzle portion and the pressurizing chamber is formed by tilting the central axis of the nozzle portion and the central axis of the pressurizing chamber with respect to the normal direction of the opening surface of the discharge port. By tilting the inside, the rebound drop is prevented from being ejected from the ejection port by colliding with the side surface of the nozzle. And by making the direction of inclination of the central axis of the nozzle part and the central axis of the pressurizing chamber opposite to each other, the discharge direction of the satellite drop can be corrected, and the image quality deterioration due to the bending of the flying direction of the satellite drop can be prevented. I can do it.

According to the second aspect of the present invention, the angle between the normal direction of the opening surface of the discharge port and the central axis of the nozzle portion is θ ₁ , the normal direction of the opening surface of the discharge port and the central axis of the pressurizing chamber angle theta _2, the average cross-sectional area of the nozzle portion S ₁ and, when the average cross-sectional area of the pressurizing chamber and S _2, characterized in that it is a _{0 <Sinθ 1 / S 1 <} Sinθ 2 / S 2 The liquid jet recording head according to claim 1 is provided.

With the configuration of the above invention, a satellite drop having a momentum in a direction having an angle of θ ₂ and the normal direction of the opening surface of the discharge port in the pressurizing chamber is generally discharged straight in the normal direction at the discharge port. It is possible to effectively prevent deterioration in image quality due to satellite drops.

  The invention according to claim 3 is configured by laminating a first silicon substrate and a second silicon substrate provided with a thermal resistance portion, the nozzle portion, the pressurizing chamber, the liquid supply path, and the common liquid. 2. The liquid jet recording head according to claim 1, wherein the chamber is formed by performing an etching process on the second silicon substrate.

  With the configuration of the above invention, the thermal expansion coefficient of the heating element substrate (first silicon substrate) and the nozzle substrate (second silicon substrate) is the same with high density. In addition, the flow channel shape can be easily realized on a virtual plane parallel to the surface of the heating resistor portion.

  According to the present invention, it is possible to suppress the occurrence of rebound drop, suppress contamination in the printer even in high-speed printing, prevent deterioration in image quality due to bending of the flying direction of the satellite drop, and realize high-quality printing.

  Hereinafter, a liquid jet recording head according to an embodiment of the invention will be described with reference to the drawings. FIG. 1 is a plan view showing a flow path shape of a liquid jet recording head according to an embodiment of the present invention. FIG. 2 is a perspective view showing the flow path shape of the liquid jet recording head according to the embodiment of the invention.

  As shown in FIG. 1, the flow shape of the liquid jet recording head according to the present embodiment includes a liquid flow channel 9 that communicates with an ejection port 3 that ejects liquid (ink), and a liquid that communicates with the liquid flow channel 9. And a common liquid chamber 5 to be supplied. The liquid flow path 9 communicates with the nozzle portion 6 communicating with the discharge port 3 for discharging the liquid, the pressurizing chamber 7 communicating with the nozzle portion 6, and the pressurizing chamber 7 from the opposite direction to the nozzle portion 6. The liquid supply path 8 communicates with the common liquid chamber 5. The heating resistor 2 is provided corresponding to the pressurizing chamber 7.

  In the liquid jet recording head according to the present embodiment, the heat generation resistor 2 provided corresponding to the pressurizing chamber 7 causes heat to act on the liquid on the heat generation resistor 2 (thermal action portion) to cause a foaming phenomenon in the liquid. The liquid is discharged from the discharge port 3 through the nozzle portion 6.

  At this time, as shown in FIG. 3, in order to discharge the main droplet 11 and the satellite drop 12, the bubble expands on the heating resistor 2 and then contracts, and the rebound drop 13 is released from the meniscus surface 14 retracted into the nozzle. However, if the inside of the liquid flow path 9 is inclined (that is, if the central axis of the nozzle portion 6 and the central axis of the pressurizing chamber 7 are inclined), the meniscus surface 14 retracted into the nozzle portion 6. The normal line direction is deviated from the discharge port 3 direction, and the generated rebound drop 13 collides with the inner surface of the nozzle portion 6 and is not discharged to the outside.

  Here, the satellite drop 12 is a droplet having a slow flight speed following the main droplet, which is formed by separating long elongated droplets. The rebound drop 13 is a minute droplet that is ejected from the nozzle several μs to 10 μs after the droplets corresponding to the main droplet 11 and the satellite drop 12 are ejected.

However, as shown in FIG. 4A, when the normal direction of the opening surface of the discharge port 3 and the central axis of the nozzle portion 6 are the same direction (the normal direction of the opening surface of the discharge port 3 and the nozzle portion). If the angle theta ₁ between the center axis 6 is 0), issues the satellite drop 12 in the X direction is discharged shift occurs. The main droplet 11 is ejected without much influence of the flow in the nozzle portion 6, but the satellite drop 12 is the one in which the liquid at the back comes out, so that the inside of the liquid channel 9 is inclined. Because it is affected.

  Therefore, in the liquid jet recording head according to the present embodiment, the normal direction of the opening surface of the discharge port 3 (denoted as the normal line of the discharge port in the drawing) on a virtual plane parallel to the surface of the heating resistor 2. The central axis of the nozzle portion 6 (denoted as the center line of the nozzle in the drawing) and the central axis of the pressurizing chamber 7 (denoted as the central line of the pressurizing chamber in the drawing) are each inclined, and the central axis of the nozzle portion 6 And the central axis of the pressurizing chamber 7 are inclined in opposite directions. As a result, the satellite drop 12 corrects the displacement in the ejection direction affected by the inclination of the liquid channel 9 inside.

  As described above, in the present embodiment, by inclining the inside of the liquid flow path 9, discharge of the rebound drop 13 to the outside is suppressed, and contamination in the printer is suppressed even in high-speed printing. Then, while tilting the inside of the liquid flow path 9, the ejection direction of the satellite drop 12 is corrected to prevent the satellite drop 12 from being bent and flying, thereby preventing the satellite drop 12 from degrading the image quality and improving the image quality. be able to. Moreover, since the bubble generation direction by the heating resistor 2 and the liquid discharge direction are approximated, the liquid discharge stability is improved.

  Here, the “opening surface of the discharge port” refers to the surface of the recording head where the discharge port is provided. The “nozzle portion” is a flow path from a position where the cross-sectional area is narrowed down from the pressurizing chamber to the discharge port, and is a flow path that determines the liquid discharge direction. The “center axis of the nozzle portion” is a line connecting the midpoint of the discharge port and the midpoint of the boundary between the nozzle portion and the pressurizing chamber (position where the cross-sectional area is narrowed from the pressurizing chamber). It is a line which shows the average direction of a liquid flow. The “pressurizing chamber” is a flow path on the heating resistor. The “center axis of the heating chamber” is a line connecting the midpoints on both ends of the heating resistor 2 in the direction in which the liquid flows.

On the other hand, if the central axis of the nozzle portion 6 is too inclined with respect to the central axis of the pressurizing chamber 7, for example, the satellite drop 12 may be displaced in the X ′ direction as shown in FIG. Accordingly, it is preferable that the inclination amount of the center line of the nozzle satisfies the relationship of the relational expression: 0 <Sinθ ₁ / S ₁ <Sinθ ₂ / S ₂ with respect to the inclination amount of the pressurizing chamber. More preferably, the above relational expression is: 1/3 × Sinθ ₂ / S ₂ <Sinθ ₁ / S ₁ <2/3 × Sinθ ₂ / S ₂ .

In this specification, the angle between the normal direction of the opening surface of the discharge port 3 and the central axis of the nozzle portion 6 is θ ₁ , the normal direction of the opening surface of the discharge port 3 and the central axis of the pressurizing chamber 7. Is the angle θ ₂ , the average cross-sectional area of the nozzle portion 6 is S ₁ , and the average cross-sectional area of the pressurizing chamber is S ₂ .

By satisfying the relationship of the above formula, the satellite drop 12 having momentum in the direction having the angle θ ₂ with respect to the normal direction of the opening surface of the discharge port in the pressurizing chamber 7 is generally normal at the discharge port 3. The ink is discharged straight in the direction, and the deterioration of image quality due to satellites can be prevented more effectively. The reason is as follows.

First, assuming that the liquid flow rate in the nozzle unit 6 is V ₁ , the liquid flow rate in the pressurizing chamber is V ₂ , and the liquid is considered as an incompressible fluid, S ₁ V ₁ = S ₂ V ₂ = Const (constant) is there. Therefore, the component in the X direction is V ₁ Sinθ ₁ for the flow in the nozzle and V ₂ Sinθ ₂ for the flow of the liquid in the pressurized chamber.

In order for the satellite to fly without bending in the X direction, V ₁ Sinθ ₁ = V ₂ Sinθ ₂ suffices. In reality, however, the nozzle portion 6 is closer to the discharge port than the pressurizing chamber 7, so V Satellites will fly under the condition of ₁ Sinθ ₁ <V ₂ Sinθ ₂ . Here, since V ₁ = Const / S ₁ and V ₂ = Const / S ₂ , Sinθ ₁ / S ₁ <Sinθ ₂ / S ₂ . Furthermore, since the phenomenon of theta ₁ = 0 In the satellite bends occur, the formula: 0 <a _{Sinθ 1 / S 1 <Sinθ 2} / S 2. Therefore, by satisfying the relationship of the above formula, it is possible to prevent image quality degradation due to satellites.

Further, as a result of further intensive investigations, it was found that it is preferable to satisfy the formula: 1/3 × Sinθ ₂ / S ₂ <Sinθ ₁ / S ₁ <2/3 × Sinθ ₂ / S ₂ .

Tables 1, 2 and 3 show the experimental results when the levels of θ ₁ and θ ₂ are changed when the nozzle length 6 is 30 μm, 40 μm and 50 μm, respectively. The average cross-sectional area S ₁ = 323μm ² of the nozzle section 6 is an experimental example of the average cross-sectional area S ^₂ = 513μm ₂ of the pressurizing chamber. From this experimental result, the range in which the occurrence of rebound drop and the prevention of image quality degradation due to satellites are compatible is the formula: 0 <Sinθ ₁ / S ₁ <Sinθ ₂ / S ₂ , and more preferably the formula: 1/3 × Sinθ ₂ / S ₂ <Sinθ ₁ / S ₁ <2/3 × Sinθ ₂ / S ₂ .

In the table, the left column of each column shows two determination results of rebound drop / satellite, and the numerical value of the right column is a value of (Sinθ ₁ / S ₁ ) / (Sinθ ₂ / S ₂₎ .

In addition, the determination criteria for the rebound drop / satellite determination result in the left column of each column are as follows.
―Criteria―
Rebound drop ○: No rebound drop occurs and no mist contamination occurs. Δ: Rebound drop occurs depending on the image pattern and frequency.
X: Rebound drop occurs depending on any image pattern and frequency.
-Satellite ○: No satellite is generated and the image quality is good.
Δ: Not conspicuous in terms of image quality, but satellites are generated when viewed closely.
X: Satellite was conspicuous and image quality deteriorated.

  Next, a method for manufacturing the liquid jet recording head according to the present embodiment will be described. 5 and 6 are process diagrams showing an example of a method for manufacturing a nozzle substrate of the liquid jet recording head according to the present embodiment.

First, an SiO ₂ film 32 is formed as a first etching-resistant masking layer by thermal oxidation in FIG. 5B on the Si substrate 31 that becomes the nozzle substrate shown in FIG. In FIG. 5C, the portion that becomes the liquid flow path 9 including the nozzle portion, the pressurizing chamber, and the liquid supply path in the SiO ₂ film 32 and the portion that becomes the common liquid chamber 5 are formed by using the photolithography method and the dry etching method. Pattern. The crystal orientation of the Si substrate 31 used is the <100> plane.

  Subsequently, as shown in FIG. 5D, a SiN film 33 is formed as a second etching resistant masking layer by a low pressure CVD method. The thickness of the SiN film 33 formed at this time can be about 300 nm, for example. With respect to the SiN film 33, in FIG. 5E, a portion that becomes the common liquid chamber 5 and the stepped portion 10 and a portion that becomes the concave portion provided in the liquid flow path 9 are formed using a photolithography method and a dry etching method. Pattern.

Subsequently, as shown in FIG. 5F, an SiO ₂ film 34 to be an H ₃ PO ₄ etching protection film (third etching resistance masking layer) is formed by a low pressure CVD method. The thickness of the SiO ₂ film 34 formed at this time can be about 500 nm, for example. The SiO ₂ film 34 is patterned using a photolithography method and a dry etching method in FIG. The SiO ₂ film 34 is formed so as to cover the SiN film 33.

  Subsequently, as shown in FIG. 5H, a second SiN film 35 to be a fourth etching resistant masking layer is formed by a low pressure CVD method. The thickness of the SiN film 35 formed at this time can be about 300 nm, for example. In FIG. 6A, a region that becomes the common liquid chamber 5 is patterned on the SiN film 35 by using a photolithography method and a dry etching method.

  Subsequently, the Si substrate 31 is etched with an aqueous KOH solution using the SiN film 35 as an etching mask. This etching is performed until the Si substrate 31 is penetrated as shown in FIG. 6B, and the through hole becomes the liquid supply port 4. This processing is a wet anisotropic etching similar to the conventional one. As described above, since the dimension of the SiN film 35 is set small by a predetermined amount, the common liquid chamber 5 formed here is formed small by a predetermined amount. Further, the processed through-hole is formed as a slope having a predetermined angle on the side wall due to the characteristics of wet anisotropic etching. Here, since processing is performed from one surface of the Si substrate 31, a through-hole whose cross-sectional area decreases toward the liquid supply port 4 is formed. The wet anisotropic etching used here has a higher processing speed than RIE and is suitable for processing with a deep processing depth that penetrates the Si substrate 31.

Subsequently, as shown in FIG. 6C, the SiN film 35 is selectively removed by etching with a phosphoric acid aqueous solution. At this time, since there is the SiO ₂ film 34 which becomes the H ₃ PO ₄ etching protection film, the underlying SiN film 33 is not eroded.

Next, as shown in FIG. 6D, the SiO ₂ film 34 is selectively removed by etching with an HF solution. Subsequently, in FIG. 6E, wet anisotropic etching with a KOH aqueous solution is performed on the Si substrate 31 using the SiN film 33 as an etching mask. In this wet anisotropic etching, processing of only a desired depth is performed without penetrating. The processing depth can be about 200 μm, for example. However, it should be set shallower than the finished depth.

Subsequently, in FIG. 6F, the SiN film 33 is selectively removed by etching with a phosphoric acid solution. Subsequently, in FIG. 6G, RIE processing of the Si substrate is performed using the SiO ₂ film 32 as an etching mask. The processing depth at this time can be, for example, about 20 μm. In the RIE process, as described above, the portion other than the masked portion can be uniformly etched in the thickness direction without depending on the Si crystal direction.

  Here, the processing accuracy of the liquid flow path 9 greatly affects the liquid ejection characteristics. In wet anisotropic etching, a rectangular pattern in a plane can be processed with high precision, but a complicated pattern in a plane cannot be processed with high precision. The RIE used in the present invention can be processed with high accuracy even with a complicated pattern, and the liquid flow path 9 having desired ejection characteristics can be formed with high accuracy. Further, unlike wet anisotropic etching, the processing depth is not limited by the planar size, and an arbitrary processing depth can be obtained. Conversely, RIE cannot be processed into an arbitrary shape in the depth direction. Therefore, a predetermined pattern can be accurately formed in the depth direction by accurately forming the concave portion 43 in the previous step for the portion to be formed deep. In this way, the liquid flow path 9 having a three-dimensional structure can be formed.

  Further, the step portion 10 is also etched by this RIE process to form a deeper step, and the capacity of the common liquid chamber 5 also increases. If the common liquid chamber 5 is made small and the stepped portion 10 is shallowly formed at the time of processing in FIGS. 6B and 6E, a predetermined size is obtained by this RIE.

Finally, in FIG. 6 (H), the SiO ₂ film 32 is selectively removed by etching with a hydrofluoric acid solution to complete the processing of the Si substrate 31 that becomes the nozzle substrate. Through the manufacturing process as shown in FIGS. 5 and 6, the Si substrate 31 has a groove that becomes the liquid flow path 9 having the front throttle 41, the rear throttle 42, and the recess 43 corresponding to a large number of nozzle substrates. A through-hole serving as the common liquid chamber 5 and the liquid supply port 4, a stepped portion 10 serving as a connection portion between the liquid flow path 9 and the common liquid chamber 5 are formed. In this way, even the liquid flow path 9 having a complicated structure in plan can be formed by RIE processing, and a structure having irregularities in the depth direction by combining wet anisotropic etching and RIE processing. Even if it exists, it can form.

  On the other hand, another Si substrate on which a large number of element substrates (thermal resistance substrates) are formed by another process is formed. On the element substrate, an energy conversion element corresponding to each liquid flow path 9, wiring for supplying electric energy to the energy conversion element, a drive circuit and the like as necessary are formed. Here, a heating resistor is used as the energy conversion element, but the present invention is not limited to this. Further, as these protective layers, a thick film layer made of, for example, polyimide is formed. The thick film layer is removed on the heating resistor. A protective film or the like is separately formed on the heating resistor.

  Then, the nozzle substrate and the element substrate are overlapped and separated into individual pieces to obtain a liquid jet recording head.

  By using the above-described manufacturing method, the flow channel shape shown in FIG. 1 can be precisely created, and since it is manufactured using a Si substrate, there is no difference in thermal expansion from the heater substrate, and multiple nozzles. A long configuration can be realized. Further, since the liquid flow path 9 is formed in the nozzle substrate (silicon substrate), the relationship of the flow path shape shown in FIG. 1 can be satisfied on a virtual plane parallel to the surface of the heater substrate (heating resistor 2). it can.

FIG. 4 is a plan view showing a flow path shape of the liquid jet recording head according to the embodiment of the invention. FIG. 4 is a plan view showing a flow path shape of the liquid jet recording head according to the embodiment of the invention. It is a schematic diagram explaining a mode that a rebound drop generate | occur | produces. It is a schematic diagram which shows the relationship between the discharge direction of a satellite, and the inclination of the centerline of a nozzle part. FIG. 5 is a process diagram illustrating an example of a method for manufacturing a nozzle substrate of a liquid jet recording head according to the present embodiment. It is process drawing which shows an example of the manufacturing method of the nozzle substrate of the liquid jet recording head which concerns on this embodiment.

Explanation of symbols

2 Heating resistor 3 Discharge port 5 Common liquid chamber 6 Nozzle part 7 Pressurizing chamber 8 Liquid supply path 9 Liquid flow path 11 Main droplet 12 Satellite drop 13 Rebound drop 14 Meniscus surface

Claims (3)

An ejection port for ejecting liquid, a nozzle portion communicating with the ejection port, a pressurizing chamber communicating with the nozzle portion, a liquid supply path communicating with the pressurizing chamber in a direction opposite to the nozzle portion, A common liquid chamber that communicates with the liquid supply path and supplies a liquid, and a pressurizing chamber is provided corresponding to the pressure chamber. In a liquid discharge recording head having a thermal resistance portion that discharges liquid from the discharge port,
The central axis of the nozzle part and the central axis of the pressurizing chamber are respectively inclined with respect to the normal direction of the opening surface of the discharge port, and the central axis of the nozzle part and the central axis of the pressurizing chamber are A liquid jet recording head characterized in that the directions of the inclinations are opposite to each other. The angle between the normal direction of the opening surface of the discharge port and the central axis of the nozzle portion is θ ₁ , the angle between the normal direction of the opening surface of the discharge port and the central axis of the pressurizing chamber is θ ₂ , 2. The nozzle section according to claim ₁ , wherein S < _b > _{1 is} an average sectional area of the nozzle portion and S < _b > ₂ is an average sectional area of the pressurizing chamber, and 0 <Sinθ ₁ / S ₁ <Sinθ ₂ / S _2. Liquid jet recording head.   The first silicon substrate and the second silicon substrate provided with a thermal resistance portion are laminated, and the nozzle portion, the pressurizing chamber, the liquid supply path, and the common liquid chamber are formed on the second silicon substrate. The liquid jet recording head according to claim 1, wherein the liquid jet recording head is formed by performing an etching process.

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