JP2008254027A - Laser beam machining method and method for manufacturing ink-jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method and a method for manufacturing an ink-jet head by which resultants produced from machining can be easily removed by forming, in a plate, through holes having an opening part with a uniform edge shape and a small diameter error. <P>SOLUTION: The laser beam machining method includes steps of: providing an upper face fluidized layer 2a having flowability and an upper face protective film 3 in this order on the laser irradiation surface of an orifice plate 1, which is irradiated with a laser beam 5; providing a lower face fluidized layer 2b having a higher viscosity coefficient than the upper face fluidized layer 2a and a lower face protective film 4 in this order on the ink-jetting face of the orifice plate 1; forming the orifice 8 on the orifice plate 1 by irradiating the laser irradiation surface of the orifice plate 1 with the laser beam 5; removing the upper face protective film 3 and the lower face protective film 4; and removing the upper face fluidized layer 2a and the lower face fluidized layer 2b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser processing method for forming a through hole in a plate and a method for manufacturing an ink jet head including the plate.

  The ink-jet head includes a head main body that stores ink and an orifice plate in which an orifice that is an ink discharge port is formed. The orifice plate is a thin plate provided on the ink outlet surface of the head body. In order to improve the print quality of the inkjet head, it is desirable to make the shape of each orifice formed on the orifice plate uniform and to clean the surface of the orifice plate.

  The orifice is formed by irradiating the orifice plate with laser light from an excimer laser. By forming the orifice in the orifice plate, the scraped resin of the orifice plate is generated as a by-product such as carbon. The generated by-product accumulates in the vicinity of the opening on the ink ink ejection surface side and laser irradiation surface side of the orifice and in the ink flow path on the inner wall of the orifice. The by-product has strong adhesion to the orifice plate and is difficult to remove completely by ultrasonic cleaning or the like.

  When the by-product is attached in the vicinity of the opening on the ink ejection surface side of the orifice, and when the water-repellent film is formed after the orifice is formed, the formation of the water-repellent film is inhibited at the attached portion. The adhering site is hydrophilic. Even when the orifice is formed after the water repellent film is formed on the orifice plate, it is difficult to completely remove the by-product attached in the vicinity of the opening on the ink ejection surface side of the orifice. For this reason, an ink pool is generated at the adhering portion, and the straightness of the ink is lost. As a result, the print quality of the inkjet head decreases.

  Further, when the by-product adheres to the vicinity of the opening on the laser irradiation surface side of the orifice and in the ink flow path, the by-product is clogged in the orifice by peeling or floating in the ink. As a result, the inkjet head becomes defective in ejection, and the print quality is degraded.

  Techniques for solving the above problems are disclosed in Patent Document 1 and Patent Document 2. In Patent Document 1, by applying a liquid that can be easily removed onto the laser irradiation surface of an orifice plate, a by-product generated during the formation of the orifice is transferred to the liquid, and the liquid is removed. Thereby, the laser irradiation surface of the orifice plate can be kept clean. In Patent Document 2, a melt removing material for removing by-products is provided on the surface of the plate opposite to the laser irradiation surface. Further, a carrier film is provided between the plate and the melt removing material for facilitating peeling of the both. Thereby, the surface on the opposite side to the laser irradiation surface of the said plate can be kept clean.

  However, in the configurations of Patent Document 1 and Patent Document 2 described above, by-products attached to either the laser irradiation surface side of the orifice plate or the surface opposite to the laser irradiation surface can be removed. By-products attached to the surface cannot be removed. Therefore, conventionally, the following laser processing methods are used. A conventional laser processing method will be described below with reference to FIG. 6A to 6D are cross-sectional views showing a conventional method for manufacturing an orifice plate.

As shown in FIG. 6A, the laser irradiation surface of the plate 91 before forming the orifice (hereinafter referred to as the orifice plate) 91 is irradiated with laser light and has a viscosity that can be easily removed, for example, polypropylene. A liquid 92 such as glycol and an upper surface protective film 93 are provided in this order. Further, a liquid 92 and a lower surface protective film 94 are provided in this order on the ink ejection surface, which is the surface opposite to the laser irradiation surface of the orifice plate 91. Then, a mask pattern (not shown) having a plurality of holes formed on the upper surface of the upper surface protective film 93 is provided. The orifice 98 is formed by irradiating the excimer laser beam 95 on the mask pattern. Here, ablation processing is performed to a part of the lower surface protective film 94 by the laser beam 95 through the upper surface protective film 93, the liquid 92, and the orifice plate 91. A by-product 96 generated by forming the orifice is deposited on the upper surface of the upper surface protective film 93.

  Next, as shown in FIG. 6B, after the orifice 98 is formed, the upper surface protective film 93 and the lower surface protective film 94 are removed. The liquid 92 applied to the laser irradiation surface and the ink ejection surface of the orifice plate 91 is ultrasonically cleaned with an organic solvent. Thereby, as shown in FIG.6 (c), the clean orifice plate 91 in which the by-product 96 does not adhere is obtained.

Next, as shown in FIG. 6D, a water repellent layer 97 is formed on the ejection surface of the orifice plate 91.
JP 10-505557 Gazette (International publication date March 21, 1996) Japanese Patent Laying-Open No. 2003-340818 (Publication date: December 2, 2003)

  However, in the conventional configuration, as shown in FIGS. 7 and 8, the shape of the edge of the opening on the ink ejection surface side and the laser irradiation surface side of the orifice 98 is distorted. FIG. 7 is a view showing an SEM photograph of the ink ejection surface side of the orifice 98 formed by the conventional laser processing method shown in FIG. FIG. 8 is an SEM photograph of the laser irradiation surface side of the orifice 98 formed by the conventional laser processing method shown in FIG.

  When forming the orifice, a mask pattern provided with a plurality of holes is provided on the upper surface protective film 93, and a laser beam 95 is irradiated from the mask pattern. As a result, a plurality of orifices 98 are formed in the orifice plate 91 at a time. In the conventional laser processing method, the roundness of the hole formed in the mask pattern (variation of the diameter of the circle) is 0.1 μm, whereas the roundness of the formed orifice 98 is 1.5 μm. ing.

  FIG. 9 is a graph obtained by measuring the diameter of the opening on the ink ejection surface side of the orifices 98 formed in a lump by the conventional laser processing method shown in FIG. In the figure, the Y axis indicates the diameter of the opening, and one scale is 0.5 μm. The X axis indicates the number of orifices formed at once (hereinafter referred to as the number of channels). As shown in FIG. 9, the diameter of the opening for each channel shows a variation of about 1.2 μm at the maximum.

As described above, in the conventional laser processing method, the shape of the edge of the opening on the ink ejection surface side and the laser irradiation surface side of the formed orifice 98 becomes distorted. Further, the variation in the diameter of the opening on the ink ejection surface side of the orifice 98 is large. When the shape of the edge of the opening on the ink ejection surface side and the laser irradiation surface side of the orifice 98 is distorted, the direction of the ink ejected from the orifice varies. In addition, if the diameter of the opening on the ink ejection surface side of the orifice 98 varies, the amount of ink ejected from the inkjet head differs for each orifice. As a result, the print quality of the ink jet head including the orifice plate having the orifice formed by the conventional laser processing method is deteriorated.

  The present invention has been made in view of the above problems, and its purpose is to form a through-hole in the plate with a uniform edge shape of the opening and a small error in the diameter of the opening. Provided are a laser processing method and an ink jet head manufacturing method capable of easily removing a generated product.

  In order to solve the above problems, the laser processing method of the present invention has fluidity on the laser irradiation surface of the plate irradiated with the laser light in the laser processing method of forming a through hole in the plate with laser light. A step of providing a first fluidized bed and a first protective film in this order; a second fluidized bed having a viscosity higher than that of the first fluidized bed; A step of providing two protective films in this order, a step of irradiating the laser irradiation surface of the plate with laser light to form a through hole in the plate, and removing the first protective film and the second protective film. And a step of removing the first fluidized bed and the second fluidized bed.

  In the conventional laser processing method, since the viscosity of the liquid applied to the surface of the plate opposite to the laser irradiation surface is low, the stability of the plate is low. For this reason, when the plate is irradiated with a laser, the plate moves to cause a focus position shift of the laser. Then, when the laser focus position shifts, the diameters of the openings in the surface of the formed through hole on the side opposite to the laser irradiation surface of the plate vary. In addition, the adhesion between the plate and the protective film provided on the liquid is weak, and the impact of laser irradiation is dispersed in the liquid. Then, due to the impact dispersed in the liquid, the shape of the edge of the opening on the surface side of the formed through hole opposite to the laser irradiation surface of the plate becomes distorted.

  Further, in the conventional laser processing method, since the viscosity of the liquid applied to the laser irradiation surface of the plate is high, the liquid does not spread over the entire laser irradiation surface and undulates on the protective film provided on the liquid. Occurs. As a result, the thickness from the upper surface of the protective film to the laser irradiation surface of the plate changes depending on the location. The laser irradiated with the focus on the upper surface of the protective film causes a focus shift. As a result, the diameter of the opening on the side opposite to the laser irradiation surface of the plate of the formed through hole varies, and the shape of the edge of the opening on the laser irradiation surface side of the through hole is I'm in trouble.

  In the present invention, a second fluidized bed having a higher viscosity than the first fluidized bed is provided on the surface opposite to the laser irradiation surface of the plate, and a second protective film is provided thereon, whereby the plate and the plate Stability and adhesion with the second protective film can be enhanced. In addition, by providing the first fluidized bed having a lower viscosity than the second fluidized bed on the laser irradiation surface side of the plate, the first fluidized bed spreads evenly on the plate, and on the first fluidized bed. The wave | undulation which arises in the provided 1st protective film is suppressed. Therefore, the focus position shift due to the laser irradiation is suppressed, and the variation in the diameter of the opening on the surface opposite to the laser irradiation surface of the formed through hole can be reduced. In addition, the shape of the edge of the opening on the laser irradiation surface side and the surface opposite to the laser irradiation surface of the through hole can be made uniform.

Further, by providing a first protective film and a second protective film on both sides of the laser irradiation surface and the surface opposite to the laser irradiation surface of the plate, a by-product generated by forming a through hole is obtained. Prevents adhesion to the plate. And since the said 1st fluidized bed and the said 2nd fluidized bed can be removed easily, the clean plate which has an elaborate through-hole can be obtained.

In the laser processing method of the present invention, the plate is preferably made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more for an excimer laser having a wavelength of 248 nm.

In general, ablation processing is the center of processing using an excimer laser. Therefore, the processing state of the material to be processed depends on the light absorption coefficient of the material. That is, if the light absorption coefficient of the material is less than a certain threshold value, it cannot be processed with an excimer laser having a predetermined power. Therefore, the light absorption coefficient of the plate needs to be a certain value or more. In the above configuration, since the plate is made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more, it is possible to easily perform ablation using an excimer laser having a wavelength of 248 nm.

  Moreover, in the laser processing method of this invention, the said plate may be comprised from the material containing a polyimide derivative.

  Accordingly, the plate has a light absorption coefficient that can be suitably processed by an excimer laser having a wavelength of 248 nm. Therefore, the plate can be easily ablated using an excimer laser.

  In the laser processing method of the present invention, the viscosity of the first fluidized bed is preferably 220 cP or less at 25 ° C.

  Thereby, a 1st fluidized bed spreads over the whole laser irradiation surface of a plate, and can suppress the waviness which arises in the protective film provided on this 1st fluidized bed. Therefore, the focus position shift due to the laser irradiation is suppressed, and the variation in the diameter of the opening on the surface opposite to the laser irradiation surface of the formed through hole can be reduced. Further, the shape of the edge of the opening on the laser irradiation surface side of the through hole can be made uniform.

  In the laser processing method of the present invention, the viscosity of the first fluidized bed is more preferably 56 cP or less at 25 ° C.

  Thereby, a 1st fluidized bed spreads uniformly by the whole laser irradiation surface of a plate, and can further suppress the undulation which arises in the protective film provided on this 1st fluidized bed. Therefore, the focus position shift due to the laser irradiation is further suppressed, and the variation in the diameter of the opening on the surface opposite to the laser irradiation surface of the formed through hole can be further reduced. Further, the shape of the edge of the opening on the laser irradiation surface side of the through hole can be made more uniform.

  In the laser processing method of the present invention, the viscosity of the second fluidized bed is preferably 650 cP or more at 25 ° C.

  Thereby, stability and adhesiveness of the surface on the opposite side to the laser irradiation surface of a plate and the protective film provided on the 2nd fluidized bed can be improved. Therefore, in the formed through hole, the shape of the edge of the opening is uniform on the surface opposite to the laser irradiation surface of the plate, and the variation in the diameter of the opening is small.

  In the laser processing method of the present invention, the first fluidized bed and the second fluidized bed may be composed of polypropylene glycol.

  In the above method, since polypropylene glycol has low reactivity with the plate, the influence on the plate can be reduced by using it as a fluidized bed. In addition, since polypropylene glycol has low volatility, the distance between the plate and the protective film provided on the fluidized bed can be kept constant for a long time. For this reason, a cleaner plate having an elaborate through hole can be obtained.

Moreover, in the laser processing method of this invention, it is preferable that the said 1st protective film is comprised from the polymer whose optical absorption coefficient with respect to the excimer laser with a wavelength of 248 nm is 1000 cm < ^-1 > or more.

In the above method, by forming both the first protective film and the plate from a polymer having an optical absorption coefficient of 1000 cm ⁻¹ or more for an excimer laser having a wavelength of 248 nm, it is possible to obtain a clean plate having more elaborate through holes. it can.

  The inkjet head manufacturing method of the present invention is a method of manufacturing an inkjet head in which an orifice is formed on an orifice plate by laser light. A step of providing a fluidized first fluidized layer and a first protective film in this order on the laser irradiation surface of the plate, and a surface on the side opposite to the laser irradiation surface of the plate. A step of providing a second fluidized bed having a higher viscosity than the first fluidized bed and a second protective film in this order, and irradiating the laser irradiation surface of the plate with laser light to form an orifice in the plate A step, a step of removing the first protective film and the second protective film, and a step of removing the first fluidized bed and the second fluidized bed. It is characterized in that it comprises a.

  In the above method, a water repellent film is formed on the surface of the orifice plate opposite to the laser irradiation surface before forming the orifice. As a result, a by-product generated by forming the orifice does not affect the formation of the water-repellent film, and a cleaner orifice plate can be formed as compared with the conventional method of forming the water-repellent film after forming the orifice. It is possible to obtain.

  Further, by providing a second fluidized bed having a higher viscosity than the first fluidized bed on the surface opposite to the laser irradiation surface of the orifice plate and providing a second protective film thereon, the orifice plate and the first 2 Stability and adhesion with the protective film can be improved. Further, by providing the first fluidized bed having a lower viscosity than the second fluidized bed on the laser irradiation surface side of the orifice plate, the first fluidized bed spreads evenly on the orifice plate, and the first fluidized bed The wave | undulation which arises in the 1st protective film provided on the top is suppressed. Therefore, the focus position shift due to the laser irradiation is suppressed, and the variation in the diameter of the opening on the surface opposite to the laser irradiation surface of the formed orifice can be reduced. Further, the shape of the edge of the opening on the laser irradiation surface side and the surface side opposite to the laser irradiation surface of the orifice can be made uniform.

  Further, by providing the first protective film and the second protective film on both the laser irradiation surface and the surface opposite to the laser irradiation surface of the orifice plate, a by-product generated by forming the orifice is obtained. It is prevented from adhering to the orifice plate. And since the said 1st fluidized bed and the said 2nd fluidized bed can be removed easily, the clean orifice plate which has an elaborate orifice can be obtained.

  In the inkjet head manufacturing method of the present invention, the water repellent film is preferably composed of a fluorine-based silane coupling agent.

  Thereby, the water-repellent film can be formed very thin. This is because the fluorine-based silane coupling agent has water repellency even with a monomolecular film (2 to 3 nm), and a water-repellent film can be formed very thin compared to other water-repellent materials. For this reason, the influence on the shape of the orifice on the discharge surface side of the orifice plate can be reduced. In addition, the range of applicable laser processing conditions is wider than other water-repellent materials, and an orifice can be easily formed.

  Further, the ink jet head manufacturing method of the present invention is characterized in that the through hole of the plate formed by the laser processing method described above is used as an ink discharge port.

  By the above method, the through-hole of the plate formed by the laser processing method described above is used as an ink discharge port of the inkjet head. Thereby, an inkjet head can be manufactured using the clean plate which has an elaborate through-hole.

  In the laser processing method of the present invention, as described above, the step of providing the fluidized first fluidized layer and the first protective film in this order on the laser irradiation surface irradiated with the laser beam of the plate, A step of providing a second fluidized bed having a higher viscosity than the first fluidized bed and a second protective film in this order on the surface of the plate opposite to the laser irradiation surface.

  In addition, as described above, the inkjet head manufacturing method of the present invention includes a step of providing a fluidized first fluidized layer and a first protective film in this order on the laser irradiation surface of the plate; And a step of providing a second fluidized bed having a higher viscosity than the first fluidized bed and a second protective film in this order on the surface opposite to the laser irradiation surface.

  Therefore, there is provided a laser processing method and an inkjet head manufacturing method in which a through-hole having a uniform edge shape and a small error in the diameter of the opening is formed in the plate, and a product generated by the processing can be easily removed. There is an effect that it can be provided.

  One embodiment of the present invention will be described below. First, a study of a conventional laser processing method will be described.

[Examination of conventional laser processing methods]
As described above, in the conventional laser processing method, the shape of the edge of the opening on the laser irradiation surface side and the ink ejection surface side of the formed orifice is distorted. Further, the diameter of the opening on the ink ejection surface side of the orifice varies. The above problem is considered to be caused by the viscous liquid applied to the laser irradiation surface and the ink ejection surface of the orifice plate. Therefore, the cause of the above problem will be discussed with reference to FIGS.

  FIG. 10A is a cross-sectional view showing a configuration for examining the influence of the liquid applied to the laser irradiation surface side of the orifice plate on the orifice formation. FIG. 10B is a cross-sectional view showing a configuration for examining the influence of the liquid applied to the ink ejection surface side of the orifice plate on the formation of the orifice.

First, as shown in FIG. 10A, the liquid 12 is applied to the laser irradiation surface of the orifice plate 11, and the upper surface protective film 13 is provided thereon. Then, the upper surface of the upper surface protective film 13 is irradiated with a laser beam 15 through a mask pattern formed by chromium deposition on a quartz substrate. By irradiating the laser beam 15, the upper surface protective film 13 and the orifice plate 11 are scraped, and a by-product 16 is deposited on the upper surface protective film 13. Since the main component of the by-product 16 is carbon, it can be removed by ashing, but plasma damage to the orifice plate 11 occurs.

  In the above process, the liquid 12 is made of polypropylene glycol (PPG: molecular weight 2000, viscosity of 163.7 cP at 25 ° C.), the orifice plate 11 is made of a polyimide film having a thickness of 50 μm, and the upper surface protective film 13 is made of A polyimide film having a thickness of 12.5 μm is used. The laser beam 15 is irradiated by an excimer laser having a wavelength of 243 nm. In the excimer laser, the oscillation conditions are set to laser power: 680 mJ / cm 2, frequency: 100 Hz, and number of shots: 450 shots. As a result, the diameter of the opening on the laser irradiation surface side of the orifice is about 40 μm, and the diameter of the opening on the ink ejection surface side is about 20 μm.

  Further, in order to study the influence of the liquid applied to the ink discharge surface side of the orifice plate on the orifice formation, the liquid 12 is applied to the ink discharge surface of the orifice plate 11 as shown in FIG. The lower surface protective film 14 is provided thereon. Then, the laser beam 15 is irradiated onto the laser irradiation surface of the orifice plate 11 through the mask pattern. In the above process, a polyimide film having a thickness of 75 μm is used for the lower surface protective film 14. In addition, about the other member, the thing similar to the member used in Fig.10 (a) is used.

  By the above method, it is possible to confirm the influence of the liquid 12 applied to the laser irradiation surface and the ink ejection surface of the orifice plate 11 on the orifice formation.

  11 (a) and 11 (b) are micrographs of the laser irradiation surface of the orifice formed with the configuration of FIGS. 10 (a) and 10 (b). Here, after the orifice is formed, the orifice plate 11 is subjected to ultrasonic cleaning using a neutral detergent or an organic solvent.

  In the configuration of FIG. 10A, the by-product 16 generated by laser processing is deposited on the upper surface protective film 13. Therefore, by removing the upper surface protective film 13 from the orifice plate 11 and washing the liquid 12, the orifice plate 11 in a clean state can be obtained as shown in FIG. On the other hand, in the configuration of FIG. 10B, the by-product 16 generated by the laser processing is directly deposited on the orifice plate 11. In this case, the by-product 16 cannot be completely removed even by cleaning, and the by-product 16 is formed around the orifice opening on the laser irradiation surface side of the orifice plate 11 as shown in FIG. Is deposited.

  Although not shown, the variation in the diameter of the opening on the ink ejection surface side of the orifices formed in a lump is different from that in the case where laser processing is performed in the configuration of FIG. The case where the laser processing is performed with the configuration is larger. Although not shown, the shape of the edge of the opening on the ink ejection surface side of the orifice is the laser processing with the configuration of FIG. 10B compared to the case of laser processing with the configuration of FIG. If you do, you will be more angry. Further, in the configuration of FIG. 10A, the edge of the opening on the laser irradiation surface side of the formed orifice has an irregular shape as shown in FIG. Hereinafter, in the configuration of FIG. 10A, the orifice plate 11 having an irregular edge shape on the laser irradiation surface side of the formed orifice is regarded as a defective product.

As described above, when laser processing is performed with the configuration of FIG. 10A, the opening on the ink ejection surface side of the formed orifice is compared with the case where laser processing is performed with the configuration of FIG. 10B. The variation in the diameter of the portion is small, and the shape of the edge of the opening is uniform. However, the shape of the edge of the opening on the laser irradiation surface side of the orifice is not uniform. From this, it is determined that the liquid 12 provided on the laser irradiation surface of the orifice plate 11 affects the shape of the formed orifice on the laser irradiation surface side. Further, it is determined that the liquid 12 provided on the ink ejection surface of the orifice plate 11 affects the shape of the formed orifice on the ink ejection surface side.

  Therefore, first, in the configuration of FIG. 10A, refer to FIG. 12 for the influence of the difference in the viscosity of the liquid 12 on the shape of the edge of the opening on the laser irradiation surface side of the orifice formed in the orifice plate 11. To explain.

  FIG. 12 is a graph showing the relationship between the non-defective product ratio of the orifice plate 11 formed by using PPG having four different viscosity ratios as the liquid 12 in the configuration of FIG. It is. Here, the non-defective product ratio of the orifice plate indicates a ratio in which the defective product is not included in the orifices collectively formed in the configuration of FIG. Here, the PPG used as the liquid 12 has a molecular weight of 400 (viscosity at 25 ° C .: 40 cP), a molecular weight of 800 (viscosity at 25 ° C .: 60 cP), and a molecular weight of 2000 (viscosity at 25 ° C.). Ratio: 163.7 cP) and molecular weight of 2200 (viscosity at 25 ° C .: 200 cP).

  As shown in FIG. 12, the non-defective product rate of the orifice plate 11 decreases as the viscosity of PPG increases. For this reason, it is determined that the viscosity of the liquid 12 provided on the laser irradiation surface of the orifice plate 11 is preferably low. At the point where the viscosity of PPG is about 220 cP, the yield rate of the orifice plate 11 is zero. Therefore, in order to obtain even one good orifice plate 11, the viscosity of the liquid 12 provided on the laser irradiation surface of the orifice plate 11 needs to be 220 cP or less.

  Furthermore, when the orifice plate 11 is used as a nozzle of an inkjet head, it is desirable that the yield rate of the orifice plate 11 is 50% or more. In order to increase the yield rate of the orifice plate 11 to 50% or more, the viscosity of the liquid 12 provided on the laser irradiation surface of the orifice plate 11 is preferably about 56 cP or less from the graph of FIG.

  Next, the influence of the difference in the viscosity of the liquid 12 on the opening on the ink ejection surface side of the orifice formed in the orifice plate 11 in the configuration of FIG. 10B will be described with reference to FIG.

  FIGS. 13 (a) and 13 (b) show a liquid having a molecular weight of 3000 (viscosity at 25 ° C .: 650 cP) and a molecular weight of 2000 (viscosity at 25 ° C. in the configuration of FIG. 10 (b): 163.7 is a diagram showing variation in the diameter of the opening on the ink ejection surface side of the orifice when a plurality of orifices are collectively laser processed using PPG of 163.7 cP). In the figure, the Y axis indicates the diameter of the opening, and one scale is 0.5 μm. The X axis indicates the number of orifices formed at once (hereinafter referred to as the number of channels).

As shown in FIG. 13A, when laser processing is performed using PPG having a molecular weight of 3000 (viscosity at 25 ° C .: 650 cP) as the liquid 12 in the configuration of FIG. The diameter of the opening of the film shows a variation of about 0.7 μm at the maximum. Further, as shown in FIG. 13B, in the configuration of FIG. 10B, laser processing is performed using PPG having a molecular weight of 2000 (viscosity at 25 ° C .: 163.7 cP) as the liquid 12. The variation of the diameter of the opening for each channel is about 1.3 μm at the maximum. Thus, the smaller the viscosity of the liquid 12 provided on the ink ejection surface of the orifice plate 11, the larger the variation in the diameter of the opening on the ink ejection surface side of the formed orifice.

  Although not shown, the shape of the edge of the opening on the ink ejection surface side of the formed orifice is the configuration shown in FIG. 13B compared to the case where laser processing is performed in the configuration shown in FIG. When laser processing is performed at, it becomes more distorted. Although not shown, when laser processing is performed using PPG having a molecular weight of 2500 (viscosity at 25 ° C .: 400 cP) as the liquid 12 in the configuration of FIG. ) And similar results. For these reasons, as the viscosity of the liquid 12 provided on the ink ejection surface of the orifice plate 11 increases, the shape of the edge of the opening on the ink ejection surface side of the formed orifice is uniform, and The variation in diameter is reduced. Specifically, the viscosity of the liquid 12 provided on the ink ejection surface of the orifice plate 11 is preferably at least 650 cP.

[Laser processing method of this embodiment]
An embodiment of the present invention will be described below with reference to FIGS.

  With reference to FIG. 1 and FIG. 2, the laser processing method of this embodiment is demonstrated. 1A to 1C are cross-sectional views illustrating a laser processing method according to the present embodiment. FIG. 2 is a flowchart showing the laser processing method of this embodiment.

  First, the water repellent film 7 is formed on the ink ejection surface of the orifice plate (plate) 1 (S1).

  Next, as shown in FIG. 1A, an upper surface fluidized layer (first fluidized layer) 2a is provided on the laser irradiation surface of the orifice plate 1 where the laser is irradiated, and the surface opposite to the laser irradiation surface. The lower surface fluidized layer (second fluidized layer) 2b is provided on the ink ejection surface (S2). An upper surface protective film (first protective film) 3 is provided on the upper surface fluidized layer 2a, and a lower surface protective film (second protective film) 4 is provided on the lower surface fluidized layer 2b. Then, the orifice plate 1, the upper surface fluidized bed 2a, the lower surface fluidized bed 2b, the upper surface protective film 3 and the lower surface protective film 4 are laminated at room temperature (25 ° C.) (S3). Then, a laser beam (laser light) 5 is irradiated from above the upper surface protective film 3 to form an orifice (through hole) 8 (S4). The processing by the laser beam 5 is performed from the upper surface of the upper surface protective film 3 to a part of the lower surface protective film 4 through the upper surface fluidized layer 2a, the orifice plate 1 and the lower surface fluidized layer 2b. At that time, the by-product 6 generated by scraping each member is deposited on the upper surface of the upper surface protective film 3 and in the vicinity of the opening of the formed orifice 8.

  Next, as shown in FIG.1 (b), the upper surface protective film 3 and the lower surface protective film 4 are peeled from the upper surface fluidized layer 2a and the lower surface fluidized layer 2b (S5). The orifice plate 1 is ultrasonically cleaned using an organic solvent, and the upper surface fluidized layer 2a and the lower surface fluidized layer 2b provided on the laser irradiation surface and the ink ejection surface of the orifice plate 1 are cleaned (S6). Thereby, as shown in FIG.1 (c), the clean orifice plate 1 in which the by-product 6 produced by laser processing does not adhere can be obtained.

  The formed orifice 8 has a so-called taper shape in which the diameter becomes smaller as it goes from the laser irradiation surface of the orifice plate 1 to the ink ejection surface.

  The laser processing method of this embodiment is used for forming an orifice of an orifice plate provided in an ink jet head. In addition, the laser processing method of this invention is not restricted to the use mentioned above, It can be used in order to form a through-hole in a plate.

  The water repellent film 7 is for suppressing ink from adhering to the ink ejection surface side of the orifice plate 1. In the present embodiment, the water repellent film 7 is formed on the ink ejection surface of the orifice plate 1 before the orifice 8 is formed. As a result, the by-product 6 generated by forming the orifice 8 does not affect the formation of the water-repellent film 7, and is cleaner than the conventional method of forming the water-repellent film after forming the orifice. It is possible to obtain an orifice plate 1.

  In the present embodiment, the water repellent film 7 is composed of a fluorine-based silane coupling agent. Since the fluorinated silane coupling agent has water repellency even with a monomolecular film (2 to 3 nm), the water repellent film 7 can be formed very thin compared to other water repellent materials. Therefore, the influence of the water repellent film 7 on the shape of the orifice 8 on the ink ejection surface side of the orifice plate 1 can be reduced. In addition, compared with other water repellent materials, the range of applicable laser processing conditions is wide, and the orifice 8 can be easily formed.

  In this embodiment, the water repellent film 7 is formed on the ink ejection surface side of the orifice plate 1 before the orifice 8 is formed, but the present invention is not limited to this. That is, the water repellent film 7 may be formed on the ink ejection surface side of the orifice plate 1 after the orifice 8 is formed. In the laser processing method of the present invention, the water repellent film 7 may not be formed.

  The laser beam 5 is for forming the orifice 8 in the orifice plate 1. The laser beam 5 is irradiated by an excimer laser having a wavelength of 248 nm. In the excimer laser, the oscillation conditions are set to laser power: 680 mJ / cm 2, frequency: 100 Hz, and number of shots: 450 shots. As a result, the diameter of the opening on the laser irradiation surface side of the orifice 8 is about 40 μm, and the diameter of the opening on the ink ejection surface side is about 20 μm.

  The orifice plate 1 is an ink jet head in which an orifice that is an ejection port for ejecting ink is formed. In general, ablation processing is the center of processing using an excimer laser. Therefore, the processing state of the material to be processed depends on the light absorption coefficient of the material. That is, if the light absorption coefficient of the material is below a certain threshold value, it cannot be processed by an excimer laser having a predetermined power. Therefore, in order to form the orifice 8 in the orifice plate 1 by the laser beam 5, the light absorption coefficient of the orifice plate 1 needs to be a certain value or more.

Therefore, in the present embodiment, the orifice plate 1 is made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more with respect to an excimer laser having a wavelength of 248 nm. The polymer is mainly composed of a material containing a polyimide derivative. In addition to the polyimide derivative, polystyrene, polyamide, polymethyl methacrylate, and the like can be used as the polymer. Thereby, it becomes possible to easily ablate the orifice plate 1 using an excimer laser having a wavelength of 248 nm. Moreover, since the said polymer containing the polyimide derivative is excellent in chemical resistance, it can be used suitably also as a nozzle of an inkjet head.

The upper surface protective film 3 is for preventing the by-product 6 generated by the formation of the orifice 8 from adhering to the laser irradiation surface of the orifice plate 1. The lower surface protective film 4 is for preventing the by-product 6 generated by the formation of the orifice 8 from adhering to the ink ejection surface of the orifice plate 1. Similar to the orifice plate 1, the upper surface protective film 3 and the lower surface protective film 4 are made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more for an excimer laser having a wavelength of 248 nm. Since the polymer used is the same as that of the orifice plate 1, description thereof is omitted. Thus, by forming the upper surface protective film 3 and the lower surface protective film 4 from the same material as that of the orifice plate 1, it is possible to obtain the clean orifice plate 1 having the orifice 8 formed more elaborately. In the present invention, it is only necessary that at least the upper surface protective film 3 is made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more for an excimer laser having a wavelength of 248 nm.

  Here, the structure of the upper surface fluidized bed 2a and the lower surface fluidized bed 2b used in the laser processing method of the present embodiment will be described based on the results obtained by examining the conventional laser processing method shown in FIGS.

  In the conventional laser processing method, the viscosity of the liquid 12 applied to the ink ejection surface of the orifice plate 11 is low, so that the stability of the orifice plate 11 is lowered. For this reason, when the orifice plate 11 is irradiated with the laser beam 15, the focus position of the laser beam 15 is shifted due to the movement of the orifice plate 11. As a result of the focus position shift of the laser beam 15, the diameter of the opening on the ink ejection surface side of the orifice formed in the orifice plate 11 varies. Further, since the viscosity of the liquid 12 is low, the adhesion between the orifice plate 11 and the lower surface protective film 14 is weak, and the impact of laser irradiation is dispersed in the liquid 12. Then, due to the impact dispersed in the liquid 12, the shape of the edge of the opening on the ink ejection surface side of the orifice plate 11 becomes distorted.

  Further, since the viscosity of the liquid 12 applied to the laser irradiation surface of the orifice plate 11 is high, the liquid 12 does not spread over the entire laser irradiation surface, and undulation occurs in the upper surface protective film 13 provided on the liquid 12. . Therefore, when the upper surface protective film 13 is irradiated with the laser beam 15, a focus position shift of the laser beam 15 occurs. Due to the focus position shift of the laser beam 15, the diameter of the opening on the ink ejection surface side of the orifice formed on the orifice plate 11 varies, and the opening on the laser irradiation surface side of the orifice Edge shape is non-uniform.

  Therefore, in the present embodiment, the viscosity of the upper surface fluidized bed 2a and the lower surface fluidized bed 2b is characterized to reduce the variation in the diameter of the opening on the ink ejection surface side of the orifice 8, and the ink ejection surface. The shape of the edge of the opening on the side and the laser irradiation surface side is made uniform.

  The upper surface fluidized bed 2 a is for adhering the upper surface protective film 3 to the laser irradiation surface of the orifice plate 1. From the examination of the conventional laser processing method, it is determined that the liquid provided on the laser irradiation surface of the orifice plate preferably has a low viscosity. The viscosity of the upper fluidized bed 2a necessary for obtaining at least one good orifice plate 1 is about 220 cP or less as shown in FIG. Furthermore, in order to use the orifice plate 1 as a nozzle of an ink jet head, it is desirable that the yield rate is 50% or more. From FIG. 12, in order to make the yield rate of the orifice plate 1 50% or more, the viscosity of the upper surface fluidized bed 2a is preferably 56 cP or less.

  In the present embodiment, PPG having a molecular weight of 400 (viscosity at 25 ° C .: 40 cP) is used as the upper surface fluidized bed 2a. Thereby, the upper surface fluidized bed 2a spreads over the entire laser irradiation surface of the orifice plate 1, and the upper surface protective film 3 does not swell. For this reason, the focus position of the laser beam 5 does not shift, the variation in the diameter of the opening on the ink ejection surface side of the orifices 8 collectively formed on the orifice plate 1 is small, and the opening on the laser irradiation surface side of the orifice 8. The shape of the edge becomes uniform.

  The lower surface fluidized bed 2 b is for adhering the lower surface protective film 4 to the ink ejection surface of the orifice plate 1. From the examination of the conventional laser processing method, it is determined that the liquid provided on the ink ejection surface of the orifice plate preferably has a higher viscosity. From FIG. 13 (a) and FIG. 13 (b), the preferred viscosity for the lower fluidized bed 2b is 650 cP or more.

  In the present embodiment, PPG having a molecular weight of 3000 (viscosity at 25 ° C .: 650 cP) is used as the lower surface fluidized bed 2b. Thereby, stability and adhesiveness of the orifice plate 1 and the lower surface protective film 4 can be improved. Therefore, in the present embodiment, it is possible to form the orifice 8 in which the shape of the edge of the opening on the ink ejection surface side of the orifice plate 1 is uniform and the variation in the diameter of the opening is small.

  As described above, in this embodiment, polypropylene glycol (PPG) is used as the upper surface fluidized bed 2a and the lower surface fluidized bed 2b. The reason why PPG is preferably used in the present invention is that PPG is a material having low volatility, and therefore, a predetermined distance is maintained between the orifice plate 1 and the upper surface protective film 3 and the lower surface protective film 4 for a long time. In view of the fact that the reactivity with the material containing the polyimide derivative constituting the orifice plate 1 is low, it is possible to prevent generation of extra by-products during laser processing, organic solvents and neutral detergents. For example, the orifice plate 1 can be easily removed by washing it. As described above, in the present embodiment, by using PPG as the upper surface fluidized bed 2a and the lower surface fluidized bed 2b, a cleaner orifice plate 1 having a fine orifice 8 can be obtained.

  In this embodiment, PPG is used at room temperature (25 ° C.). However, it can be changed to a predetermined temperature in order to adjust the viscosity of PPG. In the present embodiment, PPG is described as the material of the upper surface fluidized bed 2a and the lower surface fluidized bed 2b, but the present invention is not limited to this. For example, a fluid material such as a sol may be used (refers to a material having a viscosity of 10,000 cP or less).

  Next, the state of the orifice plate 1 in which the orifice 8 is formed by the laser processing method of the present embodiment will be described with reference to FIGS.

  FIG. 3 is a view showing an SEM photograph of the ink ejection surface side of the orifice formed by the laser processing method of the present embodiment. As shown in FIG. 3, the orifice 8 formed by the laser processing method of this embodiment has a uniform edge shape on the ink ejection surface side of the orifice plate 1. The roundness of the mask pattern used for forming the orifice 8 (variation in the diameter of the circle) is 0.1 μm, whereas the roundness of the opening on the ink ejection surface side of the orifice 8 is 0.5 μm. It is. Thus, by using the laser processing method of this embodiment, it is possible to form a very elaborate orifice 8.

  FIG. 4 is a view showing a micrograph of the laser irradiation surface side of the orifice 8 formed by the laser processing method of the present embodiment. Here, after the orifice 8 is formed, the orifice plate 1 is ultrasonically cleaned using an organic solvent. As described above, most of the orifices 8 collectively formed by the laser processing method according to the present embodiment have a uniform edge shape on the laser irradiation surface side of the orifice plate 1 as shown in FIG. Specifically, the ratio of manufacturing the defective product with the irregular shape of the opening edge on the laser irradiation surface side of the orifice 8 is about 3% or less in the laser processing method of this embodiment.

FIG. 5 is a graph showing measured values of the diameters of the openings on the ink ejection surface side of the orifices 8 formed collectively by the laser processing method of the present embodiment. In the figure, the Y axis indicates the diameter of the opening, and one scale is 0.5 μm. Further, the X axis indicates the number of orifices 8 formed collectively (hereinafter referred to as the number of channels). In the conventional laser processing method, the diameter of the opening for each channel showed a variation of about 1.2 μm at the maximum, but in the laser processing method of the present embodiment, the diameter is about 0.5 μm at the maximum. As described above, in the laser processing method according to the present embodiment, the variation in the diameter of the opening on the ink ejection surface side of the formed orifice 8 is smaller than that in the prior art.

  As described above, in the laser processing method of the present embodiment, the lower surface fluidized layer 2b having a higher viscosity than the upper surface fluidized layer 2a is provided on the ink ejection surface of the orifice plate 1, and the lower surface protective film 4 is provided thereon. The stability and adhesion between the orifice plate 1 and the lower surface protective film 4 can be improved. Further, by providing the upper surface fluidized bed 2a having a lower viscosity than the lower surface fluidized bed 2b on the laser irradiation surface side of the orifice plate 1, the upper surface fluidized bed 2a spreads over the orifice plate 1 evenly. The wave | undulation which arises in the upper surface protective film 3 provided in is suppressed. Therefore, the focus position shift due to the laser irradiation is suppressed, and the variation in the diameter of the opening on the surface opposite to the laser irradiation surface of the formed orifice 8 can be reduced. Further, the shape of the edge of the opening on the laser irradiation surface side and the ink ejection surface side of the orifice 8 can be made uniform.

  Further, by providing the upper surface protective film 3 and the lower surface protective film 4 on the laser irradiation surface and the ink discharge surface of the orifice plate 1, the by-product 6 generated by forming the orifice 8 adheres to the orifice plate 1. To prevent. And since the upper surface fluidized bed 2a and the lower surface fluidized bed 2b can be removed easily, a clean orifice plate having an elaborate orifice can be obtained.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention is suitably used when a through hole is formed in a plate, or when an orifice is formed in an orifice plate provided in an ink jet head.

It is sectional drawing which shows one Embodiment of the laser processing method in this invention. It is a flowchart which shows the said laser processing method. It is the figure which showed the SEM photograph of the ink discharge surface of the orifice formed by the said laser processing method. It is the figure which showed the SEM photograph of the laser irradiation surface of the orifice formed by the said laser processing method. It is a graph which shows the measured value of the diameter of the opening part in the ink discharge surface side of the orifice collectively formed by the said laser processing method. (A)-(d) is sectional drawing which shows the conventional laser processing method. It is the figure which showed the SEM photograph by the side of the ink discharge surface of the orifice formed by the conventional laser processing method. It is the figure which showed the SEM photograph by the side of the laser irradiation surface of the orifice formed by the conventional laser processing method. It is a graph which shows the measured value of the diameter of the opening part in the ink discharge surface side of the orifice collectively formed by the conventional laser processing method. (A) is sectional drawing which showed the structure for examining the influence which the liquid apply | coated to the laser irradiation surface side of an orifice plate has on orifice formation, (b) is the ink discharge surface side of an orifice plate. It is sectional drawing which showed the structure for examining the influence which the apply | coated liquid has on orifice formation. (A) is the figure which showed the microscope picture of the laser irradiation surface of the orifice formed with the structure of Fig.10 (a), (b) is the laser of the orifice formed with the structure of FIG.10 (b). It is the figure which showed the microscope picture of the irradiated surface. FIG. 11 is a graph showing a relationship between a non-defective product rate of an orifice plate formed by using PPG having different viscosity in four stages as a liquid in the configuration of FIG. 10A shows an ink ejection surface of an orifice when a plurality of orifices are collectively laser processed using PPG having a molecular weight of 3000 (viscosity at 25 ° C .: 650 cP) as a liquid in the configuration of FIG. It is the figure which showed the measured value of the diameter of the opening part in the side, (b) is the case where several orifices are collectively laser-processed using PPG whose molecular weight is 2000 (viscosity at 25 degreeC: 163.7 cP) FIG. 6 is a diagram showing measured values of the diameter of the opening on the ink ejection surface side of the orifice.

Explanation of symbols

1 Orifice plate (plate)
2a Upper surface fluidized bed (first fluidized bed)
2b Lower surface fluidized bed (second fluidized bed)
3 Top surface protective film (first protective film)
4 Bottom protective film (second protective film)
5 Laser beam (laser light)
6 By-product 7 Water repellent film 8 Orifice (through hole)

Claims (11)

In a laser processing method for forming a through hole in a plate by laser light,
A step of providing a fluidized first fluidized bed and a first protective film in this order on the laser-irradiated surface irradiated with the laser beam of the plate;
A step of providing a second fluidized bed having a higher viscosity than the first fluidized bed on the surface opposite to the laser irradiation surface of the plate, and a second protective film in this order;
Irradiating the laser irradiation surface of the plate with laser light to form a through hole in the plate;
Removing the first protective film and the second protective film;
And a step of removing the first fluidized bed and the second fluidized bed. The laser processing method according to claim 1, wherein the plate is made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more for an excimer laser having a wavelength of 248 nm.   The laser processing method according to claim 1, wherein the plate is made of a material containing a polyimide derivative.   The laser processing method according to claim 1, wherein the viscosity of the first fluidized bed is 220 cP or less at 25 ° C.   The laser processing method according to claim 1, wherein the viscosity of the first fluidized bed is 56 cP or less at 25 ° C.   The laser processing method according to claim 1, wherein the viscosity of the second fluidized bed is 650 cP or more at 25 ° C.   The laser processing method according to claim 1, wherein the first fluidized bed and the second fluidized bed are made of polypropylene glycol. The laser processing method according to claim 2, wherein the first protective film is made of a polymer having a light absorption coefficient of 1000 cm ⁻¹ or more for an excimer laser having a wavelength of 248 nm. In an inkjet head manufacturing method for forming an orifice in an orifice plate by laser light,
Forming a water repellent film on a surface opposite to the laser irradiation surface irradiated with the laser light of the orifice plate;
Providing a fluidized first fluidized bed and a first protective film in this order on the laser irradiation surface of the plate;
A step of providing a second fluidized bed having a higher viscosity than the first fluidized bed on the surface opposite to the laser irradiation surface of the plate, and a second protective film in this order;
Irradiating the laser irradiation surface of the plate with laser light to form an orifice in the plate;
Removing the first protective film and the second protective film;
And a step of removing the first fluidized bed and the second fluidized bed.   The ink jet head manufacturing method according to claim 9, wherein the water repellent film is made of a fluorine-based silane coupling agent.   An ink jet head manufacturing method, wherein a through hole of a plate formed by the laser processing method according to claim 1 is used as an ink discharge port.

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