Ink jet printer head

Abstract: An ink jet printer head includes a substrate (112) having a heat resisting body (114), an ink chamber barrier (122) installed on the substrate (112) so as to form a side wall of an ink chamber (124) filled with ink introduced through an ink channel (125), and a nozzle plate (121) having a nozzle hole (126) communicating with the ink chamber (125) and installed on the ink chamber barrier (122), and an ink separating wall (123) protruding from a periphery of the nozzle hole (126) towards the substrate (112) located on the ink channel (125) to interrupt a flow of the ink is provided in the nozzle plate (121). The backflow of the ink into the interior of the ink channel (125) and an ink tail generated in the nozzle and a satellite droplet are reduced by using the ink separating wall (123), thereby improving printing efficiency and printing quality.

Description: The present invention relates to an ink jet printer head, and more particularly, to an ink jet printer head capable of increasing printing efficiency and quality by improving a structure of an ink passage, to decrease ink backflow and improve an ink droplet shape. Generally, an ink jet printer head uses a thermal driving method or a piezoelectric driving method to discharge ink. According to the thermal driving method, ink is instantly heated by a heat resisting body, generating a bubble. As the bubble is inflated, ink is discharged to a nozzle hole by the pressure of the bubble. According to the piezoelectric driving method, ink is discharged to a nozzle hole by the force applied from the displacement of a piezoelectric body. US 5,900,894 discloses an ink jet print head, method for the same and ink jet recording device. Conventional thermal driving ink jet printer heads are grouped into two types based upon a discharge direction with respect to a substrate and a nozzle plate: (1) a side shooting type (as shown in Figure 1A) and (2) an upper surface shooting type (as shown in Figure 1B). According to the side shooting type ink jet printer head 10 of Figure 1A, a nozzle hole 16 is formed at one side end portion of an ink channel 13, which is formed between a substrate 11 and a nozzle plate 12. A bubble 2 is generated from ink 1 of the ink channel 13, which is instantly heated by a thin film heat resisting body 14. Due to the growing pressure exerted by the bubble 2, the ink 1 is discharged from the nozzle hole 16 to the outside. The upper surface shooting type ink jet printer head 20 of Figure 1B comprises an ink chamber barrier 23, which is formed on a substrate 11 (not shown) on which a thin film radiating resistance body (not shown) is disposed to form an ink chamber 24 communicating with an ink channel 22, and a nozzle plate 25, which is formed on the ink chamber barrier 23 and has a nozzle hole 26 communicating with the ink chamber 24. According to the ink jet printer head 20, the ink (not shown) of the ink chamber 24 is instantly heated by heating a thin film heat resisting body (not shown). A bubble (not shown) is generated from the heated ink and expands, creating pressure against an interior of the ink chamber 24, and discharging the ink to the outside through the nozzle hole 26. However, in the conventional ink jet printer heads 10 and 20, an ink backflow phenomenon occurs due to an inflating pressure of the bubble 2, in which the ink 1 reverses into the ink channels 13 and 22. The ink backflow accompanies a cross-talk in the printing operation, and deteriorates the printing quality. Furthermore, in the conventional ink jet printer heads 10 and 20, a tail is generated in a discharging ink drop when the bubble 2 decreases in size. The ink drop tail is extended by the surface tension and the viscosity of the ink 1. The ink drop tail generates several fragments, and accordingly decreases the resolution and print quality. In order to overcome the above-mentioned problems, in the conventional side shooting type ink jet printer head 10, the length of the ink channel 13 is increased to restrain the generation of the backflow and the ink drop tail. However, such a structure increases the size of the ink jet printer head and decreases the ink discharging efficiency. In the upper surface shooting type ink jet printer head 20, a neck is formed by machining step portions 23a and 23b in the ink channel 22 of the ink chamber barrier 23, formed on substrate 21, to restrain the backflow of the ink. However, such a structure requires a complex manufacturing process. Also, because the height of the ink channel 22 formed between the ink chamber 24 and the nozzle plate 25 remains constant, printer efficiency is restricted. Accordingly, it is an aim of embodiments of the present invention to solve or reduce at least some of the above-mentioned problems of the conventional printer heads. It is another aim of embodiments of the present invention to provide an ink jet printer head with increased printing efficiency and printing quality. It is a further aim of embodimentsof the present invention to provide an ink jet printer head with an improved ink passage, reduced backflow, and improved [the shape of the] ink droplet shape. Additional aims and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention. According to a first aspect of the present invention there is provided an ink jet printer head comprising: a substrate having a heat resisting body; an ink chamber barrier formed on the substrate so as to form a side wall of an ink chamber to be filled with ink introduced through an ink channel; and a nozzle plate having a nozzle hole formed in the nozzle plate communicating with the ink chamber, the nozzle plate being formed on the ink chamber barrier, and the nozzle plate further having an ink separating wall protruding from a periphery of the nozzle hole towards the substrate located on the ink channel to interrupt a flow of the ink; wherein ink disposed in said ink chamber is heated to form a bubble, said bubble blocking a flow in a reverse direction of said ink from said ink chamber into said ink channel; characterised by: the thickness (t) of the ink separating wall being less than a distance between an upper surface of the heat resisting body and a lower surface of the nozzle plate. Preferably, an upper surface of the substrate is spaced from a tip end portion of the ink separating wall (123) by a predetermined distance. Preferably, a tip end portion of the ink separating wall is disposed on an upper side of a peripheral border line of the heat resisting body. A length (1) of the ink separating wall is preferably less than a length of the ink channel. A width (w) of the ink separating wall is preferably less than a width of the ink chamber and larger than a width of the heat resisting body. Preferably, a flow resistance in the reverse direction is greater than a flow resistance of said ink in a discharge direction from said ink chamber through said nozzle hole. Preferably, the flow resistance of said ink in the reverse direction corresponds to a width of said ink channel. According to a second aspect of the present invention there is provided a method to manufacture an ink jet printer head comprising: forming a heat resisting body on a substrate; partially forming an ink chamber barrier by machining a polymer plate and shaping ends of the ink chamber barrier and an ink separating wall by using a first mask and an excimer laser, wherein the thickness of the ink separating wall is less than a distance between an upper surface of the heat resisting body and a lower surface of the nozzle plate; completely forming the ink chamber barrier, the ink separating wall, and a nozzle plate by secondly machining the polymer plate and shaping sides of the ink separating wall by using a second mask and the excimer laser; forming a nozzle hole in the secondly machined polymer plate by using a third mask and the excimer laser; and bonding the substrate to the ink chamber barrier. According to a third aspect of the present invention there is provided a method of manufacturing an ink jet printer head comprising: forming a heat resisting body on a substrate; laminating a sacrifice layer on the substrate; patterning the sacrifice layer by a predetermined width and a predetermined length; forming a polymer layer on the sacrifice layer; etching the polymer layer to form an ink chamber barrier forming an ink chamber to receive ink through an ink channel; forming an ink separating wall protruding into the ink channel by removing the sacrifice layer, wherein the thickness of the ink separating wall is less than a distance between an upper surface of the heat resisting body and an upper surface of the ink chamber; and bonding the substrate to the ink chamber barrier. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figure 1A is a partial cross-sectional view of a conventional side shooting type ink jet printer head; Figure 1B is a partial cross-sectional view of a conventional upper surface shooting type ink jet printer head; Figure 2 is a perspective view schematically showing a portion of an ink jet printer head according to a first embodiment of the present invention; Figure 3 is a top view of the ink jet printer head of Figure 2; Figure 4 is a schematic cross-sectional view of the ink jet printer head taken along line I-I of Figure 2; Figure 5 is a vertical cross-sectional view of the heat radiating driving section of Figure 2; Figure 6 is a perspective view of the nozzle section of Figure 2; Figures 7a to 7c are perspective views for explaining the manufacturing process of the nozzle section of Figure 6; Figures 8A to 8H are cross-sectional views for explaining an ink discharging process of the ink jet printer head shown in Figure 2; Figure 9 is a perspective view schematically showing an ink jet printer head according to a second embodiment of the present invention; Figure 10 is a top view schematically showing the ink jet printer head of Figure 9; Figure 11 is a cross-sectional view schematically showing the ink jet printer head of Figures 9 and 10; Figure 12 is a perspective view of the nozzle section of Figure 9; Figure 13 is a perspective view schematically showing an ink jet printer head according to a third embodiment of the present invention; Figure 14 is a top view schematically showing the ink jet printer head of Figure 13; Figure 15 is a cross-sectional view schematically showing the ink jet printer head of Figures 13 and 14; Figure 16 is a perspective view of the nozzle section of Figure 13; Figures 17 is a perspective view schematically showing an ink jet printer head according to the fourth embodiment of the present invention; Figure 18 is a top view schematically showing the ink jet printer head of FIG 17; Figure 19 is a cross-sectional view schematically showing the ink jet printer head of Figures 17 and 18; and Figure 20 is a perspective view of the nozzle section of Figure 17. Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. Figures 2 to 4 show a unit discharging structure of an ink jet printer head according to a first embodiment of the present invention. Although the head of an ink jet printer is formed by aggregating a plurality of unit discharging structures, here, a single unit discharging structure will be referred to as an ink jet printer head for simplicity. The ink jet printer head 100 (i.e., one unit discharging head) comprises a heat radiating section 110 and a nozzle section 120. As shown in Figures 2 and 5, the heat radiating section 110 includes an oxide film 112a formed on a substrate 112 and a heat resisting body 114 formed at a central portion of the oxide film 112a. A wire 116 is formed on the oxide film 112a and the heat resisting body 114. The wire 116 is etched, except at the periphery of the heat resisting body 114. A heat protecting layer 114a is formed on the wire 116. The oxide film 112a acts as an insulating member, and the heat resisting body 114 converts an electrical signal, applied from an outside driving circuit (not shown) through the wire 116, into heat energy. The heat protecting layer 114a is formed on the heat resisting body 114 and the upper portion of the wire 116 to prevent damage generated by the impact when a bubble 2 (shown in Figures 8A to 8H) formed of ink 1 shrinks. The heat protecting layer 114a also acts as an insulating member. The substrate 112 is made of a silicon wafer, and the heat resisting body 114 is made of Ta-Al or polysilicon. The heat protecting layer 114a is made of a complex material of a silicon oxide film or a silicon nitride film and a metal layer. As shown in Figures 2 and 6, the nozzle section 120 is formed by forming an ink chamber barrier 122, an ink separating wall 123, and a nozzle hole 126 on a nozzle plate 121. The ink separating wall 123 is formed on the nozzle plate 121 to interrupt the ink flow through an ink channel 125. A bonding layer is formed on the upper surface of the ink chamber barrier 122 to bond the ink chamber barrier 122 to the substrate 112. The ink jet printer head 100 of embodiments of the present invention is formed by bonding the heat driving section 110 of Figure 5 to the nozzle section 120 of Figure 6. The bonding is accomplished by bonding a bonding layer of the upper surface of the ink chamber barrier 122 to the substrate 112 by a thermal compression. The upper and lower surfaces of the ink jet printer head 100 are created by the substrate 112 and the nozzle plate 121, and the front and rear side walls are created by the ink chamber barrier 122. An ink chamber 124 is a space defined in the ink separating wall 123. The ink channel 125 is a passage through which the ink 1 is supplied to the ink chamber 124 from an ink receptacle (not shown). For simplicity, the oxide film 112a of the upper surface of the substrate 112, the wire 116, and the heat protecting layer 114a are omitted from Figures 2 to 4. As shown in Figures 3 and 4, a tip end portion 123a of the ink separating wall 123 is separated vertically from the heat resisting body 114. The ink separating wall 123 and a portion of both ends of the heat resisting body 114 are laid horizontally over the substrate 112 so that the ink chamber 124 and the ink channel 125 can be automatically blocked by the bubble 2 generated by the heat resisting body 114. A thickness (t) of the ink separating wall 123 is less than a height from the upper surface of the heat resisting body 114 installed on the substrate 112 to the lower surface of the nozzle plate 121. A length ( l ) of the ink separating wall 123 is less than the length of the ink channel 125. A width (w) of the ink separating wall 123 is less than the width of the ink chamber 124 and is larger than the width of the heat resisting body 114. Referring to Figures 7A to 7C, a method of forming the nozzle section 120 will be explained. In order to form the nozzle section 120 of the ink jet printer head 100 of the present invention, the nozzle plate 121 is machined by using an excimer laser. The nozzle plate 121, the ink chamber barrier 122, the ink separating wall 123, and the nozzle hole 126 are formed by processing a polymer plate with the excimer laser. First, as shown in Figure 7A, by using a first mask (not shown) having openings corresponding to an area where the ink chamber barrier 122 is to be formed, a rectangular polymer plate is first machined by the excimer laser to a predetermined depth, shaping an upper side of the ink chamber barrier 122 and an end of the ink separating wall 123, and thus partially forming the ink chamber barrier 122. Second, as shown in Figure 7B, an ink chamber 124 is defined by machining the polymer plate to a predetermined depth by using a second mask (not shown) and the excimer laser, completely shaping the ink separating wall 123. Accordingly, after the second machining process, the nozzle plate 121, the ink chamber barrier 122, and the ink separating wall 123 are completely shaped. Finally, as shown in Figure 7C, by using a third mask (not shown) and irradiating the excimer laser to the nozzle plate 121, a nozzle hole 126 is formed in the nozzle plate 121 having a gradually decreasing diameter toward an ink exiting side. Accordingly, the nozzle section 120 is completely formed. Although not shown, another method of forming the nozzle section 120 is to laminate and pattern a photosensitive polymer. A sacrifice layer of a predetermined thickness is laminated on the substrate 112 by vapor deposition or sputtering. Here, the predetermined thickness of the sacrifice layer corresponds to a length from the nozzle plate 121 to an upper portion of the ink chamber barrier 122. Next, the sacrifice layer is patterned to have a certain width and length, the suitable measurements for the ink separating wall 123, and to define a space between the ink separating wall 123 and the heat resisting body 114. Then a photosensitive polymer film is laminated on the substrate 112 as a material to form the ink chamber 124 on the patterned sacrifice layer, and the photosensitive polymer film is etched. Then, the nozzle section 120 is completed by removing the sacrifice layer from the lower portion of the ink chamber 124 and thus forming the ink separating wall 123. The ink chamber 124 can be formed by spin coating a photoresist. Figures 8A to 8H show the processes in which the ink 1 is discharged from the ink jet printer head 100 according to the first embodiment of the present invention. As shown in Figure 8A, before generation of the bubble 2, the ink 1 is reserved in the ink chamber 124. Then, with an electrical signal applied to the heat resisting body 114, the bubble 2 is generated by the heat energy generated from the heat resisting body 114. Accordingly, as shown in Figure 8B, the ink 1 is discharged through the nozzle hole 126 by the bubble 2. Since the bubble 2 does not reach the ink separating wall 123, which is separated from the heat resisting body 114, there is an ink flow only between the ink chamber 124 and the ink channel 125. However, as shown in Figure 8C, if the heating by the heat resisting body 114 continues, the bubble 2 is inflated and the interior pressure is increased, and, as shown in Figure 8D, the phase varying sections 2a reach the ink separating wall 123 and the ink chamber 124. As a result, the ink channel 125 is blocked by the bubble 2. Therefore, as shown in Figures 8D and 8E, once the ink chamber 124 and the ink channel 125 are blocked by the bubble 2, these elements remain blocked until the electrical signal to the heat resisting body 114 is cut off and the bubble 2 loses inertia. Since a flowing resistance in the reverse direction (arrow B) is larger than that in the discharging direction (arrow A), an amount of backflow of the ink 1 is reduced, and the inflating force of the bubble 2 can be efficiently used to discharge the ink 1 through the nozzle hole 126. As shown in Figures 8F to 8H, while the ink 1 is discharged through the nozzle hole 126, the interior pressure on the bubble 2 decreases, and the bubble 2 loses its inertia and shrinks. The ink 1 is ejected to a printing medium (not shown) from the nozzle hole 126 to accomplish the printing. As mentioned above, according to the ink jet printer head 100 of the first embodiment of the present invention, since the ink chamber 124 is separated from the ink channel 125 by the bubble 2, only the ink 1 isolated in the ink chamber 124 is ejected. Therefore, generation of the ink tail and the satellite droplet is reduced. On the other hand, if the flow resistance in the ink channel 125 is too large, the time to recharge the ink 1 in the ink chamber 124 is lengthened, and the printing speed is decreased. In such a case, the flow resistance can be reduced by decreasing the thickness (t) of the ink separating wall 123. Figures 9 to 11 are views of an ink jet printer head 100 according to a second embodiment of the present invention, showing an ink separating wall 123 being installed in an ink channel 125 having a reduced width (w p ) to increase the flow resistance in the reverse direction. By regulating the width (w p ) of the ink channel 125, i.e., by installing the ink separating wall 123 and extending both ends of the ink chamber barrier 122 towards the ink channel 125, the flow resistance in the reverse direction can be regulated. Figure 12 illustrates the nozzle section 120 of Figure 9. Figures 13 to 15 show an ink jet printer head 100 according to the third embodiment of the present invention and Figure 16 shows the nozzle section 120 of the ink jet printer head 100 of Figures 13 to 15. Figures 17 to 20 show an ink jet printer head 100 according to the fourth embodiment of the present invention. Except for the fact that the third and fourth embodiments have only one ink channel 125, the first and second embodiments are identical to the third and fourth embodiments. Accordingly, an explanation of the third and fourth embodiments will be omitted. According to the ink jet printer head 100 of embodiments of the present invention, by installing the ink separating wall 123, the ink flow between the ink chamber 124 and the ink channel 125 is blocked by the bubble 2 which is generated to discharge the ink 1. Thus, the backflow of the ink 1 and the ink tail generated in the nozzle and the satellite droplet are reduced, and the printing efficiency and quality of the printing operation are improved. Furthermore, energy consumption is [not needed] reduced, and still further, because the process of installing the ink separating wall 123 is combined with the conventional chamber forming process without requiring separate devices or complex processes, the operational cost and the process cost are decreased. Also, since the ink channel 125 can be varied in the height direction to regulate the ink flow resistance, the length of the unit discharging structure can be reduced and the integration of the unit discharging structures in the inkjet printer head is improved.

Claims: An ink jet printer head comprising: a substrate (112) having a heat resisting body (114); an ink chamber barrier (122) formed on the substrate (112) so as to form a side wall of an ink chamber (124) to be filled with ink introduced through an ink channel; and a nozzle plate (121) having a nozzle hole (126) formed in the nozzle plate (121) communicating with the ink chamber (124), the nozzle (121) plate being formed on the ink chamber barrier (122), and the nozzle plate (121) further having an ink separating wall (123) protruding from a periphery of the nozzle hole (126) towards the substrate located on the ink channel to interrupt a flow of the ink; wherein ink disposed in said ink chamber (124) is heated to form a bubble, said bubble blocking a flow in a reverse direction of said ink from said ink chamber (124) into said ink channel (125); characterised by : the thickness (t) of the ink separating wall (123) being less than a distance between an upper surface of the heat resisting body (114) and a lower surface of the nozzle plate (121). The ink jet printer head of claim 1, wherein an upper surface of the substrate (112) is spaced from a tip end portion (123a) of the ink separating wall (123) by a predetermined distance. The ink jet printer head of claim 1 or 2, wherein a tip end portion (123a) of the ink separating wall (123) is disposed on an upper side of a peripheral border line of the heat resisting body (114). The ink jet printer head of claim 1, 2 or 3, wherein a length (1) of the ink separating wall (123) is less than a length of the ink channel. The ink jet printer head of claim 1, 2, 3 or 4, wherein a width (w) of the ink separating wall (123) is less than a width of the ink chamber (124) and larger than a width of the heat resisting body (114). The printer head of any of claims 1 to 5, wherein a flow resistance in the reverse direction is greater than a flow resistance of said ink in a discharge direction from said ink chamber (124) through said nozzle hole (126). The printer head of claim 6, wherein the flow resistance of said ink in the reverse direction corresponds to a width of said ink channel (125). A method to manufacture an ink jet printer head comprising: forming a heat resisting body (114) on a substrate (112); partially forming an ink chamber barrier (122) by machining a polymer plate and shaping ends of the ink chamber barrier (122) and an ink separating wall (123) by using a first mask and an excimer laser; completely forming the ink chamber barrier (122), the ink separating wall (123), and a nozzle plate (121) by secondly machining the polymer plate and shaping sides of the ink separating wall (123) by using a second mask and the excimer laser wherein the thickness (t) of the ink separating wall (123) is less than a distance between an upper surface of the heat resisting body (114) and a lower surface of the nozzle plate (121); forming a nozzle hole (126) in the secondly machined polymer plate by using a third mask and the excimer laser; and bonding the substrate (112) to the ink chamber barrier (122). The method of claim 8, wherein the nozzle hole (126) has a gradually decreasing diameter. A method of manufacturing an ink jet printer head comprising: forming a heat resisting body (114) on a substrate (112); laminating a sacrifice layer on the substrate (112); patterning the sacrifice layer by a predetermined width and a predetermined length; forming a polymer layer on the sacrifice layer; etching the polymer layer to form an ink chamber barrier (122) forming an ink chamber (124) to receive ink through an ink channel; forming an ink separating wall (123) protruding into the ink channel by removing the sacrifice layer, wherein the thickness (t) of the ink separating wall (123) is less than a distance between an upper surface of the heat resisting body (114) and an upper surface of the ink chamber (124); and bonding the substrate (112) to the ink chamber barrier (122).

Inventors: LIM SEONG-TAEK, SHIN KYU-HO, SHIN SU-HO, LIM, SEONG-TAEK, SHIN, KYU-HO, SHIN, SU-HO, Lim, Seong-taek, 708-1504 Seogwang Apart., Shin, Kyu-ho, 103-1205, Woobang Apartment, Shin, Su-ho, 324-903 Daewoo Apartment
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 2001
Main classification: B41J2
IPC codes: B41J2