KR100474838B1 - Ink-jet print head having semispherical ink chamber - Google Patents

Abstract

An ink jet print head with a hemispherical ink chamber is disclosed. The disclosed ink jet print head comprises: a substrate in which an manifold for supplying ink, an ink chamber having a substantially hemispherical shape, and an ink channel for supplying ink from the manifold are integrally formed; A nozzle plate stacked on the substrate and having a nozzle formed at a position corresponding to the center of the ink chamber; A heater provided on the nozzle plate and formed in an annular shape surrounding the nozzle; And an electrode provided on the nozzle plate to apply a current to the heater. Then, the ink channel is formed to a predetermined depth on the upper surface of the substrate so that both ends thereof are connected to the manifold and the ink chamber, respectively, and to form an ink channel on the nozzle plate, a plurality of ink spaced apart from each other at a position corresponding to the ink channel Grooves for channel formation are formed. Here, the at least two ink channel forming grooves may be arranged to be parallel to each other, or as the at least two are closer to the ink chamber, the gaps may be gradually increased. According to the present invention, it is possible to meet all the requirements of the print head, in particular, the cross-sectional area of the ink channel is sufficiently secured to shorten the refill time of the ink through it to increase the drive frequency of the print head.

Description

Ink-jet print head having semispherical ink chamber

The present invention relates to a bubble jet ink jet print head, and more particularly, to an ink jet print head having a hemispherical ink chamber.

In general, an ink jet print head is an apparatus for ejecting a small droplet of printing ink to a desired position on a recording sheet to print an image of a predetermined color. As an ink ejection method of such an ink jet printer, an electro-thermal transducer (bubble jet method) in which a bubble is generated in the ink by using a heat source to eject ink by this force, and a piezoelectric body are used. Therefore, there is an electro-mechanical transducer in which ink is ejected by a volume change of ink caused by deformation of the piezoelectric body.

1A and 1B are cut-away perspective views showing an ink ejection unit structure disclosed in US Pat. No. 48,825,95, and a cross-sectional view for explaining an ink droplet ejection process, as an example of a conventional bubble jet ink jet print head.

The conventional bubble jet type ink jet print head shown in FIGS. 1A and 1B has a partition wall that forms a substrate 10 and an ink chamber 13 provided on the substrate 10 and filled with ink 19. The member 12, the heater 14 provided in the ink chamber 13, and the nozzle plate 11 in which the nozzle 16 which discharges the ink droplet 19 'are formed are included. The ink 19 is filled in the ink chamber 13 through the ink channel 15, and the ink 19 is also filled in the nozzle 16 in communication with the ink chamber 13 by capillary action. In such a configuration, when current is supplied to the heater 14, the bubble 14 is formed in the ink 19 filled in the chamber 13 while the heater 14 is heated. Thereafter, the bubble 18 continuously expands, and thus pressure is applied to the ink 19 filled in the chamber 13 to push the ink droplet 19 'out through the nozzle 16. Then, the ink 19 is filled in the chamber 13 again while the ink 19 is sucked through the ink channel 15.

By the way, an ink jet print head having such a bubble jet ink ejecting portion must satisfy the following requirements. First, the production should be as simple as possible, inexpensive to manufacture, and capable of mass production. Second, in order to obtain clear picture quality, the generation of fine satellite droplets smaller than the main droplets following the main droplets to be discharged should be suppressed as much as possible. Third, when ejecting ink from one nozzle or refilling the ink into the ink chamber after ejecting the ink, cross talk with other adjacent nozzles that do not eject ink should be suppressed as much as possible. To this end, it is necessary to suppress back flow of ink in the opposite direction of the nozzle during ink ejection. Fourth, for high speed printing, the period of refilling after ink discharge should be as short as possible. In other words, the driving frequency must be high.

However, these requirements often conflict with each other, and the performance of the ink jet print head is in turn closely related to the structure of the ink chamber, the ink flow path and the heater, the resulting bubble formation and expansion, or the relative size of each element. have.

Accordingly, in addition to the above-described US patent US 4882595, US 4339762, US 5760804, US 4847630, US 5850241, EP 317171, Fan-Gang Tseng, Chang-Jin Kim, and Chih-Ming Ho, " A Novel Microinjector with Virtual Chamber Neck ", IEEE MEMS '98, pp.57-62, have been proposed ink jet print heads of various structures. However, the ink jet print heads of the structures shown in these patents and documents are not entirely satisfactory, although some of the above requirements are satisfied.

The present invention has been made to solve the above problems of the prior art, and in particular, the ink chamber has a hemispherical shape in order to satisfy the above-mentioned requirements, and ink having an ink channel formed so that ink can be refilled more quickly. The purpose is to provide a jet print head.

In order to achieve the above technical problem, the present invention provides a manifold for supplying ink, an ink chamber having a substantially hemispherical shape and filled with ink to be ejected, and ink for supplying ink from the manifold to the ink chamber. A substrate in which channels are integrally formed; A nozzle plate stacked on the substrate and having a nozzle configured to discharge ink at a position corresponding to the center of the ink chamber; A heater provided on the nozzle plate and formed in an annular shape surrounding the nozzle; And an electrode provided on the nozzle plate, the electrode being electrically connected to the heater to apply a current to the heater, wherein the ink channel has both ends thereof connected to the manifold and the ink chamber, respectively. Is formed on the upper surface with a predetermined depth, the nozzle plate for forming the ink channel ink having a hemispherical chamber, characterized in that a plurality of ink channel forming grooves are formed spaced apart from each other at a position corresponding to the ink channel Provides a jet print head.

Here, it is preferable that the at least two ink channel forming grooves are arranged to be parallel to each other, or that the at least two ink channels are gradually spaced from each other as the closer to the ink chamber.

According to the present invention, it is possible to meet the above-described requirements of the print head, in particular, the cross-sectional area of the ink channel is sufficiently secured to shorten the refill time of the ink through it to increase the drive frequency of the print head.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the examples exemplified below are not intended to limit the scope of the present invention, but are provided to fully explain the present invention to those skilled in the art. In the drawings, like reference numerals refer to like elements, and the size of each element may be exaggerated for clarity and convenience of description. In addition, when one layer is described as being on top of a substrate or another layer, the layer may be present over and in direct contact with the substrate or another layer, with a third layer in between.

2 is a schematic plan view of an ink jet print head having a hemispherical chamber according to the present invention.

Referring to FIG. 2, the print head according to the present invention includes two ink ejecting portions 100 arranged in zigzag at left and right centering on the ink supply manifold 112 indicated by dotted lines, and each ink ejecting portion 100 is arranged in two rows. Bonding pads 102 are arranged that are electrically connected to and to which the wire is to be bonded. In addition, the manifold 112 is connected with an ink container (not shown) containing ink. On the other hand, in the drawings, the ink ejecting portions 100 are arranged in two rows, but may be arranged in one row, or may be arranged in three or more rows to further increase the resolution. In addition, one manifold 112 may be formed for each column of the ink ejection unit 100. Further, although a print head using only one color of ink is shown in the drawing, three or four groups of ink ejecting portions may be disposed for each color for color printing.

3 is an enlarged plan view of the ink ejecting portion illustrated in FIG. 2, and FIGS. 4A to 4C are cross-sectional views illustrating vertical structures of the ink ejecting portions along the lines A-A, B-B, and C-C of FIG. 3, respectively.

Referring to FIGS. 3 and 4A through 4C, the substrate 110 of the ink ejection part 100 may be formed in a substantially hemispherical shape on the surface thereof, and may be filled with ink, and the ink chamber 114 may be formed in the substrate 110 of the ink ejection part 100. An ink channel 116 is formed to have a shallow depth and supplies ink to the ink chamber 114, and a manifold 112 that meets the ink channel 116 and supplies ink to the ink channel 116 at a rear side thereof. Is formed. In addition, at the point where the ink chamber 114 and the ink channel 116 meet, a bubble catching jaw 118 is formed to prevent the bubble from being pushed toward the ink channel 116 when it expands.

Here, the substrate 110 is preferably made of silicon widely used in the manufacture of integrated circuits. This is because silicon wafers widely used in the manufacture of semiconductor devices can be used as they are and are effective for mass production. In addition, the manifold 112 may be formed by inclining or anisotropically etching the rear surface of the substrate 110, and the ink chamber 114 and the ink channel 116 may include the nozzle 122 and the ink channel forming groove, which will be described later. It may be formed by isotropic etching the surface of the substrate 110 exposed through the (124). At this time, the ink chamber 114 and the ink channel 116 where the bubble catching jaw 118 is formed by etching are formed at the connection portion between the ink chamber 114 and the ink channel 116. The ink chamber 114 is formed to have an approximately hemispherical shape whose depth and radius are approximately 20 mu m. On the other hand, the ink chamber 114 may be formed by isotropic etching after anisotropically etching the surface of the substrate 110 to a predetermined depth.

The nozzle plate 120 is formed on the surface of the substrate 110 to form an upper wall of the ink chamber 114. When the substrate 110 is made of silicon, the nozzle plate 120 may be formed of a silicon oxide film formed by oxidizing the silicon substrate 110, and may be formed of an insulating film such as a silicon nitride film deposited on the substrate 110. .

On the nozzle plate 120, an annular bubble generating heater 130 surrounding the nozzle 122 is formed. The heater 130 is formed by depositing a resistive heating element such as polysilicon doped with impurities on the entire surface of the nozzle plate 120 to a thickness of about 0.7 to 1 μm and then patterning it in an annular shape. The deposition thickness of this polysilicon film may be set in another range so as to have an appropriate resistance value in consideration of the width and length of the heater 130. In addition, an electrode 150 made of a metal is usually connected to the heater 130 to apply a pulsed current. The electrode 150 is formed by depositing and patterning a metal having good conductivity and easy patterning, such as aluminum or an aluminum alloy, by sputtering to a thickness of about 1 탆.

The nozzle plate 120 is formed at a position corresponding to the center of the ink chamber 114. The nozzle 122 is formed by etching the nozzle plate 120 into the heater 130 to a diameter smaller than the diameter of the heater 130, for example, a diameter of about 16 to 20 μm.

In addition, a plurality of ink channel forming grooves 124 are formed in the nozzle plate 120 to form the ink channel 116. The ink channel forming grooves 124 may be formed by etching the nozzle plate 120 in a straight line from the outside of the heater 130 to the top of the manifold 112, each of which has a length of about 50 μm Each width is about 2 탆. The width of the ink channel forming groove 124 is determined to be approximately 2 μm as described above. If the width is smaller than this, it is difficult to form the ink channel 116 by etching the substrate 110 below it. The channel 116 can be made larger, but ink supplied through the ink channel 116 is likely to leak out through it.

On the other hand, the ink channel 116 preferably has a sufficient cross-sectional area to increase the refill rate of the ink. That is, the ink channel 116 preferably has a maximum width and depth within a limit smaller than the width and depth of the ink chamber 114. However, if the depth of the ink channel 116 is too deep, bubbles (192 'in FIG. 7B) formed in the ink chamber 114 can be pushed toward the ink channel 116 as described below, thereby reducing the backflow prevention effect of the ink. There is a problem that can be done. Therefore, it is desirable to form the ink channel 116 so that its total cross-sectional area becomes larger while being wider in the width direction than its depth. However, as described above, it is difficult to form the ink channel 116 having the shape as described above with only one ink channel forming groove whose width is limited.

Accordingly, in the present invention, a plurality of the ink channel forming grooves 124 are arranged to form the ink channel 116 wider in the width direction than the depth thereof. The number of the ink channel forming grooves 124 is determined to form an ink channel 116 having a width suitable for the size of the ink chamber 114. At least two ink channel forming grooves 124 may be formed. As described above, three or four ink chambers 114 having a depth and a radius of approximately 20 μm are preferable. 3 shows an example in which three ink channel forming grooves 124 are provided, and FIG. 5 shows an example in which four ink channel forming grooves 124 ′ are provided.

As described above, the plurality of ink channel forming grooves 124 may be disposed side by side at a predetermined interval. When the substrate 110 exposed through the plurality of ink channel forming grooves 124 isotropically etched with XeF ₂ gas, an ink channel 116 having a cross-sectional shape as shown in FIG. 4B is formed. In this case, the depth of the ink channel 116 is preferably about 8 μm to 14 μm when the depth of the ink chamber 114 is about 40 to 70%, for example, when the depth of the ink chamber 114 is 20 μm. The maximum width of the ink channel 116 is preferably about 28 to 36 µm when the width of the ink chamber 114 is about 70 to 90%, for example, when the width of the ink chamber 114 is 40 µm.

5 is a plan view illustrating a modified example of the ink ejecting unit, and FIGS. 6A to 6C are cross-sectional views illustrating vertical structures of the ink ejecting unit along the lines D-D, E-E, and F-F of FIG. 5, respectively. Referring to FIGS. 5 and 6A through 6C, the heater 130 ′ of the ink ejecting portion 100 ′ of the present embodiment has an approximately omega shape, and the electrodes 150 are respectively provided at both ends of the heater 130 ′. Connected. That is, the heater shown in FIG. 3 is connected in parallel between the electrodes, whereas the heater 130 'shown in FIG. 5 is connected in series between the electrodes 150.

And, the bottom surface of the ink chamber 114 'is substantially spherical as in the ink chamber (114 in Fig. 4A) of the above-described embodiment, but the top extends from the edge of the nozzle 122' toward the ink chamber 114 '. A bubble guide 170 is formed around the droplet guide 160 and the droplet guide 160 below the nozzle plate 120 forming the upper wall of the ink chamber 114 ′. The function of the droplet guide 160 and the bubble guide 170 will be described later. The droplet guide 160 and the bubble guide 170 may be simultaneously formed in the process of forming the ink chamber 114 ′. In more detail, first, the substrate 110 is anisotropically etched to a predetermined depth, and then a predetermined material layer, for example, a TEOS oxide layer, is deposited on the exposed surface of the substrate 110 to a thickness of about 1 μm. Subsequently, when the TEOS oxide film is anisotropically etched and removed only at the bottom thereof, the droplet guide 160 is formed. Next, when the exposed substrate 110 is isotropically etched, an ink chamber 114 ′ and a bubble guide 170 having a shape as shown in FIG. 6A are formed.

On the other hand, the ink channel 116 'is formed to gradually increase in width as it approaches the ink chamber 114' side so that ink can be smoothly and quickly filled in the ink chamber 114 '. The four ink channel forming grooves 124 'provided in the nozzle plate 120 in order to form the ink channel 116' having such a shape are gradually spaced from each other as the ink channel 114 'is closer to the ink chamber 114'. Arranged to lose. The method of forming the ink channel 116 'is as described above, and the formed ink channel 116' has a cross-sectional shape as shown in Fig. 6B. At this time, the depth and width of the formed ink channel 116 ′ are also determined as described above.

In FIG. 3, an annular heater 130 and three side-by-side ink channel forming grooves 124 are combined. In FIG. 5, an omega-shaped heater 130 ′ and four open ink channel forming grooves 124 ′ are combined. ) And the droplet guide 160 and the like, but combinations therebetween may be different. That is, an embodiment in which four open ink channel forming grooves 124 'are combined with the annular heater 130 is possible, and three parallel ink channel forming grooves 124 are formed in the omega heater 130'. Combined embodiments are also possible. In addition, the droplet guide 160 and the bubble guide 170 may also be combined with the ink ejection unit 100 of FIG. 3.

Hereinafter, an ink droplet ejection mechanism in the ink ejection unit illustrated in FIG. 3 will be described with reference to FIGS. 7A and 7B.

Referring first to FIG. 7A, ink 190 is supplied into the ink chamber 114 through the manifold 112 and the ink channel 116 by capillary action. In the state where the ink 190 is filled in the ink chamber 114, when a pulsed current is applied to the heater 130 through the electrode 150 of FIG. 3, the heat generated from the heater 130 is lowered through the nozzle plate ( It is delivered to the ink 190 through 120, whereby the ink 190 boils and bubbles 192 are generated. The bubble 192 has an approximately donut shape as shown on the right side of FIG. 7A according to the shape of the heater 130.

As the donut shaped bubble 192 expands over time, it expands under the nozzle 122 and expands into a generally disk shaped concave bubble 192 ′, as shown in FIG. 7B. At the same time, ink droplets 190 'are ejected from the ink chamber 114 through the nozzle 122 by the expanded bubble 192'.

When the applied current is cut off, the bubble 192 'contracts or bursts before cooling, and ink 190 is filled again through the ink channel 116 in the ink chamber 114.

According to the ink ejection mechanism of the print head as described above, the donut-shaped bubble 192 is combined at the center to form a disk-shaped bubble 192 'to cut the tail of the ejected ink droplet 190'. No satellite droplets are formed.

In addition, since the heater 130 has an annular or omega shape and its area is wide, the heating and cooling is fast, and accordingly, the time required for the generation and dissipation of the bubbles 192 and 192 'is faster, so that the heater 130 may have a fast response and a high driving frequency. . Moreover, the shape of the ink chamber 114 is hemispherical, so that the expansion path of the bubbles 192 and 192 'is stable by the conventional rectangular parallelepiped or pyramid-shaped ink chamber, and the creation and expansion of the bubbles are quick, so that the ink can be quickly developed. Discharge is made.

As the expansion of the bubbles 192 and 192 ′ is limited to the hemispherical ink chamber 114, the reverse flow of the ink 190 is suppressed, so that cross talk with other adjacent ink ejecting portions is suppressed. Further, the ink channel 116 is not only shallower than the ink chamber 114, but also bubble buckle 118 is formed at the point where the ink chamber 114 and the ink channel 116 meet, so that the ink 190 And the backflow phenomenon in which the bubble 192 'itself is pushed toward the ink channel 116.

In particular, the width of the ink channel 116 can be made wide by the plurality of ink channel forming grooves 124, so that the cross-sectional area through which the ink passes is secured, so that the refilling speed of the ink is increased so that high driving is achieved. It can have a frequency. On the other hand, the ink channel 116 ′ of the type shown in FIGS. 5 and 6 is formed to gradually increase in width as it approaches the ink chamber 114, so that ink can be smoothly and quickly filled in the ink chamber 114. Will be.

8A and 8B are cross-sectional views taken along the line D-D of FIG. 5 for explaining a mechanism of ejecting ink from the ink ejecting portion shown in FIG.

Only differences from the ink droplet ejection mechanism of the above-described embodiment will be described. First, when the bubble 193 generated below the heater 130 expands, the probability that it expands downward by the bubble guide 170 around the nozzle 122 'and merges under the nozzle 122' becomes less. However, the probability that this expanded bubble 193 'will merge under the nozzle 122' can be adjusted by adjusting the length extending downward of the droplet guide 160 and the bubble guide 170. Meanwhile, the discharged droplet 190 ′ is guided in the discharge direction by the droplet guide 160 extending downward from the edge of the nozzle 122 ′ and discharged in a direction perpendicular to the substrate 110.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and equivalent other embodiments are possible. For example, the number and arrangement of grooves for forming an ink channel may vary somewhat depending on the width and depth of the ink channel set to suit the size of the ink chamber. Further, in the present invention, the materials used to construct each element of the print head may use materials not illustrated. That is, the substrate may be replaced with another material having good processability even if it is not necessarily silicon. The same applies to the heater and the electrode.

As described above, the manufacturing method of the ink jet print head having the hemispherical chamber according to the present invention has the following effects.

First, by forming the components of the print head, that is, the substrate on which the manifold, the ink chamber and the ink channel, and the nozzle plate and the heater are integrally formed on the substrate, the conventional nozzle plate, the ink chamber and the ink channel portion are manufactured separately. The inconvenience and misalignment that had to go through complicated process such as bonding is solved. In addition, it is compatible with the general manufacturing process of semiconductor devices, and mass production becomes easy.

Second, since the width of the ink channel can be formed wide by the plurality of ink channel forming grooves, the cross-sectional area through which ink passes is secured, so that the refilling speed of the ink can be increased to have a high driving frequency. In particular, when the ink channel is formed to gradually become wider as it approaches the ink chamber, the ink can be filled in the ink chamber more smoothly and quickly.

Third, by forming the heater annularly and forming the shape of the ink chamber in a hemispherical shape, backflow of ink is suppressed to avoid interference with other ink ejecting portions, and bubbles are formed in a donut shape to suppress the occurrence of side droplets. You can do it. In addition, according to the embodiment in which the bubble and the droplet guide are formed, the droplet may be discharged in a direction perpendicular to the substrate.

1A and 1B are cutaway perspective views and a cross-sectional view for explaining an ink droplet ejection process showing an example of a conventional bubble jet ink jet printing head.

2 is a schematic plan view of an ink jet print head having a hemispherical chamber according to the present invention.

3 is an enlarged plan view of the ink ejecting portion illustrated in FIG. 2, and FIGS. 4A to 4C are cross-sectional views illustrating vertical structures of the ink ejecting portions along the lines A-A, B-B, and C-C of FIG. 3, respectively.

FIG. 5 is a plan view illustrating a modified example of the ink ejecting portion illustrated in FIG. 3, and FIGS. 6A to 6C are cross-sectional views illustrating vertical structures of the ink ejecting portions along the lines D-D, E-E, and F-F of FIG. 5, respectively.

7A and 7B are cross-sectional views taken along line C-C of FIG. 3 for explaining a mechanism of discharging ink from the ink ejecting portion shown in FIG.

8A and 8B are cross-sectional views taken along the line D-D of FIG. 5 for explaining a mechanism of ejecting ink from the ink ejecting portion shown in FIG.

<Explanation of symbols for the main parts of the drawings>

100,100 '... ink discharge section 110 ... substrate

112 ... Manifold 114, 114 '... Ink chamber

116,116 '... ink channel 120 ... nozzle plate

122,122 '... Nozzle 124,124' ... Inch channel forming groove

130 ... heater 150 ... electrode

160 ... Drop Guide 170 ... Bubble Guide

Claims (8)

A substrate having an integrally formed manifold for supplying ink, an ink chamber having a substantially hemispherical shape and filled with ink to be ejected, and an ink channel for supplying ink from the manifold to the ink chamber; A nozzle plate stacked on the substrate and having a nozzle configured to discharge ink at a position corresponding to the center of the ink chamber; A heater provided on the nozzle plate and formed in an annular shape surrounding the nozzle; And An electrode provided on the nozzle plate and electrically connected to the heater to apply a current to the heater; The ink channel is formed at a predetermined depth on an upper surface of the substrate such that both ends thereof are connected to the manifold and the ink chamber, and the nozzle plate is formed to form the ink channel. An ink jet print head having a hemispherical chamber, wherein a plurality of spaced grooves for forming ink channels are formed. The method of claim 1, And the ink channel forming grooves are arranged so that at least two are parallel to each other. The method of claim 1, The ink channel forming grooves are arranged such that the distance between each other gradually increases as the at least two grooves approach the ink chamber, and the width of the ink channel gradually widens as the width of the ink channel approaches the ink chamber. Inkjet printhead with The method of claim 1, And a plurality of ink channel forming grooves each having a width of substantially 2 [mu] m. The method of claim 1, The maximum width of the ink channel is 70% to 90% of the width of the ink chamber, the depth of the ink channel is 40% to 70% of the depth of the ink chamber, the ink jet print head having a hemispherical chamber . The method of claim 1, And the ink channel is formed by isotropically etching the substrate through the ink channel forming grooves. The method of claim 1, And an ink jet print head having a hemispherical chamber formed at a connection portion between the ink chamber and the ink channel. The method of claim 1, An ink jet print head having a hemispherical chamber, wherein bubbles and droplet guides extending from the edge of the nozzle in the depth direction of the ink chamber are formed.