RU2144472C1 - Method for creating thick-film layer in microinjection device - Google Patents

Abstract

FIELD: jet printing equipment. SUBSTANCE: according to method, created on liner is thin-film layer. Thick-film layer is built up on thin-film layer without performing additional thermal treatment. Simultaneously subjected to thermal treatment is thin-film layer and thick-film layer which both are successively created on liner. Thus obtained is single thick-film layer. Single thick-film layer is created according to process of successive application of coating without interruption for thermal treatment, therefore formation of separating boundary is prevented. This specific feature allows for considerable prolonging of general service life of thick-film layer. EFFECT: higher efficiency. 15 cl, 5 dwg

Description

 The present invention relates to a micro-injection device applicable to inkjet printing devices, medical device micropumps and fuel injection devices, and more particularly, to a method for forming a thick film layer in a micro-injection device in which the number of heat treatment operations is reduced in order to improve the durability of the device.

 In general, a micro-injection device is a device that is designed to provide printed paper, a human body or an automobile with a certain amount of liquid, for example, printing ink, injection liquid or oil, using a method in which a predetermined amount of electric or thermal energy is supplied to the above liquid, so that you can change the volume of such a liquid. Thus, a predetermined specific amount of such a liquid can be supplied to a specific object.

 Recently, the development of electrical and electronic technology allows you to quickly improve such micro-injection devices. Therefore, microinjection devices are widely used in everyday life. An example of micro-injection devices used in everyday life are inkjet printers.

 Unlike conventional dot matrix printers, inkjet printers, i.e. a kind of micro-injection device is capable of printing in different colors due to the use of cartridges and has advantages in less noise and higher print quality. For this reason, inkjet printing devices are becoming increasingly popular.

 An inkjet printing device is usually provided with a printhead in which the ink in a liquid state assumes a bubble state when the electrical signal supplied from the external device is turned on or off. Then, the ink thus expanded into bubbles expands and is discarded to perform a printing operation on printing paper. Various designs and principles of operation of known inkjet printheads are described in US Pat. No. 4,490,728, entitled "Thermal Inkjet Device", US Pat. No. 4,809,428, entitled "Thin-Film Device for Inkjet Printhead and its Production Method," US Pat. No. 5 140,345 entitled, “Method for Manufacturing a Substrate for a Liquid Inkjet Recording Head and a Substrate Made by this Method,” US Pat. No. 5,274,400, entitled “Geometry of the Injection Path for High-Temperature Inkjet Printing their heads "and U.S. Patent N 5,420,627, entitled" Inkjet Printhead ".

 To perform the printing operation in such a conventional inkjet printhead, chemicals are usually used, for example, ink or a working fluid. For this reason, chambers for storing chemicals are inevitably provided in the print head.

 Therefore, a thick film layer is formed on the substrate constituting the print head to limit (determine) the cameras. In addition, in chambers bounded by a thick film layer, chemicals such as paint or working fluid are safely stored.

 In general, a thick film layer has a thickness of 10 μm or more, so as to provide sufficient internal space for the chambers, and is made from organic substances, given their chemical resistance to paint and working fluid.

 It is known from the prior art that in order to obtain a thick film layer of a desired thickness, a layer made of an organic substance and having a predetermined thickness is applied at a time by centrifugal method, and then it is dried and heat treated. Thus, the main thin film layer is formed on the substrate on which the protective film is formed. Then, numerous thin film layers are continuously formed on the main thin film layer, repeatedly performing the above operation of forming the thin film layer.

 For example, to obtain a thick film layer having a thickness of 10 μm, the operation of forming a thin film film with a thickness of 1 μm is performed ten times. There is no need to say that after each operation of forming a thin film layer, drying and heat treatment operations are carried out.

 When such an operation of forming a thin film layer is repeated several times, a plurality of thin film layers are applied to form a multilayer coating. Thus, it is possible to obtain a thick film layer of the desired thickness. The finished thick film layer is firmly placed in the appropriate place on the print head.

 However, such a conventional method of forming a thick film layer in an inkjet printhead is associated with several serious problems.

 As described above, a conventional thick film layer can be formed by depositing a plurality of thin film layers by repeating the operations of forming thin film layers. So, each thin-film layer constituting a thick-film layer forms a certain interface with the corresponding boundary surfaces.

 The interface will exist until a thick film layer is placed in a specific design of the print head, which causes a decrease in the total service life of the print head.

 In addition, it is known from the prior art that the formation of a thick film layer requires repeated repetition of the drying and heat treatment operations. Thus, the total time required for the manufacture of the device is increased.

 Since when forming a thick film layer, the operations of forming single thin film layers cannot be performed simultaneously, it is very difficult to form thin film layers with the same thickness. More specifically, impurities, such as particles, may occur during each operation of forming thin film layers.

 As a result, the overall performance of the print head is significantly reduced.

 Therefore, the aim of the present invention is to provide a method of forming a thick film layer in a microinjection device, in which the interface between thin-film layers is excluded in order to increase the durability of this device.

 Another objective of the present invention is to provide a method of forming a thick film layer in a microinjection device, in which the production time of the thick film layer is reduced.

 Another objective of the present invention is to provide a method of forming a thick film layer in a microinjection device, in which the thick film layer has a uniform thickness.

 An additional objective of the present invention is to provide a method of forming a thick film layer in a microinjection device, which prevents the inclusion of impurities in the thick film layer.

 Another additional objective of the present invention is to provide a method of forming a thick film layer in a microinjection device, which improves the overall injection ability of the microinjection device.

 To achieve the above objectives and other advantages of the present invention, an organic substance, for example, liquid polyimide, is applied to a substrate on which a protective film is formed, and the substrate is rotated at a high speed, for example, 450-550 rpm. Thus, a thin-film layer with a thickness of 0.5-5 microns is formed on the protective film.

 Then, without performing the heat treatment operation, the organic substance is again applied to the already formed thin film layer, rotating, for example, 20-40 rpm, the substrate on which the thin film layer is formed. Thus, a thick film layer about 18-22 microns thick is formed on the protective film.

 In the future, the thin film layer and the thick film layer on the substrate are simultaneously heat treated, forming, therefore, a single thick film layer. In this case, a single thick film layer is formed by a series of coating operations without interruption by heat treatment operations, thereby eliminating the interface. As a result of this, the overall service life of the thick film layer can be significantly increased.

The above objectives and advantages of the present invention will become more apparent through a detailed description of preferred embodiments of the invention with reference to the accompanying drawings, in which:
- FIG. 1A-1C are views showing a method of forming a thick film layer in an inkjet printhead according to the present invention;
- FIG. 2 is an isometric view showing an embodiment of a thick film layer according to the present invention; and
- FIG. 3 is a sectional view of an inkjet printhead to which a thick film layer according to the present invention is applied.

 Now the present invention will be more fully described with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

 Although the terms mentioned in the description are defined based on the purpose of the present invention and can be changed at the request of specialists or in accordance with normal practice, these terms should be defined taking into account the general content of the description of the present invention.

As shown in FIG. 1A, a silicon substrate 1 on which a protective film made of SiO _{2 is formed} is initially coated with a liquid organic substance, for example liquid polyimide, using a coating agent 100 and for the first time rotating the substrate 1 to set it in motion rotating means (not shown). Thus, on the protective film 2 of the substrate 1, a first layer of organic matter 31 'is formed.

 In this case, the viscosity coefficient of the liquid polyimide is preferably 1.03.

 In addition, first, the substrate 1 is rotated with a higher rotation speed, preferably 450-550 rpm for a period of time from 35 to 45 seconds. As described above, when the substrate 1 is rotated at a high speed, the liquid polyimide deposited on the substrate 1 by the coating device 100 is distributed by the centrifugal force over the entire substrate 1. As a result, a first layer forms on the protective film 2 of the substrate 1 31 'of liquid organic matter having a uniform thickness. The first liquid organic material layer 31 'has a thickness of preferably 0.5-5 microns and more preferably 1-2 microns.

 Subsequently, the liquid organic material is secondly coated onto the first liquid organic material layer 31 'using the coating agent 100 and the substrate 1 is rotated again, driving it with a rotating means. Thus, on the first layer 31 ′ of liquid organic matter, a second layer 32 ′ of liquid organic matter is formed.

In this case, it is preferable that the liquid organic substance is re-applied in an amount of 0.6-0.8 m ³ and has a viscosity coefficient of 1.03.

 In addition, the substrate is re-rotated at a low speed, preferably 20-40 rpm, for a period of 30 to 40 seconds. As described above, when the substrate 1 is rotated at a low speed, the liquid polyimide deposited on the first layer 31 'of liquid organic matter by means of a coating device 100 is distributed by centrifugal force throughout the entire first layer 31' of liquid organic matter. At this time, due to the viscosity of the liquid polyimide, a normal wave forms in it. Thus, on the first layer 31 'of liquid organic matter, a second layer 32' of liquid organic matter is formed having a uniform thickness. The second liquid organic material layer 32 'has a thickness of preferably 18-22 microns.

где h - суммарная толщина первого и второго слоев из жидкого органического вещества, h₁ - толщина первого слоя из жидкого органического вещества, h₂ - толщина второго слоя из жидкого органического вещества, подлежащего образованию, ε - коэффициент, который обозначает уменьшения в первом и втором слоях из жидкого органического вещества во время операции термообработки, А - константа, ν - коэффициент вязкости жидкости, ω - частота повторного вращения подложки, S - площадь поверхности подложки и V-количество жидкого органического вещества при повторном нанесении.So, the amount of liquid organic matter during repeated application and the frequency of repeated rotation of the substrate can be correctly calculated using the following equation (1):

where h is the total thickness of the first and second layers of liquid organic matter, h ₁ is the thickness of the first layer of liquid organic matter, h ₂ is the thickness of the second layer of liquid organic matter to be formed, ε is the coefficient that indicates the decrease in the first and second layers of liquid organic matter during the heat treatment operation, A is a constant, ν is the coefficient of viscosity of the liquid, ω is the frequency of repeated rotation of the substrate, S is the surface area of the substrate, and V is the amount of liquid organic matter application.

 In this case, various experimental data can be entered into equation (1), and based on the thickness of the second liquid organic layer 32 ′ to be finally formed, it is possible to determine the amount of liquid organic matter upon re-deposition and the frequency of re-rotation of the substrate.

In the present invention, various experimental data selected as data for determining the amount of liquid organic matter upon re-deposition and the frequency of re-rotation of the substrate can be entered into equation (1) based on the thickness of the second layer of the substance equal to 18-22 μm. Thus, the amount of liquid organic matter during repeated application can be determined equal to 0.6 m ³ and 0.8 m ³ and the frequency of repeated rotation of the substrate equal to 20-40 rpm

 As a result, a first layer 31 ′ of liquid organic matter as a thin film layer and a second layer 32 ′ of liquid organic matter as a thick film layer are applied to the substrate 1 on which the protective film 2 is formed, thereby forming a single layer 30 ′ of liquid organic substances.

 Subsequently, the substrate 1, on which a single layer 30 'of liquid organic matter is formed, is removed from the place of its rotation and transferred to a heating device (not shown). Then the first and second layers 31 'and 32' of liquid organic matter, which make up a single layer 30 'of liquid organic matter, are dried and heat treated.

Drying is carried out preferably at a temperature of 80-90 ^o C for 25-30 minutes, and heat treatment, preferably at temperatures of 200-220 ^o C, 300-330 ^o C for respectively 25-35 minutes, 60-70 minutes.

 As a result of this, the first and second liquid organic matter layers 31 ′ and 32 ′ are cured and, as shown in FIG. 1B are converted respectively into a first layer 31 of organic matter as a thin film layer and a second layer 32 of organic matter as a thick film layer, thereby forming a single thick film layer 30.

 As described above, in the present invention, the first and second layers 31 'and 32' of liquid organic matter are formed sequentially without additional heat treatment and cured by simultaneous heat treatment. Thus, a single thick film layer 30 can be obtained by sequentially depositing the first film layer 31 of organic matter as a thin film layer and the second film layer 32 of organic matter as a thick film layer. Thus, the interface between the first and second film layers 31 and 32 of organic matter can be eliminated. As a result of this, the durability of the inkjet print head does not decrease even after a single thick film layer 30 is placed therein.

 In addition, in the present invention, drying and heat treatment are carried out only once to form a single thick film layer 30. Thus, the time required to complete the production process is significantly reduced.

 Further, in the present invention, due to the successive formation of a thin film layer and a thick film layer to obtain a single thick film layer, the duration of the film forming process can be reduced. Thus, the problem of preventing the ingress of impurities into the process can be solved and a single thick film layer after formation can have a uniform thickness. As a result of this, the overall performance of the inkjet printhead can be significantly improved.

 As shown in FIG. 1B, a screen film (not shown) is formed on the second film layer 32 of organic matter and, using a screen film as a mask, the first and second film layers 31 and 32 of the organic substance are etched so that the protective film 2 can be exposed. Then, with chemicals the remaining screen-film is removed, and thus, a single thick film layer 30 is obtained that defines the area 33 of the chambers.

 After the formation of zone 33 of the chambers, a single thick film layer 30 is separated from the substrate 1 using chemicals such as hydrogen fluoride, as shown in FIG. 1C. Then a single thick film layer 30 is firmly fixed in the appropriate place of the inkjet print head.

 As shown in FIG. 2, on the substrate 1, a single thick film layer 30 according to the present invention is attached to the nozzle plate 8, which defines the nozzles 10.

 A channel 200 for supplying paint from an external device in the direction indicated by the arrow is formed near the area 33 of the cameras in order to fill the area 33 of the cameras.

 In the nozzle plate 8, a plurality of ink injection nozzles 10 are formed. Such nozzles 10 pass through the nozzle plate 8 and thus open at the outer surface.

 An inkjet print head using a single thick film layer according to the present invention operates as follows.

As shown in FIG. 3, when an electric signal is supplied from an external energy source to an electrode layer (not shown), the heater 11, which is in contact with the electrode layer, receives electric power and quickly heats up to a temperature of 500 ^° C. or higher. During this process, electrical energy is converted into thermal energy with a temperature of approximately 500-550 ^o C.

 Then, the thermal energy is transferred to the chamber zone 33, which was in contact with the heater 11, and the paint 300, which fills the chamber zone 33, quickly heats up and swells in the form of bubbles due to the transferred thermal energy.

 When thermal energy is continuously transmitted to the zone 33 of the chambers, the expanded ink 300 rapidly changes in volume and expands. Thus, the paint 300 leaves the zone 33 of the chambers through the nozzles 10 in the nozzle plate 8 and is almost separated. The ink 300 then, under the influence of its own weight, alternately takes an oval and round shape and is separated on the outside printed paper.

 As described above, since the single thick film layer 30 according to the present invention consists of the first and second film layers 31 and 32 of organic matter, which are successively formed without further heat treatment, the interface is eliminated, thereby improving the durability of the inkjet print head.

 Meanwhile, when the electrical signal supplied from the external source is turned off, in the state in which the ink 300 is released, the heater 11 is rapidly cooled. The expanded ink 300 remaining in the chambers 33 is rapidly reduced and creates a restoring force by which the ink can return to its original state. The restoring force created in this way serves to quickly reduce the pressure in the chamber 33 region so that the ink 300 flowing through the ink supply duct 200 can quickly fill the chamber region 33 again.

 The inkjet print head repeats the above process according to an electrical signal, thereby printing on printing paper supplied by an external device.

 In the present invention, the first film layer of organic matter as a thin film layer and the second film layer of organic matter as a thick film layer are sequentially applied without further heat treatment so as to form a single thick film layer. Thus, it is possible to eliminate the interface and in advance to prevent the possibility of ingress of impurities during the process.

 The present invention has a beneficial effect not only in inkjet printheads, but also in all microinjection devices that are used in micropumps of medical devices, fuel injection devices, etc. The invention has been described above with reference to the aforementioned embodiments. However, it is clear that in the light of the foregoing description, many alternative modifications and changes will be apparent to those skilled in the art. Thus, the present invention covers all such alternative modifications and changes that are consistent with the essence of the invention and are within the scope of patent protection of the attached claims.

Claims (16)

 1. A method of forming a thick film layer in a microinjection device, comprising the steps of: first applying liquid organic matter to a substrate on which a protective film is formed, and rotating the substrate with a first rotation speed to form a first layer of liquid organic matter as a thin film layer, re-applying liquid organic matter to the first layer of liquid organic matter and rotation of the substrate with a second rotation frequency to form a second layer of liquid organic matter as a thick film layer, drying and heat treating the first and second layers of liquid organic matter to form a first film layer of organic matter and a second film layer of organic matter, etching the first and second film layers of organic matter to partially expose the protective film and limiting the zone of the chambers and separating the first and second film layers from organic matter from the substrate.  2. The method according to p. 1, characterized in that the liquid organic substance is prepared from polyimide.  3. The method according to claim 2, characterized in that they use liquid organic matter with a viscosity coefficient equal to 1.03.  4. The method according to claim 1, characterized in that the first speed is 450 to 550 rpm.  5. The method according to claim 4, characterized in that the substrate is rotated with a first speed for 35 to 45 seconds.  6. The method according to claim 1, characterized in that the first layer of liquid organic matter is performed with a thickness of 0.5 to 5 microns.  7. The method according to claim 1, characterized in that the first layer of liquid organic matter is performed with a thickness of 1 to 2 microns. 8. The method according to claim 2, characterized in that the amount of liquid organic matter and the frequency of rotation of the substrate in the stage of re-applying liquid organic matter is calculated by the following equation:

where h is the total thickness of the first and second layers of liquid organic matter;
h ₁ - the thickness of the first layer of liquid organic matter;
h ₂ is the thickness of the second layer of liquid organic matter to be formed;
ε is a coefficient that indicates the decrease in the first and second layers of liquid organic matter during the heat treatment operation;
A is a constant;
ν is the coefficient of viscosity of the liquid;
ω is the frequency of repeated rotation of the substrate;
V is the amount of liquid organic matter upon repeated application;
S is the surface area of the substrate. 9. The method according to claim 1, characterized in that in the stage of re-applying liquid organic matter it is used in an amount of 0.6 - 0.8 m ³ .  10. The method according to claim 1, characterized in that the second speed is 20 to 40 rpm.  11. The method according to claim 10, characterized in that the substrate is rotated with a second speed for 30 to 40 seconds.  12. The method according to claim 1, characterized in that the second layer of liquid organic matter is performed with a thickness of 18-22 microns. 13. The method according to claim 1, characterized in that the drying is carried out at a temperature of 80 - 90 ^o C.  14. The method according to item 13, wherein the drying is carried out for 25 to 35 minutes 15. The method according to claim 1, characterized in that the heat treatment of the first and second layers is carried out at temperatures respectively 200 - 220 and 300 - 330 ^o C.  16. The method according to p. 15, characterized in that the heat treatment at these temperatures is carried out respectively for 25 - 35 and 60 - 70 minutes

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