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(11) | EP 0 963 842 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Device for controlling fluid movement |
| (57) The present invention relates to a device for controlling fluid movement. The device comprises: a) fluid guiding means (100, 200, 300); b) fluid moving means (120, 220, 320) comprising polymers having hydrophilic and hydrophobic properties that can be selected under the action of an external force, said fluid moving means comprising a plurality of polymer elements (130, 230, 330) whose hydrophilic and hydrophobic properties can be selected, said polymer elements being arranged along the fluid guiding means; c) at least one actuating unit (140, 240, 340) which generates said external force. Application: ink jet printing. |
[0001] The present invention relates to a device for controlling fluid movement, especially a device capable of being used in ink jet printers.
[0002] In the field of ink jet printing, it is important to control the quantity of ink to be ejected in order to obtain optimum print quality. In the case of color printing, the print quality also depends on the color rendition obtained. Generally, ink jet color printers have reservoirs each containing ink with a defined color, each color of ink being ejected through a nozzle in the ink jet head. Usually, the inks used are inks with the colors yellow, magenta, cyan and black. The printing of a series of dots of yellow, magenta, cyan and black ink is controlled by a dithering technique that enables the different colored dots to be arranged so as to represent any color. The problem with such a printing technique is that the print dots are visible.
[0003] An object of the invention is to provide a device that enables the movement of fluids to be controlled with accuracy in particular to move fluid quantities defined with precision.
[0004] A further object of the invention is to provide a device that enables the control of several fluids in order to obtain mixtures of these fluids defined with precision.
[0005] The invention relates to a device for controlling fluid movements that comprises:
a) fluid guiding means for guiding fluids;
b) fluid moving means for moving fluids polymers having hydrophilic and hydrophobic properties that can be selected under the action of an external force, said fluid moving means comprising a plurality of polymer elements whose hydrophilic and hydrophobic properties can be selected, said polymer elements being arranged along the fluid guiding means;
c) at least one actuating unit for generating said external force.
[0006] The invention further relates to a method of moving fluid comprising the steps of :
- supplying fluid to at least one guide channel, said at least one guide channel having a plurality of polymer elements arranged therealong, said plurality of polymer elements having hydrophilic and hydrophobic properties and being switchable between hydrophilic and hydrophobic states ; and
- moving said fluid in said at least one channel by applying an external force to at least one of said polymer elements to change a state of said at least one of said polymer elements.
[0007] The invention further relates to a method of moving fluid comprising the steps of :
- supplying fluid to a flat surface, said flat surface having a plurality of polymer elements arranged thereon, said plurality of polymer elements having hydrophilic and hydrophobic properties and being switchable between hydrophilic and hydrophobic states ; and
- moving said fluid on said flat surface by applying an external force to at least one of said polymer elements to change a state of said at least one of said polymer elements.
[0008] Other characteristics will appear on reading the following description, with reference to the drawings wherein:
- Figure 1 represents a first embodiment of the invention;
- Figure 2 represents a second embodiment of the invention; and
- Figure 3 represents a third embodiment of the invention.
[0009] In general, the technique used to move fluids according to the invention consists in using a polymer element whose hydrophilic and hydrophobic properties can be selected under the action of an external force. The principle of this technique is described in the French Patent Application No 9803011 filed in the name of the present applicant and not yet published.
[0010] The external force required to switch from one state to the other and thus also the means to generate the external force are determined according to the choice of polymer.
[0011] When thermo-reversible polymers are selected, that is polymers which, when their temperature exceeds a threshold temperature called the phase transition temperature, switch from a hydrophilic state to a hydrophobic state or vice-versa, the external force will be the application of thermal energy. Preferably thermo-reversible polymers should be selected that have a phase transition temperature between 20 and 100°C, and preferably between 30 and 70°C.
[0012] The thermo-reversible polymers, which are used in the present device, are organic polymers such as those described in Patent Application WO 91/15526. These are polymers that have a hydrophilic group and a hydrophobic group, the hydrophilic group being a water-soluble ionic polymerizable vinyl monomer, and the hydrophobic group comprising an acrylamide or methacrylamide monomer. For example a poly(N-alkylacrylamide), a modified glycol polyethylene or a polysilylamine is selected. Preferably a polymer is used that switches from one state to the other very quickly, for example poly(N-isopropylacrylamide).
[0013] To make the polymer element switch from its hydrophilic state to its hydrophobic state, it has to exceed a hydrophilic/hydrophobic phase transition temperature Tg proper to the polymer.
Poly(N-isopropylacrylamide) has a Tg temperature of about 32°. When the polymer is at a temperature less than 32°, it is hydrophilic. When it is higher than 32°, it becomes hydrophobic. In addition, the hydrophilic/hydrophobic phase transition temperature of a polymer can be modified by different means. For example adding a surfactant to the fluid to be moved can increase the phase transition temperature. This technique is described in the publication, Langmuir, 1995, Volume 11, No. 7, pages 2493-2495. For example the phase transition temperature Tg of poly(N-isopropylacrylamide) can be modified from 32°C to 90°C. Means to generate the external force, in this case thermal energy, are for example constituted by a temperature control element, for example a heating element arranged in contact with the polymer element. The heating element is for example constituted by a thin film of polycrystalline silicon in which a current is passed adapted to generating an amount of thermal energy to allow the polymer to exceed its phase transition temperature and to switch from one state to the other. The polymer element can then return to its initial state, its temperature having decreased by simple heat diffusion. An additional cooling system can also be provided such as for example a radiator or a Pelletier effect device.
[0014] Electrically conductive organic polymers can be selected, for example polymethylethiophene, which, under the action of an electric current as an external force, switch from the hydrophilic state to the hydrophobic state or vice-versa. Means to generate the external force in this case are those for applying an electric current to the polymer element.
[0015] Depending on the polymer selected, other external forces can be used such as for example, a pH change, a change of ionic strength, or a pressure. For each polymer, the means appropriate for generating the said force will be determined by those skilled in the art who know the force necessary to switch the polymer from the hydrophilic state to the hydrophobic state.
[0016] For the relevant polymers, it is known that the hydrophilic/hydrophobic state change causes the polymer volume to vary. However, in certain embodiments that will be described, it is preferable to deal with these volume variations. Also, it is known how to control the volume variations of polymers that can switch from a hydrophilic to a hydrophobic state. Therefore, known techniques such as those described in Polymer Communications, "Synthesis of fast response, temperature-sensitive poly(N-isopropylacrylamide) gel", can be used.
[0017] All the embodiments that are to be described below are used to control the movement of hydrophilic fluids. However, when the fluid whose movement is to be controlled is hydrophobic, the embodiments described below are used with appropriate polymers.
[0018] By referring to Figure 1 a first embodiment of the device according to the invention can be seen. The device for controlling fluid movement according to the invention comprises fluid guiding means 100 comprising a channel 110 in which the fluid flows. In order to move the fluid in the channel 110, moving means 120 is provided on the internal wall of the channel 110. The moving means 120 comprises a plurality of polymer elements 130 whose hydrophilic and hydrophobic properties can be selected under the action of an external force. The elements 130 are arranged along the channel 110. The external force is applied to the polymer elements 130 by means of an actuating unit 140. The actuating unit 140 is for example a heating element. This heating element can be arranged in contact with a polymer element 130, preferably the polymer element 130 located in the channel 110, which the fluid first contacts when moving. In this embodiment, polymer elements 130 are used that are hydrophobic when their temperature is less than their phase transition temperature. When the fluid reaches the channel 110 by whatever means, the polymer elements 130 are in a hydrophilic state. The fluid can thus fill the channel 110. The thermal force is then applied to the polymer element on which the heating element is arranged. This element becomes hydrophobic which causes the fluid to move. The thermal force propagates by thermal diffusion and is gradually transmitted to the polymer elements 130 that are arranged in succession in the channel 110 in the direction of the fluid movement. An actuating unit 140 can further be provided for each polymer element. The quantity of fluid to move is then determined according to which polymer element 130 is actuated first.
[0019] A second embodiment of the device for controlling fluid movement is shown in Figure 2. The guiding means 200 comprise a plurality of channels 210 similar to the channels 110 described above, which are made in a matrix and converge. The channels 210 for example are each connected to a reservoir of different fluids that is not shown and converge towards a single channel linked to an outlet S of the device. This embodiment for example is useful for ink jet heads. Thus three channels 210 can be planned connected respectively to three ink reservoirs, each reservoir containing one ink color, yellow, magenta and cyan respectively. The three channels converge to one channel terminated with an injection nozzle of the ink jet head. The actuation of the various polymer elements 230 present in each channel through an actuation unit 240 (only one is shown) allows the quantity of ink to be moved in a channel to be controlled, a nozzle can eject a perfectly defined mixture of the three ink colors, yellow, magenta and cyan. A fourth channel can also be provided connected to a fourth reservoir containing black ink.
[0020] In one alternative that is not shown of the first two embodiments, the polymer elements 130, 230 comprise a continuous polymer film provided for the length of the channels.
[0021] In another alternative that is not shown of these embodiments, the channels can be arranged on the surface of a matrix. They are then obtained for example by engraving.
[0022] Figure 3 represents a third embodiment of the device to control fluid movement. The device comprises moving means 320 arranged on a flat surface. The moving means 320 comprises a plurality of polymer elements 330 whose hydrophilic and hydrophobic properties can be selected under the action of an external force. The polymer elements 330 are juxtaposed so as to form a continuous polymer surface. An actuating unit 340 (only one is shown) is provided under the surface of the polymer to generate the external force. The actuating unit comprises a plurality of independent heating elements arranged contiguously. A "mosaic type" surface of heating elements is thus obtained. Such an embodiment of the invention is obtained by juxtaposing the heating elements, for example resistances, and by covering them with the polymer film whose hydrophilic and hydrophobic properties can be selected under the action of an external force. The heating elements can be actuated independently and in succession. The fluid guiding means 300 then comprises the fluid moving means 320, that is, the elements of the polymer surface according to their state. The liquid moves on the flat surface through the successive actuation of part of the polymer surface. If polymer elements 330 are used that are hydrophilic when their temperature is less than their phase transition temperature, when for example there is a hydrophilic fluid on an element of the polymer surface whose corresponding heated element is not actuated, the corresponding heating element of the polymer surface where the fluid is found is actuated so as to make it hydrophobic in order to move it and guide it on a precise path, the fluid having a tendency to be pushed away from said surface. At the same time, a closely situated heating element must then stay inactive so that the fluid moves onto the surface of the polymers corresponding to this heating element. The other heating elements situated close to the last element are actuated so that the elements of the corresponding polymer surface are hydrophobic. Thus the fluid is guided by the elements of the polymer surface that constitute the guiding means 300. If polymer elements 330 are used that are hydrophobic when their temperature is less than their phase transition temperature, successive elements of the contiguous surface are actuated where it is wanted to move the fluid.
[0023] This embodiment is especially useful in ink jet heads. For example three reservoirs can be provided, each reservoir containing one ink color, yellow, magenta and cyan. A channel enables the ink to be taken from each reservoir to the device for controlling the fluids. The different inks can be guided so as to converge on a selected surface in order to obtain a mixture of ink, this mixture then being guided to the inlet of a channel terminated by an injection nozzle of an ink jet head.
[0024] In the embodiments of the invention that have just been described and that can be used in ink jet heads, the device can be planned to control the movement of a compound to be added to the ink to be ejected, just before ejection. Such a device can be used to add a solvent to the ink in order to obtain an ink drop of a constant volume to be ejected, or even a surfactant in order to modify the surface energy of the ink drop to be ejected. It is further possible to add a bleaching agent to modify the density of the ink color, or even a catalyst enabling accelerated polymerization of the ink on ejection.
1. A device for controlling fluid movement comprising:
a) fluid guiding means (100, 200, 300) for guiding fluids;
b) fluid moving means(120, 220, 320) for moving fluids comprising polymers having hydrophilic and hydrophobic properties that can be selected under the action of an external force, said fluid moving means comprising a plurality of polymer elements (130, 230, 330) whose hydrophilic and hydrophobic properties can be selected, said polymer elements being arranged along the fluid guiding means;
c) at least one actuating unit (140, 240, 340) for generating said external force.
2. A device according to Claim 1 wherein said fluid guiding means comprises a channel
(110).
3. A device according to Claim 1 wherein said fluid guiding means comprises a plurality
of channels (210) that converge.
4. A device according to Claim 2 or 3 wherein said fluid moving means is arranged on
an internal wall of said channel(s) .
5. A device according to Claim 1 wherein said fluid guiding means (300) is provided on
a flat surface.
6. A device according to Claim 5 wherein said fluid guiding means comprises fluid movement
means on the flat surface.
7. A device according to any of the preceding claims characterized in that said polymer
whose hydrophilic and hydrophobic properties can be selected under the action of an
external force is a thermo-reversible polymer.
8. A device according to Claim 7 wherein said at least one actuating unit comprises a
temperature controlling means.
9. A device according to Claim 8 wherein said temperature controlling means comprise
a resistance in contact with a polymer element, said resistance being supplied by
an electric circuit.
10. A device according to any one of the Claims 1 to 6 characterized in that said polymer
whose hydrophilic and hydrophobic properties can be selected under the action of an
external force is an electrically conducting organic polymer.
11. A device according to Claim 10 wherein said actuating unit comprises means for applying
electrical current.
12. A printing fluid jet head comprising a device for controlling fluid movement according
to any one of the preceding claims.
13. A printing fluid jet head according to Claim 12 wherein the fluid is ink.
14. A method of moving fluid comprising the steps of :
- supplying fluid to at least one guide channel, said at least one guide channel having a plurality of polymer elements arranged therealong, said plurality of polymer elements having hydrophilic and hydrophobic properties and being switchable between hydrophilic and hydrophobic states ; and
- moving said fluid in said at least one channel by applying an external force to at least one of said polymer elements to change a state of said at least one of said polymer elements.
15. A method of moving fluid comprising the steps of :
- supplying fluid to a flat surface, said flat surface having a plurality of polymer elements arranged thereon, said plurality of polymer elements having hydrophilic and hydrophobic properties and being switchable between hydrophilic and hydrophobic states ; and
- moving said fluid on said flat surface by applying an external force to at least one of said polymer elements to change a state of said at least one of said polymer elements.