LIQUID OPTICAL DEFLECTOR AND METHOD FOR FABRICATING THE SAME

BACKGROUND OF THE INVENTION Field of Invention

[0001] The present invention relates to liquid optical deflector and method for fabricating the liquid optical deflector.

Description of Related Art

[0002] The elecctrowetting phenomenon has been well known in the art. In the elecctrowetting phenomenon, when an applied voltage between two liquids is changed, the surface tension is changed too, resulting in movement of the liquid. In further researches, if the metal surface of the electrode is formed with an insulation film with a thickness of several microns, the operation reliability can be improved. The electrode can be protected from damage. This improved technology is then called electrowetting-on-dielectric (EWOD).

[0003] The EWOD technology can be, for example, used in Lab-on-a-chip

(LOC) or optical applications. The optical application may have liquid lense and electronic paper. The operation mechanism of the electrowetting phenomenon is as follows. For example, a liquid drop is disposed on a metal substrate with a thin insulation layer thereon. Then, a voltage is applied on the metal substrate, the contact angle of the liquid drop and the metal substrate can be changed. When this liquid drop is used as the optical lens, two liquids with equal density are used. One liquid is insulating and another liquid is conductive. Due to the change of voltage, the curvature of the interface between the two liquids is accordingly changed, resulting in

the change of lens focus.

[0004] In the conventional applications, for example, U.S. patent No.

6,369,954 has proposed an application. FIG. 1 is a cross-sectional view, schematically illustrating a conventional lens with variable focus. In FIG. 1, A drop of an insulating liquid 11 is located on the internal surface of a wall of a dielectric chamber 12 filled with a conductor liquid 13. The insulating liquid 11 and the conductor liquid 13 are both transparent, not miscible, have different optical indexes and have substantially the same density. The dielectric 12 naturally has a low wetting with respect to the conductor liquid 13. A surface treatment 14 insuring a high wetting of the wall of the dielectric chamber with respect to the conductor liquid 13 surrounds the contact region 15 between the insulating liquid drop 11 and the wall of chamber 12. The surface treatment 14 maintains the positioning of drop 11, preventing the insulating liquid from spreading beyond the desired contact surface. When the system is at rest, the insulating liquid drop 11 naturally takes the shape designated by reference A. When a voltage V is established between electrodes 16 and 17, an electrical field is created which, according to the above mentioned electrowetting principle, will increase the wetting of region 15 with respect to conductor liquid 13. As a consequence, conductor liquid 13 moves and deforms the insulating liquid drop 11 into the shape designated by reference B. [0005] Although several other disclosures have been proposed by, for example, WO 2004/051323 and CN 1881003. The conventional liquid optical device basically needs to assemble several parts into the device. Alternatively in conventional structure, the indium tin oxide (ITO) electrode and the hydrophobic insulating layer are coated on an inner surface of a glass cavity, and then the glass cavity is adhered to the lower transparent substrate. The device size is about few mm. Usually, it is not easy

to align and assemble. The error could be large and the yield rate is low. Even, the size of device cannot be reduced. Other device structures and the fabrication processes are still under developments.

SUMMARY OF THE INVENTION

[0006] The invention proposes a liquid optical deflector and its fabrication.

The liquid optical deflector includes two conductive electrodes with an insulating wall to form a liquid container for adapting two kinds of liquids. By changing the operation voltages on the two conductive electrodes, an angle of the interface between the two liquids can be control, and then provides various applications.

[0007] A liquid optical deflector of an embodiment of the invention includes a substrate. An electrode layer is disposed on the substrate. An insulating layer is disposed on the electrode layer, wherein the electrode layer has an exposed region. A first electrode wall is righting up from the substrate. A first insulating wall is disposed on a surface of the first electrode wall. A second electrode wall is righting up from the substrate and facing to the first electrode wall as a first electrode pair. A second insulating wall is disposed on a surface of the second electrode wall. A side wall is righting up from the substrate and at least connecting between the first electrode wall and the second electrode wall, so as to form a containing space. A first liquid is filled in the containing space in contacting with the electrode layer on the substrate. A second liquid is filled in the containing space to have an interface with the first liquid without solving to each other. A cap layer is sealing over the containing space to form an optical deflector unit. Wherein, the interface between the first liquid and the second liquid has an angle, the angle is controlled by a first voltage on the first electrode wall

and a second voltage on the second electrode wall.

[0008] For another embodiment, an optical deflector array includes a plurality of the optical deflector units as described above to form an array. [0009] An embodiment of a method for fabricating a liquid optical deflector includes providing a substrate, wherein the substrate has an electrode layer thereon and an insulating layer disposed on the electrode layer, and the first electrode layer has an exposed region. A first electrode wall is formed with righting up from the substrate. A first insulating wall is formed on a surface of the first electrode wall. A second electrode wall is formed with righting up from the substrate and facing to the first electrode wall as a first electrode pair. A second insulating wall is formed on a surface of the second electrode wall. A side wall is formed with righting up from the substrate and connecting between the first electrode wall and the second electrode wall, so as to form a containing space. A first liquid is filled into the containing space in contacting with the electrode layer on the substrate. A second liquid is filled into the containing space to have an interface with the first liquid without solving to each other. A cap layer is formed for sealing over the containing space to form an optical deflector unit.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this

specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0012] FIG. 1 is a process flow diagram, schematically illustrating a face detection method according to a preferred embodiment of the invention. [0013] FIGs. 2A and 2B are cross-sectional views in lateral and transverse directions, schematically illustrating a liquid optical deflector, according to an embodiment of the invention.

[0014] FIGs. 3-5 are cross-sectional views, schematically illustrating the operation mechanism, according to an embodiment of the present invention. [0015] FIGs. 6A-6C and 7-8 are cross-sectional views, schematically illustrating a fabrication process, according to an embodiment of the present invention. [0016] FIGs. 9-10 are horizontal cross-sectional views, schematically illustrating the structure of the liquid optical deflector, according to embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In the invention, a liquid optical deflector is described. The liquid optical deflector is a structure, which can be fabricated in a small size, for example in micron order. The fabrication cost and time can at least be reduced and the yield can remain high. An aspect of the invention, the device body can be integrated into a small size. The fabrication process can, for example, uses the conductive photopolymer to serve as the conductive electrode and the insulating material can be, for example, photopolymer. The liquid container can be, for example, formed by the processes, including the photolithographic process, inject process, electroplating process,

screen printing, or imprinting. In other words, the walls of the liquid container can be directly formed over the substrate in reduced sized and increased alignment. The fabrication cost and speed can at least be improved.

[0018] Several embodiments are provided for description, but not for limiting the invention. In addition, the embodiments can also be properly combined to each other into another embodiment.

[0019] FIGs. 2A and 2B are cross-sectional view in lateral and transverse directions, schematically illustrating a liquid optical deflector, according to an embodiment of the invention. In FIG. 2A, a liquid optical deflector can, for example, include a lower transparent substrate 100. An electrode layer 102 is disposed on the substrate 100 to serve as a common electrode, for example. The electrode layer 102 can be applied a ground voltage in actual operation, for example. An insulating layer 104 is disposed on the electrode layer 102 at a peripheral region of a desired region, wherein the desired region of the electrode layer 102 is exposed. A first electrode wall 106A and a second electrode wall 106B are disposed over and righting up from the substrate 100. The first electrode wall 106A and the second electrode wall 106B are insulating from the electrode layer 102 by the insulating layer 104. The electrode wall 106A, 106B can be, for example, conductive photopolymer. An insulating wall 108 is disposed on a surface of the first electrode wall 106A and 106B. Basically, the first electrode wall 106A and the second electrode wall 106B form a parallel pair of electrodes for later use to control the liquid interface in electrowetting mechanism. The material for the insulting layer 108 can be, for example, hydrophobic, so that the electrowetting phenomenon can be easier controlled. [0020] If taking the liquid container with four vertical walls as the example,

the other two insulating side walls is seen in FIG. 2B but not in FIG. 2A. In order to form a liquid container, the wall should be continuously connected with the electrode walls 106A, 106B. The insulating side wall 116 is also formed disposed over substrate 100 and righting up from the substrate 100 in connecting between the first electrode walls 106A, 106B for forming a containing space. However, the shape of the side wall 108 is not limited to two wall portions in FIG. 2B. Any shape of the side wall to form the container can be taken.

[0021] A liquid 110 is filled in the containing space in contacting with the electrode layer 102 on the substrate 100. The liquid 110 includes, for example, water or conductive solution. Another liquid 112 is filled in the containing space to have an interface with the liquid 110 without solving to each other. The liquid 112 can include, for example, oil or insulating liquid. However, in general, one of the two liquids is conductive and the other one is insulating, for example. A transparent cap layer 114 seals over the containing space to form an optical deflector unit. The tow kinds of liquids can be chosen to form the interface plane, of which the tilt angle of the interface can controlled. Further, the densities of the two liquids, preferably, are substantially the same. As a result, the deflector is not affected by the gravity force. [0022] FIGs. 3-5 are cross-sectional views, schematically illustrating the operation mechanism, according to an embodiment of the present invention. The operation mechanism is described, for example. In FIG. 3, the electrode 106A and the electrode 106B with respect to the common electrode 102 are respectively applied with an equal voltage, such as the ground voltage in OV. In this situation, there is no electric field created. The angle of the liquid interface remains horizontal. For a perpendicularly incident light, the traveling direction is not deflected. In FIG. 4, for

example, when the electrode wall 106A is applied with a voltage V ₂ and the electrode wall 106B is applied with a voltage Vi, an electric field is created. According to the electro wetting phenomenon, the liquid interface 202A is tilted. The two liquids have different indices of refractions. With respect to the liquid interface 202A, the incident light 200 has an incident angle ^ ₁ , then the outgoing light is deflected to right. In FIG. 5, when the electrode wall 106A is applied with a voltage Vj and the electrode wall 106B is applied with a voltage V ₂ , another electric field is created. According to the electrowetting phenomenon, the liquid interface 202B is tilted. With respect to the liquid interface 202B, the incident light 200 has an incident angle ^ i, then the outgoing light is deflected to left. Generally, the liquid interface between the first liquid and the second liquid has an angle. This angle can be controlled by applying a first voltage on the electrode wall 106A and a second voltage on the second electrode wall 106B.

Depending on the value of the applied voltages on the electrode walls, the tilt angle of the liquid interface can be controlled. When the incident light can be deflected to the desired direction in operation.

[0023] In the actual applications, for example, the liquid optical deflector can be used in scanner for scanning different lines positions. In addition, the liquid optical deflector can also be implemented in a stereo displaying device, for displaying the left image to the left eye and right image to the right eye. Even further, several liquid optical deflectors, as light deflecting units, can be formed as an array for various uses. Here, all of the applications are not fully listed.

[0024] For the fabrication process, the aspect of the present invention introduces the process to directly form the walls of the liquid container over the substrate. FIGs. 6A-6C and 7-8 are cross-sectional views, schematically illustrating a

fabrication process, according to an embodiment of the present invention. Taking the processes based on photolithographic with the electroplating, for example in FIG. 6A, a plating seed layer 302 is formed over a substrate 300. A mask layer 304, such as photopolymer layer, is formed on the plating seed layer 302 by photolithographic. The mask layer 304 has the wall opening 306 to expose the plating seed layer 302. Then, the wall opening 306 is filled with the conductive material 308 by electroplating. In FIG. 6c, a portion of the plating seed layer 302 is removed, and the conductive material 308 with the remaining plating seed layer 302 forms the conductive wall. In order to form the liquid container, a portion of the mask layer 304 is also removed with a remaining portion, not seen in this cross-sectional view of FIG. 6C. The remaining portion of the mask layer 304 serves as the insulating wall, connected between the conductive walls 308. Further, the insulating layer 310 is, preferably, further formed over the surface of the conductive wall 308, 302. The desired two liquids 312 and 314 are filled into the containing space. [0025] In FIG. 7, another substrate 400 with the common electrode layer

402 is formed. The common electrode is a transparent conductive layer, such as the ITO or any other suitable materials. In FIG. 8, the substrate 400 with the common electrode layer 402 is disposed over the conductive wall 308, 302 and the insulating wall to seal the liquids 312, 314. Alternatively, the walls can also be formed by printing process et al., as previously mentioned. The foregoing fabrication process is just an example. According to the aspect of the invention, the liquid optical deflector can be direction formed over the substrate in fabrication process. The walls can also be formed by other various processes to form over the substrate. [0026] With respect to the structure, the conductive walls can be multiple

pairs, for example. FIGs. 9-10 are horizontal cross-sectional views, schematically illustrating the structure of the liquid optical deflector, according to embodiments of the invention. In FIG. 9, for example, three pairs of conductive walls 412 are formed on the insulating wall 410. In this situation, the angle of the liquid interface can be controlled with more degree of freedom. Even further in FIG. 10 as the example, the conductive walls 420a-420d by themselves can form the walls of liquid container, and the conductive walls 420a-420d are connected together with smaller insulating portions 422 at the joint portions. The insulation layer 424, such as the hydrophobic material, is formed over the inner surface of the conductive walls 420a-420d. The liquids can then be filled into the containing space.

[0027] In other words, the present invention uses the device structure with the proper materials in accordance with the fabrication process. The fabrication can be more easily performed without consuming much manpower. The device is directly formed over the substrate, and can be formed with reduced size. As a result, the deflector device can be more easily integrated into the final product, such scanner, stereo displaying apparatus, and so on.

[0028] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing descriptions, it is intended that the present invention covers modifications and variations of this invention if they fall within the scope of the following claims and their equivalents.