CN102053362A - Liquid lens array and filling method thereof - Google Patents

Abstract

The invention relates to a liquid lens array and a pouring method thereof. The liquid lens array includes a first substrate and a second substrate that are parallel to each other. The first substrate and the second substrate form a closed cavity through the second partition. A first partition is provided between the first substrate and the second substrate. A partition divides the above-mentioned closed cavity into two upper and lower cavities, which are used to hold the first liquid and the second liquid respectively. Mesh holes are distributed on the first partition, which can make the first liquid and the second liquid form in the holes. On the curved contact surface, a first conduction groove and a second conduction groove are provided on the second partition, and the first conduction groove and the second conduction groove are respectively arranged on both sides of the first partition. A voltage is applied between the second liquid and the second substrate to change the contact angle between the second liquid and the second substrate, so that the second liquid moves along the surface of the second substrate until it fills the gap between the first partition and the second substrate The cavity, and the driven-off first liquid flows out through the first conduction groove.

Description

Liquid lens array and its filling method

technical field

The invention relates to a liquid lens array and a pouring method thereof.

Background technique

Compared with the traditional solid lens, the liquid lens has the function of dynamic zoom, and it is an important device for the future ultra-thin optical camera and display system. Liquid lenses are usually composed of two immiscible liquids. The refractive indices of the two liquids are different, and when the interface between the two liquids is a curved surface, it functions as a lens. Changing the radius of curvature of the interface between the two liquids will change the focal length of the liquid lens. The focal length of the liquid lens can be changed in various ways, for example, using pressure, electrowetting force, dielectrophoretic force, etc.

A liquid lens array with variable focal length can be realized by preparing the above liquid lens into an array structure. However, current liquid lens arrays have problems with uniformity and consistency, mainly due to the perfusion and encapsulation process of two immiscible liquids. As shown in FIG. 1 , a current common liquid lens array structure is shown. Between the first substrate 1 and the second substrate 7 are two immiscible liquids, namely the first liquid 2 and the second liquid 4, and the first partition 6 divides the second liquid 4 into independent liquid lens units, usually the second liquid A partition 6 also has a hydrophobic layer 5 to control the contact surface 3 between the first liquid 2 and the second liquid 4 . In the liquid lens array structure shown in Figure 1, in order to achieve a lens array with the same focal length, it is necessary to precisely control the volume of the second liquid 4 divided by the first partition 6, that is, the volume of the second liquid 4 divided by the first partition 6 Must have the same volume. In order to achieve precise volume control of the second liquid 4, researchers have proposed various methods, such as using a volatile liquid as a solvent for the second liquid 4, controlling the volume of the second liquid 4 by volatilizing the solvent, or covering the The second substrate with the second liquid 4 is inserted into the container of the first liquid 2 , and the second liquid 4 is divided by the hydrophobic layer 5 . However, the liquid lens array prepared by the above method is affected by various factors such as temperature, humidity, and material surface processing accuracy during the preparation process, and once the preparation is completed, the inhomogeneous liquid lens array cannot be corrected in the later stage.

Contents of the invention

The invention provides a filling method of a liquid lens array, which can realize uniform lenses with the same focal length in a self-assembly manner.

The present invention also provides a liquid lens array using the above perfusion method.

The filling method of the liquid lens array is as follows: the liquid lens array includes a first substrate and a second substrate parallel to each other, the first substrate and the second substrate form a closed cavity through a hollow second partition in the middle, and the first substrate There is a first partition parallel to them between the second substrate, and the above-mentioned closed cavity is divided into upper and lower cavities by the first partition, which are respectively used to contain two immiscible liquids, the first liquid and the second liquid , the first partition is distributed with mesh holes, which can make the first liquid and the second liquid form a curved contact surface in the hole, the second partition is provided with a first conduction groove and a second conduction groove, the first conduction groove The groove and the second conduction groove are respectively arranged on both sides of the first partition, wherein the second conduction groove is located on the side close to the second substrate, and the filling method is as follows:

By applying a voltage between the second liquid and the second substrate, changing the contact angle between the second liquid and the second substrate, so that the second liquid gradually flows in from the second conduction groove and moves along the surface of the second substrate, Thus, the first liquid is driven away from between the first partition and the second substrate until the second liquid fills the cavity between the first partition and the second substrate, and the driven first liquid flows out through the first conduction groove .

The contact angle between the second liquid and the second substrate can be changed by dielectrophoretic force or electrowetting force generated by applying voltage.

As a preferred solution of the present invention, the second substrate is covered with a conductive layer, and the second liquid is a non-conductive liquid, or an insulating layer is also covered on the conductive layer of the second substrate, that is, the inside and outside of the second substrate are sequentially Covered with a conductive layer and an insulating layer, the second liquid is a non-conductive liquid.

The liquid lens array using the above perfusion method is characterized in that it includes a first substrate (1) and a second substrate (7) arranged up and down parallel to each other, and the first substrate (1) and the second substrate (7) pass through the middle The hollow second partition (10) forms a closed cavity, and the first partition (6) parallel to them is arranged between the first substrate (1) and the second substrate (7), and the first partition (6) will The above-mentioned closed cavity is divided into upper and lower two cavities, which are respectively used to hold the first liquid (2) and the second liquid (4) of two kinds of immiscible liquids. The first partition (6) is distributed with mesh holes, which can The first liquid (2) and the second liquid (4) form a curved surface contact surface in the hole, the second partition (10) is provided with a first conduction groove (8) and a second conduction groove (9), the second A conduction groove (8) and a second conduction groove (9) are respectively arranged on both sides of the first partition (6), wherein the second conduction groove (9) is located on the side close to the second substrate (7), and the second The second substrate (7) is covered with a conductive layer.

The above-mentioned liquid lens array is suitable for filling when the second liquid is a non-conductive liquid. When the conductive layer of the second substrate (7) is also covered with an insulating layer, the liquid lens array is suitable for filling when the second liquid is a conductive liquid. .

The liquid lens array according to claim 4 or 5, characterized in that a supporting partition (12) is further provided between the first partition (6) and the second substrate (7).

The liquid lens array according to claim 6, characterized in that, the first partition (6) and the supporting partition (12) are integrated, prepared by two exposures and one development.

As an improvement of the present invention, a supporting partition is further provided between the first partition and the second substrate. Preferably, the first partition and the supporting partition are integrated and prepared by exposing twice and developing once.

The above method of using the liquid lens array may be to change the focal length of the liquid lens array by changing the pressure difference between the two ends of the first conducting groove and the second conducting groove.

The method of using the above-mentioned liquid lens array can also be that when the second liquid in the cavity between the first partition and the second substrate is a non-conductive liquid, the first partition is a conductive material, and there is a conductive layer on the second substrate, Applying a voltage between the first partition and the second substrate realizes the change of the focal length of the liquid lens array; when the second liquid in the cavity between the first partition and the second substrate is a conductive liquid, the surface of the first partition is conductive, and The insulating layer is covered, the second substrate has a conductive layer, and a voltage is applied between the first partition and the conductive layer of the second substrate to change the focal length of the liquid lens array.

Since the first liquid and the second liquid of each liquid lens unit communicate with each other, it is guaranteed that the curved surface contact surfaces of all liquid lens units have the same Laplace pressure, that is, the curvature radii of all liquid lens units are equal, thus the preparation is completed The liquid lens unit has the same focal length, and at the same time, it can realize automatic correction of the liquid volume in the working state to ensure the consistency of the focal length.

The beneficial effect of the present invention is that a new liquid lens array structure is proposed, which realizes the self-assembly of two liquid lens arrays, ensures that the focal lengths of the liquid lens arrays are equal, and has the function of automatic focal length correction. The structure is simple, and it is suitable for the preparation of large Area of liquid lens array with uniform focal length.

Description of drawings

Fig. 1 is a schematic diagram of the structure of a traditional liquid lens array.

Fig. 2 is a schematic diagram of the first preferred embodiment of the liquid lens array structure proposed by the present invention.

Fig. 3 is a schematic diagram of self-assembly of a liquid lens array through pressure.

Fig. 4 is a schematic diagram of self-assembly of a liquid lens array through electric field force.

Fig. 5 is a schematic diagram of a second preferred embodiment of the liquid lens array structure proposed by the present invention.

Fig. 6a is a top view of the first partition, and 6b, 6c, 6d are schematic diagrams of the supporting partition 12 corresponding to Fig. 6a.

In the above figure: 1. The first substrate; 2. The first liquid; 3. The first contact surface; 4. The second liquid; 5. The hydrophobic layer; 6. The first partition; 7. The second substrate; 8. The first 1. Conducting groove; 9. Second conducting groove; 10. Second partition; 11. Second contact surface; 12. Supporting partition.

Fig. 7 Schematic diagram of the focal length change effect of the liquid lens array.

Detailed ways

Shown in Figure 2 is a first preferred embodiment of the liquid lens array of the present invention. In the figure, the first substrate 1 and the second substrate 7 are transparent substrates, which can be materials such as glass, transparent resin (such as acrylic), PET film, etc. The first substrate 1 and the second substrate 7 are connected together through the second partition 10 , the second partition 10 can be various resin glues with sealing properties, such as AB glue, its main function is to form a closed cavity between the first substrate 1 and the second substrate 7, and the closed cavity contains There are two immiscible liquids, the first liquid 2 and the second liquid 4, the refractive index of the two liquids is different, the first liquid 2 can be an alkane mineral oil, such as silicone oil, dodecane, tetradecane, Hexadecane, etc., the second liquid 4 can be immiscible alcohols with the first liquid 2, such as propylene glycol, glycerol, etc., or immiscible deionized water, the first liquid 2 and the second liquid 4 are divided by the first partition 6, the first partition 6 is fixed on the second partition 10, and the first partition 6 is a mesh hole structure, that is, a matrix, or a round hole arranged in a character shape, or a hexagonal shaped hole or square hole, the first partition 6 can be a transparent resin film, such as a PET film, or an opaque metal film, in order to increase the first contact surface of the first liquid 2 and the second liquid 4 in the hole 3, the surface of the first partition 6 can be covered with a layer of hydrophobic layer, such as a film layer formed by polytetrafluoroethylene material, that is, to increase the contact angle between the first contact surface 3 and the first partition 6, in order to realize For the perfusion of two immiscible liquids in the liquid lens array, there are two conduction grooves on the second partition 10, that is, the first conduction groove 8 and the second conduction groove 9, and the conduction grooves can be circular, Or square conduit, in Fig. 2, the second conduction groove 9 is the liquid import groove, the first conduction groove 8 is the liquid discharge groove, can realize the adjustment of the focal length of the liquid lens by controlling the pressure at both ends of the conduction groove, for example when When the pressure at the entrance of the second conduction groove 9 is greater than the pressure at the entrance of the first conduction groove 8, it will cause the inflow of the second liquid 4 and the outflow of the first liquid 2, thereby reducing the radius of curvature of the first contact surface 3 , to obtain a lens array with a smaller focal length.

The preferred embodiment shown in Fig. 2 can realize a liquid perfusion that realizes self-assembly through pressurization. Figure 3 shows the filling method for two immiscible liquids. The first substrate 1 and the second substrate 7 form a closed cavity through the second partition 10. Before the liquid is filled, the cavity is filled with air. The first liquid 2 can be poured into the first liquid 2 through the second conduction groove 9 by means of pressurization until it fills the entire cavity and flows out from the first conduction groove 8. When the first liquid 2 is filled Finally, the second conductive groove 9 is connected to the second liquid 4, and the self-assembled liquid perfusion is realized by powering on, that is, the perfusion of the second liquid 4 is realized by changing the wettability of the surface of the second substrate 7. There are two kinds of contact surfaces shown in Fig. 3 in the process that two liquids 4 are poured into, i.e. the first contact surface 3 and the second contact surface 11, at this moment, the two kinds of contact surfaces are the first liquid 2 and the second liquid 4 Contact surface, the first contact surface 3 is determined by the aperture shape of the first partition 6, for example, in the case of a circular hole, the first contact surface 3 is a spherical surface, the second contact surface 11 is a cylindrical surface, and _R1 is the second contact surface 11. The radius of curvature perpendicular to the direction of the second substrate 7 , R ₁ ′ is the radius of curvature of the first contact surface 3 in the direction perpendicular to the second substrate 7 . As shown in Figure 4, in order to realize the self-assembly of the power-on method, the surface of the second substrate 7 needs to be covered with a conductive layer, such as preparing a layer of ITO conductive film by radio frequency magnetron sputtering, when the second liquid 4 is a non-conductive liquid , such as glycerin, a voltage is applied between the second liquid 4 and the conductive layer of the second substrate 7 to generate a dielectrophoretic force, and driven by the dielectrophoretic force, the second liquid 4 will gradually flow into the second conduction groove 9 and Move along the surface of the second substrate 7, thereby driving the first liquid 2 from the lower half cavity to the upper half cavity (the space between the first partition 6 and the first substrate 1), due to the first partition 6 In the process of electrification, the first contact surface 3 is a hemispherical surface, and there is a Laplace pressure, thereby preventing the second liquid 4 from further flowing into the upper half of the cavity. When the second liquid 4 is a conductive liquid, such as an ion The liquid needs to be covered with an insulating layer on the conductive layer of the second substrate 7, such as aluminum oxide, and a voltage is applied between the second liquid 4 and the conductive layer of the second substrate 7 to generate electrowetting force. Driven by force, the second liquid 4 will gradually flow in from the second conduction groove 9 and move along the surface of the second substrate 7, thereby driving the first liquid 2 from the lower half of the cavity to the upper half of the cavity.

The preferred embodiment shown in Figure 2 can achieve a uniform liquid lens array. Assuming that the radii of curvature of the connected liquid lens units are not equal, the Laplace pressures of the two liquid lens units are not equal. When the liquid lens array is in a stable state, and the two ends of the first conduction groove 8 and the second conduction groove 9 When closed, the above two liquid lens units will be adjusted to have equal curvature radii under the action of the Laplace pressure difference, thereby eliminating the pressure difference, and so on. In a stable state, the curvature radii of all liquid lens units are equal, that is, the focal lengths are equal .

The preferred embodiment shown in FIG. 2 can realize the dynamic adjustment of the focal length, that is, the adjustment of the focal length can be realized by changing the pressure at the entrances of the first conducting groove 8 and the second conducting groove 9 . For example, increase the pressure at the entrance of the second conducting groove 9 to make it greater than the sum of the pressures at the entrance of the first contact surface 3 and the first conducting groove 8, then the second liquid 4 has a net inflow, and the first liquid 2 has a net inflow. outflow, the radius of curvature of the first contact surface 3 becomes smaller gradually, and the focal length of the liquid lens becomes smaller, or on the contrary, the sum of the pressure at the entrance of the first conduction groove 8 and the pressure of the first contact surface 3 is greater than that of the second conduction groove 9 As the pressure at the inlet increases, the radius of curvature of the first contact surface 3 gradually increases, and the focal length of the liquid lens increases.

The preferred embodiment shown in Fig. 2 can realize the electric field force to adjust the focal length. At this time, the first partition 6 can be made of a conductive material, such as a stainless steel plate, and a conductive layer, such as an ITO conductive layer, is added on the second substrate 7. When the second liquid 4 is a non-conductive liquid, such as glycerol, the first Increasing the voltage between the partition 6 and the conductive layer on the second substrate 7 will generate a dielectrophoretic force. Under the action of the dielectrophoretic force, the contact angle between the second liquid 4 and the first partition 6 will change, that is, the first contact surface 3 The radius of curvature changes, thereby changing the focal length of the liquid lens. When the second liquid 4 is a conductive liquid, such as deionized water containing Nacl, Kcl, or ionic liquid, an insulating layer needs to be added on the first partition 6 , such as alumina, at this time, increasing the voltage between the first partition 6 and the conductive layer on the second substrate 7 will generate electrowetting force. Under the action of electrowetting force, the second liquid 4 and the first partition 6 The contact angle will change, thus changing the focal length of the liquid lens.

Figure 5 shows the second preferred embodiment of the liquid lens array of the present invention. The main difference between it and the preferred embodiment shown in FIG. 2 is that a support partition 12 is added between the first partition 6 and the second substrate 7, so that when realizing a large-area liquid lens array, the support partition 12 can stabilize the first partition 6 The distance between the support partition 12 and the second substrate 7 can be made of transparent resin material, such as su8 photoresist. The structure of the supporting partition 12 can be the structure shown in FIG. 6 (the structure is represented by a black area in the figure). In order to clearly describe the corresponding relationship between the first partition 6 and the supporting partition 12, the first partition 6 is first shown in FIG. 6a The top view graphic structure of the front is an array of circular holes arranged in the shape of a character, and the support partition 12 is located at the center of three adjacent circular holes arranged in the shape of a character. The cross-sectional shape of the support partition 12 can be as shown in Figure 6b triangle, the circle shown in Figure 6c, or the polygon shown in Figure 6d, the support partition 12 needs to meet the requirements of not only ensuring the communication of the second liquid 4 between different liquid lens units, but also not blocking the liquid lens unit as much as possible. For the imaging optical path, researchers in the field can design various shapes of the support partition 12 as required.

The first partition 6 and the support partition 12 shown in FIG. 5 can also be integrated, that is, su8 material is used to complete the process of two exposures and one development. Specifically, firstly, a su8 thick film is prepared on the second substrate 7 by means of leveling or coating, and then a non-traditional exposure method is adopted, that is, the structure of the supporting partition 12 is exposed first, such as any of Fig. 6b, c, d. One or a similar pattern, at this time, use sufficient exposure to ensure that the pattern of the supporting partition 12 is always exposed to the bottom plate and completely in contact with the second substrate 7, and the second exposure of the pattern of the first partition 6, such as the pattern in Figure 6a, is at the position of the pattern twice. Under the premise of accuracy, the second exposure is not sufficient, that is, the first partition 6 pattern is only exposed to the upper half of the su8 thick film, and the structure shown in Figure 5 can be realized by developing after two exposures. Researchers in the field can use various photoresists to realize the above structure by using a similar double exposure method as required.

FIG. 7 is a schematic diagram showing the effect of changing the focal length of the liquid lens array. In the figure, the liquid lens array is arranged in a character shape, the aperture of the lens is 1mm, the first liquid is silicone oil, the second liquid is deionized water, and the back of the lens is a text picture. Figure 7a is a picture taken when the text is clearly in focus. At this time, further increasing the pressure in the second conduction groove will cause the focal length of the liquid lens array to change, resulting in a blurred picture of the text shown in Figure 7b.

Claims (7)

1. the method for filling of a liquid lens array, described liquid lens array comprises, first substrate (1) parallel to each other and second substrate (7) of following setting, it is characterized in that, first substrate (1) cuts off (10) with second substrate (7) by second of middle hollow and forms closed cavity, be provided with parallel with them first between first substrate (1) and second substrate (7) and cut off (6), cut off (6) by first above-mentioned closed cavity is divided into two cavitys up and down, be respectively applied for two kinds of immiscible liquids first liquid of splendid attire (2), second liquid (4), be distributed with reticulated cell on first partition (6), can make first liquid (2) and second liquid (4) in the hole, form the curved surface surface of contact, second cuts off (10) is provided with first conduction trough (8) and second conduction trough (9), first conduction trough (8) and second conduction trough (9) are divided into the both sides of first partition (6), wherein second conduction trough (9) is positioned at the side near second substrate (7), and described method for filling is:

After formerly pouring into first liquid (2) and making it to be full of described closed cavity, second conduction trough (9) is communicated to second liquid (4), by on-load voltage between second liquid (4) and second substrate (7), change the contact angle between second liquid (4) and second substrate (7), second liquid (4) is progressively moved by second conduction trough (9) inflow and along the surface of second substrate (7), thereby first liquid (2) is expelled between first partition (6) and second substrate (7), be full of first cavity that cuts off between (6) and second substrate (7) until second liquid (4), first liquid (2) that is expelled is flowed out by first conduction trough (8).

2. the method for filling of liquid lens array as claimed in claim 1 is characterized in that, second substrate is covered with conductive layer on (7), and described second liquid (4) is non-conductive liquid.

3. the method for filling of liquid lens array as claimed in claim 2 is characterized in that, also is covered with insulation course on the conductive layer of second substrate (7), and described second liquid (4) is conducting liquid.

4. use the liquid lens array of each described method for filling among the claim 1-3, it is characterized in that, comprise, first substrate (1) parallel to each other and second substrate (7) of following setting, first substrate (1) cuts off (10) with second substrate (7) by second of middle hollow and forms closed cavity, be provided with parallel with them first between first substrate (1) and second substrate (7) and cut off (6), cut off (6) by first above-mentioned closed cavity is divided into two cavitys up and down, be respectively applied for two kinds of immiscible liquids first liquid of splendid attire (2), second liquid (4), be distributed with reticulated cell on first partition (6), can make first liquid (2) and second liquid (4) in the hole, form the curved surface surface of contact, second cuts off (10) is provided with first conduction trough (8) and second conduction trough (9), first conduction trough (8) and second conduction trough (9) are divided into the both sides of first partition (6), wherein second conduction trough (9) is positioned at the side near second substrate (7), and second substrate is covered with conductive layer on (7).

5. liquid lens array as claimed in claim 4 is characterized in that, also is covered with insulation course on the conductive layer of second substrate (7).

6. as claim 4 or 5 described liquid lens arrays, it is characterized in that, also be provided with between first partition (6) and second substrate (7) to support and cut off (12).

7. liquid lens array as claimed in claim 6 is characterized in that, first partition (6) is as a whole with support partition (12), by double exposure, and once development preparation.

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