KR20110112598A - Method of sealing the liquid in the liquid lens using hydrophobic layer and liquid lens - Google Patents

Abstract

The present invention relates to a method of liquid sealing of a liquid lens. The liquid sealing method includes bonding a lower substrate to a lower portion of a body having a cavity to seal a lower surface of the cavity; Injecting liquid into the cavity of the body; Manufacturing an upper substrate in which a hydrophilic film is formed in a region facing the cavity into which the liquid is injected, and a range of a region is formed of a hydrophobic film from an edge of the hydrophilic film; And sealing an upper surface of the cavity by bonding an upper substrate to an upper portion of the main body so that the region where the hydrophilic film is formed and the upper portion of the cavity are coupled to each other.

Description

Method of sealing the liquid in the liquid lens using hydrophobic layer and Liquid lens

The present invention relates to a liquid sealing method of a liquid lens, and more particularly, to a liquid sealing method for sealing a cavity of a liquid lens by using an upper substrate having a patterned hydrophobic film and a hydrophilic film.

Generally, a lens module of a high performance digital camera is composed of an optical lens made of glass and a lens driving device for driving the optical lens. In order to adjust the focus and magnification of the optical lens, the lens module adjusts the position between the plurality of optical lenses using a lens driving device. As described above, since the conventional high performance digital camera must be equipped with a lens driving device for adjusting the focus and magnification, it is inevitable to increase the volume of the digital camera, and it is difficult to miniaturize the high performance digital camera.

Thus, recently, liquid lenses capable of adjusting the focus and magnification of the lens without using the lens driving apparatus have been developed. In the liquid lens, the focal length is adjusted by adjusting the curvature of the droplet by the electrowetting phenomenon.

The final package step of the manufacturing process of the liquid lens described above is a process of sealing the liquid after injection into the cavity of the device. In the process of sealing the liquid into the cavity of the device, air is trapped in the cavity to form bubbles, or the liquid flows out of the cavity due to the capillary phenomenon caused by the hydrophilic nature of the packaging substrate and the formation of microcavity between the substrate and the device, thereby completely sealing the cavity. There is this difficult problem. As such, the liquid closure process described above is a fairly demanding technique, while generally not well known.

1 is a cross-sectional view for explaining a liquid droplet sealing method of a conventional liquid lens. Referring to FIG. 1, the conventional liquid lens 10 stacks a wall 120 of several hundreds of micro heights in a cavity 100 containing liquid, and then covers the upper substrate 110 with the liquid 'a'. By allowing it to overflow from the cavity, air bubbles are trapped in the cavity and sealed with an adhesive. This conventional method requires an additional process for droplet sealing and has the disadvantage of increasing the size of the device.

The conventional liquid sealing method of the liquid lens is a method of injecting a target liquid such as oil after immersing the device in the liquid. However, this method has a problem in that the process is difficult and the liquid is difficult to control because the device and the substrate must be fastened in the liquid.

SUMMARY OF THE INVENTION An object of the present invention for solving the above technical problem is to provide a liquid sealing method of a liquid lens that can be simply and securely sealed by using an upper substrate having a hydrophobic film and a hydrophilic film patterned on a surface thereof.

A first aspect of the present invention for achieving the above technical problem is a liquid seal of a liquid lens having a body having a cavity in which a liquid is injected, a lower substrate sealing the lower portion of the body and an upper substrate sealing the upper portion of the body A liquid sealing method, comprising: bonding a lower substrate to a lower portion of a body having a cavity to seal a lower portion of the cavity; Injecting liquid into the cavity of the body; Manufacturing an upper substrate on which a hydrophilic film is formed in a region of the surface of the substrate facing the cavity into which the liquid is injected, and in which a hydrophobic film is formed in a region of the surface of the substrate from an edge of the hydrophilic film; And sealing the upper surface of the cavity by bonding the upper substrate to the upper portion of the main body such that the hydrophilic film of the upper substrate and the upper portion of the cavity are coupled to each other.

In the liquid sealing method according to the first aspect described above, the manufacturing of the upper substrate comprises: forming a hydrophobic film on the surface of the substrate; Coating a polymer on a surface of the substrate on which the hydrophobic film is formed; Selective plasma treatment of the polymer to pattern it to be hydrophilic; And forming a hydrophobic film on the surface of the substrate by coating a hydrophobic material on the surface of the substrate or CF ₄ on the surface of the substrate. It is preferable to process to form a hydrophobic film.

In the liquid encapsulation method according to the first aspect, the manufacturing of the upper substrate may include: applying a photosensitive film to a surface of the substrate and then patterning the same using a photolithography process; Applying a hydrophobic material on the substrate on which the patterned photoresist is formed; Removing the photoresist to pattern the hydrophobic material to form a hydrophobic film; It may be provided.

According to a second aspect of the present invention, there is provided a liquid lens including: a body having a cavity penetrating an upper surface and a lower surface, and having conductive droplets and insulating droplets not mixed with each other in the interior of the cavity; A lower substrate bonded to a lower surface of the body to seal a lower portion of the cavity; An upper substrate bonded to an upper surface of the main body to seal an upper portion of the cavity, wherein the upper substrate comprises: a substrate; A hydrophilic film formed by applying a hydrophilic material to a region of the surface of the substrate facing the upper portion of the cavity; And a hydrophobic film formed by applying a hydrophobic material to an edge of the hydrophilic film on the surface of the substrate.

The upper substrate and the main body are bonded to each other such that the hydrophilic film of the upper substrate and the upper surface of the cavity into which the droplets are injected are bonded to each other.

The liquid sealing method of the liquid lens according to the present invention forms a hydrophobic film in the region of the upper substrate in contact with the liquid of the cavity, thereby making the liquid in the cavity simple and reliable by using the difference in the surface tension and the interfacial tension of the liquid injected into the cavity. Can be sutured.

In addition, the liquid sealing method according to the present invention can be widely used in the sealing of the cavity or the fluid channel such as a liquid lens having a cavity, a fluid element having a fluid channel.

1 is a cross-sectional view illustrating a conventional liquid lens droplet sealing method.
Figure 2 (a) is a cross-sectional view of a simplified liquid lens to which the liquid sealing method according to the first embodiment of the present invention is applied, (b) is a front view showing the upper substrate of the liquid lens.
3 is a liquid droplet with Laplace pressure.
4 is a view for explaining the movement and bonding of the liquid due to the difference in the Laplace pressure of the two droplets in contact.
FIG. 5 is a diagram illustrating the difference in interfacial tension according to the type of solid plate of the same droplet, and FIG. 6 is a diagram illustrating a local Laplace pressure difference generated in a droplet placed on a heterogeneous solid interface. One picture.
7 is a front view illustratively showing an upper substrate of a liquid lens two-dimensionally patterned with a hydrophobic film on a hydrophilic substrate to trap droplets in a cavity of the liquid lens.
FIG. 8 is a diagram illustrating droplets trapped in a patterned hydrophobic film. FIG. 9 is a diagram illustrating the droplet restraint ability of the patterned hydrophobic film according to the amount of droplets.
10 is a flow chart schematically showing a liquid sealing method according to a second embodiment of the present invention.
11 is a cross-sectional view sequentially illustrating an embodiment of a process of manufacturing an upper substrate according to a second embodiment of the present invention.
12 is a cross-sectional view sequentially showing another embodiment of a process of manufacturing the upper substrate according to the second embodiment of the present invention.

Hereinafter, a liquid sealing method of a liquid lens according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the liquid sealing method of the liquid lens according to the present embodiment, by injecting liquid into the cavity and then bonding the upper substrate patterned with a hydrophobic film on the surface, the liquid is precisely and reliably utilized by using the difference in the surface tension and the interfacial tension of the liquid. It is possible to suture.

Figure 2 (a) is a cross-sectional view of a simplified liquid lens to which the liquid sealing method according to the first embodiment of the present invention is applied, (b) is a front view showing the upper substrate of the liquid lens.

Referring to FIG. 2, in the liquid lens 20 to which the liquid sealing method according to the first embodiment of the present invention is applied, the lower surface of the main body 200 in which the cavity 202 is formed is sealed by the lower substrate 210. The liquid 220 is injected into the cavity of the upper portion of the cavity into which the liquid is injected, and is sealed with the upper substrate 230. In the upper substrate 230, a hydrophilic film 232 is formed at a portion in contact with a liquid of the cavity, and a hydrophobic film 234 is formed at a boundary region of the cavity. As a result, the liquid in the cavity is prevented from flowing out of the cavity by the hydrophilic film of the upper substrate and the hydrophobic film of the boundary region and can be reliably sealed.

3 is a liquid droplet with Laplace pressure. As shown in FIG. 3, Laplace pressure refers to the pressure difference between the inner and outer yarns of a perfectly spherical droplet. The cause of the Laplace pressure is due to the surface tension at the interface between the liquid and the external gas, it can be expressed by the equation (1).

는 액적의 내부압력이며,

는 액적의 외부압력이며,

는 액적의 표면장력이며,

는 액적의 반경이다. 즉, 액적의 반경이 작을수록 액체 내부와 외부 기체의 계면에 존재하는 압력의 차이는 커지게 되고, 액적의 표면장력이 커질수록 상기 압력의 차이도 커지게 된다. 일한 주위 환경에 거하는 서로 다른 반경을 가지는 액적은 각각 고유한 라플라스 압력을 가지게 된다. 도 4은 접촉하는 두 액적의 라플라스 압력 차이에 의한 액체의 이동 및 결합을 설명하기 위한 도면이다. 도 4의 (a)는 반경이 다른 두 액적의 접촉 초기 상태를 도시한 것이며, (b)는 라플라스 압력 차이에 의한 액체의 이동을 도시한 것이며, (c)는 두 액적의 결합 상태를 도시한 것이다. 도 4을 참조하면, 두 액적이 접촉하게 되면(a) 각 액적의 라플라스 압력 차이에 의하여 상대적으로 압력이 큰 작은 반경(r₂)의 액적에서 큰 반경(r₁)의 액적으로 액체가 이동하게 되며(b), 최종적으로 작은 액적은 큰 액적으로 병합되게 된다(c). here,

Is the internal pressure of the droplet,

Is the external pressure of the droplet,

Is the surface tension of the droplet,

Is the radius of the droplet. That is, the smaller the radius of the droplet, the greater the difference in pressure present at the interface between the liquid inside and the outside gas, and the greater the surface tension of the droplet, the greater the difference in pressure. Droplets with different radii in the working environment each have their own Laplace pressure. 4 is a view for explaining the movement and bonding of the liquid due to the difference in the Laplace pressure of the two droplets in contact. Figure 4 (a) shows the initial contact state of two droplets of different radius, (b) shows the movement of the liquid due to the difference in Laplace pressure, (c) shows the combined state of the two droplets. will be. Referring to FIG. 4, when two droplets come into contact with each other (a), the liquid moves from a droplet of a relatively large radius r ₂ to a droplet of a large radius r ₁ due to the difference in the Laplace pressure of each droplet. (B) and finally small droplets merge into large droplets (c).

On the other hand, the droplets placed on the solid plate has an inherent interfacial tension due to the chemical properties of the solid and liquid interface, and it is as if the elements affecting the laplace pressure of the droplets are added. That is, if the droplets and their external gaseous environment are the same, various interfacial tensions will be shown depending on the properties of the solid plate. FIG. 5 is a diagram illustrating the difference in interfacial tension according to the type of solid plate of the same droplet, and FIG. 6 is a diagram illustrating a local Laplace pressure difference generated in a droplet placed on a heterogeneous solid interface. One picture. As shown in FIG. 5, it is possible to control the Laplace pressure of the droplet through the change of the interfacial tension between the solid plate and the droplet. Thus, as shown in FIG. 6, the droplets placed in the heterogeneous solid center generate local Laplace pressure differentials by the two solid surfaces, which causes the liquid to move to resolve the intra-droplet pressure differentials. In particular, in the case of a solid having a hydrophobic surface (Solid 1) and a solid having a hydrophilic surface (Solid 2), the difference in surface tension is very large, so a relatively large Laplace pressure difference (Δ p = Δ p _1- △ p ₂ ) Will be generated. As a result, the moving speed and the moving force of the droplet according to the movement in the arrow direction of FIG. 6 become large, so that the constraint force of the droplet becomes large and the large droplet can also be trapped.

FIG. 7 is a front view showing a substrate two-dimensionally patterned with a hydrophobic film on a hydrophilic substrate to trap droplets. As shown in FIG. 7, when the hydrophobic film 910 is formed on the substrate 900 having the hydrophilic surface and patterned in two dimensions, the droplets may be confined in the patterned hydrophilic region. FIG. 8 is a diagram showing the droplet 'a' trapped in the patterned hydrophobic film. FIG. 9 is a diagram illustrating the droplet restraint ability of the patterned hydrophobic film according to the amount of droplets. As shown in FIG. 9, even if the amount of droplets is increased to 4 µL, (b) is 7 µL, and (c) is 10 µL, it can be seen that the hydrophobic film has excellent droplet restraint ability.

Based on the above theoretical and experimental basis, it is easy to grasp that the liquid sealing method in the cavity according to the present invention is excellent.

Hereinafter, a liquid sealing method of a liquid lens having a cavity according to a second embodiment of the present invention will be described in detail with reference to FIG. 10. 10 is a flow chart schematically showing a liquid sealing method according to a second embodiment of the present invention. Referring to FIG. 10, first, a main body 50 having a cavity 'c' is formed (step a), a lower substrate 52 is manufactured, and a lower substrate is bonded to a lower surface of the main body to seal a lower portion of the cavity. Then, the liquid 54, 56 is injected into the cavity (step b), the upper substrate 58 is manufactured (step c), and the upper substrate is bonded to the upper surface of the main body to seal the upper part of the cavity (step d).

11 is a cross-sectional view sequentially illustrating an embodiment of a process of manufacturing an upper substrate according to a second embodiment of the present invention. Referring to FIG. 11, first, a substrate 70 such as glass is washed and prepared (step a). Glass is a hydrophilic material, and when glass is used as the substrate, a process of forming a separate hydrophilic film on the surface of the substrate may be omitted. However, when the substrate is not a hydrophilic material, a process of applying a hydrophilic material to the surface of the substrate should be added.

Next, the photoresist film 72 is applied to the substrate 70 (step b), and then the photoresist film is patterned using photolithography (step c). Next, a hydrophobic material 74 is coated on the photoresist patterned substrate (step d). Teflon, CYTOP, Parylene, etc. may be used as the hydrophobic material, and spin coating, vapor deposition, and the like may be used as the coating method. Next, the photosensitive film is removed to form a hydrophobic film 76 by patterning the hydrophobic material 74 on the substrate 70 (step e).

When the liquid sealing method according to the second embodiment is applied to the manufacture of a liquid lens, it is preferable to pattern the hydrophobic film so as to be formed in a predetermined range from the edge of the region where the upper substrate and the upper portion of the cavity of the liquid lens contact each other.

12 is a cross-sectional view sequentially showing another embodiment of a process of manufacturing the upper substrate according to the second embodiment of the present invention. Referring to FIG. 12, first, a hydrophobic material is coated on a flexible substrate 80, such as a PET film, or treated with CF ₄ to form a hydrophobic film 81 to form hydrophobic film 81, and then a polymer 82 such as PDMS is formed. Coating. Next, the PDMS is cured, and then subjected to selective plasma treatment using a mask to pattern the hydrophilic layer 86 to form hydrophilicity on a portion of the region. Next, after bonding the liquid lens and the PDMS substrate by lamination (lamination) by bonding the PET film is separated.

Although the present invention has been described above with reference to preferred embodiments thereof, this is merely an example and is not intended to limit the present invention, and those skilled in the art do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications which are not illustrated above in the scope are possible. And differences relating to such modifications and applications should be construed as being included in the scope of the invention as defined in the appended claims.

The liquid sealing method according to the present invention can be usefully used in the liquid sealing of the liquid lens.

20: liquid lens
202: Cavity
200: main body
210: lower substrate
230: upper substrate
232: hydrophilic membrane
234 hydrophobic membrane

Claims (5)

A liquid sealing method of a liquid lens having a main body having a cavity into which a liquid is injected, a lower substrate sealing a lower part of a main body, and an upper substrate sealing an upper part of a main body,
Bonding the lower substrate to the lower portion of the body having the cavity to seal the lower portion of the cavity;
Injecting liquid into the cavity of the body;
Manufacturing an upper substrate on which a hydrophilic film is formed in a region of the surface of the substrate facing the cavity into which the liquid is injected, and in which a hydrophobic film is formed in a region of the surface of the substrate from an edge of the hydrophilic film; And
Sealing the upper surface of the cavity by bonding the upper substrate to an upper portion of the main body such that the hydrophilic film of the upper substrate and the upper portion of the cavity are coupled;
Liquid sealing method of a liquid lens having a. The method of claim 1, wherein the manufacturing of the upper substrate comprises:
Forming a hydrophobic film on the surface of the substrate;
Coating a polymer on a surface of the substrate on which the hydrophobic film is formed;
Selective plasma treatment of the polymer to pattern it to be hydrophilic;
Liquid sealing method of a liquid lens, characterized in that it comprises a. The method of claim 1, wherein the manufacturing of the upper substrate comprises:
Applying a photoresist to the surface of the substrate and patterning the same using a photolithography process;
Applying a hydrophobic material on the substrate on which the patterned photoresist is formed;
Removing the photoresist to pattern the hydrophobic material to form a hydrophobic film;
Liquid sealing method of a liquid lens, characterized in that it comprises a. The method of claim 2, wherein forming a hydrophobic film on the surface of the substrate comprises:
Coated hydrophobic material on the surface of the substrate or CF ₄ on the surface of the substrate A liquid sealing method of a liquid lens, characterized in that the treatment to form a hydrophobic film. A main body having a cavity penetrating an upper surface and a lower surface thereof, wherein conductive droplets and insulating droplets that are not mixed with each other are injected into the cavity;
A lower substrate bonded to a lower surface of the body to seal a lower portion of the cavity;
An upper substrate bonded to an upper surface of the main body to seal an upper portion of the cavity;
The upper substrate,
Board;
A hydrophilic film formed by applying a hydrophilic material to a region of the surface of the substrate facing the upper portion of the cavity; And
And a hydrophobic film formed by applying a hydrophobic material to an edge of the hydrophilic film on the surface of the substrate.
And the upper substrate and the main body are bonded to each other such that the hydrophilic film of the upper substrate and the upper surface of the cavity into which the droplet is injected are bonded to each other.

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