WO2007081086A1

WO2007081086A1 - Method for attaching a front panel to a lens body in manufacturing a liquid lens

Info

Publication number: WO2007081086A1
Application number: PCT/KR2006/005021
Authority: WO
Inventors: Jung Wook Kim; Myung Jin Jin; Joon Young Kim
Original assignee: Top Engineering Co., Ltd.
Priority date: 2006-01-09
Filing date: 2006-11-27
Publication date: 2007-07-19
Also published as: KR100667654B1

Abstract

Provided is a method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens, including coating a contact surface of the lens body and a hardening agent receptacle with a first hardening agent, attaching the front panel to the lens body, hardening the first hardening agent, coating a side of the front panel and a non-contact of the lens body with a second hardening agent, and hardening the second hardening agent. The use of two kinds of hardening agents in attaching the front panel to the lens body assures strong adhesion of the hardening agents between the front panel and the lens body, without causing any interstice in the liquid lens.

Description

METHOD FOR ATTACHING A FRONT PANEL TO A LENS BODY IN MANUFACTURING A LIQUID LENS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a method for attaching a front panel to a lens body in manufacturing a liquid lens, and more particularly to a method for firmly and evenly attaching a front panel to a lens body using two or more kinds of hardening agents.

2. Description of the Background Art

In the liquid lens of which a liquid receptacle contains two different liquids, electrowetting modulation of liquid contact angle is used to control the curvature of a liquid meniscus. This allows creation of adjustable focal length without having to employing mechanical components.

Referring to FIGs 1 and 2, the liquid lens is now described. FIG. 1 is a cross-sectional view illustrating a structure of the liquid lens. FIG. 2 is a schematic diagram for explaining about an electrowetting phenomenon. Referring to FIG. 1 , the liquid lens includes a front panel 110, a rear panel

120, and a lens body 130. A conductive liquid 140 and a nonconductive liquid 150, which mix with each other, is contained in a space formed by a front panel 110, a rear panel 120, and a lens body 130. The cover and rear panels 110 and 120 may include a transparent material such as plastic or glass. A first insulating layer 111 is formed between the lens body 130 and the front panel 110. The first insulating layer 111 is in contact with the conductive liquid 140.

A second insulating layer 121 is formed between the lens body 130 and the rear panel 150. The second insulating layer 121 is in contact with the nonconductive liquid. An area of the second insulating layer which is in contact with the nonconductive liquid is larger than that of the first insulating layer which is in contact with the conductive liquid. Thus, surface tension between the second insulating layer 121 and the nonconductive liquid 150 is greater than that between the first insulating layer 111 and the conductive liquid 140. This prevents an exchange between a position of the nonconductive liquid 150 and a position of the conductive liquid 140.

Water is largely used as the conductive liquid. The conductive liquid 140 and the nonconductive liquid 150 do not mix with each other. The conductive liquid 140 and the nonconductive liquid 150 have different optical characteristics, but have substantially the same density. An interface between the conductive liquid 140 and the nonconductive liquid 150, when voltage applies between the conductive liquid 140 and the nonconductive liquid 150, are bent to a spherical curvature. This is known as the electrowetting phenomenon. Thus, a parallel beam of light, which travels parallel to the front panel 110 and passes through the curved interface between the liquids 140 and 150, will be converged (or focused) at a certain distance behind the curved interface (known as the focal length).

The electrowetting phenomenon, as illustrated in FIG. 1 , is defined as the change in electrode-electrolyte contact angle due to an applied potential difference between the insulated electrode and the electrolyte. The electrowetting is in wide use for actuating microdroplets in a digital microfluidic device.

Referring to FIGs 3 through 5, the conventional method is now described for attaching a front panel to a lens body.

FIG. 3A is a cross-sectional view illustrating how a conventional liquid lens is structured before applying a ultraviolet-sensitive hardening agent to a surface of the lens body to be in contact with the front panel.

Referring to FIG. 3A, a liquid lens 300 has a upside down frustum-shaped liquid receptacle 380 formed inside a lens body 370. The liquid receptacle 380 is filled with a conductive liquid 340 and a non-conductive liquid 350 which do not mix with each other. The conductive liquid 340 and the nonconductive liquid 350 have different optical characteristics, but have substantially the same density. A supplementary receptacle 360 is formed outside the liquid receptacle 300. The liquid flowing over the liquid receptacle 360 stays in the supplementary receptacle 360. A contact surface 330 of the lens body 370 is coated with a ultraviolet- sensitive hardening agent "A" to attach a front panel 310 to the lens body 370. A hardening agent receptacle 390 is formed outside the supplementary receptacle 360. The ultraviolet-sensitive hardening agent "A" is contained in the hardening agent receptacle 390, before attaching the front panel 310 to the lens body 370.

As shown in FIG. 3B, a ultraviolet-sensitive hardening agent "A" is coated with the contact surface 330 of the lens body 370. Thereafter, the front panel 310 is attached to the lens body 370. as shown in FIG. 3C.

FIG. 4 is a block diagram illustrating a conventional method for attaching the front panel 310 to the lens body 370.

Referring to FIG. 4, the conventional method is now described. The contact surface 330 of the lens body 370 and the hardening agent receptacle 390 are coated with the ultraviolet-sensitive hardening agent. Subsequently, the front panel 310 is attached to the lens body 370. This is followed by hardening of the ultraviolet-sensitive hardening agent at room temperature with a ultraviolet- generated hardening apparatus. Subsequent heat treatment is made on the ultraviolet-sensitive, hardening agent. After the heat-hardening, the liquid lens is exposed to air for cooling at room temperature.

The ultraviolet-sensitive hardening agent in use for attaching the front panel 310 to the lens body 370 is weak in adhesive strength. Thus, during a reliability test, the ultraviolet hardening agent does not meet requirements for high and low temperatures, high temperature and humidity, and heat and shock.

The ultraviolet-sensitive hardening agent may be replaced with a heat- sensitive hardening agent which has adhesive strength enough strong to pass the reliability test. However, the heat-sensitive hardening agent has to endure a temperature of above 80 degrees for 96 hours during the reliability test. Bubbles, which exist in the heat-sensitive hardening agent, may expand before the hardening agent is hardened at a high temperature during the reliability test. This causes the heat-sensitive hardening agent to swell or bend outward, thereby disrupting a plane surface of the heat-sensitive hardening agent between the front panel and the lens body. A cracked plane surface of the heat-sensitive hardening agent has a significant impact on the performance of the liquid lens.

FIG. 5 is a plane view illustrating an interstice occurring in the liquid lens manufactured according to the conventional method for attaching the front panel and the lens body.

The interstice is due to the expansion of the bubbles in the heat-sensitive hardening agent occurring at a high temperature during the reliability test. The heat-sensitive hardening agent is strong in adhesive strength, but weak in high- temperature resistance. This causes the liquid lens to be defective.

BRIEF DESCRIPTION OF THE INVENTION Therefore, an object of the present invention is to firmly and evenly attach a front panel to a lens body using different hardening agents.

According to one aspect of the present invention, there is provided a method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens, including coating a contact surface of the lens body and a hardening agent receptacle with a first hardening agent, attaching the front panel to the lens body, hardening the first hardening agent, coating a side of the front panel and a non-contact of the lens body with a second hardening agent, and hardening the second hardening agent.

The method may further include exposing the liquid lens to air for cooling after attaching the front panel to the lens body.

The first hardening agent includes a ultraviolet-sensitive hardening agent and the second hardening agent includes a heat-sensitive hardening agent

The method may further include performing forced circulation of air after finishing hardening the first harden agent. According to another aspect of the present invention, there is provided a method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens, including holding the front panel to the lens body, coating one portion of a side of the front panel, one portion of a non-contact surface of the lens body, and a hardening agent receptacle with a first hardening agent, hardening the first hardening agent, coating the first hardening agent, the other portion of the side of the front panel, and the other portion of the non-contact surface of the lens body with a second hardening agent and hardening the second hardening agent.

The method may further include performing forced circulation of air after finishing hardening the first harden agent.

The foregoing and other object, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a cross-sectional view illustrating a structure of a liquid lens; FIG. 2 is a schematic diagram for explaining about an eletrcowetting phenomenon; FIG. 3A is a cross-sectional view illustrating how a conventional liquid lens is structured before applying a ultraviolet-sensitive hardening agent to a surface of a lens body to be in contact with a front panel;

FIG. 3B is a cross-sectional view illustrating how the conventional liquid lens is structured after applying the ultraviolet-sensitive hardening agent to the surface of the lens body to be in contact with the front panel; FIG. 3C is a cross-sectional view illustrating how the conventional liquid lens is structured after attaching the front panel to the lens body using the ultraviolet-sensitive hardening agent.

FIG. 4 is a block diagram illustrating a conventional method for attaching the front panel to the lens body .

FIG. 5 is a plane view illustrating an interstice occurring in the liquid lens manufactured according to the conventional method for attaching the front panel and the lens body;

FIG. 6A is a cross-sectional view illustrating how the liquid lens is structured before coating the lens body with the hardening agent according to one embodiment of the present invention;

FIG. 6B is a cross-sectional view illustrating how the liquid lens is structured after coating the lens body with the ultraviolet-sensitive agent according to the embodiment of the present invention; FIG. 6C is a cross-sectional view illustrating how the liquid lens is structured after attaching the front panel to the lens body using the ultraviolet- sensitive agent according to the embodiment of the present invention;

FIG. 6D is a cross-sectional view illustrating how the liquid lens is structured after coating a side of the front panel and a non-contact surface of the lens body with a heat-sensitive hardening agent

FIG. 7 is a block diagram for describing a method for firmly and evenly attaching a front panel to a lens body according to the embodiment of the present invention;

FIG. 8 is a block diagram for describing a method for firmly and evenly attaching a front panel to a lens body according to another embodiment of the present invention; and

FIG. 9 is a block diagram for describing a method for firmly and evenly attaching a front panel to a lens body according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Referring to FIGs 6 through 9, one embodiment is now described in detail.

FIG. 6A is a cross-sectional view illustrating how a liquid lens is structured before coating a lens body with a hardening agent.

Referring to FIG. 6A, the liquid lens 600 is made up of a front panel 610, a rear panel 620, and a lens body 670. A upside down frustum-shaped liquid receptacle 680 is formed inside the lens body 670. The liquid receptacle 680 is filled with a conductive liquid 640 and a non-conductive liquid 650, such as electrolytic liquid and oil, which do not mix with each other. The conductive liquid 640 and the nonconductive liquid 650 have different optical characteristics, but have substantially the same density. A supplementary receptacle 660 is formed outside the liquid receptacle 680. The liquid flowing over the liquid receptacle 680 stays in the supplementary receptacle 660. A contact surface 630 of the lens body 670 is coated with a hardening agent to attach a front panel 610 to the lens body 670. A hardening agent receptacle 690 is formed outside the supplementary receptacle 660. The hardening agent is contained in the hardening agent receptacle 690, before attaching the front panel 610 to the lens body 670.

A ultraviolet-sensitive hardening agent and a heat-sensitive hardening agent, as shown in FIG. 6B, are sequentially applied in attaching the front panel 610 to the lens body 670. As shown in FIG. 6B, the contact surface 630 of the lens body 670 and the hardening agent receptacle 690 is coated with the ultraviolet-sensitive hardening agent "a." That is, only the contact surface of the lens body 670, which is in contact with the front panel, is coated with the ultraviolet-sensitive hardening agent "a." Subsequently, the front panel 610 is attached to the lens body 670, as shown in FIG. 6C. Thereafter, the ultraviolet-sensitive hardening agent is hardened by a ultraviolet-generated hardening apparatus.

A side of the front panel and a non-contact surface of the lens body which is not in contact with the front panel are coated with the heat-sensitive agent "b," as shown in FIG. 6D. This is followed by heat-hardening of the heat-sensitive agent "b".

FIG. 7 is a block diagram for describing a method for firmly and evenly attaching a front panel to a lens body according to the embodiment of the present invention.

The contact surface 630 of the lens body 670 and the hardening agent receptacle 690 are coated with the ultraviolet-sensitive agent before attaching the front panel 610 to the lens body 670. After attaching the front panel 610 to the lens body 670, the ultraviolet-sensitive agent is hardened at room temperature by the ultraviolet-generating hardening apparatus. Thereafter, a side of the front panel and a non-contact surface of the lens body which is not in contact with the front panel are coated with the heat-sensitive hardening agent. This is followed by heat-hardening of the heat-sensitive hardening agent. The liquid lens is exposed to air for cooling at room temperature. A variety of the air cooling steps may be selectively executed according to a type of hardening agent. In the embodiments of the present invention, the liquid lens is exposed to air for cooling at room temperature to expedite the hardening of the hardening agent. The heat treatment of the heat-sensitive hardening agent simultaneously gives a finishing effect of heat treatment to the ultraviolet-sensitive hardening agent.

Referring to FIG. 8, a method is described for firmly and evenly attaching a front panel to a lens body according to another embodiment of the present invention.

After the liquid receptacle 670 is filled with the conductive liquid 640 and the non-conductive liquid 650, the front panel 610 is held to the lens body 670. The contact surface 630 of the lens body 670 and the hardening agent receptacle 690 are coated with the ultraviolet-sensitive hardening agent, with the front panel 610 held to the lens body 670. Subsequently, the ultraviolet-sensitive hardening agent is hardened at room temperature by the ultraviolet-generating hardening apparatus. Thereafter, the side of the front panel and the non-contact surface of the lens body which is not in contact with the front panel are coated with the heat- sensitive hardening agent. This is followed by heat-hardening of the heat- sensitive hardening agent.

After the liquid receptacle 670 is filled with the conductive liquid 640 and the non-conductive liquid 650, the front panel 610 is held to the lens body 670. The contact surface 630 of the lens body 670 and the hardening agent receptacle 690 are coated with the ultraviolet-sensitive hardening agent, with the front panel 610 held to the lens body 670. Subsequently, the ultraviolet-sensitive hardening agent is hardened at room temperature by the ultraviolet-generating hardening apparatus. At this point, forced circulation of air around the front panel 610 decreases temperature on the liquid lens which rises due to the hardening of the ultraviolet-sensitive hardening agent by the ultraviolet-generated hardening apparatus. The forced circulation of air may be performed through an air nozzle provided to a side of the liquid lens. The air propelled from the air nozzle cools down one side of the liquid lens and passes along the other side of the liquid lens. The forced circulation of air during the ultraviolet-hardening makes it possible to locally cool down the front panel, thereby preventing the bubbles from occurring in the ultraviolet-sensitive hardening agent. After performing the forced air circulation, the side of the front panel and the non-contact surface of the lens body which is not in contact with the front panel are coated with the heat-sensitive hardening agent. This is followed by heat-hardening of the heat-sensitive hardening agent.

In above-described embodiments, the order of applying the hardening agents may be reversed. That is, the heat-sensitive hardening agent, instead of the ultraviolet-sensitive hardening agents, may be applied to the contact surface of the lens body and the hardening agent receptacle. Also, the ultraviolet-sensitive hardening agent, instead of the heat-sensitive hardening agent, may be applied to the side of the front panel and the non-contact surface of the lens body which is not in contact with the front panel. The locations which are coated with the hardening agents are not limited to those described above, but changeable.

The use of two kinds of hardening agents in attaching the front panel to the lens body assures strong adhesion of the hardening agents between the front panel and the lens body, without causing any interstice in the liquid lens. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.

Claims

What is claimed is:

1. A method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens, comprising: coating a contact surface of the lens body and a hardening agent receptacle with a first hardening agent; attaching the front panel to the lens body; hardening the first hardening agent; coating a side of the front panel and a non-contact of the lens body with a second hardening agent, and hardening the second hardening agent.

2. The method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens according to claim 1 , further comprising exposing the liquid lens to air for cooling after attaching the front panel to the lens body.

3. The method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens according to claim 1 , wherein the first hardening agent comprises a ultraviolet-sensitive hardening agent and the second hardening agent comprises a heat-sensitive hardening agent.

4. The method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens according to claim 3, further comprising performing forced circulation of air after finishing hardening the first harden agent.

5. A method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens, comprising: holding the front panel to the lens body; coating one portion of a side of the front panel, one portion of a non- contact surface of the lens body, and a hardening agent receptacle with a first hardening agent; hardening the first hardening agent; coating the first hardening agent, the other portion of the side of the front panel, and the other portion of the non-contact surface of the lens body with a second hardening agent; and hardening the second hardening agent.

6. The method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens according to claim 5, wherein the first hardening agent comprises a ultraviolet-sensitive hardening agent and the second hardening agent comprises a heat-sensitive hardening agent.

7. The method for firmly and evenly attaching a front panel to a lens body in manufacturing a liquid lens according to claim 6, further comprising performing forced circulation of air after finishing hardening the first harden agent.