JP4798013B2 - Liquid for liquid lens and liquid lens - Google Patents

Description

  The present invention relates to a liquid lens having an automatic focusing function or an autofocus function, and a liquid for a liquid lens.

  Due to the recent popularization of camera-equipped mobile phones, smaller cameras with higher performance such as high resolution are desired. In addition, it is desired to realize an autofocus function and an optical zoom function with an internal camera. However, in the technology using a plurality of conventional solid lenses, in order to realize these functions, it is necessary to move the position of the lens along the optical axis, and there is a problem that the mounting space for closing the camera module becomes too large. there were. On the other hand, a technique using a liquid lens is drawing attention as a technique for realizing these functions in a smaller size (for example, Patent Documents 1 and 2 and Non-Patent Documents 1 and 2).

  This technology is a technology that realizes an autofocus function without moving the lens by controlling the interface shape of two types of liquids by voltage. Optical zooming is also possible by using two liquid lenses (zoom liquid lens, autofocus liquid lens) and a solid lens.

JP 2005-518052 gazette JP 2006-72295 A NIKKEI ELECTRONICS 2005.10.24 p. 129 European Physical Journal E Vol3 (2000) p. 159-163

  In a liquid lens, it is important to control the interface of the liquid by voltage, to keep the density of the two types of liquids equal, and to keep the droplet shape stable. As the first liquid of the two types of liquids, a conductive aqueous solution is used for facilitating control of the liquid interface by voltage. For example, an example using a sodium sulfate aqueous solution is specifically known. On the other hand, specific characteristics of the second liquid include hydrophobicity from the viewpoint of separability from conductive water, and a refractive index sufficiently higher than water in order to lower the applied voltage when the interface is deformed. In order to reduce coma due to the influence of gravity, water and density are very close, visible light transmittance is high, liquid is low-viscosity at operating temperature, and insulation is required. It is necessary to satisfy these properties at the same time. As the second liquid, liquids such as 1-bromodecane and chloronaphthalene, bromonaphthalene, and silicone oil are known, but these liquids do not satisfy these properties at the same time.

  An object of the present invention is to provide a second liquid of a liquid lens liquid that is used together with a conductive aqueous solution that is a first liquid and has the above characteristics.

  As a result of diligent investigations on this problem, the inventors have found that a composition containing a naphthalene derivative satisfies the above-mentioned characteristics, and have completed the invention. That is, according to the present invention, the following liquid for liquid lens and liquid lens are provided.

[1] A liquid for liquid lenses containing an alkylnaphthalene containing any one of 1-methylnaphthalene, 1-ethylnaphthalene, 2-methylnaphthalene, and 2-ethylnaphthalene .

[2] The liquid for a liquid lens according to [1], which is used together with a conductive aqueous solution, has a hydrophobic property and separates from the conductive aqueous solution to form an interface.

[ 3 ] The density according to [1] or [ 2 ], wherein the density at 25 ° C. is 1.0 to 1.1 g / cm ³ , and the refractive index at 25 ° C. of light having a wavelength of 589 nm is 1.6 or more. Liquid for liquid lens.

[ 4 ] The liquid for a liquid lens according to [ 3 ], wherein the transmittance per 2 mm of light having a wavelength of 400 to 700 nm is 90% or more.

[ 5 ] The liquid for a liquid lens according to any one of [1] to [ 4 ] is included as a second liquid and a conductive aqueous solution as a first liquid, and the first light transmissive member and the second light transmissive member are included. A voltage application unit for applying a voltage to the first liquid and the second liquid contained in the gap, and applying a voltage by the voltage application unit. A liquid lens that deforms an interface formed by the first liquid and the second liquid, refracts light incident from the first transparent member, and emits the light from the second transparent member.

  A liquid containing an alkylnaphthalene has insulating properties and hydrophobicity, has high visible light transmittance, has low viscosity at room temperature, and can be used as a liquid for a liquid lens. Since the liquid containing alkylnaphthalene has hydrophobicity, it forms an interface with the conductive aqueous solution, and the interface can be deformed by applying a voltage to refract incident light. Further, since the transmittance is high, incident light can be efficiently emitted. Furthermore, since the viscosity is low, the refractive index can be easily changed by applying a voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

  The liquid for a liquid lens of the present invention is used as a second liquid for a lens for liquid (hereinafter also referred to as a second liquid) together with a first conductive aqueous solution (hereinafter also referred to as a first liquid). Yes, containing alkyl naphthalene alone or a mixture of a plurality of alkyl naphthalenes.

  The liquid lens liquid of the present invention is used for a liquid lens 1 as shown in FIG. In the liquid lens 1, the first translucent member 4 and the second translucent member 7 are arranged with a gap. And the 1st liquid 2 which is the electroconductive aqueous solution included in the gap | interval and the 2nd liquid 3 which has the alkylnaphthalene of this invention are included.

  Between the first translucent member 4 and the second translucent member 7, the first electrode 5 and the second electrode are used as voltage application units for applying a voltage to the first liquid 2 and the second liquid 3. 8 is provided. The first electrode 5 and the second electrode 8 are connected to an external power source 11. Further, in order to prevent short-circuiting between the electrodes 5 and 8, the first electrode 5 and the second electrode 8 are provided with insulating portions 6 and 9, respectively.

  Since the second liquid 3 of the present invention has hydrophobicity, it forms an interface in a state separated from the first liquid. By applying a voltage by the voltage application unit, the first liquid is attracted to the electrode and deformed, and thus the interface formed by the first liquid and the second liquid can also be deformed. If it does in this way, the light which injected from the 1st transparent member can be refracted | emitted, and can be discharge | released from a 2nd transparent member. The refractive index can be changed by changing the applied voltage.

  The alkyl group of the alkylnaphthalene used as the second liquid of the liquid lens liquid of the present invention is preferably an alkyl group having 1 to 4 carbon atoms. When the number of carbon atoms in the alkyl group exceeds 5, the refractive index decreases, and it tends to be solid at the use temperature. Preferred alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, and tert-butyl.

  Preferred alkylnaphthalenes in the present invention include 1-methylnaphthalene, 1-ethylnaphthalene, 1-n-propylnaphthalene, 1-i-propylnaphthalene, 1-n-butylnaphthalene, 1-sec-butylnaphthalene, 1-tert. -Butylnaphthalene, 2-methylnaphthalene, 2-ethylnaphthalene, 2-n-propylnaphthalene, 2-i-propylnaphthalene, 2-n-butylnaphthalene, 2-sec-butylnaphthalene, 2-tert-butylnaphthalene Can be mentioned. Further, when the liquid is composed of a mixture of a plurality of alkyl naphthalenes, any one of the alkyl naphthalene needs to be a liquid. Further, the liquid of the present invention preferably has the following physical properties.

(Melting point, boiling point)
Since the liquid of the present invention needs to be a liquid at the camera operating temperature, the melting point is −25 ° C. or lower, preferably −40 ° C. or lower. The boiling point is 60 ° C. or higher, preferably 85 ° C. or higher.

(Hydrophobic)
Since the lens of the present invention has a structure in which the liquid is refracted using the interface between the first liquid and the second liquid, it is necessary to form a stable interface between the first liquid and the second liquid. For this reason, it is preferable that the liquid of this invention has hydrophobicity.

(Transmittance)
Since the liquid of the present invention is used as a part of a lens, it preferably has a sufficient transmittance with visible light. Specifically, the transmittance per 2 mm in visible light (400 nm to 700 nm) is 90% or more, more preferably 95% or more.

(Refractive index)
Moreover, in order to lower the applied voltage required for interface deformation, it is preferable to have a high refractive index with visible light. Specifically, the refractive index at the d-line (589 nm) is preferably 1.6 to 1.8, and particularly preferably the refractive index is 1.6 to 1.7.

(density)
In addition, when the density of the conductive aqueous solution that is the first liquid is different from the density of the second liquid, the shape of the interface between the two liquids changes due to the influence of gravity. For example, when the density of the second liquid exceeds the density of the first liquid, the interface shape becomes an S-shape and aberrations occur. Therefore, the density of the second liquid is preferably close to the density of the first conductive water, and the value of Δρ (density difference between the two liquids) / ρ (density) is preferably 10 ⁻² or less. The preferable density range of the second liquid is 1.0 to 1.2 g / cm ³ , more preferably 1.0 to 1.1 g / cm ³ .

(viscosity)
Moreover, since it is necessary to change the shape of the lens interface of the present invention rapidly by applying a voltage, the viscosity of the liquid of the present invention is preferably low, and specifically, preferably 10 cp or less.

(Purification)
Since the liquid of the present invention is composed of alkyl naphthalenes, the intrinsic transmittance in visible light is high, but it may be colored by a trace amount of impurities and is preferably purified by an appropriate method. Examples of the purification method include a method of immersing in an adsorbent such as silica gel, alumina, zeolite, activated carbon or the like, or passing through a packed column of these adsorbent, precision distillation, and the like.

(Other ingredients)
The liquid of the present invention contains alkylnaphthalene as a main component, but may be mixed with other components for the purpose of adjusting various physical properties such as refractive index, density, transmittance, melting point, boiling point and the like. Examples of other components include, but are not limited to, naphthalene derivatives, anthracene derivatives, saturated hydrocarbon compounds, organic halogen compounds, organic sulfurated products, and silicon oil.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

  The refractive index at d line (589 nm) at 25 ° C., the density at 25 ° C., the separability from water (25 ° C. and 40 ° C.), and the transmittance per 2 mm at 400 to 700 nm were evaluated. In this example, the refractive index at the d-line (589 nm) was measured using an Abbe refractometer. The density at 25 ° C. was measured using a pycnometer. Separation from water is carried out by shaking and mixing 5 g of water and 5 g of liquid in a screw tube, and then allowing to stand, and visually observing the interface between water and liquid, and when a clear interface is observed, The case where it was not so was regarded as bad. The transmittance is measured with a UV-visible spectrophotometer (VSCO 7100 made by JASCO), the UV spectrum at 400 to 700 nm using a 2 mm cell. In this range, the transmittance is good when there is no wavelength less than 90%, and less than 90%. A case where there was a wavelength was regarded as defective.

Example 1
Commercially available 1-methylnaphthalene was purified by a silica gel column, and the refractive index, density, separability from water (25 ° C., 40 ° C.), transmittance per 2 mm of light having a wavelength of 400 nm to 700 nm, and melting point were measured as described above. It was evaluated with.

(Example 2)
Commercially available 1-methylnaphthalene 90 g / 2-ethylnaphthalene 10 g mixture was purified by silica gel column, refractive index, density, separability from water (25 ° C., 40 ° C.), transmittance per 2 mm at 400 nm to 700 nm, melting point Was evaluated by the method described above.

(Comparative Example 1)
The same evaluation was performed for 1-bromodecane.

(Comparative Example 2)
The same evaluation was performed for bromonaphthalene.

  Comparative Examples 1 and 2 had poor transmittance, but Examples 1 and 2 of the present invention had good transmittance and good separability from water.

  It can be suitably used as a small liquid lens having an autofocus function or an autofocus function mounted on a camera-equipped mobile phone or the like and a liquid for the liquid lens.

It is a liquid lens which is one embodiment of the present invention.

Explanation of symbols

1: liquid lens, 2: first liquid, 3: second liquid, 4: first translucent member, 5: first electrode, 6: insulating portion, 7: second translucent member, 8: second Electrode, 9: insulation part, 11: power supply.

Claims (5)

A liquid for liquid lenses containing an alkylnaphthalene containing any one of 1-methylnaphthalene, 1-ethylnaphthalene, 2-methylnaphthalene, and 2-ethylnaphthalene .   The liquid for a liquid lens according to claim 1, which is used together with a conductive aqueous solution, has a hydrophobic property, and separates from the conductive aqueous solution to form an interface. The density at 25 ° C. is 1.0 to 1.1 g / cm ³ , and 25 of light having a wavelength of 589 nm
The liquid for a liquid lens according to claim 1 or 2 , wherein the refractive index at ° C is 1.6 or more. The liquid for a liquid lens according to claim 3 , wherein a transmittance per 2 mm of light having a wavelength of 400 to 700 nm is 90% or more. The liquid for a liquid lens according to any one of claims 1 to 4 is contained as a second liquid and a conductive aqueous solution as a first liquid.
A first light-transmitting member and a second light-transmitting member are disposed with a gap, and have a voltage application unit that applies a voltage to the first liquid and the second liquid contained in the gap,
By applying a voltage by the voltage application unit, the interface formed by the first liquid and the second liquid is deformed, and the light incident from the first transmissive member is refracted to cause the second transmissive property. A liquid lens released from a member.

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