WO2019131933A1

WO2019131933A1 - Optical element, and method for producing optical element

Info

Publication number: WO2019131933A1
Application number: PCT/JP2018/048301
Authority: WO
Inventors: 山田　泰美; 利博平井
Original assignee: 日東電工株式会社; 国立大学法人信州大学
Priority date: 2017-12-28
Filing date: 2018-12-27
Publication date: 2019-07-04

Abstract

Provided are: an optical element having a simple structure and with which the optical properties thereof can be adjusted; and a method for producing same. This optical element (10A) comprises: a first electrode layer (12A); a second electrode layer (14A); a polymer material layer (11) positioned in between the first electrode layer (12A) and the second electrode layer (14A); and an insulating spacer layer (13A) positioned between the polymer material layer (11) and the second electrode layer (14A), to form a predetermined space (17) between the polymer material layer (11) and the second electrode layer (14A). The polymer material layer (11) deforms when a voltage is applied, to form one or more light-scattering bodies (15) in the predetermined space.

Description

Optical element and method of manufacturing optical element

The present invention relates to an optical element and a method of manufacturing the optical element.

Conventionally, a focusing mechanism (see, for example, Patent Document 1), a lens driving mechanism (see, for example, Patent Document 2), and the like that move a lens in the optical axis direction using a polymeric material that deforms by application of a voltage It is done. A polymer material is used for a lens holder for holding a lens, and the position of the lens is moved along the optical axis by using expansion and contraction of the polymer material by applying a voltage.

In addition, an organic material can be obtained by sandwiching an organic material that expands and contracts in the application direction of the electric field with a pair of electrodes, and providing an electrostrictive strain amount per unit electric field in a plane perpendicular to the application direction of the organic material layer. A method of forming a convex lens, a concave lens and the like by deforming a layer and an electrode has been proposed (see, for example, Patent Document 3).

As a polymer flexible actuator applied to an artificial muscle actuator, a gel material containing 1 to 30 parts by weight of an ionic liquid to 1 to 50 parts by weight of polyvinyl chloride is known (see, for example, Patent Document 4).

Patent No. 4530163 Patent No. 5180117 Patent No. 5029140 Patent No. 5392660

The configuration in which the lens is moved along the optical axis changes the position of a single lens by expanding and contracting the polymer material disposed in the lens holder. In this configuration, the holder is first deformed, and the lens position is changed by the deformation of the holder, so it is difficult to sufficiently improve the responsiveness and accuracy of the lens drive.

In the configuration in which the distribution of the electrostrictive strain amount is given in the in-plane direction of the organic material layer, a minute amount of material having different characteristics is applied to a desired position by ink jet or micro contact printing. Complex and time consuming.

In addition, although all the conventional configurations described above aim at adjusting a single lens, in imaging and image related products, the demand for a microlens array using a large number of fine lenses is increasing. If the microlens array can be provided with a focusing function, added value can be increased.

In view of the above problems, the present invention has an object to provide an optical element capable of adjusting optical characteristics with a simple configuration and a method of manufacturing the same.

The present invention provides an optical element capable of controlling light collection and diffusion by using expansion and contraction or deformation of a polymer material by voltage application.

In a first aspect, the optical element
A first electrode layer,
A second electrode layer,
A polymer material layer disposed between the first electrode layer and the second electrode layer;
An insulating spacer layer disposed between the polymer material layer and the second electrode layer to form a predetermined space between the polymer material layer and the second electrode layer;
The polymer material layer deforms under voltage application to form one or more light scatterers in the predetermined space.

In a second aspect, a method of manufacturing an optical element is
Forming a polymer material layer on the first electrode layer;
An insulating spacer layer and a second electrode layer are disposed on the polymer material layer to form a predetermined space between the polymer material layer and the second electrode layer,
A voltage is applied between the first electrode layer and the second electrode layer to deform the polymer material layer to form one or more light scatterers in the space.
Including the steps.

With the above-described configuration and method, an optical element capable of adjusting optical characteristics with a simple configuration and a method of manufacturing the same can be realized.

It is a schematic diagram which shows the basic composition of the optical element of embodiment. It is a figure explaining the operation principle of the optical element of an embodiment. It is the schematic of the microlens array obtained by forming several light-scattering bodies in the optical element of embodiment. FIG. 4 is a cross-sectional view taken along line X-X ′ of FIG. 3; It is a manufacturing-process figure of the optical element which has several light-scattering bodies. It is a manufacturing-process figure of the optical element which has several light-scattering bodies. It is a manufacturing-process figure of the optical element which has several light-scattering bodies. It is a 3D image which shows the deformation process of the optical element of embodiment. It is a figure which shows the cross-sectional profile of the optical element (micro lens array) of FIG. 6 as a function of voltage. It is a figure which shows the modification of an optical element, and operation | movement. It is a schematic diagram of an imaging device using an optical element of an embodiment. It is a schematic diagram of the illuminating device using the optical element of embodiment. It is a schematic diagram of the sample for measuring the characteristic of the polymeric material which added the ionic liquid. It is a figure which shows the response characteristic of a polymeric material layer when various ionic liquids are added to a polymeric material by the sample of FIG. It is a figure which shows the physical property of an ionic liquid, and the displacement state of a polymer gel. It is a figure which shows the relationship between the addition amount of an ionic liquid, and the displacement of a polymer gel. It is a figure which shows the evaluation result of the light-scattering body formed by voltage application for every addition amount of an ionic liquid. It is a figure which shows the influence on the electrode degradation of an ionic liquid.

FIG. 1 shows a basic configuration of an optical element 10A as one configuration example of the optical element 10 according to the embodiment. The optical element 10A includes a first electrode layer 12, a second electrode layer 14A, a polymer material layer 11 disposed between the first electrode layer 12 and the second electrode layer 14A, and a polymer material. A spacer layer 13A is disposed between the layer 11 and the second electrode layer 14A. The spacer layer 13A has an opening 16 of a predetermined pattern, and a space 17 is formed between the polymer material layer 11 and the second electrode layer 14A at the position of the opening 16.

The polymeric material layer 11 elastically deforms under voltage application to form the light scatterer 15 in the space 17. The light scatterer 15 has a convex shape as described later.

The spacer layer 13A may be of any material as long as it is electrically insulating. It may be either an inorganic insulating film or an organic insulating film. In the example of FIG. 1, the spacer layer 13A is an insulating resin film having a predetermined pattern of the openings 16. The planar shape and dimensions of the opening 16 are appropriately designed according to the volume of the space 17 and the shape of the light scatterer 15 generated in the space 17, and are, for example, a circle, an ellipse, a polygon or the like.

The diameter of the opening 16 of the spacer layer 13A is set to, for example, less than 1 mm, preferably 300 μm or less. When the diameter of the opening 16 is 1 mm or more, it becomes difficult to project the polymer material layer 11 into the opening 16 by application of a voltage. When the diameter of the opening 16 is 300 μm or less, the deformation efficiency of the polymer material layer 11 with respect to voltage application is improved, and a convex shape can be formed.

The polymer material layer 11 and the light scattering body 15 are formed of a gel-like polymer material (hereinafter, appropriately referred to as “polymer gel”). The light scatterer 15 is formed by using expansion and contraction or deformation of the polymer gel by application of a voltage.

The polymer gel is polyvinyl chloride (PVC), polymethyl methacrylate, polyurethane, polystyrene, polyvinyl acetate, polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polyacrylonitrile, silicone rubber, etc., and is transparent to the used wavelength. Polymer (or resin) material can be selected appropriately.

In the embodiment, PVC which is easily modified due to the action of the electric field is used. A suitable plasticizer may be added to PVC, or PVC may be dissolved in a solvent. When a plasticizer is used, dibutyl adipate (DBA: dibutyl adipate), diethyl adipate (DEA: diethyl adipate), diethyl sebacate (DES: diethyl sebacate), dioctyl phthalate (DOP: dioctyl phthalate), diethyl phthalate (DEP: diethyl phthalate) etc. can be used. Tetrahydrofuran (THF) etc. can be used as a solvent.

The mixing ratio of the plasticizer is 50 wt% or more, preferably 75 wt% or more. If the mixing ratio is less than 50 wt%, it becomes difficult to deform the polymer material layer 11 even if a voltage is applied. When the mixing ratio is 50 wt% or more and less than 75 wt%, the polymer material layer 11 can be deformed by voltage application, but the voltage level to be applied may be high. By setting the mixing ratio to 75 wt% or more, the polymer material layer 11 can be deformed at an appropriate voltage level.

The first electrode layer 12 is not particularly limited as long as it is a conductive material. When the first electrode layer 12 is formed of a metal, platinum, gold, silver, nickel, chromium, copper, titanium, tantalum, indium, palladium, lithium, niobium, an alloy of these, or the like can be used. The first electrode layer 12 may be formed of a transparent oxide semiconductor material such as ITO (Indium Tin Oxide: indium tin oxide), or a conductive polymer, conductive carbon, or the like may be used.

The second electrode layer 14A is preferably a transparent electrode layer. By using the second electrode layer 14A as a transparent electrode layer, light collected or diffused by the light scatterer 15 can be transmitted.

The polarities of the first electrode layer 12 and the second electrode layer 14A can be set according to the direction in which the shape of the polymer material layer 11 is changed. In the example of FIG. 1, the polymer material layer 11 is made of a material that is easily negatively charged, the first electrode layer 12 is a cathode, and the second electrode layer 14A is an anode.

A part of the surface on the anode side of the polymer material layer 11 is in surface contact with the spacer layer 13A. The polymer material layer 11 is deformed in a region not in surface contact with the spacer layer 13A (ie, a region exposed in the opening 16) by application of a voltage, and is pulled toward the second electrode layer 14A.

The optical element 10A can be manufactured, for example, by the following procedure. On the first electrode layer 12 formed to a predetermined size, a solution of PVC to which a plasticizer is added is applied by a cast method or the like to form a polymer material layer 11. On the polymer material layer 11, the spacer layer 13A in which the pattern of the openings 16 is formed in advance and the second electrode layer 14A are disposed. The arrangement of the spacer layer 13A and the arrangement of the second electrode layer 14A may be simultaneous or sequentially.

A predetermined voltage is applied between the first electrode layer 12 and the second electrode layer 14 A to form the light scatterer 15 in the space 17 formed by the opening 16.

The thickness of the polymer material layer 11 is appropriately determined in accordance with the diameter and depth of the opening 16, the height of the light scatterer 15 to be formed, the thickness of the first electrode layer 12 and the thickness of the second electrode layer 14A, etc. Be done. As an example, the thickness of the polymer material layer 11 is 1 mm or less, preferably 0.1 mm to 0.5 mm. When the thickness of the polymer material layer 11 is 0.1 mm or less, it becomes somewhat difficult to handle, but it is designed in consideration of the size of the opening 16 to the last. Therefore, in the case of producing a microlens array sheet having a large number of fine lenses, the thickness of the polymer material layer 11 may be 0.1 mm or less. The thickness of the spacer layer 13A is 1 mm or less, preferably 0.1 mm or less.

FIG. 2 is a diagram for explaining the operation principle of the optical element 10A of the embodiment. (A) of FIG. 2 shows the state to which the voltage is not applied. (B) of FIG. 2 shows the state when a voltage is applied.

In the state of FIG. 2A, the polymer material layer 11 is positioned between the first electrode layer 12 and the second electrode layer 14A in a state where the surface is flat. Since the spacer layer 13A is provided between the polymer material layer 11 and the second electrode layer 14A, a part of the polymer material layer 11 is in surface contact with the spacer layer 13A. At the position of the opening 16 formed in the spacer layer 13A, a space 17 is formed between the polymer material layer 11 and the second electrode layer 14A.

As shown in FIG. 2B, when a voltage is applied between the first electrode layer 12 and the second electrode layer 14A, a gel polymer material layer is formed from the first electrode layer 12 which is a cathode. Electrons are injected into 11. The polymer gel containing electrons is pulled toward the surface of the second electrode layer 14A which is an anode. On the other hand, the spacer layer 13A is insulating, and the polymer gel is pulled toward the second electrode layer 14A preferentially at the center rather than the side surface of the opening 16, and the light scatterer 15 is formed.

The polymer material layer 11 is deformed by the elasticity and voltage response of the polymer gel itself, and a convex light scatterer 15 is formed around the central axis of the opening 16. If the composition of the polymer material layer 11 and the shape of the opening 16 are uniform, by applying the same level of voltage, it is possible to form a light scatterer 15 having a convex shape with less variation in the opening 16.

Since the total volume of the polymer gel is the same, the thickness of the polymer material layer 11 is slightly reduced by the amount of pulling up of the polymer gel in the opening 16. When the thickness of the polymer material layer 11 is reduced, the positions of the spacer layer 13A in surface contact with the polymer material layer 11 and the positions of the second electrode layer 14A supported by the spacer layer 13A are also lowered slightly. .

The deformation of the polymer material layer 11 is reversible, and can be returned to the initial state of FIG. 2 (B) by stopping the application of the voltage. Further, as described later, the height of the light scatterer 15 can be adjusted according to the level of the voltage to be applied.

The number of openings 16 formed in the spacer layer 13A is not limited to one. By forming the plurality of openings 16 in the spacer layer 13A, the polymer material layer 11 can be deformed by voltage application, and the plurality of light scatterers 15 can be formed. Also in this case, if the composition of the polymer material layer 11 and the shape of the plurality of openings 16 are uniform, it is possible to simultaneously form the plurality of light scatterers 15 of uniform shape by voltage application.

FIG. 3 is a schematic view of a microlens array 100 obtained by forming a plurality of light scatterers 15 in the optical element 10A. The microlens array 100 includes a first electrode layer 12A, a second electrode layer 14A, a polymer material layer 11 disposed between the first electrode layer 12A and the second electrode layer 14A, and a polymer. A spacer layer 13A is inserted between the material layer 11 and the second electrode layer 14A. In the example of FIG. 3, both the first electrode layer 12A and the second electrode layer 14A are transparent electrodes.

A plurality of openings 16 are formed in the spacer layer 13A. When a voltage is applied between the first electrode layer 12A and the second electrode layer 14A, the polymer material layer 11 is deformed, and the light scatterers 15 are formed in the respective openings 16.

The first electrode layer 12A is a cathode layer, and the second electrode layer 14A is an anode layer. On the surface of the polymer material layer 11 on the anode side, an array of light scatterers 15 is formed. As an example, the thickness of the polymer material layer 11 is 500 μm, the diameter of the bottom of the light scatterer 15 is 150 μm, the height is 50 μm, and the pitch between the centers is 200 μm.

The polymer material layer 11 is, as described with reference to FIG. 1, polymer gel such as PC, polymethyl methacrylate, polyurethane, polystyrene, polyvinyl acetate, polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polyacrylonitrile, silicone rubber and the like. It is. A plasticizer such as DBA, DEA, DES, DOP, DEP may be added to the polymer gel. The mixing ratio of the plasticizer is 50 wt% or more, more preferably 75 wt% or more.

The light scattering body 15 of the microlens array 100 is formed by the polymer material layer 11 being electrically attracted to and deformed by the second electrode layer 14A in the internal space of the plurality of openings 16, On the surface of the material layer 11, the light scatterers 15 having a uniform convex shape are arranged.

As described with reference to FIG. 2, depending on the level of the voltage applied between the first electrode layer 12A and the second electrode layer 14A, the arrangement of the light scatterers 15 appears and / or light The height of the scatterer 15 can be changed.

FIG. 4 is a cross-sectional view taken along the line X-X 'of FIG. 3 when no voltage is applied. The surface of the polymer material layer 11 is flat between the first electrode layer 12A and the second electrode layer 14A. A part of the surface of the polymer material layer 11 is in surface contact with the spacer layer 13A, and the other part is exposed in the space 17 in the opening 16 formed in the spacer layer 13A. The diameter φ of the opening 16 is 150 μm, and the thickness of the spacer layer 13A is 30 μm.

5A to 5C are manufacturing process diagrams of a microlens array 100 which is an example of an optical element having a plurality of light scatterers 15. FIG. In FIG. 5A, the first electrode layer 12A is formed on the base material 21, and the polymer material layer 11 is formed on the first electrode layer 12A. The first electrode layer 12A is, for example, a 100 μm thick ITO film. The polymer material layer 11 is prepared by adding dibutyl adipate (DBA) to PVC so that the mixing ratio is 80 wt% and completely dissolving in a solvent of THF to form a gel solution, and then the gel solution is used as the first electrode It is cast at a thickness of 500 μm on the layer 12A. DBA, which is a plasticizer, tends to have negative ions, and application of a voltage causes the polymer gel to be attracted to the anode.

In FIG. 5B, on the polymer material layer 11, the spacer layer 13A in which the plurality of openings 16 are formed, and the second electrode layer 14A are disposed. For example, a polyimide film having a thickness of 30 μm is used as the spacer layer 13A. The second electrode layer 14A is an ITO film having a thickness of 100 μm. In this example, the spacer layer 13A and the second electrode layer 14A are bonded in advance to form an electrode assembly 19A. The electrode assembly 19A may be supported on a substrate (not shown).

In the spacer layer 13A, the openings 16 with a diameter of 150 μm are arranged in a 30 × 30 matrix. The pitch P of the openings 16 is 200 μm, and the distance between the adjacent openings 16 and the openings 16 is 50 μm.

In FIG. 5C, the substrate 21 is peeled off to complete the thin film of the microlens array 100. Thereafter, a voltage of a desired level is applied between the first electrode layer 12A and the second electrode layer 14A to generate the light scatterer 15 in the opening 16.

FIG. 6 is a 3D image observed while changing the level of the voltage applied to the optical element 10 having the plurality of light scatterers 15. 3D observation is performed using a digital microscope VHX1000 manufactured by Keyence Corporation.

6A shows an image when the applied voltage is 600V, FIG. 6B shows an image when the applied voltage is 700V, and FIG. 6C shows an image when the applied voltage is 800V. It can be seen that the application of voltage causes the polymer gel to be pulled up from the center.

FIG. 7 is a plot of the height of three consecutive light scatterers 15 as a function of voltage application from the 3D image of FIG. The ordinate represents the height from the surface position of the polymer material layer 11 in the initial state (state without application of voltage), the abscissa represents the in-plane position of the opening 16 of the spacer layer 13A, and one grid is 150 μm. .

When no voltage is applied (0 V), the height position of the polymer material layer 11 inside the opening 16 is in the vicinity of −20 μm. This is the effect of an error (about ± 20 μm) in the depth direction where light does not easily enter in optical measurement, and the profile of the polymer material layer 11 in the opening 16 is flat.

When the voltage application is 500 V, the polymer gel is largely deformed to form a protrusion with the center of the opening 16 as a central axis. At voltage levels of 600 V and 700 V, the height position of the peak is further increased, and a vertically long convex profile is obtained. The height of the light scatterer 15 at this time reaches 50 μm. When the voltage application is 800 V, the height position of the peak is slightly reduced, but the width is also reduced and the steepness is further increased. The radius of curvature near the peak is smaller.

As can be seen from the profile of FIG. 7, by controlling the voltage level applied to the optical element 10 (or the microlens array 100), the optical element 10 (or the microlens array 100) having a desired lens shape can be obtained.

Even when 800 V is applied, the current flowing through the polymer gel is as low as 10 μA or less, the calorific value is suppressed, and it can withstand long-term use.

FIG. 8 is a schematic view of an optical element 10B according to a modification. In the embodiment described above, the insulating spacer layer 13A having the opening 16 is used by being bonded to the flat second electrode layer 14A. In the modified example, an opening 143 is provided in the main surface 141 opposite to the polymer material layer 11 of the second electrode layer 14B, and the sidewall in the main surface 141 and the opening 143 is covered with the insulating spacer layer 13B. The bottom surface 145 of the opening 143 is exposed without being covered by the spacer layer 13B.

The second electrode layer 14B having the opening 143 and the spacer layer 13B may be integrally formed as the electrode assembly 19B. The opening 143 can be formed into a desired shape by wet etching or dry etching. For example, the planar shape of the opening 143 is a circle, an ellipse, a polygon or the like having a predetermined diameter.

The insulating spacer layer 13B is formed on the entire main surface 141 of the second electrode layer 14B in which the opening 143 is formed, and the spacer layer 13B on the bottom surface 145 of the opening 143 is removed by photolithography and etching. The second electrode layer 14 B is exposed in 143. A predetermined space 17 is formed between the second electrode layer 14 B and the polymer material layer 11 by the spacer layer 13 covering the side wall of the opening 143.

As shown in (a) of FIG. 8, the surface of the polymer material layer 11 is flat inside the space 17 when no voltage is applied. The polymer material layer 11 is in surface contact with the spacer layer 13 B in the region other than the opening 143.

As shown in (b) of FIG. 8, when a voltage is applied between the first electrode layer 12B and the second electrode layer 14B, the polymer material layer 11 is deformed, and the central portion in the opening 143 is formed. Are preferentially pulled toward the second electrode layer 14B. Thus, the light scatterer 15 having a convex shape is formed in the space 17.

The optical element 10B of FIG. 8 can also be used as a microlens array by forming a plurality of light scatterers 15. In this case, after the plurality of openings 143 are formed in the second electrode layer 14B and the spacer layer 13B is formed on the entire surface, the bottom surface of the opening 143 may be exposed. By applying a voltage, it is possible to form the light scatterer 15 having a uniform shape inside the plurality of openings 143.

FIG. 9 is a schematic view of an imaging device 150 using the microlens array 100 of the embodiment. As the microlens array 100, any of the optical element 10A of the embodiment and the optical element 10B of the modification may be used. In the example of FIG. 9, the optical element 10A in which the first electrode layer 12, the polymer material layer 11, the spacer layer 13, and the second electrode layer 14 are stacked in this order is used as the microlens array 100.

The imaging device 150 has a microlens array 100 having an array of a plurality of light scatterers 15, and an imaging element array 130 in which a plurality of imaging elements are arrayed. The imaging device is formed of a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) sensor, or the like. Three color filters 131 may be arranged corresponding to the arrangement of the imaging elements. In this example, red (R), green (G) and blue (B)

color filters

131R, 131G and 131B are alternately arranged.

FIG. 10 is a schematic view of a lighting device 250 using the microlens array 100 of the embodiment. The lighting device 250 includes a light source 230 such as an LED lamp, and a microlens array 100 disposed on the front side of the light source 230 on the output side. As the microlens array 100, any of the optical element 10A of the embodiment and the optical element 10B of the modification may be used. In the example of FIG. 10, the optical element 10A in which the first electrode layer 12, the polymer material layer 11, the spacer layer 13, and the second electrode layer 14 are stacked in this order is used as the microlens array 100.

By applying a voltage, a light scatterer 15 having a desired shape is formed in the space formed by the spacer layer 13 to control the light diffusion, and the diffused light becomes parallel light in a state where the luminance is kept high. It can be converted.

The

optical elements

10A and 10B can be applied to an optical microscope, a lighting device for industrial use, and the like other than the application examples of FIGS. 9 and 10.

The microlens array 100 is formed to be 1 mm or less in thickness, and both the anode and the cathode can be made transparent, so application to an ultra-thin camera, head mounted display (HMD), microlens array (MLA) sheet, etc. In addition to the above, the present invention can be effectively applied to the medical field such as an endoscope system. The optical element 10 in which the number of the light scatterers 15 is single can also be applied to a light diffusion sheet, a lens sheet, and the like in the field of medicine and image formation.

<Configuration of high molecular weight material>
As described above, the optical element 10 and the microlens array 100 according to the embodiment are light scatterers having various orientation distributions by on / off control of the voltage or adjusting the voltage level without using a complicated mechanism. 15 can be generated. Here, it is desirable that the applied voltage be low. Therefore, the applied voltage is reduced by devising the composition of the polymer material used for the optical element and the microlens array.

Specifically, the driving voltage of the optical element 10 or the microlens array 100 can be obtained by adding an ionic liquid satisfying a predetermined condition to the gel-like polymer material (polymer gel) used in the polymer material layer 11. Reduce. The addition of the ionic liquid can enhance the deformation efficiency of the polymer material.

The ionic liquid is a salt composed of a cation (positively charged ion) and an anion (negatively charged ion), and is a liquid at 25 ° C. One of the predetermined conditions is that the ionic liquid has an anion (negative ion) transport number of a certain value or more at 25 ° C. Details of this condition will be described later.

The polymer material is, as described above, polyvinyl chloride (PVC), polymethyl methacrylate, polyurethane, polystyrene, polyvinyl acetate, polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polyacrylonitrile, silicone rubber and the like. In a preferred embodiment, a polymer or resin material transparent to the used wavelength is used.

The weight ratio of the ionic liquid to such a polymer material is 0.2 wt% or more and 1.5 wt% or less, more preferably 0.3 wt% or more and 1.0 wt% or less. When the weight of the polymer material is 1 (or 100%), the drive voltage of the optical element or the microlens array can be reduced by mixing this weight ratio of the ionic liquid. This basis will also be described later.

A suitable plasticizer may be added to the polymer gel or it may be dissolved in a solvent. When a plasticizer is used, dibutyl adipate (DBA: dibutyl adipate), diethyl adipate (DEA: diethyl adipate), diethyl sebacate (DES: diethyl sebacate), dioctyl phthalate (DOP: dioctyl phthalate), diethyl phthalate (DEP: diethyl phthalate) etc. can be used. As the solvent, ether solvents such as tetrahydrofuran (THF) can be used.

The polymer material to which the ionic liquid is added is applicable to any of the optical element 10A of FIGS. 1 and 2, the optical element 10B of FIG. 8, and the microlens array 100 of FIG. As described in detail below, the drive voltage of the polymer material layer 11 can be reduced to 200 V or less, more preferably 150 V or less, by adding an ionic liquid under predetermined conditions to the polymer material.

FIG. 11 is a schematic view of a sample 110 for measuring the characteristics of the polymer material to which the ionic liquid is added. FIG. 11 (a) shows a state in which no voltage is applied, and FIG. 11 (b) shows a state in which a voltage is applied.

In order to investigate various characteristics of the polymer material, a sample is prepared in which the polymer material layer 111 is sandwiched between the electrode 112 and the electrode 113. A polymer gel in which PVC having a weight average molecular weight of 230,000 is dissolved in a solvent of tetrahydrofuran (THF) is prepared, and various ionic liquids are added to prepare multiple types of samples. As a comparative example, the characteristics when using a polymer gel to which no ionic liquid is added are also measured.

The polymer gel of the sample and the comparative example is applied to a thickness of 300 μm on the electrode 112 serving as the lower electrode. On the polymer gel, a metal thin film with a thickness of 20 μm in which a hole with a diameter of 100 μm is formed is disposed as the upper electrode 113. The voltage applied between the electrode 112 and the electrode 113 is changed between 0 V and 400 V, and the height h of the peak (peak) of the light scatterer 115 protruding from the electrode 113 is measured. The height h is the height from the surface 113 s of the electrode 113. The electrode 112 is a cathode, and the electrode 113 is an anode.

The optical element 10 of the embodiment attracts the polymer gel to the electrode to form the light scatterer 15 in the space using elastic deformation of the polymer gel by voltage application, but the sample 110 in FIG. The same applies in that the light scatterer 115 is formed utilizing elastic deformation by application. The results of the property measurement of the polymer gel obtained for the sample of FIG. 11 can be applied to the configurations of FIGS. 1 to 3 and FIG.

FIG. 12 shows the voltage response characteristics of the polymer gel when various ionic liquids are added. The voltage dependency of the peak height h is measured by changing the voltage value applied to the polymer material layer 111. As a comparative example, the voltage dependence of peak height is also measured using a polymer gel to which no ionic liquid is added.

Line A shows the voltage dependence of the peak height of sample A to which 1-ethyl-3-methylimidazolium = tetrafluoroborate (EMI-BF ₄ ) is added as an ionic liquid. The weight ratio of EMI-BF _{4 to} PVC is 0.5 wt%. EMI is a cation and BF ₄ is an anion.

Line B shows the voltage dependence of the peak height of sample B to which 1-octyl-3-methylimidazolium = tetrafluoroborate (OMI-BF ₄ ) is added as an ionic liquid. The weight ratio of OMI-BF _{4 to} PVC is 0.5 wt%. OMI is a cation and BF ₄ is an anion.

Line C shows the voltage dependence of the peak height of sample C to which 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) is added as an ionic liquid. The weight ratio of EMI-DCA to PVC is 0.5 wt%. EMI is a cation, and DCA (C ₂ N ₃ ) is an anion.

The line D shows the voltage dependence of the peak height of the sample D to which tetrabutylphosphonium = tetrafluoroborate (TBP-BF ₄ ) is added as the ionic liquid. The weight ratio of TBP-BF _{4 to} PVC is 0.1 wt%. TBP is a cation, and BF ₄ is an anion.

The line E shows the voltage dependence of the peak height of the sample E to which tetrabutylphosphonium = tetrafluoroborate (TBP-BF ₄ ) is added as the ionic liquid. Type of ionic liquids are the same as sample D, but the weight ratio of TBP-BF ₄ for PVC is 0.5 wt%. TBP is a cation, and BF ₄ is an anion.

Line F shows the voltage dependence of the peak height of sample F to which 1-ethyl-3-methylimidazolium = trifluoromethanesulfonimide (EMI-TFSI) is added as an ionic liquid. The weight ratio of EMI-TFSI to PVC is 0.5 wt%. EMI is a cation and TFSI is an anion.

Line G shows the voltage dependency of the peak height of sample G to which tetrabutylphosphonium = methanesulfonic acid (TBP-MES) is added as an ionic liquid. The weight ratio of TBP-MES to PVC is 0.5 wt%. TBP is a cation and MES is an anion.

Line W shows the voltage dependence of the peak height of the PVC polymer gel of sample W to which the ionic liquid is not added as a comparative example.

From the measurement results of FIG. 12, even when the ionic liquid is not added, the polymer gel is deformed by the voltage application by using the polymer gel in which dielectric polarization occurs. In the polymer gel W of the comparative example in which the ionic liquid is not added, the height of the light scatterer 115 increases substantially linearly with the applied voltage. However, in order to cause the sample W to project from the surface 13s of the electrode 113 to a height of 20 μm, a voltage of 400 V is required.

On the other hand, Sample A to which 0.5 wt% of EMI-BF ₄ was added as an ionic liquid and Sample B to which 0.5 wt% of OMI-BF ₄ was added were polymer material layers when a voltage of 100 V or less was applied. 11 can be driven to a height of 20 μm or more. In particular, the sample A is displaced to a height of less than 40 μm by application of a voltage of 50 V and a height of 20 μm and application of a voltage of 200 V. The sample B is also displaced to a height of 25 μm at a voltage application of 100 V and a height of 30 μm at a voltage application of 200 V.

Sample C added with 0.5 wt% of EMI-DCA can obtain the same 20 μm peak height with about half applied voltage (210 to 220 V) as compared with sample W to which no ionic liquid is added. The deformation efficiency has been greatly improved.

Sample D, to which 0.1 wt% of TBP-BF ₄ is added, can cause the light scatterer 115 to project from the surface 113 s of the electrode 113 by applying a voltage of 50 V, but the peak height is It remains less than 10 μm and the change in peak height is small in the range of 50V to 400V. In the sample D, it is difficult to accurately adjust the height of the light scatterer 115 by voltage control.

Sample E with 0.5 wt% TBP-BF ₄ added, Sample F with 0.5 wt% EMI-TFSI added, and Sample G with 0.5 wt% TBP-MES applied a voltage of 400 V However, the light scatterer 115 can not protrude from the surface 113 s of the electrode 113.

From the measurement results of FIG. 12, it is considered that at least one of the type (ie, physical properties) and the addition amount of the ionic liquid is involved in the reduction of the drive voltage of the polymer material layer 111.

<Relationship between displacement of polymer gel and physical properties of ionic liquid>
FIG. 13 is a view showing the relationship between the displacement of the polymer gel and the physical properties of the ionic liquid. The physical properties of Sample H to which 1-ethyl-3-methylimidazolium = fluorosulfonylimide (EMI-FSI) is added as an ionic liquid in addition to Samples A to G in FIG. 12 are also measured.

The samples A to H to which various ionic liquids are added, in which the displacement is positive, indicate that the polymer gel protrudes from the surface 113 s of the electrode 113 by application of a voltage and the light scatterer 115 is formed. The negative displacement is one in which the polymer gel does not protrude from the surface 113s of the electrode 113 even when a voltage is applied.

As physical properties of each ionic liquid, conductivity, size of potential window, diffusion coefficient and transport number of negative ions at 25 ° C. are measured. Since some of the used ionic liquids are solid at 25 ° C., the diffusion coefficient and transport number of negative ions at 80 ° C. are measured for those melted by heating to 80 ° C.

Among the above-mentioned parameters, the conductivity will be examined first. Although the conductivity of sample C is smaller by two orders of magnitude compared with samples A and B, the polymer gel to which sample C is added is positively displaced. In contrast, sample H is much more conductive than sample C, but the polymer gel is not positively displaced. It is believed that the conductivity of the ionic liquid is not directly related to the deformation efficiency of the polymer gel.

The potential window is a potential region where the electrochemical stability is maintained in the system of FIG. The wider the voltage window (the larger the value), the wider the range in which the system is electrochemically stable. Although the potential windows of the sample A and the sample F are the same width, the polymer gel of the sample A is displaced to the plus, and the polymer gel of the sample F does not obtain the plus displacement. The width of the potential window of the ionic liquid is also considered not to be directly related to the deformation efficiency of the polymer gel.

Next, the diffusion coefficient and transport number of anions (negative ions) at 25 ° C. are examined. The diffusion coefficient of positive and negative ions contained in the ionic liquid is measured using solid-state NMR (VNMR System manufactured by Varian) as a measurement instrument. In the measurement procedure, an ionic liquid is injected into the capillary and set in the apparatus. The signal intensity with respect to the change of the magnetic field is measured at a predetermined temperature (in this case, 25 ° C. and 80 ° C.), and the diffusion coefficients of positive and negative ions are calculated from the Stokes-Einstein equation.

The transport number of negative ions represents the ratio of the current carried by the anion to the total current when a current is applied to the ionic liquid. The transport number of the negative ion is calculated as the ratio of the diffusion coefficient of the negative ion to the sum of the diffusion coefficient of the negative ion and the diffusion coefficient of the positive ion determined above (D _anion / (D _cation + D _anion )).

The ionic liquids used for the samples A, B, C, F, and H were liquids at 25 ° C., and the diffusion coefficient and transport number of negative ions of each ionic liquid were calculated from the measurement results by liquid chromatography. In samples A, B, and C where positive displacements were obtained, the transport number of negative ions of the ionic liquid at 25 ° C. is 0.4 or more. On the other hand, the transport number of negative ions at 25 ° C. of the ionic liquid used in samples F and H which can not obtain positive displacement is smaller than 0.4. From this, it is considered that the transport number of negative ions at room temperature influences the deformation efficiency of the polymer gel.

In addition, since the ionic liquid TBP-BF ₄ added to the sample D from which positive displacement was obtained is not melted at the heatable temperature (80 ° C.) of the liquid chromatograph used, the diffusion coefficient can not be measured. The

Since the ionic liquid TBP-MES added to the sample G which can not obtain positive displacement is also solid at 25 ° C., the diffusion coefficient can not be measured. When this ionic liquid was heated to 80 ° C. and melted, the diffusion coefficient and transport number of negative ions were calculated, and the transport number was 0.6.

From the results of FIG. 13, it is understood that, as a characteristic of the ionic liquid to be added to the polymer material layer 11, one having a transport number of negative ions of at least 0.4 at 25 ° C. is desirable.

From FIGS. 12 and 13, it is estimated that the smaller the size (molecular weight) of the anion of the ionic liquid, the more it contributes to the deformation efficiency of the polymer gel. On the other hand, it is considered that the size of the cation of the ionic liquid does not contribute so much to the deformation efficiency. However, since the deformation efficiency of the sample D is not sufficient, the type of cation may affect the deterioration of the cathode. This will be described later with reference to FIG.

Although the anion size and the cation size of the ionic liquid used in sample G are also moderate, the ionic liquid is solid at 25 ° C. Therefore, even if the ionic liquid is dispersed in the polymer gel by stirring, the deformation efficiency of the gel is Is considered to have contributed less.

From the above, other than BF ₄ ⁻ and DCA, Cl ⁻ or Br ⁻ having a relatively small ion size can be used as an anion. Moreover, various ionic liquids can be used by selecting the thing which does not influence deterioration of a cathode as a cation. For example, Li-BF ₄ ^- may be used as ionic liquids.

<Relationship between the amount of ionic liquid added and displacement of polymer gel>
FIG. 14 is a graph showing the relationship between the amount of ionic liquid added and the displacement of the polymer gel. The abscissa represents the content (wt%) of the ionic liquid relative to the polymer material of the polymer gel, and the ordinate represents the peak height of the displacement.

As the polymer material, PVC having a molecular weight of 230,000 is used, and EMI-BF ₄ of sample A is used as the ionic liquid. The amount of EMI-BF ₄ added is varied in the range of 0 wt% to 5.0 wt%. Further, the applied voltage is changed to 0V, 50V, 100V, 200V, and 400V.

Regardless of the level of applied voltage, positive displacement can be obtained when the amount of ionic liquid added is in the range of 0.2 wt% to 1.5 wt%. In addition, the displacement is maximized in the range of 0.3 wt% to 1.0 wt%. By the addition of the ionic liquid in this range, the light scatterer 115 can be formed on the surface 113 s of the electrode 113 by applying a voltage of 100 V or less. When the addition amount of the ionic liquid is 5.0 wt%, a memory phenomenon occurs in which the deformation does not return even when the voltage is turned off.

It can be seen from FIG. 14 that the weight ratio of the ionic liquid to the polymer is preferably 0.2 wt% to 1.5 wt%, more preferably 0.3 wt% to 1.0 wt%. This is also in agreement with the result of FIG.

FIG. 15 is a view showing the evaluation results of the light diffusion distribution of the light scatterer 115 formed by applying a voltage to the polymer material layer 111 for each addition amount of the ionic liquid. The sample 110 of FIG. 11 is manufactured using the polymer material layer 111 in which EMI-BF ₄ is used as the ionic liquid and the addition amount of EMI-BF ₄ is changed. The polymer material layer 111 contains PVC as a polymer gel and dibutyl adipate (DBA) as a plasticizer. The content ratio of DBA to the total amount of PVC and DBA is 83 wt%.

An electrode 112 to be a cathode is formed of ITO with a thickness of 150 μm, and a voltage is applied to the polymer material layer 111 sandwiched between the electrode 112 and the electrode 113 to form a light scatterer 115. The laser is disposed on the side of the electrode 112 formed of ITO, and the screen is disposed on the side on which the light scatterer 115 is formed. Laser light of red parallel light is incident on the sample 110 from the back surface side of the electrode 112, and the light diffusion state on the screen is observed.

The screen is disposed on the light exit side of the light scatterer 115 at a position farther than the focal point of the light scatterer 115. The light diffusion once focused at the focal point of the light scatterer 115 is observed on the screen. The diameter of the light scatterer 115 of the sample 110 is as small as 100 μm and the height is as small as about 0 to 40 μm, and the focal position thereof is very close to the light scatterer 115 and observation with the naked eye is difficult. By observing light diffusion at a position beyond the focus of the light scatterer 115, it is possible to evaluate the light collection state.

In the sample to which the ionic liquid is not added (denoted as “w / o IL”), the light scatterer 115 protruding from the surface of the electrode 113 is not formed even when a voltage of 200 V is applied. The red collimated light incident from the back surface of the sample 110 passes through the sample 110 as collimated light without being collected. In the range of 0 V to 400 V, spots of the same size are formed on the screen regardless of the level of applied voltage.

In the sample to which 0.05 wt% of EMI-BF ₄ is added, the application of a voltage of 100 V causes a slight swelling of the polymer gel on the surface of the electrode 113, but the light collecting function is insufficient and almost parallel light at the screen position The spot of is maintained. By applying a voltage of 200 V, a light scatterer 115 (having a gentle curvature) having a peak height of about 10 μm is formed. The light once collected at the focal position of the light scatterer 115 diffuses and spreads, and no spot appears on the screen.

In the sample to which 0.5 wt% of EMI-BF ₄ is added, a light scatterer 115 is formed on the surface of the electrode 113 by applying a voltage of 50 V, and light which has started to be diffused after being collected is observed at the screen position . At the voltage of 100 V and the voltage application of 200 V, the light scatterer 115 having a peak height larger than that at the time of 50 V application, ie, a sharp curvature, is formed on the surface of the electrode 113. The light incident from the back side of the sample 110 is greatly diffused after being collected, and no spot is observed at the screen position. These evaluation results agree with the measurement results of FIG.

From the light diffusion distribution of FIG. 15, it is confirmed that the focal length of the light scatterer 115 can be made variable by adjusting the applied voltage. When the measurement results are applied to the

optical elements

10A and 10B and the microlens array 100 according to the embodiment, the light scatterer 115 can be formed with a lower voltage, and as a variable focus lens or a variable shape lens with good deformation efficiency. It can be used.

<Effect of ionic liquid (cation) on cathode deterioration>
FIG. 16 is a view showing the influence of the ionic liquid on the cathode degradation. As a test sample, a PVC gel to which various ionic liquids are added is applied on a metal substrate, and an ITO electrode is disposed on the PVC gel as a counter electrode.

The types of PVC gel to be applied are Sample A (containing 0.5 wt% EMI-BF ₄ ), Sample B (containing 0.5 wt% OMI-BF ₄ ), Sample C (0.5 wt% EMI-DCA), Sample D (with 0.1 wt% TBP-BF ₄ ), Sample H (with 0.5 wt% EMI-FSI), and Sample G (0.5 wt%) (Including TBP-MES). Among these, the samples A to D have obtained positive displacement in FIG. Sample D is a sample in which the added amount is reduced to 0.1 wt% because displacement is not obtained when the weight ratio of the ionic liquid is set to 0.5 wt% the same as the other samples.

The surface condition of the electrode is observed from the ITO side while changing the voltage level applied to the PVC gel by using a metal substrate as a positive electrode and ITO as a negative electrode.

In the sample G which did not have the displacement effect, deterioration of the ITO (cathode) was observed at a low applied voltage of 50 V. Also in the sample D, deterioration of the ITO electrode due to voltage application is observed. It is considered that this is because the cation affects the deterioration of the ITO electrode. On the other hand, in the samples A to C having a high displacement effect, deterioration of the ITO electrode was not observed even if the applied voltage was increased.

From the consideration of FIGS. 11 to 16, by adding an ionic liquid having a transport number of negative ions of 0.4 or more at 25 ° C., large deformation is obtained at a low applied voltage as compared with a polymer gel to which no ionic liquid is added. You can get it. In particular, when an ionic liquid having a small anion size is used as in sample A and sample B, the peak height can be largely changed in the voltage range of 100 V or less. It is easy to control. That is, the light scatterer 15 can be made to appear in the space 17 and its height can be adjusted according to the level of the applied voltage. In the case of using these samples, when the

optical elements

10A and 10B are driven, the negative effect on the cathode is also small.

The polymeric material to which the ionic liquid is added is applicable to the microlens array 100 of FIG. 3 as described above. In this case, an array of light scatterers 15 can be formed in the space 17 by applying a voltage of 200 V or less between the

electrodes

12A and 14A. Depending on the type of ionic liquid to be added, an array of light scatterers 15 having a height of 20 μm or more can be formed by applying a voltage of 100 V or less.

Although the present invention has been described above based on the specific embodiments, the present invention is not limited to the above-described configuration examples. In the case of forming a plurality of light scatterers 15 in the optical element 10, the arrangement of the light scatterers 15 is not limited to the matrix arrangement, and may be alternately arranged. Alternatively, the shape of the openings 16 (or 143) of the spacer layer 13A may be hexagonal and finely arranged.

This application is related to Patent Application No. 2017-254352 filed with the Japanese Patent Office on December 28, 2017, and Patent Application No. 2018-243599 filed with the Japanese Patent Office on December 26, 2018. Based on the entire content.

10A,

10B Optical element

11, 111

Polymer material layer

12, 12A, 12B

First electrode layer

13, 13A,

13B Spacer layer

14, 14A, 14B Second electrode layer 141 Main surface 143 Opening 145

Bottom surface

15, 115 Light Scatterer 16 opening 17

space

19A, 19B electrode assembly 21 base material 100 micro lens array 110

sample

112, 113 electrode 130

imaging element array

131R, 131G, 131B color filter 150 imaging device 250 illumination device

Claims

A first electrode layer,
A second electrode layer,
A polymer material layer disposed between the first electrode layer and the second electrode layer;
An insulating spacer layer disposed between the polymer material layer and the second electrode layer to form a predetermined space between the polymer material layer and the second electrode layer;
An optical element characterized in that the polymer material layer is deformed under voltage application to form one or more light scatterers in the predetermined space.
The spacer layer is an insulating film having one or more openings,
The optical element according to claim 1, wherein under the application of the voltage, each of the one or more light scatterers is formed in the corresponding one or more apertures.
The second electrode layer has one or more openings on the main surface facing the polymer material layer,
The spacer layer is provided on the main surface so as to cover an area excluding the bottom surface of the one or more openings,
The optical element according to claim 1, wherein under the application of the voltage, each of the one or more light scatterers is formed in the corresponding one or more apertures.
The optical element according to any one of claims 1 to 3, wherein the light scattering body has a convex shape.
The optical element according to any one of claims 1 to 4, wherein the second electrode layer is an anode layer, and the first electrode layer is a cathode layer.
The optical element according to any one of claims 1 to 5, wherein the second electrode layer is a transparent electrode layer.
7. The polymer material layer according to claim 1, wherein an ionic liquid having a transport number of negative ions at 25 ° C. of 0.4 or more is added to the gel polymer material. The optical element according to item 1.
A first electrode layer,
A second electrode layer,
A polymer material layer disposed between the first electrode layer and the second electrode layer;
An insulating spacer layer disposed between the polymer material layer and the second electrode layer to form a predetermined space between the polymer material layer and the second electrode layer;
A microlens array comprising: an array of a plurality of light scatterers on a surface of the second electrode layer under voltage application.
9. The micro-computer according to claim 8, wherein the polymer material layer comprises an ionic liquid having a transport number of negative ions of at least 0.4 at 25 ° C. added to the gel-like polymer material. Lens array.
A microlens array according to claim 8 or 9,
An imaging element array disposed to face the micro lens array;
An imaging apparatus characterized by having:
A microlens array according to claim 8 or 9,
Light source,
An illuminating device characterized by having.
Forming a polymer material layer on the first electrode layer;
An insulating spacer layer and a second electrode layer are disposed on the polymer material layer to form a predetermined space between the polymer material layer and the second electrode layer,
A voltage is applied between the first electrode layer and the second electrode layer to deform the polymer material layer to form one or more light scatterers in the space.
A method of producing an optical element comprising a step.
Forming an electrode assembly in which the spacer layer having one or more openings is bonded to the second electrode layer;
Placing the electrode assembly on the polymeric material layer,
A method of producing an optical element according to claim 12, characterized in that.
One or more openings are formed in the main surface of the second electrode layer,
Forming an electrode assembly by forming the spacer layer covering an area excluding the bottom surface of the opening on the main surface;
Disposing the electrode assembly on the polymeric material layer such that the polymeric material layer and the major surface face each other;
A method of producing an optical element according to claim 12, characterized in that.
15. The polymer material layer according to any one of claims 12 to 14, wherein an ionic liquid having a transport number of negative ions at 25 ° C of 0.4 or more is added to the gel polymer material. The manufacturing method of the optical element of 1 item.