JP2919981B2 - Optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element whose refractive index changes when an external electric field is applied.

[0002]

2. Description of the Related Art As a method of changing a refractive index by an externally applied electric field, there is a prior art utilizing a nonlinear optical effect. On the other hand, ions are removed under high temperature and high voltage, and the depletion of ions reduces the refractive index as a physical property of glass,
There is a prior art in which a dopant is transferred to a glass substrate by an electric field transfer method or an optical glass having a refractive index gradient is formed by ion exchange.

[0003]

In the method using the nonlinear optical effect, it is necessary to apply a high voltage of several KV.
In addition, destruction may occur due to the high electric field. Moreover, there is a disadvantage that the change in the refractive index is not so large. On the other hand, it is possible to change the refractive index as one of the physical properties by a method of implanting or removing ions. However, this is an irreversible change to the last, and reversible refractive index control cannot be performed.

Accordingly, an object of the present invention is to provide an optical element which can control the refractive index reversibly and can operate at a low voltage.

[0005]

An optical element according to the present invention includes a light-transmitting optical member made of a polymer material containing ions, and a pair of electrodes provided on the surface of the optical member. By applying a predetermined potential difference between the electrodes, ion conduction is caused in the optical member to reversibly change the refractive index of the optical member.

[0006]

According to the present invention, the refractive index is reversibly changed based on ionic conduction, whereby the modulation of the transmitted light or reflected light of the optical element is reversibly controlled.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the structure of an optical element according to the embodiment. An optical member (ion conductor) 1 in the form of a thin film is made of a polymer material containing ions, and a pair of electrodes 21 and 22 are provided on both upper and lower surfaces of the ion conductor 1 in a film shape. And these are a pair of glass plates 31,
32 to form a single optical element. Further, between the electrodes 21 and 22, a potential difference E whose polarity is inverted is applied by operating the switch S.

In the above optical element, the electrodes 21, 22
When a potential difference E is applied with a predetermined polarity during the period, ions contained in the ion conductor 1 move in the polymer material, and polarization is equivalently generated. Then, the refractive index of the ion conductor 1 increases at one interface between the electrodes 21 and 22 and decreases at the other interface. For this reason, the light reflectance and transmittance at this interface or the total reflection condition can be switched, so that light modulation can be performed. Since the refractive index can be reversibly controlled by the applied electric field, reversible light modulation can be realized as a result.

Next, a method of manufacturing the above optical element will be described. The first production method is a polymerization method in an optical cell. Specifically, 2.0 g of ethyl methacrylate, 2.8 mmol of tetrabutylammonium bromide, and 5.0 g of tributylstannane bromide were placed in an optical cell in which a transparent electrode of ITO (indium tin oxide) was deposited face-to-face. 6m
After adding 5 mol of 2,2′-azobisisobutyronitrile as a polymerization initiator and reacting at 65 ° C. for 10 hours, the mixture can be gradually cooled to room temperature.

As a second manufacturing method, there is a casting method. Specifically, on a glass substrate on which an ITO transparent electrode has been deposited, poly (vinyl chloride)
2.0 g, tetrabutylammonium iodide 2.8 mm
ol, a mixed solution of tetrahydrofuran / methanol (4: 1) containing 5.6 mmol of tributylstannide iodide is coated. Then, an optical element is obtained by using a glass substrate on which another ITO transparent electrode is deposited, and lightly pressing the above-mentioned coating film so as to be sandwiched between the ITO transparent electrodes.

The composition of the ionic conductor can be variously combined. For example, poly (methyl methacrylate), poly (butyl methacrylate), or poly (acrylonitrile) can be used as the polymer. Further, tetrabutylammonium chloride or tetrabutylphosphonium bromide can be used as the quaternary ammonium salt. Further, the organometallic complex having an important role in ionic conduction only needs to have a Lewis acid point. Stannane, diiododimethylstannane, diiododiphenylstannane, bis (organotin) compounds tributyl borate, tripropyl borate, triethyl borate, or octyl dimethyl fluorosilane are also possible. However, tributylstannane bromide or tributylstannide having moderate Lewis acidity is suitable for obtaining high response characteristics with high ionic conductivity and rapid change in refractive index. Also, poly {(2-bromotrimethylammonium) ethyl methacrylate}
Polymer ion compounds such as are also possible.

Next, an example of measuring the change in the refractive index will be described. In the experiment, the change in the reflectance of the optical element caused by the change in the refractive index as shown in FIG. Detection was performed using a photodiode.
FIG. 3 shows the measurement results of the reflected light by applying ± 20 V at 60 ° incidence with S-polarized light. FIG. 4 shows the measurement results of the change in the refractive index and the dependence of the response time on the applied voltage. Similar changes in refractive index (reversible change) for cation conductors
Can be realized. Specifically, lithium perchlorate 56m
g, toluene diisocyanate 0.6 g and PPO
Using 1 g of (polypropylene oxide) as a starting material, a cation conductor was obtained. FIG. 5 shows the measurement results obtained by the reflectance measurement method of FIG.

Next, various structures of the optical element according to the embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 6 is a sectional view of the first embodiment. In the figure, the ion conductor 1 has a refractive index n of 1.47 to 1.
The electrodes 21 and 22 have n = 1.95.
And the glass plates 31 and 32 have n = 1.5
Glass material. The incident light is emitted from a He-Ne laser device having a wavelength of 632.8 nm, which is the light source 4,
The light is incident on the glass plate 31 at an incident angle of 82 °. As the optical path after the incidence, an optical path A ₁ (dotted line in the drawing) reflected at the interface between the electrode 21 and the glass plate 31, an optical path A ₂ reflected at the interface between the electrode 21 and the ionic conductor, and a light transmitted through the ionic conductor 1. there is an optical path A ₃ to. Here, the optical path A ₁ as to cut an aperture 5, a light detector 6 for optical path A _2, the optical path A ₃ are respectively detected by a photodetector 7. However, cutting with aperture 5
In reality, it is quite difficult, and at this time, the optical paths A ₁ ,
Detecting light of A ₂ together with the photodetector 6 may be electrically isolated. Such separation can be achieved by providing a comparator to remove a signal below a threshold level.

In this state, between the electrode 21 and the electrode 22,
When a potential difference of 20 V is applied, the refractive index of the ion conductor 1 changes from n = 1.488 to 1.473, and the incident light A ₀ exceeds the critical angle at the interface between the ion conductor 1 and the electrode 21. Therefore, the light of the optical path A ₃ by the light detector 7 will not be detected. That is, the above structure enables the transmission light to be turned on and off.

FIG. 7 shows an optical element in which the effect of light modulation is enhanced by multiple reflection. As shown in FIG.
Electrodes 21A, 22A and electrode 2 made of the same material on both surfaces
1B, a pair of ionic conductors 1 each provided with 22B
A and 1B are prepared, and these are attached to both surfaces of the glass plate 10 having a high refractive index. Then, light from the light source 4 is incident from one end of the glass plate 10, and emission light is received by the photodetector 6 from the other end. At this time, the electrodes 21A and 22A and the electrode 2
1B and 22B, the potential difference E applied to the electrode 2
1A and the electrode 21B have the same polarity, and the electrode 22A and the electrode 22
B has the same polarity. As a result, the light modulation generated at the point (a) at the interface between the ion conductor 1A and the electrode 21A is enhanced by the light modulation generated at the point (b) at the interface between the ion conductor 1B and the electrode 21B. The light modulation effect can be enhanced by reflection. If the electrodes 21A and 21B made of the same material have opposite polarities, the light modulation at the point (a) and the light modulation at the point (b) work in opposite directions, and the effect cannot be obtained. Same polarity.

FIG. 7B also functions in the same manner as FIG. What is different is that the light incident position and the light
The only difference is that blocks 11 and 12 made of optical glass are provided. The light modulation can be enhanced even when the electrodes 21A and 21B are made of optically different materials, or when the electrodes 21A and 21B have the same polarity.

FIG. 8 shows a multiple reflection type optical element using electrodes 21 and 22 made of different materials. Electrodes 21 and 22 are attached to both surfaces of the ion conductor 1,
A voltage is applied to the ion conductor 1. Then, electrode 2
The interface of the ion conductor 1 with one of the ion conductors 1 and 22 has a high refractive index, and the interface of the ion conductor 1 with the other has a low refractive index. Here, since the electrodes 21 and 22 are made of different materials and therefore have different reflectivities, the light modulation is enhanced. Since the electrodes 21 and 22 only need to have a large reflectance, opaque electrodes (for example, Al and Ag electrodes) are desirable.

FIG. 9 shows a method for measuring a solution concentration using the optical element of the present invention. As shown, the ion conductor 1
An electrode 21 and an electrode 22 made of different kinds of materials are provided on both surfaces of the device, and the solution 41 is received by the electrodes. When the concentration of the solution 41 changes, the refractive index changes, and the output of the photodetector 6 also changes.
Control the potential difference between the two. By monitoring this potential difference, the concentration of the solution 41 can be known.

FIG. 10 shows an example in which the optical element is applied to a wavelength-variable antireflection film or a reflection increasing film. As shown,
An electrode 21 and an electrode 22 are attached to both surfaces of the ion conductor 1, and are bonded to a substrate 42 which needs to be prevented from being reflected or increased.
To be provided. When a potential difference E is applied between the electrode 21 and the electrode 22, the ion conductor 1 at the interface between the electrode 22 and the ion conductor 1
Can be variably controlled in a wavelength region exhibiting a high reflectance or a low reflectance.

FIG. 11 is a cross-sectional view of an optical element that performs transmission type light modulation. As shown in the figure, electrodes 21 made of, for example, ITO and an Au, for example, are formed on both surfaces of the ion conductor 1.
Is provided, and is sandwiched between glass plates 31 and 32. When a potential difference E is applied between the electrode 21 and the electrode 22, the ion conductor 1 has a high refractive index at one interface and a low refractive index at the other interface, but these electrodes 21 and 22 are optically heterogeneous. is there. For this reason, reversible light modulation using the change in the refractive index can be performed, and the light modulation can be detected by the photodetector 6.

FIG. 12 shows another example of an optical element for performing reflection type light modulation. The feature of this optical element is that the electrode 22 is formed as a transparent electrode made of, for example, ITO, but the electrode 21 is formed of an opaque material that absorbs light (for example, carbon black). It is. For this reason, most of the incident light is absorbed by the electrode 22, so that only the light reflected at the interface between the ion conductor 1 and the electrode 21 enters the photodetector 6. This embodiment is particularly desirable when the ion conductor 1 is a thin film, whereby light reflected from the interface between the electrode 22 and the ion conductor 1 and light reflected from the interface between the electrode 21 and the ion conductor 1 are used. There is no mixing with light.

FIG. 13 shows an example of an optical element provided with a pair of electrodes at orthogonal positions. FIG. 1A is a perspective view, and FIG. 1B is a cross-sectional view. As shown, a pair of electrodes 21a and 22a is provided on the upper and lower side surfaces of the ion conductor 1 made of a polymer material, and another pair of electrodes 21b and 22b is provided on the left and right side surfaces. Since the electrodes 21b and 22b are arranged so as to be biased toward the upper electrode 22a, the electric field strength at the interface between the electrode 26a and the ion conductor 1 and the electric field strength at the interface between the electrode 22a and the ion conductor 1 Is uneven. For this reason, since the refractive index of the ion conductor 1 at each interface can be made different, light modulation can be performed by multiple reflection of these.

FIGS. 14 and 15 show the concept of information recording and reading using the optical element of the present invention. As shown in FIG. 14, a two-dimensional image recording panel 90 as an optical element
Has a plate-shaped ion conductor 1 made of a polymer material, and a horizontal electrode plate 91 and a vertical electrode plate 92 are attached to both surfaces thereof. Here, the horizontal electrode plate 91 has a number of horizontal electrodes (not shown) arranged in parallel with each other in the horizontal direction, and the vertical electrode plate 92 has vertical electrodes (not shown) arranged in parallel with each other in the vertical direction. ), Each of the horizontal electrodes is connected to each output terminal of the horizontal drive unit 93 by a wiring 95, and each of the vertical electrodes is connected to each output terminal of the vertical drive unit 94 by a wiring 96. Horizontal and vertical drive signals are supplied from the two-dimensional image signal generation unit 97 to the horizontal drive unit 93 and the vertical drive unit 94.

In the above-described two-dimensional image recording panel 90, a potential difference occurs in the ion conductor 1 at the intersection of the horizontal electrode and the vertical electrode to which a voltage is applied, and the refractive index changes. For this reason, the output of the two-dimensional image signal generator 97 is recorded as a two-dimensional image. Since this two-dimensional image is embodied as a refractive index, it can be read out by detecting a reflected light by entering a parallel light flux. That is, as shown in FIG. 14, when a parallel light beam enters the two-dimensional image recording panel 90 via the half mirror 98, reflection at the interface of the ion conductor 1 of the two-dimensional image recording panel 90 according to the distribution of the refractive index. Since the rates are different, the output light beam detected via the half mirror 98 has a two-dimensional intensity distribution. Therefore, an image on the two-dimensional image recording panel 90 can be read as the distribution of the reflectance as shown in FIG. Here, each vertical electrode of the vertical electrode plate 92 is formed of a light-absorbing material, and each horizontal electrode of the horizontal electrode plate 91 is formed of a light-transmitting material, in order to prevent mixing of reflected light. desirable.

[0027]

As described above, according to the present invention,
The refractive index is reversibly changed based on the ionic conduction, whereby the modulation of the transmitted light or the reflected light of the optical element is reversibly controlled. Therefore, it is possible to provide an optical element that can control the refractive index reversibly and operate at a low voltage.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of an optical element according to an example.

FIG. 2 is an explanatory diagram of a specific experiment by the present inventors.

FIG. 3 is an explanatory diagram of an experimental result.

FIG. 4 is an explanatory diagram of an experimental result.

FIG. 5 is an explanatory diagram of another experimental result.

FIG. 6 is a configuration diagram of a first specific example of an optical element according to an example.

FIG. 7 is a configuration diagram of a second specific example of the optical element according to the example.

FIG. 8 is a configuration diagram of a third specific example of the optical element according to the example.

FIG. 9 is a configuration diagram of a fourth specific example of the optical element according to the example.

FIG. 10 is a configuration diagram of a fifth specific example of the optical element according to the example.

FIG. 11 is a configuration diagram of a sixth specific example of the optical element according to the example.

FIG. 12 is a configuration diagram of a seventh specific example of the optical element according to the example.

FIG. 13 is a configuration diagram of an eighth specific example of the optical element according to the example.

FIG. 14 is an explanatory diagram of information recording using the optical element of the example.

FIG. 15 is a diagram showing reading of recorded information.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ion conductor 21, 22 ... Electrode 31, 32 ... Glass plate 4 ... Light source 6 ... Photodetector 90 ... Two-dimensional image recording panel 91 ... Horizontal electrode plate 92 ... Vertical electrode plate

Claims (3)

(57) [Claims] 1. A light-transmitting optical member made of a polymer material containing ions, and a pair of electrodes provided on a surface of the optical member, wherein a predetermined potential difference is applied between the pair of electrodes. An optical element characterized in that ion conduction is caused in the optical member to change the refractive index of the optical member reversibly. 2. The optical member is formed in a film shape, and the pair of electrodes are provided on both surfaces of the film-shaped optical member to form a flat plate, and are sandwiched between a pair of glass plates from both sides of the flat plate. The optical element according to claim 1, wherein 3. The optical element according to claim 1, wherein at least the light incident side of the pair of electrodes is formed of a translucent conductive material.