JP5776135B2 - Low voltage liquid crystal lens - Google Patents

Description

The present invention relates to a low-voltage driving liquid crystal lens that has a simple structure and can realize a large, multifunctional and thin lens capable of changing a focal length by a low voltage.

A liquid crystal called a nematic liquid crystal has fluidity like a liquid, exhibits anisotropy in electro-optical characteristics, and an effective refractive index can be continuously varied from a value for almost extraordinary light to a value for ordinary light by applying a voltage. Various voltage variable optical devices have been proposed by utilizing this feature.

That is, some nematic liquid crystal cells utilize the property that liquid crystal molecules are aligned in the direction of an electric field. This is a spatial parabolic refractive index distribution by using an electrode having a circular hole pattern with a diameter of several hundreds of microns and utilizing the liquid crystal molecule alignment effect due to an axisymmetric non-uniform electric field. Patent Documents 1 and 2 report methods for obtaining liquid crystal lenses having characteristics. Such a small liquid crystal lens having a diameter of millimeter or less is called a liquid crystal microlens.

In the liquid crystal microlens structure proposed in Patent Documents 1 and 2, if a lens with a large aperture diameter is formed by increasing the diameter of the circular hole pattern while keeping the thickness of the liquid crystal layer constant, an axial symmetry generated by the aperture of the electrode This non-uniform electric field does not occur to the vicinity of the center of the opening, so that there is a problem that a spatial alignment distribution of liquid crystal molecules necessary for obtaining lens characteristics cannot be obtained. As a method of increasing the effective opening diameter, a transparent high resistance film is provided so as to be in contact with the liquid crystal layer through an alignment film in a circular opening provided in electrodes on two substrates sandwiching the liquid crystal layer. Thus, there has been proposed a liquid crystal lens having a structure in which an electric field is generated up to the center of the opening using the potential distribution due to the electric resistance of the high resistance film surface (Patent Document 3).

However, with this method, the potential distribution due to the resistive film provided on the substrate surface facing the liquid crystal layer has a predetermined potential distribution shape that provides a parabolic refractive index distribution based on the orientation distribution of the liquid crystal molecules. It is extremely difficult to change the focal length over a wide range while maintaining good lens characteristics because the relationship between the electric field strength distribution and the liquid crystal molecule alignment effect is nonlinear. There was a problem that there was.

Further, an electrode having an opening having a structure similar to the liquid crystal microlens proposed in Patent Document 1 is arranged so as to be placed at a certain distance from the liquid crystal layer without contacting the liquid crystal layer. Even if the diameter of the opening is increased, an axially symmetric non-uniform electric field can be generated up to the vicinity of the center of the opening. Based on this principle, a method has been proposed in which an insulating layer is inserted between the liquid crystal layer and the circular hole pattern electrode to maintain the distance from the liquid crystal layer to the circular hole electrode (Patent Document). 4, Non-Patent Documents 1 and 2), there is a condition that the ratio of the diameter of the circular hole pattern and the thickness of the liquid crystal layer that can obtain the best characteristics in the liquid crystal microlens needs to be about 2: 1 to 3: 1. It has been shown that liquid crystal lenses that are relaxed and have a large diameter can be constructed.

Further, in a liquid crystal lens in which an insulating layer is inserted between the liquid crystal layer and the circular hole pattern electrode, a transparent third electrode is arranged outside the circular hole pattern electrode or inside the circular pattern electrode, and the voltage is increased by two voltages. A liquid crystal lens is disclosed in which the focal length can be varied over a wide range from concave lens characteristics to convex lens characteristics while maintaining good characteristics by driving (Patent Document 5).

It has been reported in Non-Patent Document 3 and Non-Patent Document 4 that the driving voltage of the liquid crystal lens can be reduced by using a glass material having a high relative dielectric constant as the insulating layer.

However, in the structure in which an insulating layer is provided in order to set the distance between the liquid crystal layer and the circular hole pattern electrode proposed in Patent Documents 4 and 5, the insulating layer disposed between the liquid crystal layer and the electrode For this reason, there is a problem that the driving voltage becomes high, and in particular, in order to obtain a lens having a large aperture, it is difficult to obtain a lens having a large aperture because the thickness of the insulating layer is further increased and a high voltage is required. There is a problem that the thickness of the entire liquid crystal lens cannot be reduced due to the thickness of the insulating layer.

In order to solve this problem, a high-resistance liquid layer or a high-resistance thin film is provided as a transparent high-resistance layer in the transparent insulating layer to relay the potential distribution, that is, the potential of the high-resistance film surface. Patent Document 6 discloses a method for reducing the driving voltage as a result of reducing the effective thickness of the transparent insulating layer by adopting a structure in which an axially symmetric non-uniform electric field is generated up to the center using the distribution. And Non-Patent Documents 4 and 5.

However, when a transparent high resistance layer is inserted in the transparent insulating layer, at least two transparent insulating layer substrates are required, which complicates the manufacturing process and reduces the thickness of the entire lens. There was a problem that there was a limit. In addition, there is a problem that the effective refractive index variable range in the liquid crystal layer, that is, the variable focal range cannot be widened, and it is difficult to construct a lens having a complicated function in addition to simple convex lens or concave lens characteristics. It was.

JP-A-11-109303 JP-A-11-109304 Japanese Patent Laid-Open No. 2003-29001 JP 2004-4616 A JP 2006-91826 A JP 2008-203360 A

Proceedings of the 49th Applied Physics-related Joint Lecture Meeting, “M.Ye and S. Sato”, “Optical properties of liquid crystal lens of any size” , March 2002, 28p-X-10, P.M. 1277 M. Ye and S. Sato, “Optical properties of liquid crystal lens of any size”, Japanese Journal of Applied Physics, May 2002, Vol. 41, No.5, P.L571-L573 Hage, Wang, S. Sato, “Effects of Dielectric Constant of Glass Substrates on Properties of Liquid Crystal Lens” , IEEE Photonics Technology Letters, Vol. 19, No. 17, P.1295-1297 (2007) Hage, Wang, Susumu Sato, “Study on Low Voltage Driving Method for Liquid Crystal Lenses”, Proceedings of the 2007 Annual Meeting of Japanese Liquid Crystal Society, September 2007, 2pC01 Hage, Wang, Maki Yamaguchi, Susumu Sato (M. Ye, B. Wang, M. Yamaguchi and S. Sato), “Lowering Driving Voltages for Liquid Crystal Lens Using Weakly Conductive Thin Film) ”, Japanese Journal of Applied Physics, June 2008, Vol. 47, No. 6, pp. 4597-4599

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal lens that solves the above problems, can be stably driven at a low voltage, and has a large aperture while maintaining good optical characteristics. The present invention also provides a liquid crystal lens that has various functions, improves the utilization efficiency of the liquid crystal layer, and is a large-sized lens that has a high reproducibility and can greatly change the focal length at a low voltage. It is in.

In order to solve the above-mentioned problems, the low-voltage drive liquid crystal lens of the present invention basically includes a first substrate having a transparent first electrode, a hole having a hole and facing the first electrode. 2 and a liquid crystal layer accommodated between the first electrode and the second electrode for aligning liquid crystal molecules in one direction, and applying a first voltage to the second electrode. A third electrode disposed in the hole and spaced from the second electrode within the hole with respect to the second electrode and the hole; The second voltage independent of the first voltage can be applied, and either the first voltage or the second voltage is a fixed value, and the first voltage The first voltage is varied with respect to the second voltage or the second voltage. A liquid crystal lens capable of variably controlling optical characteristics,
Between the hole and the liquid crystal layer and the second electrode and the liquid crystal layer, a first double layer composed of a transparent insulating layer and a transparent high resistance layer, or a first medium composed of a transparent medium and a transparent high resistance layer. Any one of the double layers is disposed , the transparent high resistance layer is not connected to any electrode, and there is no electrode between the transparent high resistance layer and the liquid crystal layer,
The resistance value of the transparent high-resistance layer is characterized by being axially symmetric from the center of the third electrode and stepwise or continuously in the radial direction.

  The transparent high resistance layer may be arranged in a circular band shape with respect to the center of the third electrode.

The second electrode is concentrically or divided into a plurality of radial directions, and an independent voltage is applied between each of the divided electrodes and the first electrode to control the alignment of liquid crystal molecules. It may be.

At least one of the first substrate and the second substrate having the second electrode and the transparent insulating layer or the transparent medium may have a lens effect.

The transparent high resistance layer may have an alignment effect on liquid crystal molecules.

Further, the lens effect may be weakened continuously or stepwise between a region having a lens effect and a region having no lens effect.

Further, the center of the region showing the lens effect may be located at a position shifted from the center of the transparent first substrate to the peripheral portion.

According to the present invention, a first electrode having a first hole is disposed on one surface of a first substrate, and a second electrode is disposed in the first hole with a space from the first electrode. A first insulating layer or a transparent medium and a first double layer of a transparent high-resistance layer overlap the first and second electrodes, and the first insulating layer or the transparent insulating film overlaps the first double layer. A first liquid crystal layer in which one surface of the center layer is opposed to each other, and the first liquid crystal molecules are aligned in one direction between the first double layer and the one surface of the center layer; A second double layer of a transparent insulating layer or a transparent medium and a transparent high resistance layer corresponds to the other surface of the center layer, and a second double layer is formed between the other surface of the center layer and the second double layer. 2 liquid crystal layers, and the second double layer has a second hole on a surface opposite to the second liquid crystal layer. A fourth electrode is disposed in the third electrode and the second hole at a distance from the third electrode, and a second substrate having the third and fourth electrodes is disposed. The first voltage and the second voltage may be supplied independently between the first electrode and the third electrode, and between the second electrode and the fourth electrode.

By the above means, it is possible to realize a multifunctional and thin lens that has a simple structure and can be driven by a low voltage. Moreover, even if the aperture of the lens is increased, the focal length can be changed with a low voltage. Further, the focal length can be varied greatly efficiently by electrical control with a low voltage without the operation of mechanically moving the lens back and forth as in the prior art.

FIG. 1A shows an embodiment of a low-voltage driving liquid crystal lens according to the present invention. In order to reduce the thickness of a transparent insulating layer, a second electrode 22 having a hole and a hole in the second electrode are provided. In the case where the second substrate 12 having the third electrode arranged at intervals in the inside is arranged on the opposite side to the liquid crystal layer, and the second electrode and the third electrode are arranged on the liquid crystal side. FIG. 1B is a configuration explanatory view, and FIG. 1B is a plan view of the electrode 22 in FIG. FIG. 2 shows a result of obtaining an optical phase difference distribution by simulation when V1 = 5 Vrms, V2 = 0 Vrms, 1 Vrms, and 2 Vrms are added with the surface resistance of the transparent high-resistance layer set to 3 MΩ in the configuration of FIG. FIG. 3 shows a portion corresponding to the third electrode provided with the transparent high resistance layer in the opening and a portion corresponding to the second electrode outside the low voltage driving liquid crystal lens having the configuration shown in FIG. It is a structure explanatory drawing at the time of setting it as a divided area and making each area | region into a different resistance value. FIG. 4 shows the optical phase difference distribution obtained by simulation when V1 = 3.5 Vrms and V2 = 0.5 Vrms are added, assuming that the surface resistance values of the transparent high resistance layer are 7 MΩ and 10 GΩ in the configuration of FIG. It is a result. FIG. 5 is an explanatory diagram showing the configuration of a more specific embodiment. The configuration shown in FIG. 3 is symmetrical, has two liquid crystal layers to increase the lens power, and is transparent. FIG. 6 is a diagram illustrating a configuration of a low-voltage driving liquid crystal lens having two high resistance layers. FIG. 6 shows the configuration shown in FIG. 3, in which the second electrode having holes is divided into concentric circles, and the transparent high resistance layer is also divided into concentric circles, and the respective regions are set to different values. FIG. FIG. 7 shows the optical in the case where V1 = 4 Vrms, V2 = 0 Vrms, and V3 = 1 Vrms are added with the surface resistance values of the transparent high resistance layers 41, 42, 43 being 3 MΩ, 10 GΩ, and 6 MΩ in the configuration of FIG. It is the result of having calculated | required phase difference distribution by simulation.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, the basic configuration will be described.

FIG. 1A shows a configuration in which a basic configuration of a liquid crystal lens according to an embodiment of the present invention is viewed from a cross section. The transparent first electrode 21 is formed on the first substrate 11 and constitutes a liquid crystal cell by overlapping the second substrate 12 via a spacer (not shown) for maintaining a predetermined thickness. Between the 1st board | substrate 11 and the said 2nd board | substrate 12, the 1st liquid crystal layer 31 which accommodated the liquid crystal molecule in one direction accommodated so that the 1st electrode 21 might be opposed is provided.

An alignment film 51 having an effect of aligning liquid crystal molecules in one direction is disposed on the surface of the first substrate 11 in contact with the liquid crystal layer 31. Further, a high resistance film is disposed as a transparent high resistance layer 41 on the side of the second substrate 12 facing the liquid crystal layer. This high resistance film is not connected to any electrode and does not apply a voltage directly.

By rubbing the alignment film 51 and the transparent high resistance layer 41 in one direction, the director corresponding to the major axis direction of the liquid crystal molecules has an angle inclined by about 1 to 2 degrees from the substrate surface called a pretilt angle. It is in a state of being oriented. When the rubbing process is not performed on the transparent high resistance layer 41, the alignment film 52 is disposed.

FIG. 1B is a plan view of the liquid crystal lens of FIG. 1A, and the second substrate 12 has a second electrode 22, and the second electrode 22 has a circular shape. A hole 22-1 is formed. A first voltage V1 from a first drive power supply is applied between the first electrode 21 and the second electrode 22. A circular transparent third electrode 23 having the same center electrically insulated by a slit is formed in the circular hole 22-1. A second voltage V2 from an external second driving power source can be applied to the circular transparent third electrode 23 through a lead portion 23-1 that is similarly insulated from the second electrode by a slit. Are arranged as follows.

Here, a case where the third electrode 23 is removed from the configuration shown in FIG. 1 will be described. When the first voltage V1 higher than the threshold value is applied between the first electrode 21 and the second electrode 22, an axially symmetric non-uniform electric field is applied to the liquid crystal layer 31, and the alignment of the liquid crystal molecules by the alignment film surface is controlled. The orientation effect of the force and the axisymmetric non-uniform electric field is oriented in an elastically balanced state, and the convex lens effect is mainly obtained. Details of this operation principle are disclosed in Patent Document 4.

In the liquid crystal lens having a configuration excluding the third electrode 23 from the configuration shown in FIG. 1, the complex characteristic that the change characteristic of the focal length of the liquid crystal lens with respect to the increase of the externally applied voltage once becomes the shortest and then increases. In addition, since there is a problem that it is difficult to obtain the concave lens characteristic, the third electrode is provided in addition to the second electrode as shown in FIG. In the case where the third electrode shown in FIG. 1 is arranged, the second voltage V2 independent of the first voltage V1 can be applied to the third electrode 23. Then, a liquid crystal lens is obtained that can obtain the first stage optical characteristics based on the first voltage V1 and the second stage optical characteristics based on the second voltage V2. The details of the operation principle of this liquid crystal lens are disclosed in Patent Document 5, and functions as a convex lens and a concave lens can be obtained.

In particular, in this liquid crystal lens, since the high resistance film as the transparent high resistance layer 41 is disposed between the transparent insulating layer 15 and the liquid crystal layer 31, the second electrode having a hole when an AC voltage is applied. Even if the thickness of the transparent insulating layer 15 is reduced due to the relay effect of the potential distribution as a result of the formation of dielectric coupling through the transparent high resistance layer 41 between the liquid crystal layer 31 and the liquid crystal layer 31 (circular pattern electrode) 22 Since the symmetrical non-uniform electric field is generated up to the position corresponding to the center of the circular hole in the liquid crystal layer, the driving voltage can be lowered. The effect of lowering the driving voltage in a structure in which a high resistance layer is inserted in the transparent insulating layer is disclosed in Patent Document 6, Non-Patent Document 4, and the like.

Next, a characteristic embodiment will be described which is a configuration capable of reducing the driving voltage while reducing the thickness with a simple configuration. That is, as shown in FIG. 1, in order to reduce the thickness of the transparent insulating layer 15, the second electrode 22 having a hole and the third electrode 22 arranged at intervals in the hole 22-1 of the second electrode 22. The second substrate 12 having the electrode 23 was disposed on the opposite side to the liquid crystal layer 31, and a liquid crystal lens was constructed in which the second electrode 22 and the third electrode 23 were disposed on the liquid crystal side. This configuration is not an idea that the conventional second substrate 12 is simply thinned in order to obtain the transparent insulating layer 15. When the second and third electrodes 22 and 23 are manufactured, it is necessary to maintain the strength of the second substrate 12. For this purpose, the second substrate 12 does not have to be simply thinned, but the second and third electrodes 22 and 23 are arranged on the second substrate, and then the second substrate 12 as described above. The surface of the substrate 12 is arranged upside down.

In this embodiment, a transparent high resistance layer 41 and an alignment layer 52 for liquid crystal molecules are disposed between the transparent insulating layer 15 and the liquid crystal layer. Since the transparent insulating layer 15 can be formed with a thickness of about 1 μm or a thinner thin film, the driving voltage can be greatly reduced.

In the configuration of FIG. 1, the diameter of the circular opening in which the third electrode 23 is disposed is 2 mm, the thickness of the liquid crystal layer 31 is 30 μm, the thickness of the transparent insulating layer 15 is 1 μm, and the sheet resistance of the transparent high resistance layer 41 is FIG. 2 shows a result obtained by simulating the optical phase difference distribution when V1 = 5 Vrms, V2 = 0 Vrms, 1 Vrms, and 2 Vrms are applied from the driving power supplies (1 kHz) 81 and 82 with the value of 3 MΩ. In all of the following examples, the driving power source is 1 kHz, the wavelength of the light source is 633 nm, MLC6080 (manufactured by Merck) is used as the liquid crystal material, and the thickness of the liquid crystal layer is 30 μm. When the focal length as a lens is obtained from the optical phase difference distribution within a diameter of 2 mm, they are about 17 cm, 31 cm, and 73 cm, respectively, and a convex lens characteristic having good optical characteristics is obtained.

Further, as a method for greatly increasing the lens power, FIG. 3 shows a configuration in which the basic configuration of the liquid crystal lens according to the embodiment in another example is viewed from a cross section. That is, in the liquid crystal lens having the configuration shown in FIG. 1, the region corresponding to the second electrode and the region corresponding to the third electrode provided in the circular opening in which the third electrode 23 is disposed are transparent high. FIG. 3 shows a configuration of a liquid crystal lens in which the resistance layer 41 is divided and the divided regions have different resistance values. In FIG. 3, the transparent high resistance layers 41 and 42 (which may be referred to as transparent high resistance layer regions 41 and 42) are illustrated so as to be separated from each other in order to clarify the separation. Actually, the transparent high resistance layers 41 and 42 having no slit portion are connected to each other. The lens power corresponds to the reciprocal when the focal length is expressed in meters, and the unit is diopter (1 / m).

As shown in FIG. 3, when transparent high resistance layers having different resistance values are separated by a slit or the like, the resistance value of the region separated by the slit or the like is set to a very large value. It will correspond. That is, it becomes the structure which provided the ring-shaped independent layer with very large resistance value, and the characteristic different from the structure shown in this Example will be obtained. Therefore, the high resistance layers 41 and 42 which are actually transparent and have no slit are connected to each other.

3, the surface resistance of the transparent high resistance layer 41 corresponding to the second electrode is 10 GΩ, and the surface resistance of the transparent high resistance layer 42 corresponding to the third electrode 23 provided in the circular opening is set. FIG. 4 shows the result of calculating the optical phase difference distribution by simulation when 7 MΩ, V1 is 3.5 Vrms, and V2 is 0 Vrms. In the circular opening where the third electrode 23 is arranged, the optical phase difference distribution is almost a square characteristic (parabola), and since it takes a constant value outside the circular opening, the utilization efficiency of the liquid crystal layer increases, Convex lens characteristics that can be driven at a low voltage and have good optical characteristics with a shorter focal length of about 12 cm are obtained.

In the configuration of FIG. 3, a transparent high resistance layer 41 having different resistance values is disposed outside the transparent high resistance layer 42 corresponding to the third electrode 23, but the high resistance layer 41 is replaced with a high resistance layer. It can also be arranged in the form of a ring or circle around 42. By reducing the width of the ring-shaped or circular-shaped high resistance layer, the outer shape of the liquid crystal lens can be further reduced.

A more specific example will be described. Since the variable range of the focal length in the liquid crystal lens, that is, the variable range of the lens power is proportional to the thickness of the liquid crystal layer, it is advantageous to increase the thickness of the liquid crystal layer from this point of view. It was difficult to be inversely proportional to the square of. Therefore, a method of dividing the liquid crystal layer into two is performed. However, in such a configuration, the potential distribution in the liquid crystal layer 32 on the second electrode 22 side having the opening becomes steep, so that there is a problem that disclination in which the liquid crystal molecular alignment becomes discontinuous easily occurs.

Therefore, as a method for solving such a problem, an embodiment in which the entire liquid crystal lens is symmetrical is described. That is, in the configuration shown in FIG. 3, the liquid crystal layer 31 to the second substrate 12 are used as one unit, and as shown in FIG. 5, the third substrate 13 that divides the liquid crystal layer into two layers is sandwiched between the upper and lower sides. Is configured to be symmetrical. In addition to the advantage of suppressing the occurrence of disclination, it is possible to cancel the anisotropy that depends on the direction in which liquid crystal molecules rise from the substrate surface by applying an electric field. Therefore, a liquid crystal lens with small aberration can be configured. In FIG. 5, in order to clarify the separation of the transparent high resistance layers 41-a and 42-a, 41-b and 42-b, they are illustrated as being separated from each other. There is no slit part and each transparent high resistance layer is connected. The lens of FIG. 5 can be described as follows. A first electrode 22-a having a first hole is disposed on one surface of the first substrate 11, and a second electrode 23-a is disposed in the first hole with an interval. A first double layer of the transparent insulating layer 15-a and the transparent high resistance layers 41-a and 42-a overlaps the first and second electrodes 22-a and 23-a, and the first two layers are overlapped. One surface of the center layer 13 made of a transparent insulating layer or a transparent insulating film is opposed to the multilayer. A first liquid crystal layer 31 for aligning the first liquid crystal molecules in one direction is provided between the first double layer and one surface of the center layer 13. Opposing the other surface of the center layer 13, a second double layer of the transparent insulating layer 15-b and the transparent high resistance layers 41-b and 42-b corresponds. A second liquid crystal layer 32 is provided between the other surface of the center layer 13 and the second double layer. On the surface of the second double layer opposite to the second liquid crystal layer 32, a third electrode 22-b having a second hole and a space in the second hole are arranged. The 4th electrode 23-b is arrange | positioned and the 2nd board | substrate 12 which has the said 3rd and 4th electrode is arrange | positioned. Here, drive power supplies 81 and 83 supply the first voltage V1 and the second voltage V2 which are independent between the first electrode and the third electrode, and between the second electrode and the fourth electrode, respectively. Is connected. The first and second holes are basically coaxial. In the above configuration, the transparent high resistance layers 41-a and 42-a are each subjected to a rubbing process. When this rubbing process is not performed, an alignment film is disposed on the surface corresponding to the liquid crystal layer.

Further, an embodiment that constitutes a liquid crystal lens having a higher function will be described. In the configuration shown in FIG. 3, the second electrodes 22 having holes are concentrically divided to apply independent voltages to each other, and the transparent high resistance layer 41 is also concentrically divided to be different from each other. FIG. 6 shows a configuration explanatory diagram in which the resistance value is set. In FIG. 6, in order to clarify the separation of the transparent high resistance layers 41, 42, and 43, they are illustrated as being separated from each other. However, in reality, the transparent high resistance layer 41 has no slit portion. , 42 and 43 are connected.

7 shows that the surface resistance values of the transparent high resistance layers 41, 42, and 43 in the configuration of FIG. 6 are 3 MΩ, 10 GΩ, and 6 MΩ, respectively, and the drive power supplies 81, 82, and 83 are used to obtain V1 = 4 Vrms, V2 = 0 Vrms, and V3. = 1 is a result of obtaining an optical phase difference distribution by simulation when 1 Vrms is applied. By dividing such an electrode and a transparent high resistance layer, a convex lens characteristic with a focal length of about 9 cm is obtained in a region where the central diameter is smaller than 2 mm, and a concave lens characteristic with a focal length of about 90 cm is provided in the peripheral region. The compound lens which has is comprised. By appropriately varying the voltages V1, V2, and V3 applied to these divided electrodes, the focal lengths of the inner and outer lenses can be variably adjusted.

By dividing the electrode and the transparent high-resistance layer into a larger number, adjusting each parameter, and varying the applied voltage and frequency, an optical device having more various characteristics can be configured.

In the liquid crystal lens having the transparent high resistance film according to the present invention, the transparent high resistance films 41, 42, 43 and the like are mainly formed by the resistance component and the capacitance component due to the relationship between the transparent insulating layer 15 and the liquid crystal layer 31 mainly composed of the capacitance component. Since it acts as a configured impedance, there is a frequency dependency of the applied power supply. Therefore, the effective impedance value can be adjusted by changing the frequency of the applied voltage by appropriately adjusting the resistivity value and the dielectric constant of each of the divided transparent high resistance layers. .

Therefore, by adjusting the value and frequency of the voltage applied to each divided electrode, not only a compound lens having a convex lens characteristic in a concave lens, but also a compound lens having a concave lens characteristic in a convex lens, and a focal length Convex and concave lenses with different focal lengths in each region, such as a lens with a convex lens characteristic with a long focal length around a short convex lens, or a compound lens with a characteristic that reverses these characteristics, and the optical phase difference distribution characteristics It is possible to construct a large-area lens or the like that has a symmetrically folded structure and that effectively has the effect of a Fresnel lens as a whole.

Instead of the transparent insulating layer, a transparent medium having slightly conductivity can be used. In this case, since the transparent medium functions as an impedance having both a dielectric constant and a resistivity, the liquid crystal lens can be driven with a lower applied voltage.

As described above, in the liquid crystal lens according to each configuration, the focal point is changed from a certain fixed focal point by using the substrate having the lens effect as the first substrate and / or the transparent insulating layer and / or the transparent medium. And a compact lens system integrated as a whole can be configured. Here, in order to give the substrate a lens effect, the shape of the substrate may be a curved surface shape, but it is more convenient when the refractive index is distributed symmetrically in a parallel plate type. is there.

As described in the embodiments of the present invention, the liquid crystal is rubbed by rubbing the resin film (TWH-1 manufactured by Gemco (currently “Mitsubishi Materials Electronics Kasei”)) used as the transparent high resistance layer. An orientation effect can be given to the molecule. Therefore, a more stable liquid crystal lens can be constructed by using a resin film having a higher orientation effect, such as a polyimide film, and having a high resistance characteristic.

Furthermore, by continuously changing the alignment effect of the liquid crystal molecules accompanying the electric field distribution in the liquid crystal layer around the circular opening, the lens effect is continuously weakened from the region having the lens effect to the region having no lens effect. Thus, a low-voltage driving liquid crystal lens characterized by having excellent characteristics can be formed.

When the liquid crystal lens according to the present invention is used as a spectacle lens, the center of the region showing the lens effect, that is, the center of the circular hole pattern is shifted from the center of the transparent first substrate to the peripheral portion, particularly the obliquely lower portion. By placing it in a different position, it is possible to configure a pair of glasses that can be switched to a convex lens state for reading, etc., and to switch to a through state by voltage removal or a slightly concave lens state in other cases. Can do. According to the present invention, by using the transparent high resistance layer, a large-diameter liquid crystal lens that operates at a low voltage can be configured, and thus it is useful as a spectacle lens for such a perspective.

In this embodiment, the transparent high resistance layer 41 is disposed between the transparent insulating layer 12 and the liquid crystal layer. However, the circular pattern electrode 22 and the transparent insulating layer 12 are opposite to the liquid crystal layer of the transparent insulating layer 12. An insulating layer may be interposed between the two. The transparent insulating layer 12 is not limited to this name as its name, but is a transparent insulator having a transparent high resistance layer, a transparent insulator having an electric field relay layer, or a transparent having a dielectric coupling function. Names such as an insulator or a transparent medium having a very high resistance value are possible.

In the present embodiment, the case where only one circular pattern electrode is used has been described. However, as shown in FIG. 5, the circular pattern electrode may be provided on both sides of the liquid crystal layer. In any lens structure, such a symmetrical structure suppresses the occurrence of disclination in which the alignment of liquid crystal molecules becomes discontinuous, and has excellent symmetry in the spatial distribution characteristics and optical characteristics of the refractive index. A liquid crystal lens can be constructed.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment. Further, although one liquid crystal lens is shown, a configuration in which a plurality of liquid crystal lenses are arranged may be used. Further, it may be a two-dimensional array such as a compound eye.

The low-voltage drive liquid crystal lens of the present invention is different from ordinary passive optical devices in that the voltage and the effective refractive index of the liquid crystal as a medium are variably controlled by applying a voltage between the electrodes. A lens capable of adjusting the aberration is realized. Therefore, various applications such as an autofocus lens, a magnifying lens, a zoom lens, a lens of an image pickup unit used as a visual function in a robot, and a spectacle lens for both perspective by increasing the aperture are possible. .

DESCRIPTION OF SYMBOLS 11 ... 1st board | substrate, 12 ... 2nd board | substrate (transparent insulation layer), 13 ... Intermediate glass plate, 15 ... Transparent insulation layer, 41, 42, 43 ... Transparent High resistance layer, 21 ... 1st electrode, 22 ... 2nd electrode, 22-1 ... Opening part, 23 ... 3rd electrode, 23-1 ... Electrode extraction part, 24 ... 3rd electrode, 31, 32 ... Liquid crystal layer, 51, 52, 53 ... Alignment film, 81, 82, 83 ... Drive power supply.

Claims (3)

A first substrate having a transparent first electrode; a second electrode having a hole and facing the first electrode; and being accommodated between the first electrode and the second electrode A liquid crystal layer for aligning liquid crystal molecules in one direction,
A first voltage is applied to the second electrode;
A third electrode is disposed in the hole and spaced from the second electrode and the hole in the hole;
A configuration is such that a second voltage independent of the first voltage can be applied to the third electrode, and either the first voltage or the second voltage is a fixed value. A liquid crystal lens capable of variably controlling optical characteristics by varying the second voltage with respect to the first voltage or the first voltage with respect to the second voltage. There,
Between the hole and the liquid crystal layer and the second electrode and the liquid crystal layer, a first double layer composed of a transparent insulating layer and a transparent high resistance layer, or a first medium composed of a transparent medium and a transparent high resistance layer. Any one of the double layers is disposed, the transparent high resistance layer is not connected to any electrode, and there is no electrode between the transparent high resistance layer and the liquid crystal layer,
The low-voltage drive liquid crystal lens, wherein a resistance value of the transparent high-resistance layer is axially symmetric from the center of the third electrode and changes stepwise or continuously in the radial direction.   2. The low voltage driving liquid crystal lens according to claim 1, wherein the transparent high resistance layer is arranged in a circular band shape with respect to the center of the third electrode. A first electrode having a first hole is disposed on one surface of the first substrate;
A second electrode is disposed in the first hole and spaced from the first electrode;
For the first and second electrodes, a first double layer comprising a transparent insulating layer and a first transparent high resistance layer, or a first double layer comprising a transparent medium and a first transparent high resistance layer. Either one of the double layers overlaps, the first transparent high resistance layer is not connected to any electrode, and there is no electrode between the first transparent high resistance layer and the liquid crystal layer,
The resistance value of the first transparent high resistance layer is axially symmetric from the center of the first electrode and changes stepwise or continuously in the radial direction,
A first liquid crystal layer for aligning liquid crystal molecules in one direction between the first double layer and one surface of the center layer;
One surface of the center layer by the transparent insulating layer or the transparent insulating film is opposed to the first liquid crystal layer,
A second liquid crystal layer for aligning liquid crystal molecules in one direction facing the other surface of the center layer,
For the second liquid crystal layer , either a second double layer composed of a transparent insulating layer and a second transparent high resistance layer, or a second double layer composed of a transparent medium and a second transparent high resistance layer One double layer corresponds, the second transparent high resistance layer is not connected to any electrode, and there is no electrode between the second transparent high resistance layer and the liquid crystal layer,
On the surface of the second double layer opposite to the second liquid crystal layer, a third electrode having a second hole and a third electrode in the second hole are spaced apart from the third electrode. 4 electrodes are disposed, and a second substrate having the third and fourth electrodes is disposed,
The resistance value of the second transparent high-resistance layer is axially symmetric from the center of the third electrode and changes stepwise or continuously in the radial direction;
The first voltage and the second voltage that are independent from each other are supplied between the first electrode and the third electrode, and between the second electrode and the fourth electrode, respectively. Voltage-driven liquid crystal lens.

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