JP2009098644A - Liquid crystal fresnel lens, and liquid crystal fresnel lens production device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal Fresnel lens, even when light is made incident from an oblique direction, which reduces reflection caused by the incident light, and can make concentric stripes characteristic of the Fresnel lens inconspicuous. <P>SOLUTION: The liquid crystal Fresnel lens comprises: a first transparent substrate in which a Fresnel lens is formed on one side; a first transparent electrode formed only at all lens faces in the Fresnel lens; a second transparent substrate having a second transparent electrode on one side, and arranged in such a manner that the face of the second transparent electrode side is confronted with the first transparent electrode; and a liquid crystal arranged between the first and the second transparent substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal Fresnel lens having a convex or concave shape and a spherical or aspherical shape, and a liquid crystal Fresnel lens manufacturing apparatus.

  Focus by liquid crystal Fresnel lens system that forms a Fresnel lens on a flat or curved transparent substrate, fills the liquid crystal along the Fresnel lens shape, and changes the refractive index of the liquid crystal by applying voltage across the liquid crystal A variable lens has been devised. In this method, an alignment film and electrodes rubbed in a certain direction are formed on both end faces of the liquid crystal, and a voltage is applied to change the orientation direction of the liquid crystal, thereby changing the optical path through the liquid crystal and changing the focal length. It is possible to make it.

  In order to efficiently apply a voltage to the rubbing-aligned liquid crystal, transparent conductive films are formed on both ends of the liquid crystal that are perpendicular to the light transmission direction.

In a conventional liquid crystal Fresnel lens, a SiOxNy film is formed by sputtering on a glass substrate that is a transparent substrate. Further, after patterning the resist by photolithography using a photomask, the SiOxNy film is processed by a reactive ion etching method. The processed SiOxNy film becomes a Fresnel lens. Next, a transparent conductive film (ITO film) is formed on the surface of the uneven portion, and this is used as a transparent electrode. (For example, refer to Patent Document 1).
JP 2006-79669 A (page 21, FIG. 6)

  However, in the conventional configuration, a transparent conductive film (ITO) 42a is formed on all surfaces (lens surface and non-lens surface) of the Fresnel lens 44 as shown in FIG. Since ITO has a high refractive index (n≈2.1) in the visible light region, when the liquid crystal Fresnel lens 40 is observed from an oblique direction, the ITO film on the non-lens surface is reflected by external light and appears white on the Fresnel lens. Come on. For this reason, the concentric fringes peculiar to the Fresnel lens tend to be conspicuous and are unfavorable in appearance.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a liquid crystal Fresnel lens that can reduce the reflection of concentric fringes of the Fresnel lens due to reflection by external light.

  In order to solve the above-described conventional problems, the liquid crystal Fresnel lens and the liquid crystal Fresnel lens manufacturing apparatus of the present invention include a first transparent substrate having a Fresnel lens formed on one side, and all lenses having the Fresnel lens formed thereon. The first transparent electrode formed only on the surface and the second transparent electrode on one surface, and the second transparent electrode side surface is disposed so as to face the first transparent electrode. Liquid crystal is disposed between the two transparent substrates, the first transparent substrate, and the second transparent substrate.

  Further, the liquid crystal Fresnel lens and the liquid crystal Fresnel lens manufacturing apparatus of the present invention are the liquid crystal Fresnel lens manufacturing apparatus in which a transparent electrode is formed on the lens surface of the first transparent substrate having the Fresnel lens formed on one surface. A substrate holder for fixing the first transparent substrate, an evaporation source containing an electrode material for forming the transparent electrode, and a metal mask disposed between the first transparent substrate and the evaporation source And a mask holder for holding the metal mask.

  According to the liquid crystal Fresnel lens of the present invention, even if light is incident on the lens from an oblique direction, reflection due to the incident light can be reduced and concentric fringes unique to the Fresnel lens can be made inconspicuous.

  Embodiments of a liquid crystal Fresnel lens according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a cross-sectional structure diagram of a liquid crystal Fresnel lens according to Embodiment 1 of the present invention. In FIG. 1, a liquid crystal Fresnel lens 10 has a convex Fresnel lens 14 formed on a first transparent substrate 11a. The Fresnel lens 14 has a surface opposite to the surface in contact with the first transparent substrate 11a. A lens surface 16 is formed. The lens surface 16 in the present invention refers to a surface optically refracted or diffractive so as to satisfy the optical characteristics of the Fresnel lens. The first transparent electrode 12a is formed on all the lens surfaces 16. A second transparent electrode 12b is formed on one surface of the flat second transparent substrate 11b. A resin material such as a high refractive glass material or PMMA polycarbonate is used for the first transparent substrate 11a and the second transparent substrate 11b. The first transparent electrode 12a and the second transparent electrode 12b are made of ITO, and are formed on the surface of each transparent substrate by vapor deposition or sputtering.

  After that, a second transparent substrate 11b having a second transparent electrode 12b is disposed so as to face the first transparent electrode 12a, and between the first transparent substrate 11a and the second transparent substrate 11b. The liquid crystal 13 is filled. After filling, the both ends of the first transparent substrate 11a and the second transparent substrate 11b are sealed with the seal 15 to complete the liquid crystal lens 10. In the present embodiment, the first transparent substrate 11a and the second transparent substrate 11b have been described as planes, but they may be spherical or aspherical.

  When a voltage is applied between the first transparent electrode 12 a and the second transparent electrode 12 b of the liquid crystal lens 10 shown in FIG. 1, the refractive index of the liquid crystal 13 becomes lower than the refractive index of the Fresnel lens 14. Therefore, the liquid crystal Fresnel lens 10 becomes a convex lens due to the light condensing effect of the Fresnel lens 14. On the contrary, when no voltage is applied between the first transparent electrode 12a and the second transparent electrode 12b, there is no difference between the refractive index of the liquid crystal 13 and the refractive index of the Fresnel lens 14, and the focal length becomes infinity. So it is no longer a convex lens. That is, the focal length of the liquid crystal Fresnel lens 10 can be varied by ON / OFF of the voltage applied between the first transparent electrode 12a and the second transparent electrode 12b.

  FIG. 2 is a perspective view of the Fresnel lens 14 according to Embodiment 1 of the present invention, and FIG. 3 is a plan view thereof. As shown in FIG. 2, the first transparent electrode 12 a is applied only to the lens surface 16 of the Fresnel lens 14 and is not applied to the non-lens surface 17. Therefore, the first transparent electrode 12a is electrically independent for each ring body of the Fresnel lens. The common electrode 12 c is formed along the shape of the surface of the Fresnel lens 14 in order to make these independent first transparent electrodes 12 a conductive. The common electrode 12c has a thickness of 2 to 30 mm, a width of 70 to 80 μm, and is formed along the shape of the surface of the Fresnel lens 14. In this embodiment, the material used for the common electrode is the same ITO as the first transparent electrode 12a.

  Below, the manufacturing method of the liquid crystal Fresnel lens 10 of this invention is demonstrated. First, a resin for lens is filled in a Fresnel lens mold and cured to obtain a Fresnel lens 14. Next, a method of forming the first transparent electrode 12a only on the lens surface 16 of the obtained Fresnel lens 14 will be described.

  FIG. 4 is a schematic diagram showing how the first transparent electrode 12a and the common electrode 12c are formed on the lens surface of the Fresnel lens 14, and FIG. 5 shows the Fresnel lens and the metal mask when the transparent electrode is formed. A plan view is shown. In the present embodiment, the first transparent electrode 12a is formed only on the lens surface 16 of the Fresnel lens 14 by vacuum deposition. In addition, ITO was used as the material of the first transparent electrode 12a. On the non-lens surface 17 described with reference to FIG. 1, a metal mask having a fan-shaped opening so as to surround the range of the central angle of 320 deg from the center of the Fresnel lens 14 as shown in FIG. Cover with 104 (a). The metal mask 104 (a) is placed so that its opening is located immediately above the ITO evaporation source 102, and is fixed by the mask holder 106 inside the vacuum evaporation apparatus 100. Thereafter, ITO is vapor-deposited on the lens portion while the Fresnel lens 14 is obliquely fixed to the substrate holder and rotated (rotational oblique vapor deposition method).

  Here, the angle of the Fresnel lens 14 is adjusted. Specifically, the Fresnel lens 14 is shaded so that the non-lens surface 17 becomes a shadow when viewed from the ITO evaporation source 102 so as not to be deposited on the non-lens surface 17. It is important to have an inclination in the. In this embodiment, the Fresnel lens 14 is inclined to the substrate holder 105 by about 1 to 2 deg so that the ITO does not deposit on the non-lens surface 17 so that the non-lens surface 17 is perpendicular to the first transparent substrate 11a. I fixed it.

  Subsequently, when the substrate holder 105 to which the Fresnel lens 14 is fixed is rotated and the ITO evaporation source 102 is heated by the heater 101 at the lower part of the vacuum chamber, the ITO 103 is sublimated and formed on the lens surface 16 of the Fresnel lens 14. . The first transparent electrode 12a is formed on the lens surface 16 of each Fresnel lens 14 by performing vapor deposition so that the thickness of the film is optimized while rotating the substrate holder 105 around the center of the Fresnel lens 14. .

  Subsequently, the common electrode 12c is formed.

  As shown in FIG. 6, the common electrode 12c is formed using a metal mask 104 (b) provided with a slit having a width of 100 μm, which is different from that used when forming the first transparent electrode 12a. The metal mask 104 (b) is fixed to the mask holder 106, and the angle of the Fresnel lens 14 is adjusted. In this angle adjustment, the angle is adjusted so that ITO is uniformly formed on both the lens surface and the non-lens surface. Thereafter, an ITO film is formed by a vacuum evaporation method in the same manner as when forming the first transparent electrode 12a. In addition, although formation of the common electrode 12c is possible also by sputtering method, in order to form a common electrode so that it may not stand out when observing with the naked eye, the vacuum evaporation method is more preferable.

  After forming the common electrode 12c, a nematic liquid crystal having an ordinary light refractive index no and an extraordinary light refractive index ne is applied so as to fill the uneven shape of the Fresnel lens 14, and a first transparent electrode 12a is formed thereon. The first transparent substrate 11a is sandwiched so that the surface on which the first transparent electrode 12a is formed is in contact with the liquid crystal side. Then, the edges of the first transparent substrate 11 a, the second transparent substrate 11 b, and the liquid crystal 13 are sealed with a seal 15 so as not to cause displacement of each element constituting the liquid crystal Fresnel lens 10.

  With respect to the liquid crystal 13, an alignment film is formed on the surfaces of the first transparent electrode 12a and the second transparent electrode 12b so that the applied nematic liquid crystal molecules are aligned in a certain direction. The alignment film is made of polyimide or the like and is rubbed in a specific direction. The liquid crystal 13 internally held by the first transparent substrate 11a, the second transparent substrate 11b, and the Fresnel lens 14 is given a potential difference to the first transparent electrode 12a and the second transparent electrode 12b, thereby aligning the liquid crystal molecules. The refractive index changes with the direction of polarization.

  Below, the dimension of the liquid crystal Fresnel lens 10 produced in the present Example is shown. The thickness of the liquid crystal Fresnel lens 10 was 1.6 mm, and the effective diameter of the Fresnel forming portion (portion where the irregularities were formed) in the liquid crystal Fresnel lens 10 was 40 mm. The first transparent substrate 11a and the second transparent substrate 11b constituting the liquid crystal Fresnel lens 10 each have a thickness of 0.7 mm, and the thickness from the bottom surface of the Fresnel lens 14 to the top located at the center is 0.12 mm. The distance from the top of the Fresnel lens 14 at the center position to the first transparent substrate 11a was 0.08 mm. The curvature of the Fresnel lens 14 was 35 mm near the center, and the pitch length of the Fresnel lens irregularities was 0.1 mm. The thickness of the first transparent electrode 12a was 400 mm. The resistance value of the formed common electrode 12c was 20Ω with a length of 20 mm.

  When the concentric reflection was visually confirmed for the Fresnel lens 10 manufactured with the above configuration, reflection was observed in the conventional configuration, but the transfer was hardly noticeable in the present embodiment. Further, the convex lens and the non-convex lens can be operated according to the presence / absence of a voltage applied between the first transparent electrode and the second transparent electrode, and characteristics as intended are obtained. In this embodiment, the common electrode is composed of the transparent conductive film, but it is not necessary to stick to the transparent conductive film.

In the conventional configuration, the refractive index difference Δn between the liquid crystal 13 or the Fresnel lens 14 and a transparent electrode such as ITO is 0.4 to 0.6. By not forming the film 12b, the refractive index difference Δn between the liquid crystal 13 and the Fresnel lens 14 is reduced to 0 to 0.2, and the reflection of light incident on the non-lens portion 17 of the Fresnel lens 14 is greatly increased. It is possible to reduce it.

  In the present embodiment, it is more preferable to set the refractive index of the Fresnel lens 14 to be larger than that of the liquid crystal 13 in order to suppress reflection of the irregularities of the Fresnel lens 14 by the non-lens surface.

(Embodiment 2)
FIG. 7 shows a cross-sectional structure diagram of a liquid crystal Fresnel lens according to Embodiment 2 of the present invention. The difference from the first embodiment is the cross-sectional shape of the Fresnel lens, which is a concave shape in this embodiment.

  In FIG. 7, the liquid crystal Fresnel lens 20 has a concave Fresnel lens 24 formed on a first transparent substrate 21a, and the lens is arranged on the surface opposite to the surface in contact with the first transparent substrate 21a in the Fresnel lens 24. A surface 26 is formed. The definition of the lens surface 26 is the same as in the first embodiment. The definition of the non-lens surface 27 is the same as that in the first embodiment. Although not shown in FIG. 7, a common electrode similar to that of the first embodiment is also provided in this example. Other structures and materials to be used are the same as those in the first embodiment, and will be omitted.

  When a voltage is applied between the first transparent electrode 22 a and the second transparent electrode 22 b of the liquid crystal lens 20 shown in FIG. 7, the refractive index of the liquid crystal 23 becomes lower than the refractive index of the Fresnel lens 24. Therefore, the liquid crystal Fresnel lens 20 becomes a concave lens due to the divergence effect of the Fresnel lens 24. On the other hand, when no voltage is applied between the first transparent electrode 22a and the second transparent electrode 22b, there is no difference between the refractive index of the liquid crystal 23 and the refractive index of the Fresnel lens 24, and the focal length becomes infinity. So it is no longer a concave lens. That is, the focal length of the liquid crystal Fresnel lens 20 can be varied by ON / OFF of the voltage applied between the first transparent electrode 22a and the second transparent electrode 22b.

  Since the manufacturing method of the liquid crystal Fresnel lens 20 of the second embodiment is the same as the manufacturing method described in the first embodiment, the description thereof is omitted. Below, the dimension of the produced liquid crystal Fresnel lens 20 is shown.

  The thickness of the liquid crystal Fresnel lens 20 manufactured in the second embodiment was 1.6 mm, and the effective diameter of the Fresnel forming portion (portion where the irregularities were formed) in the liquid crystal Fresnel lens 20 was 40 mm. The first transparent substrate 21a and the second transparent substrate 21b constituting the liquid crystal Fresnel lens 20 each have a thickness of 0.7 mm, and the thickness from the bottom of the Fresnel lens 24 to the top located at the center is 0.12 mm. The distance from the top of the Fresnel lens 24 at the center position to the first transparent substrate 21a was 0.08 mm. The curvature of the Fresnel lens 24 was 35 mm near the center, and the pitch length of the Fresnel lens irregularities was 0.1 mm. The thickness of the first transparent electrode 22a was 400 mm. The formed common electrode 22c has a resistance value of 6Ω with a length of 20 mm, which is the same value as in the first embodiment.

  When the concentric reflection was visually confirmed for the Fresnel lens 20 manufactured with the above configuration, reflection was observed in the conventional configuration, but the transfer was hardly noticeable in the present embodiment. Further, when a voltage for controlling the liquid crystal was applied between the first transparent electrode and the second transparent electrode, the operation as designed was confirmed.

  In the conventional configuration, the refractive index difference Δn between the liquid crystal 23 or the Fresnel lens 24 and a transparent electrode such as ITO is 0.4 to 0.6. However, the second transparent electrode is formed on the uneven lens surface of the Fresnel lens 24. By not forming the film 22b, the refractive index difference Δn between the liquid crystal 23 and the Fresnel lens 24 is reduced to 0 to 0.2, and the reflection of the light incident on the non-lens portion 27 of the Fresnel lens 24 is greatly increased. It is possible to reduce it.

  In the present embodiment, it is more preferable to set the refractive index of the Fresnel lens 24 to be larger than that of the liquid crystal 23 in order to suppress reflection of the irregularities of the Fresnel lens 24 by the non-lens surface.

(Embodiment 3)
FIG. 8 shows a plan view of a Fresnel lens according to Embodiment 3 of the present invention. The difference from Embodiment 1 and Embodiment 2 is that a plurality of common electrodes are provided. Thus, the response speed of the liquid crystal molecules can be increased by arranging a plurality of common electrodes and arranging them radially from the center to the outer periphery of the Fresnel lens.

  The basic structure of the liquid crystal Fresnel lens 34 shown in FIG. 8 is the same as that of the first embodiment. That is, as shown in FIG. 1, the liquid crystal Fresnel lens 34 includes a first transparent substrate 11a, a second transparent substrate 11b, a first transparent electrode 32a (indicated by 12a in FIG. 1), and a second. Transparent electrode 12b, liquid crystal 13, convex lens type Fresnel lens 14, and seal 15. There are four common electrodes 32c radially from the center of the Fresnel lens, and each is located at a position where the plurality of Fresnel lenses are divided into four. The first transparent electrodes 32a are connected to each other by these common electrodes 32c.

  FIG. 9 illustrates a method for manufacturing the common electrode described in Embodiment 3. A plurality of common electrodes are manufactured by rotating the metal mask 104 (b) each time one common electrode is manufactured using the metal mask 104 (b) for manufacturing the common electrode used in the first embodiment. it can.

  First, the metal mask 104 (b) having a slit having a width of 100 μm shown in FIG. 6 is placed on the mask holder 306 in FIG.

  Subsequently, in order to form the first common electrode, the first transparent substrate is placed on the substrate holder 305, and the substrate holder is rotated to match the place where the common electrode is formed, and this state is maintained. Then, an ITO film is formed by vapor deposition. Subsequently, in order to form the second common electrode, this time, the substrate holder 305 is rotated 90 degrees around the axis, and ITO is deposited in the same manner as before. Subsequently, in order to form the third and fourth common electrodes, the substrate holder 305 is rotated by 90 degrees to form an ITO film.

  In the above description, four common electrodes 32c are formed by fixing the metal mask 304 (a) and rotating the substrate holder 305. However, as shown in FIG. Alternatively, the mask 304 (b) may be attached to the Fresnel lens and the metal mask 304 (b) may be rotated each time the common electrode 32c is formed.

  Specifically, a metal mask 304 (b) is provided as shown in FIG. 10 (a) in order to form the first common electrode. While maintaining this state, an ITO film is formed by vapor deposition or sputtering. Subsequently, in order to form the second common electrode, as shown in FIG. 10B, the metal mask 304 (b) is rotated 90 degrees from the state of FIG. Form a film. At this time, the orientation of the Fresnel lens is also adjusted so that the common electrode is formed on the lens surface and the non-lens surface. Subsequently, in order to form the third and fourth common electrodes, the metal mask 304 (b) is rotated by 90 degrees as shown in FIGS. 10C and 10D, and the orientation of the Fresnel lens is adjusted. An ITO film is formed. Since the process after forming the common electrode is the same as that of the first embodiment, the description thereof is omitted.

  With the above configuration, it is possible to obtain a liquid crystal Fresnel lens having better liquid crystal response than the liquid crystal Fresnel lens manufactured in the first embodiment.

  The liquid crystal Fresnel lens according to the present invention has reduced reflection due to external light, and is useful as electronically controlled glasses. Further, the present invention can be suitably used for electronically controlled glasses using a liquid crystal Fresnel lens whose focal length is varied by an applied voltage.

1 is a cross-sectional structure diagram of a liquid crystal Fresnel lens in Embodiment 1 of the present invention The perspective view of the Fresnel lens in Embodiment 1 of this invention The top view of the Fresnel lens in Embodiment 1 of this invention Schematic showing how a transparent electrode is formed on the lens surface of a Fresnel lens according to Embodiment 1 of the present invention. Plan view of Fresnel lens and metal mask when forming transparent electrode in Embodiment 1 of the present invention Plan view of Fresnel lens and metal mask when forming a common electrode in Embodiment 1 of the present invention Cross-sectional structure diagram of a liquid crystal Fresnel lens according to Embodiment 2 of the present invention Plan view of a Fresnel lens provided with a plurality of common electrodes in Embodiment 3 of the present invention Schematic showing how a common electrode is formed on the lens surface and non-lens surface of a Fresnel lens according to Embodiment 3 of the present invention. Plan view of Fresnel lens and metal mask when forming a common electrode in Embodiment 3 of the present invention Cross-sectional structure of a conventional liquid crystal Fresnel lens

Explanation of symbols

10, 20, 40 Liquid crystal lens 11a, 21a, 41a First transparent substrate 11b, 21b, 41b Second transparent substrate 12a, 22a, 42a First transparent electrode 12b, 22b, 32b, 42b Second transparent electrode 12c 32c Common electrode 13, 23, 43 Liquid crystal 14, 34, 44 Fresnel lens (convex lens type)
15, 25, 45 Seal 16, 26 Lens surface 17, 27 Non-lens surface 24 Fresnel lens (concave lens type)
100, 300 Vacuum evaporation apparatus 101, 301 Heater 102, 302 ITO evaporation source 103, 303 ITO
104 (a), 104 (b), 304 (a), 304 (b) Metal mask 105, 305 Substrate holder 106, 306 Mask holder

Claims (11)

A first transparent substrate having a Fresnel lens formed on one side;
A first transparent electrode formed only on all lens surfaces on which the Fresnel lens is formed;
A second transparent substrate having a second transparent electrode on one surface and disposed so that the surface on the second transparent electrode side faces the first transparent electrode;
A liquid crystal Fresnel lens in which liquid crystal is disposed between the first transparent substrate and the second transparent substrate. The liquid crystal Fresnel lens according to claim 1, further comprising a common electrode for electrically connecting all the first transparent electrodes. The liquid crystal Fresnel lens according to claim 1, wherein a cross-sectional shape of the Fresnel lens is one of a convex type and a concave type. The liquid crystal Fresnel lens according to claim 1, wherein a cross-sectional shape of the Fresnel lens is one of a spherical surface and an aspherical surface. The liquid crystal Fresnel lens according to claim 2, wherein at least one common electrode is formed. In a liquid crystal Fresnel lens manufacturing apparatus for forming a transparent electrode on a lens surface of a first transparent substrate having a Fresnel lens formed on one surface,
A substrate holder for fixing the first transparent substrate;
An evaporation source containing an electrode material for forming the transparent electrode;
A metal mask disposed between the first transparent substrate and the evaporation source;
A mask holder for holding the metal mask;
A liquid crystal fresnel lens manufacturing apparatus. The apparatus for manufacturing a liquid crystal Fresnel lens according to claim 6, wherein the substrate holder is capable of varying an angle between the first transparent substrate and the evaporation source. The liquid crystal Fresnel lens manufacturing apparatus according to claim 6, wherein the substrate holder can freely rotate the first transparent substrate. The metal mask has a fan-shaped notch from the center to the outside, and has a size that covers the first transparent substrate when the center is arranged to be the same as the center of the first transparent substrate. An apparatus for manufacturing a liquid crystal Fresnel lens according to claim 6. The metal mask has a rectangular cut from the center to the outside, and has a size that covers the first transparent substrate when the center is arranged to be the same as the center of the first transparent substrate. An apparatus for manufacturing a liquid crystal Fresnel lens according to claim 6. The liquid crystal Fresnel lens manufacturing apparatus according to claim 6, wherein the mask holder defines the center of the metal mask to be the same as the center of the first transparent substrate.

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