JP4833782B2 - LCD lens - Google Patents

Description

  The present invention relates to a liquid crystal lens, and more particularly to a liquid crystal lens used for adjusting a focal length in an optical device such as an optical disk device, a camera, a microscope, and glasses.

  2. Description of the Related Art Conventionally, a liquid crystal lens capable of controlling a focal length by a voltage applied as an optical element using liquid crystal is known. In the liquid crystal lens system, a glass substrate or other transparent substrate has a plano-convex lens or plano-concave lens shape, and a variable focal point is realized by using a change in the refractive index of the liquid crystal, or a Fresnel pattern on one of the transparent substrates. Similarly, there is one that realizes a variable focus by utilizing the change in the refractive index of the liquid crystal, but these can only realize either a convex lens or a concave lens. However, a liquid crystal lens that realizes variable focus by forming a transparent ring electrode on one of a flat transparent substrate can be a convex lens or a concave lens simply by changing the voltage application method, and is very convenient in use.

  In a system that realizes a variable focal point by a transparent ring electrode, a plurality of ring electrodes must be formed so that different voltages can be applied to the respective ring electrodes. For this reason, a lead wire is drawn from each ring electrode, or a plurality of ring electrodes are connected by a resistor having a preset resistance value, and the lead wire is drawn only from two points of the center electrode and the outer edge electrode. There is a method to take out. When the number of annular electrodes is large, the latter can reduce the number of lead lines to two, which is advantageous in realizing a liquid crystal lens having a small effective diameter as a lens.

  Here, the configuration of the above-described conventional liquid crystal lens will be described. FIG. 7 shows an electrode pattern configuration of a liquid crystal lens and a circuit configuration electrically connected to this pattern in Patent Document 1.

  This conventional liquid crystal lens has a configuration in which a liquid crystal layer is sandwiched between two glass substrates provided with a pattern electrode and a common electrode. The pattern electrode has a central electrode 110 and a plurality of annular electrodes 112 and 113, and the central electrode 110 and the annular electrodes 112 and 113 are connected by a voltage drop resistance electrode 106. It has become. The lead electrode 105b, which is insulated from the ring electrodes 112 and 113 and connected to the center electrode 110, is connected to the variable resistor 103 via the power amplifier 104b. The lead electrode 105a connected to the electrode) is connected to the variable resistor 102 via the amplifier 104a. Further, the AC voltage supplied from the AC source 101 connected in parallel to the variable resistors 102 and 103 is stepped down by the variable resistors 102 and 103.

  In this manner, a voltage distribution is formed by the voltage signal applied to the extraction electrodes 105a and 105b and the voltage drop resistance electrode 106, and a voltage distribution is formed in the liquid crystal layer. Various voltage distributions can be generated by adjusting the variable resistors 102 and 103.

Japanese Patent No. 3047082 (page 3-5, Fig. 1-4)

However, in the configuration of the liquid crystal lens described in Patent Document 1, since the voltage drop resistor electrode 106 is arranged in the radial direction in the lens region, the length of the voltage drop resistor electrode 106 is determined by the size of the lens region. It will be. Therefore, if the effective diameter of the lens corresponding to the lens region has to be reduced (when the size of the liquid crystal lens itself is reduced), even if the width of the voltage drop resistor electrode 106 can be reduced, the resistance It becomes difficult to make the value sufficiently large. In addition, a method of increasing the resistance value by reducing the thickness of the voltage drop resistance electrode 106 is conceivable, but there is a limit to the thickness of the voltage drop resistance electrode 106, and it is difficult to sufficiently increase the resistance value. is there. That is, with the configuration of the liquid crystal lens described in Patent Document 1, the current flowing through the voltage drop resistor electrode 106 cannot be reduced, which causes a problem that it is difficult to reduce power consumption.

  Furthermore, as described above, when the effective diameter of the lens is reduced, the length of the voltage drop resistance electrode 106 is shortened, and the position error sensitivity of the leader point of the leader line supplied to each of the annular electrodes 112 and 113 is high. Also occurs. That is, the slope of the voltage change between both ends of the voltage drop resistor electrode 106 is steep, and the desired applied voltage value changes greatly only by slightly shifting the position of the extraction point. Therefore, in the configuration of the liquid crystal lens in which the effective diameter of the lens is reduced in this way, a desired voltage distribution is not formed, and unnecessary lens aberration may occur.

  Therefore, in order to eliminate the above-mentioned problems caused by the prior art, the present invention provides a voltage drop resistor outside the effective area as a lens, thereby reducing power consumption during driving and applying precise voltage to each annular electrode. An object of the present invention is to provide a liquid crystal lens that makes it possible to achieve this.

  In order to solve the above-described problems and achieve the object, the liquid crystal lens of the present invention basically adopts the following configuration.

  The liquid crystal lens according to the present invention includes a liquid crystal layer sandwiched between first and second transparent substrates, a common electrode formed on the liquid crystal layer side of the first transparent substrate, and a liquid crystal layer side of the second transparent substrate. A plurality of annular electrodes formed on the annular electrodes, and a voltage drop resistor electrode connected to the plurality of annular electrodes for applying a resistance-divided control voltage to each annular electrode, the voltage drop resistor electrode Is provided in a ring shape with a predetermined gap from the outermost peripheral portion of the lens effective diameter region formed by a plurality of annular electrodes, and a predetermined position of the annular electrode. The liquid crystal layer is driven by supplying a driving voltage to both ends of the electrode formed by cutting out part of the voltage drop resistance electrode. A control voltage can be applied to each of multiple annular electrodes It is characterized in that the.

  According to the above-described invention, even if the size of the lens region in the liquid crystal lens is reduced, the resistance value of the voltage drop resistance electrode can be clearly increased as compared with the configuration of the conventional liquid crystal lens, and at the same time, the voltage drop The slope of the change with respect to the resistance length can be made gentle.

  In addition, the liquid crystal lens of the present invention is characterized in that the above-described lead line and the plurality of annular electrodes are formed on different surfaces via an insulating film.

  In addition, the liquid crystal lens of the present invention is characterized in that the aforementioned annular electrode and the voltage drop resistance electrode are formed on the same surface.

  The liquid crystal lens of the present invention is characterized in that the above-described voltage drop resistance electrode and the lead wire are formed on the same surface.

  In addition, the liquid crystal lens of the present invention is characterized in that the connection between the lead wire and the zonal electrode described above is connected through an opening provided in the insulating film.

  In addition, the liquid crystal lens of the present invention is characterized in that the above-described insulating film is not provided in a region other than the region where the lead wire is provided.

  According to the present invention, there is an effect of reducing lens aberration as well as reducing power consumption of a liquid crystal lens.

  Exemplary embodiments of a liquid crystal lens according to the present invention will be explained below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a pattern electrode in the liquid crystal lens of the present embodiment. 2 and 3 are an upper plan view and a cross-sectional view (A-A 'cross section in FIG. 1) showing a schematic configuration of the liquid crystal lens of the present invention.

  As shown in FIG. 3, the liquid crystal lens 7 of the present invention has a structure in which a liquid crystal layer 14 is sandwiched between two opposing transparent substrates 8 and 9. The material of the transparent substrates 8 and 9 used here is glass or polycarbonate.

  The liquid crystal lens 7 has a pattern electrode 10 shown in FIG. 1 on the surface of the transparent substrate 8. In the drawing, only the pattern electrodes 3a to 3e, the voltage drop resistance electrode 1, and the lead wires 2a and 2c are shown as the pattern electrodes.

  Specifically, as shown in FIG. 1, the pattern electrode 10 is formed of a transparent electrode material, and includes a plurality of annular electrodes 3 a to 3 e having a closed loop annular shape, and the plurality of annular electrodes. The voltage drop resistance electrode 1 for applying a control voltage for driving the liquid crystal layer 14 (see FIG. 3) connected to the ring electrodes 3a to 3e and resistance-divided into the annular electrodes 3a to 3e is provided.

  Further, the voltage drop resistance electrode 1 is partially cut out with a predetermined gap from the outer periphery of the liquid crystal lens effective diameter region 15 (see FIG. 2) formed by the plurality of annular electrodes 3a to 3e. It is formed in a C shape.

  Further, as shown in FIGS. 1 and 3, the plurality of annular electrodes 3 a to 3 e and the voltage drop resistance electrode 1 are connected to the annular electrodes 3 a to 3 e from a predetermined position of the voltage drop resistance electrode 1. The voltage drop resistance electrode 1 and the annular electrodes 3a to 3e are connected to each other by lead wires 2a to 2e provided on different surfaces.

  Further, as shown in FIG. 1, annular electrodes 3a to 3e are arranged at both ends of the C-shaped voltage drop resistance electrode 1 where a part thereof is cut out (locations corresponding to the lead wires 2a and 2e). The control voltage for driving the liquid crystal layer 14 (see FIG. 3) is supplied to the plurality of annular electrodes 3a to 3 by supplying a driving voltage to give the refractive index distribution to the effective diameter area 15 (see FIG. 2) of the liquid crystal lens. It is comprised so that it can apply to each of 3e. The pattern electrode 10 shown in FIG. 1 is formed on the main surface of the transparent substrate 8 shown in FIG. 3, and the surface is provided with an alignment film 12 and then subjected to a rubbing process.

  In the above configuration, as shown in FIG. 3, the lead wires 2 a to 2 e (only the lead wires 2 a and 2 c are shown in the drawing) and the plurality of annular electrodes 3 a to 3 e form the insulating film 4. The annular electrodes 3a to 3e and the voltage drop resistance electrode 1 are formed on the same surface. The lead wires 2 a to 2 e and the annular electrodes 3 a to 3 e are electrically connected through five openings provided at the connection point 5. Similarly, the lead wires 2 a to 2 e and the voltage drop resistance electrode 1 are electrically connected via the five connection points 5. Therefore, in the liquid crystal lens 7 according to the present embodiment, the lead wires 2a to 2e, the ring-shaped electrodes 3a to 3e, and the voltage drop resistance electrode 1 are respectively connected by a total of ten connection points 5.

As shown in FIG. 3, the transparent substrate 9 is formed with a common electrode 11 made of a transparent electrode material. This transparent electrode material is a material having a high transmittance in the wavelength range of light that is expected to have a lens action. In the visible light range, indium tin oxide (hereinafter abbreviated as ITO) or the like is used.

  Similarly, an alignment film 13 for aligning liquid crystals is formed on the surface layer of the common electrode 11. For the alignment film 13, polyimide or the like is often used. The polyimide is rubbed after firing so that the liquid crystal has a pretilt angle.

  In this description, for convenience of explanation, description will be made by showing a configuration example in which the number of annular electrodes 3a to 3e in the pattern electrode 10 shown in FIG. 1 is five. However, the number of annular electrodes is five. It is not limited.

  As shown in FIGS. 1 to 3, the liquid crystal layer 14 in the liquid crystal lens 7 is sealed by a sealing member 16, and the thickness of the liquid crystal layer 14 is kept constant by a spacer member 17. . A flexible printed wiring board (hereinafter abbreviated as FPC) 19 is connected to the electrode extraction portion 18 of the pattern electrode 10 using an anisotropic conductive film, and both ends of the voltage drop resistance electrode 1 are connected via the FPC 19. The lead wires 2a and 2e provided on the ring electrodes are fed, and the control voltage divided by the voltage drop resistance electrode 1 with respect to the ring electrodes 3a to 3e can be applied to the ring electrodes 3a to 3e. It becomes like this. A part of the electrode lead-out portion 18 is insulated from the pattern electrode 10 (see FIG. 1) and connected to the common electrode 11.

  Although it does not specifically limit, the dimension of the liquid crystal lens 7 is shown as an example. The length of one side of the transparent substrates 8 and 9 is about several mm to several tens of mm, for example, 10 mm. However, the transparent substrate 8 provided with the pattern electrode 10 has dimensions excluding the portion of the pattern electrode 10 that covers the electrode extraction portion 18. The thickness of the transparent substrates 8 and 9 is about several hundred μm, for example, 300 μm. The thickness of the liquid crystal layer 14 is about several tens of μm to several tens of μm, for example, 20 μm. The diameter of the effective diameter area 15 of the liquid crystal lens is about several mm, for example, 3 mm.

  Next, the manufacturing method of the liquid crystal lens 7 and the operation of the liquid crystal lens will be described in more detail.

  As shown in FIGS. 1 and 3, the lead lines 2 a to 2 e are first formed on the transparent substrate 8. The lead wires 2a to 2e extend in the radial direction of the annular electrodes 3a to 3e, and have a length that reaches the annular electrodes 3a to 3e from the voltage drop resistor 1 on the outermost periphery.

  In order to form the lead lines 2a to 2e, first, ITO is formed on the transparent substrate 8 using a sputtering method, and a necessary pattern is left using a photolithography process. Next, the insulating film 4 covering the lead lines 2a to 2e formed by the above process is applied by spin coating or the like. Next, the leader line pattern is covered using a photolithography process in the same manner as the leader lines 2 a to 2 e are formed, and an opening is formed at the connection point 5. This opening is for electrical connection between the annular electrodes 3a to 3e and the voltage drop resistance electrode 1 formed in the following process.

  Here, the area from the pattern center of the annular electrode to the inside of the voltage drop resistance electrode 1 or the annular electrode 3e is referred to as a liquid crystal lens effective diameter area 15. In the liquid crystal lens effective diameter area 15, Even if the insulating film 4 shown remains, it does not cause a big problem.

Further, when the transmittance of the insulating film 4 is not 100% in the wavelength range of light expected to have a lens action, the lead lines 2a to 2e and the annular electrodes 3a to 3e are not provided in an overlapping area. The provided insulating film is preferably removed at the same time in the step of forming the opening.

  Next, ITO is formed again on the surface of the insulating film 4 from which the opening provided in the insulating film 4 and a part of the region are removed as necessary. Then, the annular electrodes 3a to 3e and the voltage drop resistance electrode 1 are formed by a photolithography process. Since the opening is already provided in the insulating film 4, the necessary electrical connection is obtained when the ITO film is formed by sputtering. Unlike the annular electrodes 3a to 3e, the voltage drop resistance electrode 1 has a C shape in which a circle is interrupted at one place between the lead wires 2a and 2e. Since the voltage drop resistor electrode 1 formed in this way is formed to have a constant width and film thickness, the resistance value when tapped in the middle should be a value proportional to the length of the electrode. Can do.

  In addition, the voltage drop resistance electrode 1 shown above is cut out at one place because it is necessary to alternately flow current from the lead wire 2a to the lead wire 2e or from the lead wire 2e to the lead wire 2a. is there. This configuration enables AC driving.

  Next, ITO is similarly formed on the transparent substrate 9, and the common electrode 11 is formed by a photolithography process.

  Then, after the alignment films 12 and 13 are formed on the transparent substrates 8 and 9, respectively, a rubbing process is performed, and the transparent substrate 9 and the transparent substrate 8 are disposed facing each other with both electrodes facing inward, and a liquid crystal layer is interposed therebetween. By encapsulating 14, the target liquid crystal lens can be manufactured.

  The lead wire 2a formed by the above-described process realizes electrical connection with both the annular electrode 3a and the voltage drop resistance electrode 1. The lead wire 2b realizes electrical connection with both the annular electrode 3b and the voltage drop resistance electrode 1. Similarly, the lead wire 2c is the ring electrode 3c and the voltage drop resistor electrode 1, the lead wire 2d is the ring electrode 3d and the voltage drop resistor electrode 1, and the lead wire 2e is the ring electrode 3e and the voltage drop resistor. Electrical connection with the electrode 1 is realized.

  By supplying power to the voltage drop resistance electrode 1, it becomes possible to extract an intermediate voltage at the lead line 2d from the lead line 2b existing between the lead line 2a and the lead line 2e.

  For example, when 10 [V] is applied to the lead wire 2a and 2 [V] is applied to the lead wire 2e, if the length of the voltage drop resistance electrode 1 is equally divided by the lead wires 2b to 2d, the lead wire A voltage of 8 [V] is generated in the line 2b, 6 [V] in the lead line 2c, and 4 [V] in the lead line 2d. That is, it is possible to apply a voltage having a considerably high degree of freedom to each of the annular electrodes 3a to 3e depending on the voltage applied to the lead wires 2a and 2e and the connection point position of the lead wires 2b to 2d.

  Assuming that the diameter of the voltage drop resistance electrode 1 is 2 mm, the length is about 6283 μm, and assuming that the position accuracy of the connection point is 1 μm, the minimum resolution of the resistance value is 1/6283, and sufficient resolution is obtained. Can be obtained. When voltage drop resistance electrodes are arranged in the radial direction as in the conventional configuration, the length is 1000 μm for the same effective diameter, so the minimum resolution of the resistance value is about 1/1000. Therefore, it can be seen that the merit of disposing the voltage drop resistance electrode 1 (see FIG. 1) outside the effective diameter area 15 of the liquid crystal lens (see FIG. 2) as in the liquid crystal lens 7 of the present invention is great.

  Next, driving of the liquid crystal lens 7 of the present invention will be described. FIG. 4 shows a change in retardation when an applied voltage is changed to the liquid crystal lens 7.

In this embodiment, since P-type liquid crystal is used as the liquid crystal material, the retardation is reduced when the voltage is high. Here, V is such that the retardation difference due to the following voltages is equalized.
The voltages 1, V2, V3, V4 and V5 are determined. Since each lead-out line 2a to 2e (see FIG. 1) has the lead-out position of the voltage drop resistance electrode 1 determined so as to have an equal resistance between adjacent lead-out lines in this embodiment, the lead-out line 2a and the lead-out line are connected to each other. When voltages V5 and V1 (V5> V1) are respectively applied to the power supply side of the wire 2e, the voltage V4 is applied to the annular electrode 3b via the lead wire 2b, and the voltage V3 is applied to the annular electrode 3c via the lead wire 2c. The voltage V2 is applied to the annular electrode 3d via the lead wire 2d, and the voltage V1 is applied to the annular electrode 3e via the lead wire 2e. At this time, the liquid crystal lens 7 acts as a concave lens by advancing the phase of light passing through the center with respect to polarized light parallel to the alignment direction of the liquid crystal layer 14 and relatively delaying the phase toward the periphery. .

  Conversely, when voltages V1 and V5 (V5> V1) are applied to the power supply sides of the lead wire 2a and the lead wire 2e, respectively, the voltage increases as the zone electrodes 3a to 3e go around the zone electrode formation region. Since the distribution occurs, the phase of the light incident on the liquid crystal lens 7 acts as a convex lens by being delayed in the center from the periphery. By changing the voltage distribution in this way, the refractive index distribution of the liquid crystal lens 7 is changed, so that the liquid crystal lens 7 can be in a convex lens state, a parallel glass state, or a concave lens state.

  Although it does not specifically limit, the dimension and characteristic value of each part of the ring electrode 3a-3e are shown as an example. Although the total number of the annular electrodes 3a to 3e was five in FIG. 1, more, for example, 27, good performance was obtained. The width of the space between adjacent ones of these annular electrodes is, for example, 3 μm. Further, the resistance value of the voltage drop resistance electrode 1 is, for example, 50 kΩ.

  Next, another embodiment will be described with reference to FIGS. 5 and 6 are a top plan view and a cross-sectional view (cross-section B-B ′ in FIG. 5) showing a schematic configuration of the liquid crystal lens.

  As shown in FIG. 5 and FIG. 6, the liquid crystal lens 7 in the present embodiment has the leader lines 2 a to 2 e and the plurality of annular electrodes 3 a to 3 e formed on different surfaces via insulating films, and the leader line. 2a to 2e and the voltage drop resistance electrode 1 are shown as being formed on the same surface.

  In this manner, the lead wires 2a to 2e and the voltage drop resistor electrode 1 are integrally provided on the same surface, thereby establishing conduction between the lead wires 2a to 2e and the voltage drop resistor electrode 1 shown in the previous embodiment. Therefore, the five connection points 5 (see FIG. 1) are not necessary. That is, in the liquid crystal lens shown in the previous embodiment, it is necessary to provide 10 connection points 5, but in the liquid crystal lens shown in this embodiment, 5 points are sufficient. The securing of the electrical connection in the opening provided in the insulating film 4 for providing the connection point 5 is highly likely to reduce the manufacturing yield in view of the reliability of the liquid crystal lens. Similarly, this problem can be suppressed as much as possible by reducing the number of connection points 5 as much as possible. This problem becomes more prominent as the size of the liquid crystal lens 7 is reduced and the diameter of the opening is reduced.

  In addition, according to the present embodiment, the lead wires 2a to 2e and the voltage drop resistor electrode 1 can be formed by a simultaneous patterning process, so that the positioning of the voltage drop resistor electrode 1 and the lead wires 2a to 2e can be performed. No longer needed. Therefore, in the structure of the liquid crystal lens 7 shown in the present embodiment, the resistance setting accuracy determined by the positions of the voltage drop resistance electrode 1 and the lead lines 2a to 2e is further improved as compared with the previous embodiment.

  The configuration of the liquid crystal lens shown in the previous embodiment is the same as that of the previous embodiment except that the voltage drop resistance electrode 1 and the lead wires 2a to 2e are integrated. To do. In this way, even if the voltage drop resistance electrode 1 and the lead wires 2a to 2e are integrally formed, the voltage drop resistance electrode 1 and the lead wires 2a to 2e function in the same manner as a variable focus lens, thereby enabling precise voltage application to each of the annular electrodes 3a to 3e. .

  In the above, this invention is not restricted to each embodiment mentioned above, A various change is possible. For example, values such as dimensions, characteristic values, and time described in the embodiments are examples, and the present invention is not limited to these values. The type of liquid crystal is not limited to nematic liquid crystal.

  In addition, liquid crystal alignment methods include homogeneous (horizontal) alignment, homeotropic (vertical) alignment, hybrid alignment, twist alignment, or bend alignment, and these alignments may be used.

  As described above, the liquid crystal lens according to the present invention is useful for a device having a variable focus function. In particular, the liquid crystal lens is mounted on a camera, a digital camera, a movie camera, a camera unit of a camera-equipped mobile phone, a vehicle, etc. This is suitable for a camera used for a monitor, a camera part of an endoscope, and a function for changing the degree of a lens.

It is a figure which shows the electrode structure of the liquid crystal lens of this invention. It is a front view which shows the structure of the liquid crystal lens of this invention. It is sectional drawing which shows the structure of the liquid crystal lens of this invention. It is a figure explaining the relationship between the voltage applied to a liquid crystal, and retardation. It is a figure which shows the other electrode structure of the liquid crystal lens of this invention. It is sectional drawing which shows the other structure of the liquid crystal lens of this invention. It is a figure explaining the electrode structure of the liquid crystal lens of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage drop resistance electrode 2a-2e Leader 3a-3e Ring zone electrode 4 Insulating film 5 Connection point 7 Liquid crystal lens 8, 9 Transparent substrate 10 Pattern electrode 11 Common electrode 12, 13 Orientation film 14 Liquid crystal layer 15 Liquid crystal lens effective diameter area 16 Seal member 17 Spacer member 18 Electrode extraction part 19 Flexible printed wiring board (FPC)

Claims (6)

A liquid crystal layer sandwiched between first and second transparent substrates;
A common electrode formed on the liquid crystal layer side of the first transparent substrate;
A plurality of annular electrodes formed on the liquid crystal layer side of the second transparent substrate;
A voltage drop resistance electrode connected to the plurality of ring electrodes for applying a control voltage resistance-divided to each of the ring electrodes; and the voltage drop resistance electrode is formed by the plurality of ring electrodes Each annular zone having a predetermined gap from the outermost peripheral portion of the lens effective diameter region to be cut out and provided in a circular shape with a part cut away from the predetermined position of the annular electrode via a lead wire Connected to the electrode,
The control voltage can be applied to each of the plurality of annular electrodes by supplying a drive voltage to both ends of the voltage drop resistor electrode formed by cutting out part of the voltage drop resistor electrode. LCD lens. The liquid crystal lens according to claim 1, wherein the lead wire and the plurality of annular electrodes are formed on different surfaces with an insulating film interposed therebetween. The liquid crystal lens according to claim 2, wherein the annular electrode and the voltage drop resistance electrode are formed on the same surface. The liquid crystal lens according to claim 2, wherein the voltage drop resistance electrode and the lead wire are formed on the same surface. The liquid crystal lens according to any one of claims 2 to 4, wherein the lead wire and the annular electrode are connected through an opening provided in the insulating film. The liquid crystal lens according to claim 2, wherein the insulating film is provided only in a region where the lead wire is provided.

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