Liquid crystal lens with curved surface bottom electrode and bottom electrode design method

Abstract

The invention discloses a liquid crystal lens with a curved surface bottom electrode and a bottom electrode design method, and relates to the technical field of liquid crystal lenses. On the basis of a conventional high-resistance layer type lens, a bottom electrode is designed to be a curved surface, a relational expression between an electric field intensity z-direction component and an effective refractive index of a liquid crystal layer is obtained through simulation, and the electric field intensity z-direction component corresponding to an x coordinate can be obtained by combining an ideal effective refractive index distribution curve; after the potential of the high-resistance layer corresponding to the x coordinate in the simulation model is extracted, the distance distribution between the bottom electrode and the high-resistance layer can be calculated, so that the liquid crystal lens closer to the ideal lens effective refractive index distribution condition is designed; spatial electric field intensity distribution between the high-resistance layer and the bottom electrode of the high-resistance layer type liquid crystal lens is adjusted by changing the shape of the bottom electrode, so that the effective refractive index of the liquid crystal lens is closer to the effective refractive index distribution condition of an ideal lens, and the imaging quality of the liquid crystal lens is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid crystal lens, and particularly to a liquid crystal lens with a curved bottom electrode and a bottom electrode design method. BACKGROUND

[0002] With the continuous development of social economy, lenses play an increasingly important role in the fields of medicine, laser, and film and television. People have put forward new requirements for the imaging quality, portability, and variable focus of lenses. Among them, the variable focus lens can adapt to the scene with changing lens focal length compared with the traditional non-variable focus lens, and therefore has great research value.

[0003] The high-resistance layer type liquid crystal lens is a variable focus lens with broad market prospects. It drives the orientation of liquid crystal molecules to gradually change to achieve refractive index adaptation through the high-resistance layer to control the gradient electric field. The high-resistance layer type liquid crystal lens has no mechanical structure, is electrically controllable in focus / adjustment plane, and has the advantages of compactness, fast response, stable imaging, etc. However, the voltage application range of the high-resistance layer type liquid crystal lens needs to be in the near-linear region of the optical path difference (optical path difference, optical path difference) characteristic curve of the liquid crystal material. If you want to improve the optical power of the lens, the voltage applied to the liquid crystal lens will cover the nonlinear region of the optical path difference characteristic curve of the liquid crystal material. The effective refractive index distribution curve of the liquid crystal lens will deviate from the ideal quadratic parabola, causing the imaging quality of the lens to decline. SUMMARY

[0004] The present application provides a liquid crystal lens with a curved bottom electrode and a bottom electrode design method, which aims to make the effective refractive index distribution of the high-resistance layer type liquid crystal lens closer to the effective refractive index distribution of the ideal lens, thereby improving the imaging quality of the liquid crystal lens.

[0005] The liquid crystal lens with a curved bottom electrode provided by the present application comprises:

[0006] A first transparent substrate and a second transparent substrate are oppositely arranged;

[0007] A liquid crystal layer is located between the first transparent substrate and the second transparent substrate;

[0008] A first alignment layer is located on one side of the liquid crystal layer close to the first transparent substrate; and a second alignment layer is located on one side of the liquid crystal layer close to the second transparent substrate;

[0009] A high-resistance layer is arranged between the first alignment layer and the first transparent substrate;

[0010] A control electrode is arranged between the first alignment layer and the first transparent substrate, and is connected to the outer edge of the high-resistance layer.​

[0011] a bottom electrode disposed between the second alignment layer and the second transparent substrate; the bottom electrode has a curved surface shape, and a distance between the bottom electrode and the high-resistance layer is d(x), which is configured as:

[0012] ;

[0013] wherein x represents a coordinate axis along a diameter direction of the liquid crystal lens, U HRL (x) represents a potential of the high-resistance layer corresponding to the x coordinate, represents a z-direction component of an electric field intensity corresponding to the x coordinate; wherein, the z-direction component of the electric field intensity is determined according to a relationship formula of and an effective refractive index of the liquid crystal layer ; the effective refractive index of the liquid crystal layer is determined according to a preset ideal effective refractive index distribution curve;

[0014] a filling layer disposed between the bottom electrode and the second alignment layer and between the bottom electrode and the second transparent substrate.

[0015] Optionally, the ideal effective refractive index distribution curve is a quadratic parabola.

[0016] Optionally, the ideal effective refractive index distribution curve is expressed as:

[0017] ;

[0018] wherein, is an effective refractive index at the center of the liquid crystal lens, R is a radius of the liquid crystal lens, is a thickness of the liquid crystal layer, is a focal length of the liquid crystal lens.

[0019] Optionally, the liquid crystal lens with the curved bottom electrode further comprises a driving circuit; the driving circuit is electrically connected with the control electrode and the bottom electrode, and is configured to apply an alternating voltage with a preset effective value and a preset frequency between the high-resistance layer and the bottom electrode.

[0020] Optionally, the material of the bottom electrode is a transparent oxide conductive film or a transparent carbon-based conductive film.

[0021] Optionally, the material of the first alignment layer and the second alignment layer is polyimide or modified polyimide.

[0022] Optionally, the filling layer is a transparent polymer material.

[0023] ​The application provides a design method of a bottom electrode of a liquid crystal lens.

[0024] S1, constructing a simulation model of the liquid crystal lens, obtaining a z-direction component of an electric field intensity based on thickness of a liquid crystal layer and liquid crystal material through simulation and a relationship formula of an effective refractive index of the liquid crystal layer ; ;

[0025] S2, obtaining an ideal effective refractive index distribution curve corresponding to the liquid crystal lens of a target optical power;

[0026] S3, obtaining a z-direction component of an electric field intensity corresponding to an x coordinate based on the relationship formula and the ideal effective refractive index distribution curve ;

[0027] S4, extracting a high-resistance layer potential U HRL (x) corresponding to the x coordinate in the simulation model, and calculating a distance d(x) between the bottom electrode and the high-resistance layer according to the following formula:

[0028] ;

[0029] S5, designing a shape of the bottom electrode according to the distance d(x) between the bottom electrode and the high-resistance layer.

[0030] Optionally, the ideal effective refractive index distribution curve is a quadratic parabola.

[0031] Optionally, the ideal effective refractive index distribution curve is expressed as the following formula:

[0032] ;

[0033] In the formula, n is the effective refractive index of the center of the liquid crystal lens, R is the radius of the liquid crystal lens, is the thickness of the liquid crystal layer, is the focal length of the liquid crystal lens.

[0034] The application has the following beneficial effects:

[0035] The application adjusts the distance between the high-resistance layer and the bottom electrode by changing the shape of the bottom electrode, and then adjusts the spatial electric field intensity distribution between the high-resistance layer and the bottom electrode, so that the effective refractive index of the liquid crystal lens is closer to the effective refractive index distribution of an ideal lens, thereby improving the imaging quality of the liquid crystal lens. BRIEF DESCRIPTION OF DRAWINGS

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of some embodiments of the liquid crystal lens with a curved bottom electrode of the present invention;

[0038] Figure 2 This is a schematic diagram of the structure of a conventional high-resistivity liquid crystal lens;

[0039] Figure 3 This is a schematic diagram of the equivalent circuit of a conventional high-resistivity liquid crystal lens.

[0040] Figure 4 This is a graph showing the change of electric field intensity with the position of the liquid crystal lens in the x-direction.

[0041] Figure 5 for Figure 4 The curve showing the change of the effective refractive index of the liquid crystal lens with position in the x-direction;

[0042] Figure 6 U-OPD for liquid crystal materials LC Characteristic curve diagram;

[0043] Figure 7 The optical path difference (OPD) of the liquid crystal lens with a curved bottom electrode in Embodiment 1 of the present invention, compared with that of an ideal lens and a conventional high-resistivity liquid crystal lens, is shown. LCL (x) Curve showing the change in position along the x-direction.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1. First transparent substrate; 2. Second transparent substrate; 3. Liquid crystal layer; 4. First alignment layer; 5. Second alignment layer; 6. High resistivity layer; 7. Control electrode; 8. Bottom electrode; 9. Filler layer. Detailed Implementation

[0046] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0047] SeeFigure 2 The structure of the conventional high-resistance layer type liquid crystal lens from top to bottom is first transparent substrate 1, control electrode 7 and high-resistance layer 6, first alignment layer 4, liquid crystal layer 3, second alignment layer 5, bottom electrode 8, and second transparent substrate 2; wherein the outer edge of the control electrode 7 and the high-resistance layer 6 are connected, used for connecting the high-resistance layer 6 to the driving voltage, and at the same time, forming an electric field loop with the bottom electrode 8; the high-resistance layer 6 is the core electric field control layer, which converts the input driving voltage into a continuous electric field gradient from the center to the edge by using high resistivity to form a gradient voltage drop; the first alignment layer 4 and the second alignment layer 5 provide a pre-tilt angle through a rubbing process, so that the initial orientation of the liquid crystal molecules is consistent, and at the same time, the interface compatibility between the liquid crystal layer 3 and the electrode and the high-resistance layer 6 is matched; the liquid crystal layer 3 contains liquid crystal molecules, the orientation of the liquid crystal molecules changes with the external electric field, and in turn changes the refractive index of the liquid crystal layer 3, which is a dynamic optical medium for realizing the lens effect.

[0048] The equivalent circuit of the high-resistance layer type liquid crystal lens is shown in Figure 3 The liquid crystal lens can be divided into N equal parts along the x-axis direction from the center to the edge, and according to the circuit knowledge, the potential on both sides of the capacitor decreases from the edge to the center of the liquid crystal lens, which is equivalent to the z-axis direction electric field strength of the liquid crystal layer decreasing from the edge to the center of the lens, as shown in Figure 4 ; assuming that the greater the electric field strength of the liquid crystal material used by the lens, the smaller the effective refractive index, the gradual distribution of the electric field strength drives the effective refractive index of the lens to decrease along the center to the edge of the lens, that is, the quadratic parabola distribution as shown in Figure 5 .

[0049] Figure 6 The U-OPD characteristic curve of a typical liquid crystal material is shown in LC ; the voltage range applied to the high-resistance layer type liquid crystal lens is in the near-linear region of the U-OPD characteristic curve of the liquid crystal material, at this time, the effective refractive index of the lens is approximately a quadratic parabola distribution; if the optical power of the liquid crystal lens is to be improved, the voltage range applied to the liquid crystal lens will cover the nonlinear region of the U-OPD characteristic curve of the liquid crystal material, so that the effective refractive index distribution generated by the liquid crystal lens deviates from the ideal quadratic parabola distribution, causing the imaging quality of the liquid crystal lens to decrease. LC LC

[0050] In order to improve the imaging quality of the liquid crystal lens, on the basis of the conventional high-resistance layer type liquid crystal lens, the embodiment of the present application proposes a liquid crystal lens with a curved bottom electrode.

[0051] Referring to Figure 1 ​​The liquid crystal lens with a curved bottom electrode has the following structure from top to bottom: first transparent substrate 1, control electrode 7 and high resistive layer 6, first alignment layer 4, liquid crystal layer 3, second alignment layer 5, bottom electrode 8 and filling layer 9, and second transparent substrate 2.

[0052] Among them, the control electrode 7 is connected to the outer edge of the high-resistivity layer 6 to provide a driving voltage to the high-resistivity layer 6, and at the same time forms an electric field loop with the bottom electrode 8; the high-resistivity layer 6 is the core electric field control layer, which uses high resistivity to form a gradient voltage drop, and converts the input driving voltage into a continuous electric field gradient from the center to the edge; the first alignment layer 4 and the second alignment layer 5 provide a pretilt angle through a friction process to make the initial orientation of the liquid crystal molecules consistent, and at the same time match the interface compatibility between the liquid crystal layer 3 and the electrode and the high-resistivity layer 6; the liquid crystal layer 3 contains liquid crystal molecules, and the orientation of the liquid crystal molecules changes with the external electric field, thereby changing the refractive index of the liquid crystal layer 3, which is a dynamic optical medium to achieve the lens effect; the filling layer 9 is disposed between the bottom electrode 8 and the second alignment layer 5 and between the bottom electrode 8 and the second transparent substrate 2.

[0053] In this embodiment of the invention, the high-resistivity layer is planar, and the bottom electrode is curved. Figure 1 The surface shape in the example is only for illustration purposes. Let d(x) be the distance between the bottom electrode and the high-resistivity layer, and d(x) be configured as follows:

[0054] ;

[0055] In the formula, x represents the coordinate axis along the diameter direction of the liquid crystal lens, and U HRL (x) represents the high-resistivity layer potential corresponding to the x-coordinate. This represents the z-direction component of the electric field intensity corresponding to the x-coordinate; where, Based on the z-direction component of the electric field intensity and the effective refractive index of the liquid crystal layer relational formula Determined; Effective refractive index of the liquid crystal layer Determined based on the preset ideal effective refractive index distribution curve.

[0056] Specifically, the distance d(x) between the bottom electrode and the high-resistivity layer is designed through the following steps:

[0057] S1. Construct a simulation model of the liquid crystal lens. Based on the thickness of the liquid crystal layer and the liquid crystal material, obtain the z-direction component of the electric field intensity through simulation. With the effective refractive index of the liquid crystal layer relational formula ;

[0058] S2, Obtain the ideal effective refractive index distribution curve corresponding to the liquid crystal lens with the target optical power;

[0059] S3, based on the relationship and the ideal effective refractive index distribution curve, the x coordinate corresponding to the electric field strength z direction component ;

[0060] S4, extracting the high resistance layer potential U of the x coordinate in the simulation model HRL (x), the distance d(x) between the bottom electrode and the high resistance layer is calculated according to the following formula:

[0061] ;

[0062] S5, the shape of the bottom electrode is designed according to the distance d(x) between the bottom electrode and the high resistance layer.

[0063] In the embodiment of the application, the ideal effective refractive index distribution curve is a quadratic parabola.

[0064] The embodiment of the application adjusts the spatial electric field strength distribution between the high resistance layer and the bottom electrode of the high resistance layer type liquid crystal lens by changing the shape of the bottom electrode, so that the effective refractive index of the liquid crystal lens is closer to the effective refractive index distribution of the ideal lens, thereby improving the imaging quality of the liquid crystal lens.

[0065] In some embodiments, the ideal effective refractive index distribution curve is expressed as follows:

[0066] ;

[0067] In the formula, is the effective refractive index of the center of the liquid crystal lens, R is the radius of the liquid crystal lens, is the thickness of the liquid crystal layer, is the focal length of the liquid crystal lens.

[0068] In some embodiments, the liquid crystal lens with a curved bottom electrode further comprises a driving circuit; the driving circuit is electrically connected with the driving electrode and the bottom electrode, and is used to apply an alternating voltage with a preset effective value and a preset frequency between the high resistance layer and the bottom electrode, so that the liquid crystal lens stably presents the preset effective refractive index distribution.

[0069] In some embodiments, the material of the bottom electrode is a transparent oxide conductive film (such as ITO, IZO, AZO, etc.) or a transparent carbon-based conductive film (such as graphene, carbon nanotube, etc.). The transparent oxide conductive film and the transparent carbon-based conductive film have high light transmittance, high conductivity, and especially have the compatibility of curved surface processing. The curved surface profile can be prepared by photolithography, etching, 3D printing, etc. The processing technology is mature, and the liquid crystal lens with a curved bottom electrode has the possibility of mass production (compared with the high resistance layer, which is usually a brittle material such as Ta2O5 or ZrO2, and it is difficult to process the curved structure. In addition, the liquid crystal lens has high requirements for the thickness uniformity and flatness of the high resistance layer, which further increases the difficulty of processing the curved structure).

[0070] In some embodiments, the material of the first alignment layer and the second alignment layer is polyimide (PI) or modified polyimide. Polyimide has good flexibility, low dielectric loss, and dielectric constant matching the liquid crystal lens structure, and is an excellent alignment layer material that can improve the stability of the liquid crystal lens.

[0071] In some embodiments, the filling layer is a transparent polymer material. The polymer material needs to meet the requirements of high light transmittance, insulation, curved surface adaptability, and layer compatibility. The optional transparent polymer material includes but is not limited to polydimethylsiloxane, cyclic olefin copolymer, polymethyl methacrylate, etc.

[0072] Based on the above embodiments, in order to more clearly illustrate the implementation manner and beneficial effects of the technical scheme of the present application, the present application further proposes the following specific embodiments. It should be noted that the following specific embodiments are only exemplary in nature and do not limit the scope of protection of the present application in any form.

[0073] Embodiment 1

[0074] In this embodiment, the distance between the high resistance layer and the bottom electrode is changed by the curved surface of the bottom electrode, and then the electric field matching the ideal effective refractive index distribution curve between the high resistance layer and the bottom electrode is modulated.

[0075] Step 1, construct a simulation model of the liquid crystal lens. The simulation model of the liquid crystal lens is shown in FIG. 1. Figure 2 The simulation parameters used are shown in Table 1.

[0076] Table 1 Simulation parameters of the high resistance layer type liquid crystal lens

[0077]

[0078] Select the thickness of the liquid crystal layer At this time, the relationship expression between the z-direction component of the electric field intensity and the effective refractive index is:

[0079]

[0080]

[0081] ;

[0082] Step 2, the liquid crystal molecule director simulation under the electric field of the simulation model, the driving voltage parameters of the liquid crystal lens are: effective voltage V rms = 3V, frequency 14kHz; the simulation gets the effective refractive index n p of the edge of the liquid crystal lens is 1.582, the central effective refractive index n c is 1.706, at this time the optical power of the liquid crystal lens is 1.99m -1 ; the following formula is used to calculate the ideal effective refractive index distribution curve with x coordinate:

[0083] ;

[0084] In the formula, is the effective refractive index at the center of the liquid crystal lens, R is the radius of the liquid crystal lens, is the thickness of the liquid crystal layer, is the focal length of the liquid crystal lens.

[0085] Step 3, combining the relationship expression of the z direction component of the electric field intensity and the effective refractive index obtained in step 1, the z direction component of the electric field intensity corresponding to x coordinate can be obtained.

[0086] Step 4, extract the high resistance layer potential U HRL (x) corresponding to x coordinate in the simulation model:

[0087] ;

[0088] According to the following formula, the distance d(x) between the bottom electrode and the high resistance layer can be calculated:

[0089] ;

[0090] According to the relationship between d(x) and x calculated, the specific curved surface shape of the bottom electrode can be designed, and then the target liquid crystal lens is designed.

[0091] Further, for the application scenario of large optical power of the liquid crystal lens, the embodiment designs a liquid crystal lens with a curved bottom electrode with an optical power of 2.59m -1 , and compares it with an ideal liquid crystal lens with the same optical power of 2.59m -1 , and the optical path difference OPDLCL (x) the distribution is compared; wherein, OPD LCL (x) the relationship with the effective refractive index is as follows:

[0092] ;

[0093] wherein, is the effective refractive index of the lens edge.

[0094] By Figure 7 the optical path difference OPD LCL (x) The distribution curve simulation result can know that compared with the conventional high resistance layer type liquid crystal lens, the optical path difference distribution of the liquid crystal lens with the curved bottom electrode obtained by optimization is closer to the quadratic parabola of the ideal liquid crystal lens, which indicates that the liquid crystal lens after optimization can realize better imaging quality.

[0095] From the above embodiments, it can be known that the application adjusts the spatial electric field intensity distribution between the high resistance layer and the bottom electrode of the high resistance layer type liquid crystal lens by changing the shape of the bottom electrode, so that the effective refractive index of the liquid crystal lens is closer to the effective refractive index distribution of the ideal lens, thereby improving the imaging quality of the liquid crystal lens; in addition, the curved surface processing of the bottom electrode is compatible with the existing mature electrode material curved surface processing process, so that the liquid crystal lens with the curved bottom electrode has the mass production feasibility.

[0096] The above-mentioned embodiments are only used to illustrate the technical solutions of the present application, but not limit them; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A liquid crystal lens having a curved bottom electrode, characterized by, The application relates to a liquid crystal lens, comprising: a first transparent substrate and a second transparent substrate arranged oppositely; a liquid crystal layer between the first transparent substrate and the second transparent substrate; a first alignment layer on the side of the liquid crystal layer close to the first transparent substrate; a second alignment layer on the side of the liquid crystal layer close to the second transparent substrate; a high-resistance layer between the first alignment layer and the first transparent substrate; a control electrode between the first alignment layer and the first transparent substrate and connected to the outer edge of the high-resistance layer; a bottom electrode between the second alignment layer and the second transparent substrate; the bottom electrode is in a curved shape, and the distance between the bottom electrode and the high-resistance layer is d(x), which is configured as: ； In the formula, x represents the coordinate axis along the diameter direction of the liquid crystal lens, and U HRL (x) represents the high-resistivity layer potential corresponding to the x-coordinate. This represents the z-direction component of the electric field intensity corresponding to the x-coordinate; where, Based on the z-direction component of the electric field intensity With the effective refractive index of the liquid crystal layer relational formula Determined; Effective refractive index of the liquid crystal layer Determined based on the preset ideal effective refractive index distribution curve; a filling layer between the bottom electrode and the second alignment layer and between the bottom electrode and the second transparent substrate.

2. The liquid crystal lens having a curved bottom electrode according to claim 1, characterized by The ideal effective refractive index distribution curve is a quadratic parabola.

3. The liquid crystal lens having a curved bottom electrode according to claim 1, characterized by, The ideal effective refractive index distribution curve is expressed as: ； wherein n is the effective refractive index of the center of the liquid crystal lens, R is the radius of the liquid crystal lens, d is the thickness of the liquid crystal layer, f is the focal length of the liquid crystal lens.

4. The liquid crystal lens having a curved bottom electrode according to claim 1, characterized by, The application further comprises a driving circuit; the driving circuit is electrically connected to the control electrode and the bottom electrode, and is used for applying an alternating voltage with a preset effective value and a preset frequency between the high-resistance layer and the bottom electrode.

5. The liquid crystal lens having a curved bottom electrode according to claim 1, characterized by, The material of the bottom electrode is a transparent oxide conductive film or a transparent carbon-based conductive film.

6. The liquid crystal lens having a curved bottom electrode according to claim 1, wherein, The material of the first alignment layer and the second alignment layer is polyimide or modified polyimide.

7. The liquid crystal lens having a curved bottom electrode according to claim 1, wherein, The filling layer is made of a transparent polymer material.

8. A method of designing a bottom electrode of a liquid crystal lens, characterized by, The application further comprises the following steps: S1, construct a simulation model of the liquid crystal lens, based on the thickness of the liquid crystal layer and the liquid crystal material, obtain the z-direction component of the electric field intensity through simulation and the effective refractive index of the liquid crystal layer relationship ; S2, obtaining an ideal effective refractive index distribution curve corresponding to a liquid crystal lens with a target optical power; S3, based on the relationship and the ideal effective refractive index distribution curve, the x coordinate corresponding to the electric field strength z direction component ; S4, extracting the high-resistance layer potential U corresponding to the x coordinate in the simulation model HRL (x), calculating the distance d(x) between the bottom electrode and the high-resistance layer according to the following formula: ； S5, designing the shape of the bottom electrode according to the distance d(x) between the bottom electrode and the high-resistance layer.

9. The method of designing a bottom electrode of a liquid crystal lens according to claim 8, wherein, The ideal effective refractive index distribution curve is a quadratic parabola.

10. The method of designing a bottom electrode of a liquid crystal lens according to claim 8, wherein, The ideal effective refractive index distribution curve is expressed as: ； wherein n is the effective refractive index of the center of the liquid crystal lens, R is the radius of the liquid crystal lens, d is the thickness of the liquid crystal layer, f is the focal length of the liquid crystal lens.

Images