KR101886792B1 - Bi-focal lens using reactive mesogen - Google Patents

Abstract

The present invention relates to a bifocal lens. Wherein the bifocal lens comprises: a transparent substrate having a flat surface; An alignment layer oriented in a single direction and formed on the transparent substrate; And a lens layer formed on the alignment layer and having a birefringent photo-curable liquid crystal polymer material oriented in a single direction by the alignment layer and having one surface in contact with the air layer having a concave lens shape or a convex lens shape, , The lens layer has a normal refractive index (n _o ) and an extraordinary refractive index (n _e ), and the lens structure has a refractive index n _p different from the normal refractive index and the extraordinary refractive index for the lens layer And a refractive index difference at an interface between the lens structure and the lens layer is generated in accordance with the polarization of the incident light and two focal distances are determined by the refractive index difference at the interface.

Description

The present invention relates to a bi-focal lens using a liquid crystalline polymer,

The present invention relates to a bifocal lens, and more particularly, to a bifocal lens using a liquid crystal polymer configured to change a focal distance according to a polarization direction of incident light.

2. Description of the Related Art [0002] Recently, as technologies for three-dimensional display devices and the like have been variously studied, various lens technologies have been proposed in which driving is determined according to incident polarized light.

1 is a cross-sectional view and a conceptual view illustrating a conventional gradient index (GRIN) lens using an electric field distribution. FIG. 1 (a) is a graphical representation of the composition of the present invention as described in H. Ren, et al , Opt. Express, 14, 11292 (2006), and FIG. 10B is a conceptual view of the GRIN lens using the electric field distribution shown in Y.-C. Chang, et al ., Opt. Expression, 22, 2714 (2014).

Referring to FIG. 1, the GRIN Lens technology using an electric field distribution is a technique for causing an electric field applied to the liquid crystal in the upper and lower directions to be spatially varied in a liquid crystal cell (LC cell), thereby exhibiting a GRIN lens refractive index profile for specific polarized light. The GRIN Lens refractive index profile means that the refractive index profile is formed spatially in the x-axis direction with a low-high-low profile. If the GRIN lens refractive index profile is used, the focal plane can be formed like a convex lens even if the object is flat.

1 (a) shows a case in which the electric field applied to the liquid crystal layer is adjusted by realizing the space between the upper and lower ITO electrodes to be different in the x-axis direction. If the magnitude of the electric field applied to the liquid crystal layer is represented by a simple expression, E _a = V _a / d. Here, E _a is the magnitude of the electric field, V _a is the magnitude of the applied voltage, and d is the distance between the electrode and the electrode. Even if the voltages applied to the upper and lower electrodes are the same, as the distance between the electrodes is changed, the magnitude of the electric field applied in the z-axis direction changes along the x-axis direction, and as a result, the GRIN lens refractive index profile can be derived.

In FIG. 1 (b), a fringe-field is formed when voltage is applied to upper and lower portions by patterning the upper electrode. Vector decomposition of the formed fringe-field results in a change in the magnitude of the electric field applied in the z-axis direction along the x-axis direction, and as a result, the GRIN lens refractive index profile can be derived.

The GRIN lens technology using the above electric field distribution has an advantage of compatibility with the conventional LCD process. However, it has various disadvantages in terms of operation. First, the cell gap of the liquid crystal device must be enlarged to have a short focal length, and accordingly, the driving voltage increases and the response speed is slowed down. Secondly, a fringe-field is not formed directly above the patterned electrode, resulting in a dead-zone, resulting in a drawback that the fill-factor is reduced.

Therefore, the GRIN lens using the electric field distribution can have a continuous variable focus characteristic according to the voltage applied to the liquid crystal element from the infinity focal distance (2D mode) to a specific focal distance. However, since the response speed is about 50 ms or more and the response speed is slow, it has technical limitations that are difficult to apply to the time division technique.

2 is a schematic view showing a GRIN lens applying the conventional lens structure, Y. Choi, et al, Opt . Mater., 21, 643 (2002), which is incorporated herein by reference in its entirety.

Referring to FIG. 2, a GRIN lens technology using a lens structure has a structure in which liquid crystals of a liquid crystal element are oriented on a lens structure. As the distribution of the liquid crystal varies depending on the voltage value applied to the upper and lower electrodes, the effective refractive index value of the lens having the above-described structure varies for specific polarized light such as the x-axis polarized light of FIG. 2, The refractive index difference between the layers is variable, and a variable focus can be realized.

The GRIN lens technology using the above-described lens structure has continuous variable focus characteristics from a concave lens to a convex lens having a specific focal length according to the voltage applied to the liquid crystal element. However, because of the isotropic lens structure formed between the upper and lower electrodes for switching the liquid crystal, the driving voltage increases, and the response speed is slowed down. Accordingly, it is difficult to apply to the time division technique.

FIG. 3 is a structural view illustrating a polarization-dependent GRIN lens technology using a liquid crystal polymer according to the related art. FIG. 3 shows a polarization-dependent GRIN lens technology using a liquid crystal polymer disclosed in GJ Woodgate, et al , SID03 Digest, Fig.

Referring to FIG. 3, a polarization-dependent GRIN lens technology using a liquid crystal polymer is a structure in which a liquid crystal polymer (Reactive Mesogen (RM)) is oriented in a lens structure and actively operates according to the polarization of incident light. Generally, RM has an extraordinary refractive index ( n _e ) in the major axis direction and an ordinary refractive index ( n ₀ ) in the uniaxial direction, and has a birefringence according to the polarization direction of incident light. 3A, when the polarization direction of light incident as linearly polarized light coincides with the minor axis direction of RM, the refractive index of RM with respect to the linearly polarized light becomes n ₀ , which is the refractive index n of isotropic polymer _The lens function disappears in accordance with _p . As shown in FIG. 3 (b), when the polarization direction of incident light coincides with the long axis direction of RM, the refractive index of RM with respect to the linearly polarized light is n _e Which is inconsistent with the refractive index n _p of the isotropic polymer and thus acts as a lens.

Further, in the polarization dependence type GRIN lens using the above-mentioned liquid crystal polymer, since the polarization switching part and the polarization dependent type lens part exist separately, they can have the same driving voltage and switching speed as the conventional liquid crystal device. The conventional polarization-dependent GRIN lens technology using a liquid crystalline polymer has a refractive index n _p of the lens structure having n _o and an isotropic phase of RM And the infinite focal length state in which the lens is operated as a convex lens having a specific focal length or does not operate as a lens is switched for the two polarization states that are variably incident.

Korean Patent Laid-Open Publication No. 10-2015-0032231 Korean Patent Publication No. 10-2015-0084631

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems described above and provide a bifocal lens having two different focal lengths according to the polarization of incident light using a photo-curable liquid crystal polymer.

Another object of the present invention is to provide a method for manufacturing a bifocal lens using a photo-curable liquid crystal polymer.

According to a first aspect of the present invention, there is provided a bifocal lens comprising: a transparent substrate; An alignment layer oriented in a single direction and formed on the transparent substrate; And a lens layer formed on the alignment layer and having a lens shape in which a photo-curable liquid crystal polymer material having birefringence is oriented in a single direction by the alignment layer and one surface of the lens layer is in contact with the air layer, the ordinary ray refraction index (n _o) and extraordinary refractive index (n _e) for having, ordinary ray refraction index and the extraordinary refractive index of the lens layer has a refractive index (n _air) of the air layer and different from each other, according to the incident light polarization air layer and Refractive index difference occurs at the interface of the lens layer and has two focal lengths determined by the refractive index difference at the interface.

In the bifocal lens according to the first aspect, it is preferable that one surface of the lens layer which abuts the air layer has a convex lens shape or a concave lens shape.

A bifocal lens according to a second aspect of the present invention includes: a substrate having a flat surface; A reflective layer formed on the substrate; An alignment layer oriented in a single direction and formed on the reflective layer; And a lens layer formed on the alignment layer and having a lens shape in which a photo-curable liquid crystal polymer material having birefringence is oriented in a single direction by the alignment layer and one surface of the lens layer is in contact with the air layer, the ordinary ray refraction index (n _o) and extraordinary refractive index (n _e) for having, ordinary ray refraction index and the extraordinary refractive index of the lens layer has a refractive index (n _air) of the air layer and different from each other, according to the incident light polarization air layer and Refractive index difference occurs at the interface of the lens layer and has two focal lengths determined by the refractive index difference at the interface.

In the above-described bifocal lens according to the second aspect, one surface of the lens layer which abuts the air layer is formed into a convex lens shape or a concave lens shape.

A method for manufacturing a bifocal lens according to a third aspect of the present invention includes the steps of: (a) depositing an isotropic polymer material on a first substrate and imprinting a stamp having a lens structure to produce a lens structure having a reversed phase structure of the lens step; (b) forming a first alignment layer on the upper surface of the lens structure to complete a lower substrate; (c) forming a second alignment layer on the transparent substrate to complete an upper substrate; (d) applying a photocurable liquid crystalline polymeric material on an alignment layer of the lower substrate, covering the upper substrate with a laminating material, and then curing the photocured liquid crystalline polymeric material layer; And (e) picking up the upper substrate coupled with the solidified photo-curable liquid crystal polymer layer from the lower substrate, wherein one side of the photo-curable liquid crystal polymer layer exposed in the air layer has a lens shape.

In the above-described method for manufacturing a bifocal lens according to the third aspect, it is preferable that one side of the photo-curable liquid crystal polymer layer exposed to the air layer has a concave lens shape or a convex lens shape.

In the method of manufacturing a bifocal lens according to the third aspect, in the step (b), the isotropic polymer layer constituting the lens structure is subjected to UVO treatment before spin-coating the first alignment layer on the upper surface of the lens structure, To increase the surface energy of the first alignment film.

In the method for manufacturing a bifocal lens according to the third aspect, in the step (c), the substrate is hydrophilized by UVO treatment before the second alignment film is spin-coated on the surface of the substrate to increase the surface energy of the second alignment film .

The bifocal lens according to the present invention is a polarization-dependent GRIN lens-based technique using a photo-curable liquid crystal polymer as a birefringent material. The refractive index n _o and n _e of a lens layer made of a birefringent material and the refractive index n _air A double focal point is obtained by the refractive index relationship of FIG.

The transmissive bifocal lens according to an embodiment of the present invention has a convex lens shape on one surface of a lens layer exposed to an air layer so that the refractive index n _{air of the air} layer and the normal refractive index n _o of the lens layer N _air & lt _; / RTI & _gt ; to the ideal light refraction index ( n _e ) < N _o < n _e , it is possible to operate as convex lenses having two different focal lengths (focal planes) according to the polarization of incident light.

In the transmissive bifocal lens according to another embodiment of the present invention, the refractive index ( n _air ) of the _air layer and the normal refractive index ( n _o ) of the lens layer are different from each other According to the relationship of n _air < n _o < n _{e to} the extraordinary ray refraction index ( n _e ), the concave lenses having two different focal length distances can be operated according to the polarization of the incident light.

In the reflective bifocal lens according to another embodiment of the present invention, one side of the lens layer exposed in the air layer is formed into a convex lens shape and the reflective layer is further provided on the other side of the lens layer, so that the refractive index ( n _air ) ( N _o ) and the extraordinary ray refraction index ( n _e ) of the lens layer, n _air < N _o < n _e , it is possible to operate as reflective convex lenses having two different focal lengths (focal planes) according to the polarization of the incident light.

Blank versification bifocal lens in accordance with another embodiment of the present invention, by forming the one surface of the lens layer exposed to the air layer in a concave lens shape, and further comprising a reflective layer on the other surface of the lens layer, the refractive index (n _air) of the air layer, and ( N _o ) and the extraordinary ray refraction index ( n _e ) of the lens layer, n _air < N _o < n _e , it is possible to operate as reflective concave lenses having two different focal length distances in accordance with the polarization of the incident light.

1 is a cross-sectional view and a conceptual view illustrating a conventional gradient index (GRIN) lens using an electric field distribution.
FIG. 2 is a configuration diagram showing a GRIN lens to which a conventional lens structure is applied.
3 is a structural view illustrating a polarization dependent GRIN lens technology using a liquid crystal polymer.
4 is a conceptual diagram illustrating a configuration and operation of a bifocal lens according to a first embodiment of the present invention.
5 is a conceptual diagram illustrating a configuration and operation of a bifocal lens according to a second embodiment of the present invention.
6 is a conceptual diagram illustrating a configuration and operation of a bifocal lens according to a third embodiment of the present invention.
7 is a conceptual diagram illustrating a configuration and operation of a bifocal lens according to a fourth embodiment of the present invention.
8 is a process diagram showing a manufacturing process of a bifocal lens according to the present invention.
9 shows a micro lens array template used in the manufacturing process of a bifocal lens according to the present invention.

The bifocal lens according to the present invention is based on a polarization-dependent GRIN lens using a photo-curable liquid crystal polymer having birefringent properties. The refractive index n _o and n _{e of the} birefringent photo-curable liquid crystalline polymer material and the air layer Refractive index n _air Is characterized by having a double focus due to the refractive index relationship of the lens. The bifocal lens according to the present invention has the polarization switching unit and the polarization-dependent lens unit separately in the same manner as the conventional polarization-dependent GRIN lens technology using the liquid crystalline polymer. Therefore, the bifocal lens has the same driving voltage and fast switching speed as the conventional liquid crystal device Time-sharing technology becomes applicable.

The photo-curable liquid crystalline polymer material (RM) having birefringent properties has a unidirectional orientation, and has a refractive index of n _e when the polarization direction of the incident light coincides with the major axis direction of the RM molecule, And has a refractive index of n _o when the polarization direction of the RM molecule coincides with the direction of the short axis of the RM molecule, thereby having a double focus according to the polarization direction of incident light.

The bifocal lens according to the present invention has a structure in which an oriented birefringent medium forms an air layer and a curved interface, and the refractive index relation between layers is n _air < N _o < n _e . Accordingly, a shorter focal length than the conventional GRIN lens can be formed.

The bifocal lens according to the present invention may be formed as a planar-convex structure and operated as a bifocal convex lens, or may be formed as a planar-concave structure to operate as a bifocal concave lens. Further, by introducing the reflection layer, it is possible to operate as a reflection type lens.

Hereinafter, the structure and operation of the bifocal lens according to the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

&Lt; Embodiment 1 >

4 is a conceptual diagram illustrating a configuration and operation of a transmissive bifocal lens according to a first embodiment of the present invention. 4, the bifocal lens 1 according to the first embodiment of the present invention includes a transparent substrate 100, an orientation film 110, and a lens layer 120, do.

The transparent substrate 100 may have a flat structure.

The alignment layer 110 is formed on the transparent substrate and is oriented in a single direction. The alignment layer 110 may be formed by spin-coating polyvinylachol (PVA) on a transparent substrate and then performing an alignment treatment such as a rubbing process.

The lens layer 120 is made of a photo-curable liquid crystal polymer material having birefringence and is formed on the alignment layer and aligned in a single direction by the alignment layer. One surface of the lens layer is configured to be exposed to the air layer, and one surface of the lens layer exposed to the air layer has a convex lens shape.

The photocurable liquid crystalline polymer material (hereinafter, referred to as 'RM') constituting the lens layer is a material having birefringence and has normal refractive index (n _o ) and extraordinary refractive index n _e . On the other hand, the relationship between the ordinary ray refractive index to the refractive index (n _air) and a photo-curable liquid crystalline polymer material of the one surface of the lens layer and an abutting layer of air (n _o) and extraordinary refractive index (n _e) is n _air <n _o <n _e .

The bifocal lens according to the present invention can operate as a biconvex convex lens by forming the lens layer into a planar-convex structure.

As a result, the refractive index difference at the interface between the lens layer and the air layer occurs according to the polarization of the light incident on the bifocal lens 1 according to the present invention, and the two focal lengths determined by the refractive index difference at the interface do.

Referring to Fig. 4, the principle of operation of the transmissive bifocal lens according to the first embodiment of the present invention ( n _air < N _o < n _e ) is explained. 4 (a) shows the case where the polarization direction of incident light coincides with the long axis of the orientation direction of the RM constituting the lens layer 120, (b) the polarization direction of the incident light is the short axis of the orientation direction of RM (C) the path of light in the case where the polarization of incident light is 45 ° linearly polarized light or circularly polarized light.

4 (a), when the polarization direction of the incident light coincides with the long axis direction n _e of the RM constituting the lens layer, in the planar-convex structure, at the interface between the oriented RM layer and the air layer, n _e and n _air And is operated as a convex lens having a focal length of f ₁ because the phase delay of the central portion of the lens is larger than the edge portion of the lens.

4 (b), when the polarization direction of incident light coincides with the short axis ( n _o ) direction of the RM constituting the lens layer, at the interface between the oriented RM layer and the air layer in the planar- The focal length f ₂ is formed by the refractive index difference between n _o and n _air . n _o - n _air than n _e - since n _air is larger, the relationship between f ₁ and f ₂ of the transmission type bifocal positive lens formed in accordance with each of the incident polarization direction, according to equation (1) is f ₁ <f ₂ .

Where f is the focal length, R is the radius of curvature of the lens, n is the refractive index of the lens layer, and n _air is the refractive index of the air.

Referring to (c) of FIG. 4, when the polarization of incident light is 45 ° or circularly polarized light, when the incident light is vector-decomposed into 50% in the short axis direction of RM and 50% in the long axis direction of RM, The focus can be formed simultaneously at the f ₁ and f ₂ positions in a form in which the amount of light is reduced by 50%.

&Lt; Embodiment 2 >

5 is a conceptual diagram illustrating a configuration and operation of a transmissive bifocal lens according to a second embodiment of the present invention. The bifocal lens 2 according to the present embodiment has the same structure as the bifocal lens according to the first embodiment, except that the lens layer has a concave lens shape on one side. 5, the bifocal lens 2 according to the second embodiment of the present invention includes a transparent substrate 200, an orientation film 210, and a lens layer 220, which are stacked on each other, And the lens layer has a concave lens shape.

The bifocal lens according to this embodiment is a transmissive bifocal lens and operates as a concave lens having different focal lengths depending on the direction of the incident polarized light.

Referring to Fig. 5, the operating principle of the transmissive bifocal lens according to the second embodiment of the present invention ( n _air < N _o < n _e ) is explained. 5A shows a case where the polarization direction of the incident light coincides with the long axis of the RM orientation direction constituting the lens layer 220. FIG. 5B shows a case where the polarization direction of incident light is shorter than the orientation direction of RM (C) shows the path of the light in the case where the polarization of incident light is 45 占 linearly polarized light or circularly polarized light.

5 (a), when the polarization direction of incident light coincides with the long axis direction n _e of the RM constituting the lens layer, in the planar-concave oriented RM layer and the air layer interface, n _e and n _air And since the phase delay of the central portion of the lens is smaller than the edge portion of the lens, it operates as a concave lens having a focal length of f ₁ .

5 (b), when the polarization direction of incident light coincides with the short axis ( n _o ) direction of the RM constituting the lens layer, at the interface between the oriented RM layer and the air layer of planar-concave structure, The focal length f ₂ is formed by the refractive index difference between n _o and n _air . n _o - n _air than n _e - n because _air is larger, which are heochojeom distance transmission type double focus negative lens formed in accordance with each of the incident polarization direction, according to the equation 1 f ₁ And f ₂ The relationship f ₁ &Lt; f ₂ .

Referring to FIG. 5 (c), when the polarization of the incident light is 45 ° or circularly polarized light, when the incident light is vector-decomposed, it is decomposed into 50% in the short axis direction of RM and 50% The light intensity is reduced by 50% and the focal point is f ₁ And f ₂ Position at the same time.

&Lt; Third Embodiment >

FIG. 6 is a conceptual diagram illustrating a configuration and operation of a reflection type bifocal lens according to a third embodiment of the present invention.

6, the reflective bifocal lens 3 according to the third embodiment of the present invention includes a planar substrate 300, a reflective layer 305, an alignment layer 310, and a lens layer 320, A plurality of lens layers stacked on each other, and one surface of the lens layer exposed in the air layer has a convex lens shape.

The planar substrate 300 preferably has a flat structure.

The reflective layer 305 is formed on the planar substrate 300 and may be formed of metal or the like capable of totally reflecting incident light.

The alignment layer 310 is formed on the reflective layer 305 and is oriented in a single direction. The alignment layer 310 may be formed by spin-coating polyvinylachol (PVA) on a reflective layer, followed by orientation treatment by a rubbing process or the like.

The lens layer 320 is formed of a photo-curable liquid crystal polymer material having birefringence and is formed on the alignment layer and aligned in a single direction by the alignment layer. One surface of the lens layer contacting the air layer has a convex lens shape.

The photocurable liquid crystalline polymer material (hereinafter, referred to as 'RM') constituting the lens layer is a material having birefringence and has normal refractive index (n _o ) and extraordinary refractive index n _e . On the other hand, the relationship between the ordinary ray refractive index to the refractive index (n _air) and a photo-curable liquid crystalline polymer material of the one surface of the lens layer and an abutting layer of air (n _o) and extraordinary refractive index (n _e) is n _air <n _o <n _e .

The reflection type bifocal lens according to the present invention can be formed as a planar-convex structure and can operate as a biconvex convex lens.

As a result, the refractive index difference at the interface between the lens layer and the air layer occurs according to the polarization of the light incident on the bifocal lens 3 according to the present invention, and the two focal lengths determined by the refractive index difference at the interface do.

Referring to Fig. 6, the operation principle of the reflective bifocal lens according to the third embodiment of the present invention ( n _air < N _o < n _e ) is explained. 6 (a) shows a case where the polarization direction of incident light coincides with the long axis of the RM directional direction constituting the lens layer 320, (b) shows a case where the polarization direction of incident light is shorter than the orientation direction of RM (C) shows the path of the light in the case where the polarization of incident light is 45 占 linearly polarized light or circularly polarized light.

Referring to Figure 6 (a), when the polarization direction of light incident matches the long axis direction (n _e) of the RM constituting the lens layer, in the RM layer and the layer of air interface alignment of the planar-convex structure, n _e and n _air And the phase delay of the central portion of the lens is larger than that of the edge portion of the lens, so that it operates as a reflective convex lens having a focal length of f ₁ .

6 (b), when the polarization direction of incident light coincides with the short axis ( n _o ) direction of the RM constituting the lens layer, at the interface between the oriented RM layer and the air layer of the planar- The focal length f ₂ is formed by the refractive index difference between n _o and n _air . n _o - n _e n contrast _air - _air because of n is larger, the relationship between f ₁ and f ₂ of the reflection type bifocal positive lens formed in accordance with each of the impinging polarized light direction is f ₁ <f _2.

Referring to (c) of FIG. 6, when the polarization of incident light is 45 ° or circularly polarized light, vector decomposition of incident light decomposes to 50% in the short axis direction of RM and 50% in the long axis direction of RM The focus can be formed simultaneously at the f ₁ and f ₂ positions in a form in which the amount of light is reduced by 50%.

<Fourth Embodiment>

FIG. 7 is a conceptual diagram illustrating a configuration and operation of a reflection type bifocal lens according to a fourth embodiment of the present invention. The bifocal lens according to the present embodiment has the same structure as the bifocal lens according to the fourth embodiment, except that one surface of the lens layer has a concave lens shape.

7, the reflective bifocal lens 4 according to the fourth embodiment of the present invention includes a planar substrate 400, a reflective layer 405, an alignment layer 410, and a lens layer 420, Wherein the lens layers are stacked on each other, and one surface of the lens layer exposed in the air layer has a concave lens shape.

The reflection type bifocal lens according to the present invention can operate as a bifocal concave lens by forming a lens layer in a planar-concave structure.

The bifocal lens according to the present embodiment is a reflective bifocal lens and operates as a concave lens having different focal lengths depending on the direction of the incident polarized light.

Referring to Fig. 7, the principle of operation of the reflective bifocal lens according to the fourth embodiment of the present invention ( n _air < N _o < n _e ) is explained. 7A shows the case where the polarization direction of the incident light coincides with the long axis of the orientation direction of the RM constituting the lens layer 420. FIG. 7B shows a case where the polarization direction of the incident light is shorter than the orientation direction of RM (C) shows the path of the light in the case where the polarization of incident light is 45 占 linearly polarized light or circularly polarized light.

7 (a), when the polarization direction of the incident light coincides with the long axis direction n _e of the RM constituting the lens layer, in the planar-concave oriented RM layer and the air layer interface, n _e and n _air And since the phase delay of the central portion of the lens is smaller than the edge portion of the lens, it operates as a reflection type concave lens having a focal length f ₁ .

Referring to FIG. 7 (b), when the polarization direction of incident light coincides with the direction of the short axis ( n _o ) of the RM constituting the lens layer, at an interface between the oriented RM layer and the air layer of planar- The helix distance f ₂ is formed by the refractive index difference between n _o and n _air . n _o - n _air than n _e - relationship n f ₁ and f _2, which are _air is further allowed focal length of the reflective double-focus negative lens that is formed in accordance with each of the incident polarization direction because of the size is f ₁ <f ₂ to be.

Referring to FIG. 7 (c), when the polarization of incident light is 45 ° or circularly polarized light, vector decomposition of incident light decomposes to 50% in the short axis direction of RM and 50% in the long axis direction of RM The light intensity is reduced by 50% and the focal point is f ₁ And f ₂ Position at the same time.

Hereinafter, a method of manufacturing a bifocal lens according to a preferred embodiment of the present invention will be described in detail with reference to FIG.

8 is a process diagram showing a manufacturing process of a bifocal lens according to the present invention.

Referring to FIG. 8, in the manufacturing process of the bifocal lens according to the present invention, the lens structure 80 is first formed by applying an imprint process using an isotropic polymer, which is a photo-curing resin (a process ).

The lens structure forms a reversed phase structure of the microlenses. An isotropic polymer 810, which is a photo-curable resin, is applied to a film or a glass substrate 800, imprinted using a microlens array template 820, Thereby forming a lens structure 80 having a reversed phase structure of the lens. The photo-curable resin used as the isotropic polymer material used herein was NOA13685 ( n _p = 1.3685, Norland).

9 shows a micro lens array template used in the manufacturing process of a bifocal lens according to the present invention. Referring to FIG. 9, the microlens array template used in the manufacturing process according to the present invention is a hexagonal 2D array lens in the form of a regular hexagonal lens, and has Lx = 288 vm, Ly = 250 vm, and radius of curvature (ROC) = 320 vm .

Next, an orientation film 830, which is a rubbed PVA layer for bottom-up orientation, is formed on the lens structure 80 having a reversed phase structure of the microlens array formed by the imprinting process (step b). 2 wt% of DI water is used as a solvent for the PVA. To improve the coating property, the surface of the isotropic polymer is hydrophilized by a UVO treatment process before spin-coating the PVA. After the coating, heat treatment is performed at 100 캜 for 30 minutes, and anisotropy is imparted by the rubbing process. On the other hand, the conventional polyimide (PI) alignment layer is difficult to apply in the manufacturing process according to the present invention because the coating process requires damage due to a non-polar solvent and a heat treatment process at a high temperature of 230 캜 after coating.

Next, an alignment film 850, which is a rubbed PVA layer for a top-down orientation, is formed on an arbitrary substrate 840 to manufacture an upper substrate 85 (step c). At this time, when a transmissive bifocal lens is manufactured, it is preferable that the substrate 840 is a transparent substrate. To improve the coating properties of the PVA film, the isotropic polymer surface is hydrophilized by a UVO treatment process before spin-coating the PVA. As described above, before the anisotropy is imparted by the rubbing process, the PVA surface energy is improved through UVO treatment so that the lens layer of the photo-curable liquid crystalline polymer material oriented in the peel-off process can be picked up by the upper substrate .

Next, additionally, for the top-down orientation and lamination process, a lamination process is performed to form a RM layer 860 for the lens layer between the lower substrate 82 and the upper substrate 85, followed by heat treatment and UV curing ) Process, the photo-curable liquid crystalline polymer material is solidified. At this time, the photo-curable liquid crystalline polymer material is aligned in a single direction due to the lower and upper orientation effect. Next, the upper substrate 85 coupled with the RM layer 860, which is a lens layer, is peel-off from the lower substrate 82, and the UVO treatment process described above is used for the photocuring of the PVA surface of the upper substrate, The liquid crystalline polymer layer 860 is picked up. As a result, the bifocal lens 90 in a state where the RM layer 860 and the upper substrate 85 are combined is completed (step d).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

1, 2: transmission type double focus lens
3, 4: Reflective dual focus lens
100, 200, 300, 400: substrate
305, 405: reflective layer
110, 210, 310, 410: alignment film
120, 220, 320, 420: lens layer

Claims (8)

In a bifocal lens capable of switching the focal distance,
A transparent substrate having a flat surface;
An alignment layer oriented in a single direction and formed on the transparent substrate; And
A lens layer formed on the alignment layer and having a lens shape in which a photo-curable liquid crystal polymer material having birefringence is oriented in a unidirectional direction by the alignment layer and one surface of the lens layer is in contact with the air layer;
Wherein one surface of the lens layer abutting the air layer has a convex lens shape or a concave lens shape,
Wherein the lens layer has a normal refractive index (n _o ) and an extraordinary refractive index (n _e ), and the normal refractive index and the extraordinary refractive index of the lens layer are different from the refractive index (n _air ) of the _air layer, The refractive index difference at the interface between the air layer and the lens layer is generated according to the refractive index difference between the air layer and the lens layer, and the two focal lengths are determined by the refractive index difference at the interface.
Wherein the bifocal lens is a transmissive lens, and the focal distance is switched according to a polarization direction of light incident on the bifocal lens. delete A substrate having a planar surface;
A reflective layer formed on the substrate;
An alignment layer oriented in a single direction and formed on the reflective layer; And
A lens layer formed on the alignment layer and having a lens shape in which a photo-curable liquid crystal polymer material having birefringence is oriented in a unidirectional direction by the alignment layer and one surface of the lens layer is in contact with the air layer;
Wherein one surface of the lens layer abutting the air layer has a convex lens shape or a concave lens shape,
Wherein the lens layer has a normal refractive index (n _o ) and an extraordinary refractive index (n _e ), and the normal refractive index and the extraordinary refractive index of the lens layer are different from the refractive index (n _air ) of the _air layer, The refractive index difference at the interface between the air layer and the lens layer is generated according to the refractive index difference between the air layer and the lens layer, and the two focal lengths are determined by the refractive index difference at the interface.
Wherein the lens is operated as a reflection type lens whose focal distance is switched according to a polarization direction of incident light.

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