TWI412579B - Manufacturing method of polymer film with photonic crystal structure - Google Patents

Abstract

A manufacturing method of a polymer film with photonic crystal structure comprises the steps of a mixing step in which an achiral liquid crystal (LC), a chiral dopant, a monomer and a photo initiator are at least mixed together to form an LC-monomer mixture in a transparent container, an exposing step in which the LC-monomer mixture is exposed, an LC removing step in which the achiral LC is removed, and a filling step in which an achiral anisotropic liquid is filled. By using of the achiral LC, such as nematic LC, the photonic crystal structure is significantly imprinted to the polymer film in the invention, and thus the polymer film can reveal property of Bragg reflection when it is filled with achiral anisotropic liquid, so as to lower the cost.

Description

Method for producing polymer film having photonic crystal structure

The present invention relates to a method for producing a polymer film, and more particularly to a method for producing a polymer film having a photonic crystal structure.

With the development of flat panel display (FPD) technology, and because of the superior characteristics of thin, low power consumption and no radiation, the flat display device has gradually replaced the traditional cathode ray tube (CRT). The display device is applied to various electronic products. Among them, Cholesteric Liquid Crystal is also applied to display technology, especially to bistable displays such as electronic paper.

1 is a schematic view showing the molecular arrangement of the cholesteric liquid crystal 11, which may be a palmitic cholesteric liquid crystal, or a non-pivoting liquid crystal to which a palmitic compound is added. Cholesterol liquid crystals basically have an asymmetric chiral center. In the liquid crystal composed of such molecules, the molecules are arranged in parallel in a layered manner, and the layers and the layers are parallel to each other. In each layer, the molecules have a nematic type and are generally aligned in the same direction, and the major axis and the layer are parallel. Between adjacent layers, the long axis direction of the molecules is regularly rotated by a certain angle, and the layers are rotated to form a spiral structure. After the long-axis direction of the liquid crystal molecules is rotated by another 360 degrees, it returns to the same direction and forms a pitch P. Such liquid crystal molecules are based on a special spiral structure, which can deflect the incident light and scatter the light of a specific wavelength. The pitch determines the wavelength of the reflected light from its strongest column.

2 and 3 are schematic views showing the molecular arrangement of cholesteric liquid crystals. As shown in FIG. 2, the cholesteric liquid crystal 11 is sandwiched between the two glass substrates 12, 13, and a black absorbing layer 14 is provided at the bottom. When there is no applied electric field, the cholesteric liquid crystal 11 is a planar texture, and since its spiral period (pitch) is approximately equal to the wavelength of light, this periodic structure can cause Bragg reflection of light of a specific wavelength. The peak of the reflected light is λ = nP (n is the average refractive index). Typically, it can be used to reflect light in a specific wavelength range for use in optical components and liquid crystal display designs. Figure 3 shows a vertical spiral type cholesteric liquid crystal column.

At present, the optical film design with Bragg reflection characteristics can be designed by cholesteric liquid crystal, including a pure cholesteric liquid crystal film or a polymer film blended with cholesteric liquid crystal.

Among them, in the polymer-stabilized cholesteric liquid crystal (PSCT), a small amount of a monomer (concentration of 10% or less) is used to disperse a monomer-forming polymer in a cholesteric liquid crystal, so that the cholesteric liquid crystal reaches a stable planar spiral type. Presents the effect of Bragg reflection. However, since the cholesterol liquid crystal is expensive, the manufacturing cost is greatly increased; and thus, it has been difficult to put it into practical use.

Therefore, how to provide a low-cost and innovative manufacturing method, which can be made into a polymer film having a photonic crystal structure without containing a liquid crystal of cholesterol, has become one of the important topics in the industry.

In view of the above problems, an object of the present invention is to provide a low-cost and innovative manufacturing method capable of producing a polymer film having a photonic crystal structure without containing cholesteric liquid crystal.

In order to achieve the above object, a method for manufacturing a polymer film having a photonic crystal structure according to the present invention comprises the following steps: a mixing step of mixing at least one non-pivoting liquid crystal, an optically active additive, a monomer and a light Forming a liquid crystal monomer mixture to fill a liquid crystal monomer mixture in a light transmissive container; illuminating the liquid crystal monomer mixture in a photolithicidal step; removing a non-pivoting liquid crystal by a liquid crystal removing step; and filling a liquid crystal Step, filling a non-pivot anisotropic liquid.

In order to achieve the above object, a method for manufacturing a polymer film having a photonic crystal structure according to the present invention comprises the following steps: a mixing step of mixing at least a pair of palm liquid crystals, an optically active additive, a monomer, and a light start Forming a liquid crystal monomer mixture to fill the liquid crystal monomer mixture in a light transmissive container; illuminating the liquid crystal monomer mixture in a lighting step; a liquid crystal removing step to remove the palm liquid crystal; and a filling step, Fill a non-pivot anisotropic liquid.

In one embodiment, the mixed non-pivoted liquid crystal is a nematic liquid crystal or a smectic liquid crystal.

In one embodiment, the filled non-pivoting anisotropic liquid is a non-palphatic liquid crystal, such as a nematic liquid crystal or a smectic liquid crystal; or a monomer of the two.

In one embodiment, the weight percentage of the liquid crystal is between 40% and 80%, and the weight percentage of the monomer is between 20% and 60%. By increasing the weight percentage of the monomer, the transfer rate of the polymer of the polymer film can be improved, so that the polymer film exhibits more sufficient photonic crystal structure and Bragg reflection characteristics.

In an embodiment, the photonic crystal structure is, for example, a cholesteric liquid crystal structure having Bragg reflection characteristics. In manufacturing, it may be formed by cholesteric liquid crystal imprinting, or by transfer of an achiral LC mixed optically active chiral dopant.

In one embodiment, the non-pivoted anisotropic liquid can be further polymerized, such that the polymer film contains no liquid, is relatively stable, convenient to use, and does not require edge sealing after polymerization.

In one embodiment, the manufacturing method may further include laminating a transparent conductive film on one side of the polymer film, and may, for example, bonding the transparent conductive film to the upper and lower sides of the polymer film. The color of the reflected light can be changed by controlling the molecular arrangement of the non-pivoting anisotropic liquid and the refractive index by the transparent conductive film.

In one embodiment, the manufacturing method further comprises laminating the formed plurality of polymer films to form a polymer film having a multilayer structure, and the polymer films can be made of left-handed liquid crystal and right-handed liquid crystal, respectively. Thereby, the brightness of the reflected light of the polymer film can be enhanced. Since the right-handed or left-handed cholesterol liquid crystal is used for the transfer, theoretically only half (50%) of the incident light can be reflected. Therefore, if the polymer films replicated by the left-handed and right-handed cholesteric liquid crystals are overlapped, the whole can be obtained. Light reflective (100%) optical film.

As described above, the manufacturing method of the present invention transfers a photonic crystal structure to a polymer film by a non-pivoting liquid crystal (for example, nematic liquid crystal) and an optically active additive, or a palmitic liquid crystal, so as to be filled. In the case of a non-pivoting anisotropic liquid (for example, nematic liquid crystal), a polymer film having a photonic crystal structure can provide chirality to a non-puppet anisotropic liquid with Bragg reflection. Characteristics. Since the present invention does not require the inclusion of the cholesteric liquid crystal, the polymer film has the optical characteristics of the photonic crystal structure, so that the manufacturing cost can be greatly reduced.

Hereinafter, a method of manufacturing a polymer film having a photonic crystal structure according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein the same elements will be described with the same reference numerals.

Referring to FIG. 4, it is a flowchart of a method for manufacturing a polymer film having a photonic crystal structure according to a preferred embodiment of the present invention, and the manufacturing method includes steps S01 to S04. The details are as follows.

Step S01: a mixing step of mixing at least one achiral liquid crystal, an optical dopant, a monomer, and a photo initiator to form a A liquid crystal-monomer mixture is used to fill the liquid crystal monomer mixture in a light-transmissive container. In this step, the non-pivoting liquid crystal, the monomer and the photoinitiator may be mixed first, and then the optically active additive is added to the mixture, and then the liquid crystal monomer mixture is filled in a light-transmissive container; The light-transmitting container is mixed into a liquid crystal monomer mixture. The light-transmitting container may have, for example, a light-transmitting portion to allow light to pass through, or an opening to allow light to pass through; the light-transmitting container may be, for example, a glass or a polymer film. In this step, the palm liquid crystal, the monomer and the photoinitiator can also be mixed, and in this case, it is not necessary to add an optically active additive to the mixture. For palm liquid crystals such as all cholesterol liquid crystals.

In the present embodiment, the non-pivoting liquid crystal refers to a liquid crystal that does not have a chirality, such as a nematic LC or a smectic LC. The optically active additive can induce a helical alignment of the non-pivoted liquid crystal and impart a palmarity thereto, and the optically active additive is, for example, a cyanobiphenyl derivative. The monomer may be a monofunctional or difunctional monomer, and the bifunctional monomer is exemplified herein, which may be a monomer having a liquid crystal phase to achieve a stable alignment effect of the liquid crystal by photopolymerization. The monomer is, for example, BAHB (4,4'-Bis(6-acryloyxy-hexyloxy)biphenyl). Further, the monomer may also be a monofunctional monomer to which a polyfunctional monomer is blended, and a crosslinkable polymer may be formed to avoid dissolution in a solvent. The photoinitiator acts to cause the photopolymerization of the monomer upon exposure to light.

In this embodiment, the weight percentage of the non-pivoting liquid crystal is between 40% and 80%, and the weight percentage of the monomer is between 20% and 60%. Here, the mixing ratio of the non-pivoting liquid crystal, the optically active additive, the monomer, and the photoinitiator is 53.3%, 13.3%, 33.3%, and 0.1%. After mixing uniformly at room temperature, the liquid crystal monomer mixture exhibits a cholesteric liquid crystal phase. It should be noted that in this embodiment, by increasing the weight percentage of the monomer (known to be less than 10%), the transfer rate of the polymer of the polymer film can be increased, which helps to enhance the polymer film. Shows sufficient photonic crystal structure and Bragg reflection characteristics.

Step S02: irradiating the liquid crystal monomer mixture in a light-illuminating step. Here, the light is irradiated by ultraviolet light (for example, 254 nm), and after the light is irradiated, the monomer is photopolymerized to form a polymer, and the liquid crystal is transferred to the polymer. In the illuminating step, laser scanning, or reticle exposure can be used.

Step S03: a liquid crystal removing step to remove the non-pair liquid crystal. In this step, the liquid crystal is removed by an organic solvent such as acetone or chloroform. The liquid crystal is completely removed from the polymer film and dried. Since the difunctional group is resistant, the monomer does not dissolve after the crosslinking, so that the organic solvent can be prevented from removing the polymer.

Step S04: a filling step of filling an achiral anisotropic liquid. A non-pivoting heterosced liquid system refers to a liquid that does not have palmarity but is anisotropic, such as nematic liquid crystal or smectic liquid crystal. The polymer film with a photonic crystal structure can provide chirality to the non-pivoting anisotropic liquid, and has the characteristics of Bragg reflection, and the wavelength of the reflected light is determined by the Bragg equation. Here, the photonic crystal structure is exemplified by a cholesteric liquid crystal structure. Further, after the non-palphalinic anisotropy liquid is filled, the method for producing the polymer film may further include further polymerizing the non-pivoting anisotropic liquid. Such a polymer film does not contain a liquid, is relatively stable and convenient to use, and does not require edge sealing after polymerization.

Figures 5A and 5B show schematic diagrams of the reflectance of the products of the above steps for different wavelengths. For clarity, the product of step S01 is referred to as liquid crystal film A, the product of step S02 is referred to as liquid crystal film B, the product of step S03 is referred to as polymer film C, and the product of step S04 is referred to as polymer film D and E. As shown in FIG. 5A and FIG. 5B, the liquid crystal film A contains a liquid crystal/monomer mixture and has a cholesterol structure, so that light can be reflected and colored. The liquid crystal film B after the ultraviolet light polymerization still retains the cholesterol structure, so that it can reflect light and develop color, and the pitch may be changed by polymerization, so that there is a blue shift phenomenon. After the liquid crystal is removed, the polymer film C loses cholesteric liquid crystallinity, and thus does not have a light reflection phenomenon. Two kinds of nematic liquid crystals (having an average refractive index of, for example, 1.57 and 1.63, respectively) are filled in the polymer film C, so that the polymer films D and E are formed, and the reflection characteristics of different wavelengths are exhibited due to the different refractive indices. All light reflection phenomena conform to the following Bragg equation: λ = nP (n is the average refractive index).

In other embodiments, the mixing step of the method for producing the polymer film may be changed to at least mixing a pair of palm liquid crystals, a monomer, and a photoinitiator to form a liquid crystal monomer mixture. That is, the palmar liquid crystal is directly used to transfer the palm to the polymer film, instead of the non-pivoting liquid crystal plus the optically active additive.

In other embodiments, the method for producing a polymer film may further comprise an alignment step of aligning the liquid crystal monomer mixture. For example, the alignment effect is achieved by parallel-aligning the inner surface of the light-transmissive container. Parallel alignment treatment can be treated by a polymeric, organic, or inorganic layer. When the liquid crystal monomer mixture is filled in a light transmissive container or mixed in a light transmissive container, the alignment step allows the liquid crystal monomer mixture to assume a planar planar texture. After the alignment, the liquid crystal monomer mixture is subjected to photopolymerization, and then the subsequent steps are carried out.

In other embodiments, the method for manufacturing the polymer film can be as shown in FIG. 6 , and further includes bonding a transparent conductive film TC to one side of the polymer film F, where the two transparent conductive films TC are respectively attached. The upper and lower sides of the polymer film F are taken as an example. Of course, if the polymer film F is used for display only on the upper side, the conductive film located on the lower side may be non-transparent. The color of the reflected light can be changed by controlling the molecular arrangement of the fluid (for example, an anisotropic liquid) filled in the polymer film and the refractive index by the transparent conductive film.

In other embodiments, the method for producing a polymer film may include a polymer film in which a plurality of polymer films F are stacked to form a multilayer structure, and the polymer film is formed as shown in FIG. F can be made by using left-handed liquid crystal and right-handed liquid crystal, respectively, thereby enhancing the brightness of the reflected light of the polymer film. Since the right-handed or left-handed cholesterol liquid crystal is used for the transfer, theoretically only half (50%) of the incident light can be reflected. Therefore, if the polymer films replicated by the left-handed and right-handed cholesteric liquid crystals are overlapped, the whole can be obtained. Light reflective (100%) optical film.

The inventive spirit of the present invention lies in the flow of the steps of the manufacturing method, wherein the types of materials and the mixing ratios used as examples are well known to those skilled in the art, and the combinations of the preferred materials can be replaced and found according to different product characteristics and requirements. The mixing ratio is used to produce a polymer film having a photonic crystal structure. Therefore, the materials exemplified above and their proportions are not intended to limit the scope of the invention.

In summary, the manufacturing method of the present invention transfers a photonic crystal structure to a polymer film by a non-pivoting liquid crystal (for example, nematic liquid crystal) and an optically active additive, or a palmitic liquid crystal, so as to be filled. In the case of a non-pivoting anisotropic liquid (for example, nematic liquid crystal), a polymer film having a photonic crystal structure can provide chirality to a non-puppet anisotropic liquid with Bragg reflection. Characteristics. Since the present invention does not require the inclusion of the cholesteric liquid crystal, the polymer film has the optical characteristics of the photonic crystal structure, so that the manufacturing cost can be greatly reduced. The polymer film of the present invention can reflect only light of a specific wavelength, and light of other wavelengths can penetrate. Therefore, it can also be applied to a color pattern design of a solar cell surface, and a light enhancement film of a backlight module of an optical display element design.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

11. . . Cholesterol liquid crystal

12, 13. . . glass substrate

14. . . Black absorbing layer

F. . . Polymer film

P. . . Pitch

S01～S04. . . Method for manufacturing a polymer film having a photonic crystal structure

TC. . . Transparent conductive film

Figure 1 is a schematic view showing the molecular arrangement of cholesteric liquid crystals;

2 is a schematic view showing a cholesteric liquid crystal in a planar spiral arrangement;

3 is a schematic view showing a cholesteric liquid crystal in a vertical spiral arrangement;

4 is a flow chart showing a method of manufacturing a polymer film having a photonic crystal structure according to a preferred embodiment of the present invention;

5A and 5B are schematic diagrams showing the reflectance of products produced by the manufacturing method of FIG. 4 for different wavelengths;

Figure 6 is a schematic view showing a polymer film-bonded transparent conductive film produced by the manufacturing method of the preferred embodiment of the present invention;

Fig. 7 is a schematic view showing the stacking of a plurality of polymer films produced by the manufacturing method of the preferred embodiment of the present invention.

S01～S04. . . Method for manufacturing a polymer film having a photonic crystal structure

Claims (16)

A method for manufacturing a polymer film having a photonic crystal structure, comprising the steps of: mixing a non-pivoting liquid crystal, an optically active additive, a monomer and a photoinitiator to form a liquid crystal single a mixture of the liquid crystal monomer, the liquid crystal monomer mixture is filled in a light-transmissive container; a light-illuminating step, illuminating the liquid crystal monomer mixture; a liquid crystal removing step to remove the non-pivoting liquid crystal; and a filling step, filling a non-palm Sexually isotropic liquid. A method for producing a polymer film having a photonic crystal structure, comprising the steps of: mixing a pair of palm liquid crystals, a monomer and a photoinitiator to form a liquid crystal monomer mixture, thereby making the liquid crystal The monomer mixture is filled in a light-transmissive container; a light-illuminating step is performed to illuminate the liquid crystal monomer mixture; a liquid crystal removing step is performed to remove the pair of palmitic liquid crystals; and a filling step is performed to fill a non-pivoting anisotropic liquid. The manufacturing method according to claim 1 or 2, wherein in the liquid crystal removing step, the liquid crystal is removed by an organic solvent. The manufacturing method according to claim 1 or 2, wherein the non-pivoting anisotropic liquid is a non-pivoting liquid crystal. The manufacturing method according to claim 4, wherein the non-pivoting liquid crystal is a nematic liquid crystal or a smectic liquid crystal. The manufacturing method according to claim 1 or 2, wherein the weight percentage of the liquid crystal is between 40% and 80%, and the weight percentage of the monomer is between 20% and 60%. The manufacturing method according to claim 1 or 2, wherein the non-pivoting liquid crystal is a nematic liquid crystal or a smectic liquid crystal. The manufacturing method according to claim 1 or 2, wherein the monomer comprises a monofunctional monomer or a difunctional monomer. The manufacturing method according to claim 1 or 2, wherein the inner side surface of the light-transmitting container is treated in parallel alignment. The manufacturing method of claim 9, wherein the parallel alignment treatment is treatment with a polymer, an organic or inorganic layer. The manufacturing method according to claim 1 or 2, wherein the photonic crystal structure is a cholesteric liquid crystal structure. The manufacturing method according to claim 1 or 2, wherein the illuminating step is a laser scanning or reticle exposure method. The manufacturing method according to claim 1 or 2, wherein after the filling step, the non-pivoting anisotropic liquid is subjected to a polymerization reaction. The manufacturing method according to claim 1 or 2, further comprising: bonding a transparent conductive film to one side of the polymer film. The manufacturing method according to claim 1 or 2, further comprising: stacking the polymer films when the plurality of polymer films are formed. The manufacturing method according to claim 15, wherein the polymer films are respectively made of a left-handed liquid crystal and a right-handed liquid crystal.