阅读说明：本技术 一种量子点扩散板及其制备方法 (Quantum dot diffusion plate and preparation method thereof ) 是由 叶芸 刘裕 郭太良 林映飞 程海涛 于 2021-07-24 设计创作，主要内容包括：本发明涉及一种量子点扩散板及其制备方法,量子点扩散板包括自下而上依次设置的散热表面胶层、高聚层、光选择性激发层、高光扩散层和防水氧表面胶层,以及涂覆于以上多层结构四周的包边保护膜；光选择性激发层中部设有分隔层,分隔层下表面通过喷墨印刷均匀分布有包括红色复合材料微粒的圆状红色量子点胶膜,分隔层上表面通过喷墨印刷均匀分布有包括绿色复合材料微粒的圆状绿色量子点胶膜。量子点扩散板的制备方法包括：1)表面处理：量子点与表面活性剂及小介电常数材料形成复合材料微粒；2)纵向多层：复合材料微粒与聚合物基材界面处理,并制备多层量子点扩散板；3)包边处理：覆胶形成包边保护膜。该扩散板发光效率高,使用寿命长。(The invention relates to a quantum dot diffusion plate and a preparation method thereof, wherein the quantum dot diffusion plate comprises a heat dissipation surface adhesive layer, a high polymer layer, a light selectivity excitation layer, a high light diffusion layer, a waterproof oxygen surface adhesive layer and a wrapping protection film coated on the periphery of the multilayer structure from bottom to top; the photoselective excitation layer middle part is equipped with the separate layer, and separate layer lower surface has the red quantum dot glued membrane of circle form including red combined material particle through inkjet printing evenly distributed, and separate layer upper surface has the green quantum dot glued membrane of circle form including green combined material particle through inkjet printing evenly distributed. The preparation method of the quantum dot diffusion plate comprises the following steps: 1) surface treatment: the quantum dots, the surfactant and the low dielectric constant material form composite material particles; 2) longitudinal multilayer: carrying out interface treatment on the composite material particles and the polymer base material, and preparing a multilayer quantum dot diffusion plate; 3) and (3) edge covering treatment: and covering with glue to form a wrapping protective film. The diffusion plate has high luminous efficiency and long service life.)

1. The quantum dot diffusion plate is characterized by comprising a heat dissipation surface adhesive layer, a high polymer layer, a light selectivity excitation layer, a high light diffusion layer, a waterproof oxygen surface adhesive layer and a covered edge protective film, wherein the heat dissipation surface adhesive layer, the high polymer layer, the light selectivity excitation layer, the high light diffusion layer and the waterproof oxygen surface adhesive layer are sequentially arranged from bottom to top; the light selective excitation layer is characterized in that a separation layer is arranged in the middle of the light selective excitation layer, round red quantum dot adhesive films comprising red composite material particles are uniformly distributed on the lower surface of the separation layer through ink jet printing, and round green quantum dot adhesive films comprising green composite material particles are uniformly distributed on the upper surface of the separation layer through ink jet printing.

2. The method for preparing a quantum dot diffusion plate according to claim 1, comprising the steps of:

1) surface treatment: the quantum dots, the surfactant and the low dielectric constant material form composite material particles;

2) longitudinal multilayer: carrying out interface treatment on the composite material particles and the polymer base material, and preparing a multilayer quantum dot diffusion plate;

3) and (3) edge covering treatment: and covering with glue to form a wrapping protective film.

3. The method as claimed in claim 2, wherein in step 1, the surfactant is one or more selected from carboxylate, alkyl phosphate, alkylamine ethylene oxide adduct, quaternary ammonium salt of fatty amine, and amphoteric surfactant; the low dielectric constant material is one or a mixture of silicon dioxide, aromatic thermosetting organic materials and silicon-based high polymer materials.

4. The method according to claim 2, wherein in step 1, the quantum dots are quantum dots composed of II-VI elements, quantum dots composed of III-V elements, or ABX₃Calcium formTitanium ore quantum dots; the ABX₃The halogen element X in the perovskite quantum dot is Cl^-、Br^-Or I^-One of (1) and (b).

5. The method for preparing a quantum dot diffusion plate according to claim 2, wherein in the step 1, the method for surface treatment of the quantum dots comprises the following steps:

(1) dissolving the quantum dots in an organic solvent in a stirring device, and uniformly stirring;

(2) adding a small dielectric constant material, heating and fully stirring, and then adding the surfactant to carry out chemical reaction so as to wrap the surface of the particle;

(3) after the reaction is finished for 24-72h, adding an extraction solvent to separate out the required composite material solution;

(4) and drying, cooling and shaping the obtained composite material solution, drawing and granulating by a granulator to form composite material particles.

6. The method as claimed in claim 2, wherein in the step 2, a light diffuser and an additive are added to one or more of PC, PVC, PS, PMMA, PET and epoxy resin, and combined by co-extrusion to form the spacer layer; the thickness of separate layer is 25~120 um.

7. The method as claimed in claim 6, wherein the step 2 of processing the interface between the composite material particles and the polymer matrix comprises: uniformly mixing 1-5 wt% of the composite material particles, 5-8 wt% of oleylamine, 13-16 wt% of polystyrene, 5-10 wt% of calcium carbonate, 5-8 wt% of oligomeric amidine oil and 0.1wt% of antioxidant, and repeatedly stirring to form resin type ink; jet printing the resin type ink on the separation layer; uniformly distributing round green quantum dot glue films comprising green composite material particles and round red quantum dot glue films comprising red composite material particles on the upper surface and the lower surface of the separation layer to form the light selective excitation layer; the diameter of the round green quantum dot adhesive film is 1-5 mm, and the diameter of the round red quantum dot adhesive film is 0.2-0.8 mm.

8. The method according to claim 2, wherein in step 2, the high polymer layer is coated on the lower surface of the light selective excitation layer, blue light can pass through the high polymer layer, the reflectivity of red light and green light is greater than 90%, and the thickness of the high polymer layer is 12-30 um; the upper surface coating of light selectivity excitation layer highlight diffusion layer produces diffusion many times, makes incident light more even soft, highlight diffusion layer's thickness is 2~15 um.

9. The method according to claim 2, wherein in the step 2, graphene is used as a main raw material, a material containing metal oxide is added to mix into gel, and the gel is coated on the high polymer layer far away from the light selective excitation layer to form the heat dissipation surface glue layer, and the thickness of the heat dissipation surface glue layer is 80-200 um.

10. The method for preparing a quantum dot diffusion plate according to claim 2, wherein the raw materials of the waterproof oxygen surface glue layer and the edge-covering protective film comprise neoprene, butyl rubber, ethylene propylene diene monomer, polyvinyl chloride, polyisobutylene and polyurethane; the thickness of waterproof oxygen surface glue film is 25~55um, the thickness of the protection film of borduring is 35~48 um.

Technical Field

The invention belongs to the technical field of quantum dot optics, and particularly relates to a quantum dot diffusion plate and a preparation method thereof.

Background

Compared with the traditional display device, the liquid crystal display needs the blue light LED coated with yellow fluorescent powder to synthesize white light, and the white light is synthesized into colored light through the red, green and blue light filters. And the fluorescent powder material has wider half-peak width, low color purity and low color gamut. The properties of the nano quantum dot material are just opposite to those of the nano quantum dot material, the half-peak width is narrow, the color purity is high, the size can be adjusted to emit light with specific color, and the higher color gamut is realized. Only a common blue LED needs to excite red and green quantum dots, red light and green light can be directly emitted, and the waste of light energy is less.

On the basis of the selection of the polymer base material, the control of the compounding process is the key for preparing the high-performance quantum dot diffusion plate, and the following two problems need to be solved: firstly, how to improve the compatibility of quantum dots and polymers in the diffusion plate and enable the quantum dots to be uniformly distributed in the diffusion plate; and secondly, the adverse effects of impurities on the surface of the quantum dots on the properties of light transmittance, flexibility and the like of the polymer base material are reduced.

Disclosure of Invention

The invention aims to provide a quantum dot diffusion plate and a preparation method thereof.

In order to achieve the purpose, the invention adopts the technical scheme that: a quantum dot diffusion plate comprises a heat dissipation surface adhesive layer, a high-concentration layer, a light selectivity excitation layer, a high-light diffusion layer, a waterproof oxygen surface adhesive layer and a wrapping protection film, wherein the heat dissipation surface adhesive layer, the high-concentration layer, the light selectivity excitation layer, the high-light diffusion layer and the waterproof oxygen surface adhesive layer are sequentially arranged from bottom to top; the light selective excitation layer is characterized in that a separation layer is arranged in the middle of the light selective excitation layer, round red quantum dot adhesive films comprising red composite material particles are uniformly distributed on the lower surface of the separation layer through ink jet printing, and round green quantum dot adhesive films comprising green composite material particles are uniformly distributed on the upper surface of the separation layer through ink jet printing.

The invention also provides a preparation method of the quantum dot diffusion plate, which comprises the following steps:

1) surface treatment: the quantum dots, the surfactant and the low dielectric constant material form composite material particles;

2) longitudinal multilayer: carrying out interface treatment on the composite material particles and the polymer base material, and preparing a multilayer quantum dot diffusion plate;

3) and (3) edge covering treatment: and covering with glue to form a wrapping protective film.

Further, in the step 1, the surfactant is one or a mixture of carboxylate, alkyl phosphate ester salt, alkylamine ethylene oxide adduct, quaternary ammonium salt made of fatty amine and amphoteric surfactant; the low dielectric constant material is one or a mixture of silicon dioxide, aromatic thermosetting organic materials and silicon-based high polymer materials.

Further, in the step 1, the quantum dots are quantum dots composed of II-VI group elements or quantum dots composed of III-V group elements or ABX₃Perovskite-type quantum dots; the ABX₃The halogen element X in the perovskite quantum dot is Cl^-、Br^-Or I^-One of (1) and (b).

Further, in step 1, the method for surface treatment of the quantum dots comprises:

(1) dissolving the quantum dots in an organic solvent in a stirring device, and uniformly stirring;

(2) adding a small dielectric constant material, heating and fully stirring, and then adding the surfactant to carry out chemical reaction so as to wrap the surface of the particle;

(3) after the reaction is finished for 24-72h, adding an extraction solvent to separate out the required composite material solution;

(4) and drying, cooling and shaping the obtained composite material solution, drawing and granulating by a granulator to form composite material particles.

Further, in step 2, adding a light diffusion agent and an additive into one or a mixture of more of PC, PVC, PS, PMMA, PET and epoxy resin, and combining the mixture in a co-extrusion mode to form the separation layer; the thickness of separate layer is 25~120 um.

Further, in step 2, the method for processing the interface between the composite material particles and the polymer substrate comprises: uniformly mixing 1-5 wt% of the composite material particles, 5-8 wt% of oleylamine, 13-16 wt% of polystyrene, 5-10 wt% of calcium carbonate, 5-8 wt% of oligomeric amidine oil and 0.1wt% of antioxidant, and repeatedly stirring to form resin type ink; jet printing the resin type ink on the separation layer; uniformly distributing round green quantum dot glue films comprising green composite material particles and round red quantum dot glue films comprising red composite material particles on the upper surface and the lower surface of the separation layer to form the light selective excitation layer; the diameter of the round green quantum dot adhesive film is 1-5 mm, and the diameter of the round red quantum dot adhesive film is 0.2-0.8 mm.

Further, in the step 2, the high polymer layer is coated on the lower surface of the light selective excitation layer, blue light can penetrate through the high polymer layer, the reflectivity of red light and green light is greater than 90%, and the thickness of the high polymer layer is 12-30 um; the upper surface coating of light selectivity excitation layer highlight diffusion layer produces diffusion many times, makes incident light more even soft, highlight diffusion layer's thickness is 2~15 um.

Further, in step 2, use graphite alkene as main raw materials, add the material mixing that includes metal oxide and mix the gel coating on keeping away from the high layer that gathers on light selectivity excitation layer one side, form heat dissipation surface glue film, heat dissipation surface glue film's thickness is 80~200 um.

Further, the raw materials of the waterproof oxygen surface glue layer and the edge-covering protective film comprise chloroprene rubber, butyl rubber, ethylene propylene diene monomer rubber, polyvinyl chloride, polyisobutylene and polyurethane; the thickness of waterproof oxygen surface glue film is 25~55um, the thickness of the protection film of borduring is 35~48 um.

Compared with the prior art, the invention has the following beneficial effects:

(1) by surface treatment of the quantum dots, the compatibility of the quantum dots and the polymer in the diffusion plate and the survival rate at high temperature are improved, the agglomeration phenomenon of the quantum dots is reduced, and high-quality nano composite material particles are obtained after extraction and purification. The outer edge treatment can effectively prevent the aging phenomenon caused by heat radiation and ultraviolet radiation in the preparation and use processes, thereby prolonging the service life of the quantum dot diffusion plate.

(2) The invention provides an optical path of a quantum dot diffusion plate, which comprises the following steps: blue light emitted by the blue light LED penetrates through the heat dissipation surface adhesive layer and the high polymer layer, and red light is emitted by the red quantum dots in the exciting light selective excitation layer; part of the blue light and the red light penetrate through the separation layer, the rest of the red light is reflected to the high polymer layer, and the green quantum dots in the selective excitation layer of the part of the blue light excitation light emit green light. Blue light, red light and green light are transmitted through the high light diffusion layer and the waterproof oxygen surface adhesive layer to form light with any color. The residual red light in the high light-gathering layer is reflected again, and the three primary color lights are synthesized again in the high light diffusion layer, so that the light conversion is utilized for multiple times to improve the luminous efficiency.

(3) Because the conversion efficiency of light has been improved to multilayer quantum dot diffuser plate, the heat that produces also increases relatively, and the heat dissipation problem directly influences the conversion and the life of quantum dot diffuser plate light, therefore the heat dissipation surface glue layer that sets up plays quick radiating effect through heat transfer.

Drawings

Fig. 1 is a schematic structural diagram of a quantum dot diffusion plate according to an embodiment of the present invention.

Fig. 2 is a schematic flow chart of the preparation process of the quantum dot diffusion plate according to the embodiment of the invention.

FIG. 3 is a schematic structural diagram of a light selective excitation layer in an embodiment of the present invention.

In the figure: 1-heat dissipation surface adhesive layer, 2-high polymer layer, 3-light selective excitation layer, 4-high light diffusion layer, 5-waterproof oxygen surface adhesive layer, 6-edge protection film, 31-round red quantum dot adhesive film, 32-separation layer, 33-round green quantum dot adhesive film, 311-red composite material particle and 331-green composite material particle.

Detailed Description

The invention is further explained below with reference to the drawings and the embodiments.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

As shown in fig. 1, the present embodiment provides a quantum dot diffusion plate, which includes a heat dissipation surface glue layer 1, a high polymer layer 2, a light selective excitation layer 3, a high light diffusion layer 4, a water-oxygen-resistant surface glue layer 5, and a wrapping protection film 6 coated around the above multilayer structure, which are sequentially disposed from bottom to top. As shown in fig. 3, a separation layer 32 is disposed in the middle of the light selective excitation layer 3, a circular red quantum dot adhesive film 31 including red composite material particles 311 is uniformly distributed on the lower surface of the separation layer by inkjet printing, and a circular green quantum dot adhesive film 33 including green composite material particles 331 is uniformly distributed on the upper surface of the separation layer by inkjet printing.

As shown in fig. 2, the preparation method of the quantum dot diffusion plate includes the following steps:

1) surface treatment: the quantum dots, the surfactant and the low dielectric constant material form composite material particles;

2) longitudinal multilayer: carrying out interface treatment on the composite material particles and the polymer base material, and preparing a multilayer quantum dot diffusion plate;

3) and (3) edge covering treatment: and covering with glue to form a wrapping protective film.

In the step 1, the surfactant is one or a mixture of carboxylate, alkyl phosphate ester salt, alkylamine ethylene oxide adduct, quaternary ammonium salt prepared from fatty amine and amphoteric surfactant (amino type, betaine type, imidazole type and amine oxide type). The low dielectric constant material is one or a mixture of silicon dioxide, aromatic thermosetting organic materials and silicon-based high polymer materials (HSQ and MSQ).

In step 1, the quantum dots can be quantum dots composed of II-VI elements, quantum dots composed of III-V elements or ABX₃Perovskite-type quantum dots; the ABX₃The halogen element X in the perovskite quantum dot is Cl^-、Br^-Or I^-One of (1) and (b). The quantum dots specifically comprise CdSe, InP or CsPbBr₃One or a combination of several of them.

In the step 1, the method for surface treatment of the quantum dots comprises the following steps:

(1) dissolving the quantum dots in an organic solvent in a stirring device, and uniformly stirring;

(2) adding a small dielectric constant material, heating and fully stirring, and then adding the surfactant to carry out chemical reaction so as to wrap the surface of the particle;

(3) after the reaction is finished for 24-72h, adding an extraction solvent to separate out the required composite material solution;

(4) and drying, cooling and shaping the obtained composite material solution, drawing and granulating by a granulator to form composite material particles.

Preferably, the organic solvent is one or a mixture of toluene, ethanol, diethyl ether, acetone and acetic acid. The extraction solvent is one of n-hexane, pentane and cyclohexane. The weight ratio of the quantum dots to the organic solvent is 1: (4-5), and the concentration of the added extraction solvent is 20-40 wt%.

In step 2, adding a light diffusion agent and an additive into one or a mixture of more of PC, PVC, PS, PMMA, PET and epoxy resin, and combining the mixture in a co-extrusion mode to form the separation layer; the thickness of separate layer is 25~120 um.

In step 2, the method for processing the interface between the composite material particles and the polymer substrate comprises the following steps: uniformly mixing 1-5 wt% of the composite material particles, 5-8 wt% of oleylamine, 13-16 wt% of polystyrene, 5-10 wt% of calcium carbonate, 5-8 wt% of oligomeric amidine oil and 0.1wt% of antioxidant, and repeatedly stirring to form the resin type ink. The resin type ink is ejected from a nozzle of an ejection head under the control of an ink ejection controller and is jet-printed on the partition layer. And uniformly distributing a round green quantum dot adhesive film comprising green composite material particles and a round red quantum dot adhesive film comprising red composite material particles on the upper surface and the lower surface of the separation layer to form the light selective excitation layer. The diameter of the round green quantum dot adhesive film is 1-5 mm, and the diameter of the round red quantum dot adhesive film is 0.2-0.8 mm.

Coating the high polymer layer on the lower surface of the light selective excitation layer, wherein blue light (wavelength) can penetrate through the high polymer layer, the reflectivity of red light and green light (wavelength) is more than 90%, and the thickness of the high polymer layer is 12-30 um; the upper surface coating of light selectivity excitation layer highlight diffusion layer produces diffusion many times, makes incident light more even soft, highlight diffusion layer's thickness is 2~15 um.

Use graphite alkene as the main material, add the material mixing including metal oxide and mix the gel coating on keeping away from the high layer that gathers on light selectivity excitation layer one side, form heat dissipation surface glue film, the thickness of heat dissipation surface glue film is 80~200 um.

The raw materials of the waterproof oxygen surface adhesive layer and the edge-covering protective film comprise chloroprene rubber, butyl rubber, ethylene propylene diene monomer rubber, polyvinyl chloride, polyisobutylene, polyurethane and the like; preferably, the edge covering agent further comprises 0.1wt% of antioxidant, 0.1wt% of heat stabilizer and 0.1wt% of ultraviolet stabilizer, and the edge covering agent is subjected to edge covering treatment through thermal curing or ultraviolet curing. The thickness of waterproof oxygen surface glue film is 25~55um, the thickness of the protection film of borduring is 35~48 um.

In this example, for the surface treatment of the quantum dots in step 1, CdSe/InP/CsPbBr was added to the mixture in a stirring apparatus₃Dissolving the quantum dots in toluene, and uniformly stirring for 30 min; adding aromatic thermosetting organic material, heating to 180 deg.c and stirring, and adding carboxylate and alkyl phosphate to react to coat the surface of the particle. Adding n-hexane after the reaction is finished for 24-72h, and extracting and separating out the needed CdSe/InP/CsPbBr₃And (3) a composite material solution. Finally drying and coolingAnd shaping, drawing, and granulating by a granulator to a micron grade or a millimeter grade meeting the process requirements.

In this embodiment, the weight ratio of the quantum dot to the toluene solvent is 1: (4-5), and the concentration of the added extraction solvent is 20-40 wt%. Further preferably, the weight ratio of the quantum dots to the toluene solvent is 1: 3, the concentration after addition of the extraction solvent was 25/30/35 wt%.

In this embodiment, in step 2, the multi-layer quantum dot diffusion plate includes a heat dissipation surface glue layer 01, a high polymer layer 02, a light selective excitation layer 03, a high light diffusion layer 04, and a waterproof oxygen surface glue layer 05, which are sequentially disposed, and a hemming protection film 06 is coated on the periphery. Wherein, a separating layer 032 is arranged in the light selective excitation layer 03, a round red quantum dot adhesive film 031 which is uniformly distributed by ink-jet printing is arranged on the lower surface of the separating layer 032, and a round green quantum dot adhesive film 033 which is uniformly distributed by ink-jet printing is arranged on the upper surface of the separating layer.

In this example, 0.1kg of titanium dioxide particles and additives were added to one or more of PC, PVC, PS, PMMA, PET and epoxy resin, and combined into the separator by co-extrusion. The forming temperature is 250-290 ℃, the forming pressure is 3-13 Mpa, and the thickness of the separation layer is 25-120 um. Preferably, the shaping temperature is 270 ℃, the shaping pressure is 10Mpa, the thickness of separate layer is 110 um.

In this example, red CdSe/InP/CsPbBr was added₃2wt% of composite fine particles (0311), 7wt% of oleylamine, 15wt% of polystyrene, 8wt% of calcium carbonate, 7wt% of oligomeric amidine oil, and 0.1wt% of an antioxidant were uniformly mixed and repeatedly stirred to obtain a resin-based ink. The resin type ink is ejected from a nozzle of a nozzle to be printed on the partition layer under the control of an ink jet controller. The lower surface of the separation layer is provided with round red quantum dot glue films which are uniformly distributed. The diameter of the round red quantum dot adhesive film is 0.2-0.8 mm. Preferably, the diameter of the round red quantum dot adhesive film is 0.5 mm.

In this example, green CdSe/InP/CsPbBr was added₃3wt% of composite material particles (0331), 7wt% of oleylamine, 15wt% of polystyrene, 8wt% of calcium carbonate, 7wt% of oligomeric amidine oil and antioxidant0.1wt% of the curing agent was uniformly mixed and repeatedly stirred to obtain a resin type ink. The resin type ink is ejected from a nozzle of a nozzle to be printed on the partition layer under the control of an ink jet controller. The upper surface of the separation layer is provided with round green quantum dot glue films which are uniformly distributed. The diameter of the circular green quantum dispensing film is 1-5 mm. Preferably, the diameter of the round green quantum dot dispensing film is 2.5 mm.

In this embodiment, a high polymer layer is coated on the lower surface of the light selective excitation layer, blue light (wavelength) can transmit through the high polymer layer, and the reflectivity of red light and green light (wavelength) is larger than 90%. The thickness of the high polymer layer is 12-30 um. Preferably, the thickness of the polymeric layer is 25 um.

In this embodiment, a high light diffusion layer is coated on the upper surface of the light selective excitation layer to generate multiple diffusion, so that the incident light is more uniform and softer. The thickness of the high light diffusion layer is 2-15 um. Preferably, the thickness of the high light diffusion layer is 10 um.

In this embodiment, the heat dissipation surface glue layer is mainly made of graphene. Various materials such as metal oxide are added to the mixture to form a gel, and the gel is coated on the high polymer layer far away from the light selective excitation layer. The thickness of the heat dissipation surface glue layer is 80-200 um. Preferably, the thickness of the heat dissipation surface glue layer is 180 um.

In this embodiment, the waterproof oxygen surface adhesive layer and the sealing protective film are made of neoprene, butyl rubber, ethylene propylene diene monomer, polyvinyl chloride, polyisobutylene, polyurethane, or the like. Preferably, 0.1wt% of antioxidant, 0.1wt% of heat stabilizer and 0.1wt% of ultraviolet stabilizer are subjected to external edge treatment through thermal curing or ultraviolet curing. The thickness of waterproof oxygen surface glue film is 35um, and the thickness of borduring protection film is 40 um.

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.