KR101566811B1 - Transparent Composite Films Reinforced with Luminescent Nanofillers and Process for Preparing the Same - Google Patents

Abstract

The present invention relates to a composite film in which a calcined layered rare-earth hydroxide (c-LRH) is dispersed in a hydrophilic polymer, and a process for producing the same. The inorganic / polymer composite film according to the present invention not only exhibits transparent, flexible and color-controllable optical luminescence, but also has excellent mechanical strength.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent composite film reinforced with a luminescent nano-filler and a method of manufacturing the transparent composite film.

The present invention relates to a transparent composite film reinforced with a luminescent nano-filler and a method of manufacturing the same, and more particularly, to a transparent composite film which is transparent, flexible and color- Polymer composite film and a method of easily and easily producing the same.

Small amounts of fillers in polymer nanocomposites have significantly improved permeability and mechanical, thermal, chemical, electrical and optical properties compared to pure polymers or conventional composites. The maximum increase in mechanical strength is achieved when the nanopillar is uniformly dispersed in the matrix so that the external load can be efficiently transferred through strong interaction at the interface between the filler and the matrix.

Layered crystallite / polymer nanocomposites have been identified as one of the important inorganic / polymer hybrid materials. When layered filler materials such as hexagonal boron nitride (h-BN), clay minerals, graphene and layered double hydroxides (LDH) are used, large aspect ratios are required between the nanoparticles and the polymer Lt; RTI ID = 0.0 > polymeric < / RTI > matrix.

However, the intrinsic non-affinity of inorganic materials and organic polymers often causes phase separation and aggregation of inorganic microcrystals, making it difficult to produce flexible, thin, self-standing films. Generally, in a composite material, transparency is impaired due to an increase in light scattering due to differences in refractive index of components. Therefore, it is urgently required to develop a flexible inorganic / polymer composite film which is optically transparent, chemically stable, and excellent in mechanical strength.

On the other hand, in recent years, the LDH system has attracted a great deal of attention due to its ability to be artificially manufactured, controlled, and easily functionalized. Particularly, layered rare-earth hydroxides (LRH) of the general formula RE ₂ (OH) ₅ X n H ₂ O (RE = rare earth, X = anion) , It has attracted attention because it can produce luminescence of various colors not available in LDH. However, until now, only quartz glass has been used as a substrate for transparent LRH films [Note: Korean Published Patent Application No. 2011-0113898].

Korean Patent Publication No. 2011-0113898

The inventors of the present invention have conducted intensive research to develop a transparent transparent LRH film having a luminescence property and found that when layered rare earth hydroxides fired with a luminescent nano filler are dispersed in a hydrophilic polymer, And the present invention has been completed.

It is therefore an object of the present invention to provide a transparent and reinforced flexible composite film of luminescent properties.

Another object of the present invention is to provide a method for easily and easily producing the composite film.

An embodiment of the present invention relates to a composite film in which a calcined layered rare-earth hydroxide (c-LRH) is dispersed in a hydrophilic polymer.

In one embodiment of the present invention, the fired stratified rare earth hydroxides can be produced by firing a layered rare earth hydroxide of the following formula (1).

[Chemical Formula 1]

RE _2-x M _x (OH) ₅ Y mH ₂ O

In this formula,

RE is a rare earth, preferably Y, La, Ce or Gd, most preferably Gd,

M is an optical activator, preferably Eu, Tb, Pr, Nd, Pm, Sm, Dy, Ho, Er, Tm,

x is 0.01 to 0.4, preferably 0.02 to 0.2,

Y is F ^-, Cl ^-, Br ^-, NO ₃ ^- or SO ₄ ^2-, and preferably Cl ^-, and

m is from 0.5 to 4, preferably from 1 to 2.

In one embodiment of the present invention, calcination can be carried out by heating the layered rare earth hydroxide at 500 to 700 DEG C under a flow of a mixed gas of argon and hydrogen.

The layered rare earth hydroxides of formula (1) do not exhibit photoluminescence, but the fired layered rare earth hydroxides exhibit red, green and blue emission depending on the type of optical activator. This is probably due to the increased emission intensity due to dehydration and dehydroxylation due to firing.

The calcined layered rare earth hydroxides can be effectively dispersed in the hydrophilic polymer by keeping the layered nanosheet structure with residual hydroxyl groups. Thus, the calcined stratified rare earth hydroxides not only act as a suitable host to induce effective photoluminescence, but can also be effectively dispersed in a hydrophilic polymer matrix without extensive condensation and / or aggregation.

In one embodiment of the present invention, the hydrophilic polymer can be used without limitation as long as it is a polymer having excellent affinity with the calcined layered rare earth hydroxides. Preferably, a hydrophilic polymer having a hydroxyl group capable of forming a hydrogen bond with the residual hydroxyl group of the calcined layered rare earth hydroxide, for example, a polyvinyl alcohol (PVA), a polyethylene glycol (PEG), a polyvinyl Pyrrolidone (PVP) and the like can be used.

In one embodiment of the present invention, the content of the fired layered rare earth hydroxide to the hydrophilic polymer is 0.5 to 4.0% by weight, preferably 2.0 to 4.0% by weight. When the content of the fired layered rare earth hydroxide is less than 0.5% by weight, the luminous intensity of the composite film is decreased. When the content is more than 4.0% by weight, transparency and mechanical strength are lowered.

The composite film according to one embodiment of the present invention is such that the fired layered rare earth hydroxide acts as a nanofiller to enhance the mechanical strength of the hydrophilic polymer film and is very transparent despite the relatively large nanofiller concentration.

In addition, the composite film according to one embodiment of the present invention can control the emission color by mixing layered rare earth hydroxides containing different kinds of optical activators in an appropriate ratio.

 The composite film according to one embodiment of the present invention can be easily manufactured by a solution casting method, a spray method, a spin-coating method, a dip-coating method, or the like.

A method for producing a composite film according to an embodiment of the present invention includes:

(i) mixing an aqueous solution of a hydrophilic polymer with an aqueous colloidal solution containing fired layered rare earth hydroxides;

(ii) casting the aqueous mixture to a substrate and drying, and then removing the film from the substrate.

As the material of the substrate, glass, quartz, polymer, or the like may be used, but the present invention is not limited thereto.

The composite film formed on the substrate by the above method is easily removed from the substrate.

The detailed description of the hydrophilic polymer and the fired layered rare earth hydroxides is the same as described above, so that the substrate is omitted in order to avoid duplication.

The composite film according to the present invention exhibits a visible light transmittance comparable to that of a pure matrix, and exhibits optical luminescence capable of coloring, folding, and color control, as well as excellent mechanical strength. Accordingly, the composite film according to the present invention can be used as a flexible display, a reinforced transparent polymer film, a packaging, and an energy conversion material.

According to the manufacturing method of the present invention, the composite film can be easily and easily manufactured.

Figure 1 is a graph showing the results of a spectroscopic analysis of a mixture of (a) Gd _1.80 Eu _0.20 (OH) ₅ Cl 1.5H ₂ O (LGdH: Eu) and (b) Gd _1.80 Tb _0.20 (OH) ₅ Cl 1.5H ₂ O (The degree of insertion is a photograph of the corresponding calcined powder (c-LGdH: Eu and c-LGdH: Tb) at 254 nm UV irradiation).
Figure 2 shows a c-LGdH: Eu nanocrystal prepared by dispersing c-LGdH: Eu nanosheets of (a) pure PVA and (b) 0.5, (c) 1.0, Eu / PVA composite film.
FIG. 3 is a transmission spectrum of (a) c-LGdH: Eu / PVA and (b) c-LGdH: Tb / PVA composite film (~ 30 μm thickness).
Figure 4 shows the c-LGdH: Eu / PVA (c) composition containing (a) a pure PVA film and (b) 0.5, LGDH: Tb / PVA composite film containing c-LGdH: Tb nanopiller (f) 0.5, (g) 1.0, (h) 2.0 and (i) 4.0 wt% = 1 cm x 1 cm).
(C) a c-LGdH: Tb / PVA and (c) a c-LGdH: Eu / PVA composite film comprising c-LGdH: RE nanosheets of 0.5, 1.0, c-LGdH: Eu / c-LGdH: The optical luminescence spectrum of the Tb / PVA composite film.
6 is a photograph of c-LGdH: Eu / c-LGdH: Tb / PVA composite film at 254 nm UV irradiation.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are for illustrative purpose only and that the scope of the present invention is not limited to these embodiments.

Production Example 1: Preparation of c-LGdH: Re (Re = Eu or Tb)

Gd _{2.00- x} Re _x (OH) Refer to _{5 Cl · n H 2 O (} Re = Eu or Tb) aqueous suspension literature [B.-I. Lee, KS Lee, JH Lee, IS Lee, S.-H. Byeon, Dalton Trans. 2009 , 2490, which is hereby incorporated by reference. The optical activator concentration was fixed at 10% ( x = 0.20) for LGdH: Eu and LGdH: Tb.

Specifically, a stoichiometric amount of GdCl ₃ .6H ₂ O and EuCl ₃ .6H ₂ O or TbCl ₃ .6H ₂ O was dissolved in water to obtain an aqueous solution (5.0 mM, 100 mL). When a clear solution was formed by uniform stirring, aqueous KOH solution (10.0 mM, 100 mL) was added dropwise. The resulting mixture was stirred at room temperature for 1 hour, then the product was centrifuged and washed several times with water.

The recovered slurry was dispersed in water (~20 gL < ^-1 >) and dried at 50 [deg.] C under> 50% humidity. Then, the dried powder was heated at 600 ° C for 1 hour under a mixed gas flow of 4% H ₂ + 96% Ar to prepare a calcined layered nanofiller (c-LGdH: RE).

The solid product was dispersed in water by sonication and after one hour the precipitate was separated from the aqueous solution. The supernatant was then centrifuged to obtain a c-LGdH: RE slurry. The final process was repeated with the precipitate to maximize the recovery of the c-LGdH: RE nanosheet slurry.

To measure the X-ray diffraction pattern and SEM and AFM images, the slurry was dried at 40 占 폚 for one day. The dopant (Eu and Tb) content and chemical composition of the obtained product were confirmed using ICP and TG analysis.

The obtained Gd _1.80 Eu _0.20 (OH) ₅ Cl 1.5H ₂ O (LGdH: Eu) and Gd _1.80 Tb _0.20 (OH) ₅ Cl 1.5H ₂ O (LGdH: Tb) The excitation and emission spectra before and after calcination in the reactor are shown in Fig.

As shown in FIG. 1, LGdH: RE did not show distinguishable luminoluminescence, but c-LGdH: Eu and c-LGdH: Tb showed bright red and green emission respectively after firing at 600 ° C.

However, the XRD pattern after firing was maintained similar to that before firing. Also, in the SEM and AFM images, significant agglomeration of the nanosheets was not observed despite the firing.

Example 1: c-LGdH: RE / PVA Manufacture of composite film

Pure PVA and composite c-LGdH: RE / PVA (RE = Eu and / or Tb) films were prepared by solution casting method.

PVA (Mw = 85,000-124,000, 99 +% hydrolysis, 2.0 wt%) was dissolved in water at 70-80 < 0 > C with stirring. An aqueous colloidal solution containing c-LGdH: Eu and / or c-LGdH: Tb nanosheets (1.0 g L ^-1 ) was prepared by sonicating the c-LGdH: RE slurry obtained in Preparation Example 1 in water. An appropriate amount of c-LGdH: RE colloid solution (c-LGdH: RE / PVA ratio = 0.5, 1.0, 2.0, 4.0 wt%) was taken and diluted with water to 15.0 mL. Then, a PVA solution (2.0 wt%, 15.0 mL) was added to the colloid solution. The resulting aqueous mixture was stirred for 30 minutes and finally sonicated to remove air bubbles. The temperature of the solution was maintained near room temperature during this step. The mixture was poured into a Petri dish (diameter 8 cm) and water was allowed to evaporate at 50 캜 to produce a composite film. After drying, the film was easily removed from the plate.

Experimental Example 1: Measurement of mechanical strength

(B) 0.5, (c) 1.0, (d) 2.0, and (e) 4.0 weight% of the c-LGdH: Eu nanosheet obtained by dispersing the c-LGdH: Eu nanosheet obtained in Example 1 with pure PVA and PVA obtained in Example 1 The stress-strain curves of the -LGdH: Eu / PVA composite film and the mechanical properties obtained therefrom are shown in FIG. 2 and Table 1, respectively.

PVA 0.5% 1.0% 2.0% 4.0% Young's modulus (GPa) 0.53 + 0.07 1.42 ± 0.08 2.39 ± 0.26 2.20 ± 0.12 1.63 + 0.14 Yield strength (MPa) 9.14 + - 1.85 14.81 ± 1.08 16.24 ± 2.13 27.54 + 1.92 17.61 + - 2.42 Tensile Strength (MPa) 42.58 ± 2.13 49.52 ± 2.06 51.28 ± 1.17 56.06 + - 1.42 53.03 + - 0.82

As shown in FIG. 2 and Table 1, the pure PVA film exhibited typical behavior for flexible plastic deformation. As the concentration of added c-LGdH: Eu nanosheets increased to 2.0 wt%, the elastic modulus of the composite film increased from ~ 0.5 to ~ 2.2 Gpa. The yield strength and tensile strength increased to ~ 28 and ~ 56 MPa at ~ 9 and ~ 43 MPa, respectively. This means that the external load is effectively transferred from the weak polymer component to the inorganic nanosheet. The maximum increase in mechanical strength was achieved when the content of added c-LGdH: Eu nanofiller was about 2.0 wt%.

The increased mechanical properties of the composite film are due to the strong interaction between the hydroxide nanosheets and the OH groups of the PVA surrounding them. The remaining hydroxyl groups on the surface of the c-LGdH: RE nanosheets and PVA molecules are believed to promote the formation of a hydrogen bonding network at the organic / inorganic interface.

Experimental Example 2: Permeation Analysis

The transmission spectrum of (a) c-LGdH: Eu / PVA obtained in Example 1 and (b) c-LGdH: Tb / PVA composite film (~ 30 μm thick) was measured as a function of c-LGdH: RE concentration in PVA 3. Further, a c-LGdH: Eu / PVA complex containing (a) a pure PVA film and (b) 0.5, (c) 1.0, Film of c-LGdH: Tb / PVA composite film containing c-LGdH: Tb nanofiller of (f) 0.5, (g) 1.0, (h) 2.0, 1 cm x 1 cm) is shown in Fig.

As shown in Figures 3 and 4, the transmission of the nanocomposite film was comparable to that of the pure PVA film, even at 4.0 wt% c-LGdH: RE. There was essentially no difference in daylight photographs between the pure PVA film and the c-LGdH: RE / PVA composite film.

This suggests the formation of at least a very uniform and transparent nanocomposite film. Transparent dispersion also supports the presence of hydrogen bonds between c-LGdH: RE and the PVA matrix. The hydrogen bond inhibits the homointeraction between c-LGdH: Eu nanosheets, which leads to precipitation of larger clusters.

Experimental Example 3: Analysis of optical luminescence

(A) c-LGdH: Tb / PVA and (b) c-LGdH: Eu / Pb containing the pure PVA film obtained in Example 1 and 0.5, 1.0, 2.0 and 4.0 wt% c- The optical luminescence spectrum (? _Ex = 254 nm) of the PVA composite film (~ 30 占 퐉 thickness) is shown in Fig.

As shown in FIG. 5, the pure PVA film did not exhibit distinct optical luminescence in the visible light region whereas the emission intensity of the c-LGdH: RE / PVA composite film was c-LGdH: RE nanofiller at 543 and 615 nm Increasing with increasing concentration from 0.5 to 4.0% by weight. From this, we could confirm the effect of c-LGdH: RE nanofiller on optical luminescence.

To evaluate the color control possibilities of composite films, both c-LGdH: Eu and c-LGdH: Tb nanofillers were dispersed in different proportions in the film. However, the total concentration of c-LGdH: RE nanofiller was fixed at 4.0 wt%.

LGDH: Eu / c-LGdH: Tb as a function of the c-LGdH: Eu / c-LGdH: Tb concentration ratio in the PVA of the luminous luminescence spectrum (λ _ex = 254 nm) of the Eu / c- c).

As shown in FIG. 5 (c), the variation of the light emission intensity at 543 and 615 nm coincided with the c-LGdH: Eu / c-LGdH: Tb ratio.

In addition, the photograph of the c-LGdH: Eu / c-LGdH: Tb / PVA composite film at 254 nm UV irradiation is shown in FIG. 6 as a function of the c-LGdH: Eu / c-LGdH: Tb concentration ratio in PVA.

As shown in FIG. 6, the photographs of the composite film of the rolled and folded shape exhibited a significantly different color by the different mixing ratios of the luminousness nanofillers. In addition, the photographs show the foldable nature of the composite film.

Claims (12)

Wherein the calcined layered rare-earth hydroxide (c-LRH) is dispersed in a hydrophilic polymer having a hydroxyl group and the content of the calcined layered rare earth hydroxide to the hydrophilic polymer is 2.0 to 4.0 wt% And the firing is carried out by heating the layered rare earth hydroxide at 500 to 700 占 폚 under a flow of a mixed gas of argon and hydrogen. The composite film according to claim 1, wherein the fired layered rare earth hydroxides are prepared by firing a layered rare earth hydroxide of the following formula:
[Chemical Formula 1]
RE _2-x M _x (OH) ₅ Y mH ₂ O
In this formula,
RE is rare earth,
M is an optical activator,
x is from 0.01 to 0.4,
Y is F ^- , Cl ^- , Br ^- , NO ₃ ^- or SO ₄ ^2- ,
m is from 0.5 to 4. 3. The method of claim 2,
RE is Y, La, Ce or Gd,
M is Eu, Tb, Pr, Nd, Pm, Sm, Dy, Ho, Er, Tm,
x is 0.02 to 0.2,
Y is Cl < ^- >
m is from 1 to 2. < RTI ID = 0.0 > 11. < / RTI > The method of claim 3,
And RE is Gd. delete delete The composite film according to claim 1, wherein the hydrophilic polymer is polyvinyl alcohol (PVA).
delete delete The composite film according to claim 1, wherein the fired layered rare earth hydroxides containing different kinds of optical activators are mixed to adjust the emission color. Wherein the calcined layered rare-earth hydroxide (c-LRH) is dispersed in a hydrophilic polymer having a hydroxyl group and the content of the calcined layered rare earth hydroxide to the hydrophilic polymer is 2.0 to 4.0 wt% Wherein the firing is carried out by heating the layered rare earth hydroxide at 500 to 700 ° C under a flow of a mixed gas of argon and hydrogen,
(i) mixing an aqueous solution of a hydrophilic polymer having a hydroxyl group and an aqueous colloidal solution containing fired lamellar rare earth hydroxides; And
(ii) casting the aqueous mixture to a substrate and drying, and then removing the film from the substrate.
12. The method according to claim 11, wherein the substrate is made of glass, quartz or a polymer.

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