TW202021808A - Electroluminescence fiber - Google Patents

Abstract

An electroluminescence fiber includes a linear center electrode, a dielectric layer, an electroluminescence layer, and a transparent conductive layer. The dielectric layer wraps the linear center electrode. The electroluminescence layer wraps the dielectric layer, and includes 3 parts by weight to 7 parts by weight of Cu-containing ZnS phosphor, 0.05 parts by weight to 0.8 parts by weight of metal oxide, 0.1 parts by weight to 0.7 parts by weight of amino alcohol compound, 0.095 parts by weight to 0.24 parts by weight of alkali metal carbonates, and 2.0 parts by weight to 2.5 parts by weight of PU resin. The metal oxide includes ZnO, TiO₂, BaTiO₃, MnO₂, and the combination thereof. The transparent conductive layer wraps the electroluminescence layer.

Description

Electroluminescent fiber

The present invention relates to an electroluminescent fiber, and in particular to an electroluminescent fiber including an electroluminescent layer.

Electroluminescence (EL) light sources have been widely used in various display lighting devices. In existing electroluminescent devices, high voltage is usually required to achieve high luminous brightness. However, there are doubts and dangers in using high-voltage electroluminescent elements.

In addition, in order to improve the brightness or light extraction rate, the existing linear electroluminescent device will be coated with one or more functional layers outside the center electrode, such as a strong light reflecting layer, an inner electron emission layer, or an outer electron emission layer. However, this method complicates the manufacturing process, increases the cost and the diameter of the wire body, and thus reduces the application range of the linear electroluminescent element. Therefore, a novel electroluminescent element is needed to solve the above-mentioned problems.

The present disclosure provides an electroluminescent fiber, which includes a linear center electrode, a dielectric layer, an electroluminescent layer, and a transparent conductive layer. The dielectric layer covers the linear center electrode. The electroluminescent layer covers the dielectric layer, and the electroluminescent layer includes 3 parts by weight to 7 parts by weight of copper-containing zinc sulfide luminescent powder, 0.05 parts by weight to 0.8 parts by weight of metal oxide, and 0.1 parts by weight to 0.7 parts by weight The amine alcohol compound, 0.095 parts by weight to 0.24 parts by weight of alkali metal carbonate, and 2.0 parts by weight to 2.5 parts by weight of PU resin. The metal oxide includes zinc oxide (ZnO), titanium dioxide (TiO ₂ ), barium titanate (BaTiO ₃ ), manganese dioxide (MnO ₂ ), or a combination thereof. The transparent conductive layer covers the electroluminescent layer.

In some embodiments, the thickness of the electroluminescent layer is in the range of 25 to 40 microns.

In some embodiments, the wire diameter of the electroluminescent fiber ranges from 300 microns to 700 microns.

In some embodiments, the thickness of the dielectric layer ranges from 20 microns to 50 microns.

In some embodiments, the electroluminescent fiber further includes a protective layer covering the transparent conductive layer, wherein the protective layer includes polyethylene vinyl acetate (EVA) or polyvinyl acetate (PVAC).

In some embodiments, the transparent conductive layer includes a plurality of nano-silver wires, and each nano-silver wire has a wire diameter of 50 nanometers to 100 nanometers, and a wire length of 5 micrometers to 50 micrometers.

In some embodiments, the metal oxide is 0.1 to 0.8 parts by weight of zinc oxide (ZnO).

In some embodiments, the metal oxide is 0.05 parts by weight to 0.3 parts by weight of titanium dioxide (TiO ₂ ).

In some embodiments, the metal oxide is 0.24 parts by weight to 0.75 parts by weight of barium titanate (BaTiO ₃ ).

In some embodiments, the metal oxide is 0.05 to 0.10 parts by weight of manganese dioxide (MnO ₂ ).

100‧‧‧Electroluminescent fiber

110‧‧‧Linear center electrode

120‧‧‧Dielectric layer

130‧‧‧Electroluminescent layer

140‧‧‧Transparent conductive layer

150‧‧‧Protection layer

200‧‧‧Thin film electroluminescence device

210‧‧‧Conductive layer

220‧‧‧Dielectric layer

230‧‧‧Electroluminescent layer

240‧‧‧Transparent conductive layer

250、260‧‧‧Wire

D1‧‧‧Wire diameter

T1, T2‧‧‧thickness

When reading the accompanying drawings, you can fully understand all aspects of this disclosure from the following detailed description. It is worth noting that according to industry standard practice, various features are not drawn to scale. In fact, for clear discussion, the size of various features can be increased or decreased arbitrarily.

Figure 1 is a three-dimensional exploded schematic diagram of an electroluminescent fiber according to an embodiment of the present invention.

Figure 2 is a schematic cross-sectional view of an electroluminescent fiber according to an embodiment of the present invention.

FIG. 3 is a three-dimensional exploded schematic diagram of a thin film electroluminescence device according to an embodiment of the present invention.

Figures 4 to 6 respectively show the energy scattering spectrum (EDS) of the electroluminescent layer according to one embodiment of the present invention.

In the following, a plurality of embodiments of the present invention will be disclosed in the form of diagrams. For the sake of clarity, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. That is to say, in some embodiments of the present invention, these practical details are unnecessary. In addition, for clarity, the size or thickness of the component may be exaggerated, and the drawing is not based on the original size. In addition, to simplify the illustration, Some conventionally used structures and components are shown in a simple schematic manner in the figure.

Spatial relative terms are used in this article, such as "below", "below", "above", "above", etc. This is to facilitate the description of the relative relationship between one element or feature and another element or feature, such as Shown in the figure. The true meaning of these relative terms in space includes other directions. For example, when the icon is turned upside down by 180 degrees, the relationship between one element and another element may change from "below" and "below" to "above" and "above". In addition, the relative narratives in space used in this article should also be interpreted in the same way.

FIG. 1 is a three-dimensional exploded schematic diagram of the electroluminescent fiber 100 according to various embodiments of the present invention. Please refer to FIG. 1, the electroluminescent fiber 100 includes a linear center electrode 110, a dielectric layer 120, an electroluminescent layer 130 and a transparent conductive layer 140. In various embodiments, the linear center electrode 110 includes a conductive material, such as one or more copper wires, but is not limited thereto.

As shown in FIG. 1, the dielectric layer 120 covers the linear center electrode 110. In some embodiments, the dielectric layer 120 includes a dielectric material. In some embodiments, the dielectric layer 120 is formed by drying a dielectric layer formulation including PU resin, water and barium titanate, wherein the weight ratio of PU resin/water/barium titanate is about 12/4/15, But it is not limited to this. In some embodiments, the density of the dielectric layer is about 4.68 to 5.47 g/mL.

The electroluminescent layer 130 covers the dielectric layer 120. The electroluminescent layer 130 includes 3 parts by weight to 7 parts by weight of copper-containing zinc sulfide luminescent powder, 0.05 parts by weight to 0.8 parts by weight of metal oxide, and 0.1 parts by weight to 0.7 parts by weight of amine Alcohol compounds, 0.095 parts by weight to 0.24 parts by weight of alkali metal carbonate, and 2.0 parts by weight to 2.5 parts by weight of PU resin. In some embodiments, the solid content weight ratio of copper-containing zinc sulfide luminescent powder: metal oxide: amine alcohol compound: alkali metal carbonate: PU resin is 5: (0.05-0.08): (0.1-0.7): ( 0.095-0.24): (2.0-2.5). In one embodiment, the weight percentages of copper-containing zinc sulfide luminescent powder, metal oxides, amine alcohol compounds, alkali metal carbonates, and PU resins in the electroluminescent layer 130 are 59.6%, 5.9%, 5.9%, 1.2, respectively. %, 27.4%. In some embodiments, the density of the electroluminescent layer 130 is, for example, about 2.97-3.38 g/mL.

In some embodiments, the electroluminescent layer 130 is formed by drying the electroluminescent paint. In some embodiments, the copper-containing zinc sulfide luminescent powder, the metal oxide and the amino alcohol compound are shaken and mixed, and then the above mixture is mixed with the alkali metal carbonate aqueous solution and the PU resin to form an electroluminescent coating.

In some embodiments, the copper-containing zinc sulfide luminescent powder may be a zinc sulfide luminescent powder formed by doping copper, such as ZnS:Cu, and the particle size of the copper-containing zinc sulfide luminescent powder is, for example, 20 μm to 30 μm.

In some embodiments, the metal oxide includes zinc oxide (ZnO), titanium dioxide (TiO ₂ ), barium titanate (BaTiO ₃ ), manganese dioxide (MnO ₂ ), or a combination thereof. The conduction band energy of the above metal oxide is slightly lower than that of zinc sulfide luminescent powder. For example, the conduction band of zinc sulfide luminescent powder is -3.2eV, zinc oxide is -4.5eV, titanium dioxide is -4.2eV, and barium titanate is -4.2eV, Manganese dioxide is -6.5 eV. Therefore, the use of metal oxide mixed with copper-containing zinc sulfide luminescent powder can provide a stepped charge injection method, which reduces the energy gap and increases the capacitance value of the electroluminescent layer 130 at the same time, thereby increasing the luminous intensity of the electroluminescent layer 130 . The metal oxide can be directly mixed with the copper-containing zinc sulfide luminescent powder without annealing, sintering and other processes, so the production process can be simplified and the cost can be saved, while the brightness is improved. Figures 4 to 6 respectively show the energy scattering spectrum (EDS) of the electroluminescent layer according to an embodiment of the present invention. Figure 4 is the electroluminescent layer doped with barium titanate, and Figure 5 is the doped electroluminescent layer. Manganese electroluminescent layer. Figure 6 shows the electroluminescent layer doped with titanium dioxide. It can be seen from Figs. 4-6 that the metal oxide is directly mixed into the electroluminescent layer without undergoing high-temperature processes such as annealing or sintering. Therefore, the metal oxide in the electroluminescent layer can maintain its original oxidation state.

In some embodiments, the metal oxide is 0.1 to 0.8 parts by weight of zinc oxide (ZnO), such as 0.1, 0.5 or 0.8 parts by weight. In some embodiments, the metal oxide is 0.05 to 0.3 parts by weight of titanium dioxide (TiO ₂ ), for example, 0.05, 0.1, 0.15, 0.2, or 0.3 parts by weight. In some embodiments, the metal oxide is 0.24 to 0.75 parts by weight of barium titanate (BaTiO ₃ ), such as 0.24, 0.57, or 0.75 parts by weight. In some embodiments, the metal oxide is 0.05 to 0.10 parts by weight of manganese dioxide (MnO ₂ ), such as 0.05, 0.08 or 0.1 parts by weight, where the manganese dioxide may be α-MnO ₂ or β-MnO ₂ .

In some embodiments, the amine alcohol compound may include ethylene glycol or diethanolamine. Amino alcohol compounds can be used as surface modifiers to help disperse copper-containing zinc sulfide luminescent powder in PU resin. Amino alcohol compounds can also form an interfacial dipole on the surface of the copper-containing zinc sulfide luminescent powder, thereby reducing the barrier of injecting the electric charge from the PU resin into the copper-containing zinc sulfide luminescent powder.

In some embodiments, the alkali metal carbonate may include potassium carbonate or cesium carbonate. The alkali metal carbonate can polarize the PU resin, promote the generation of an ionic space charge field, increase the capacitance value of the electroluminescent layer 130, and thereby increase the luminous intensity.

Please continue to refer to Figure 1. The transparent conductive layer 140 covers the electroluminescent layer 130. In some embodiments, the transparent conductive layer 140 includes a plurality of nano silver wires, and the wire diameter of each nano silver wire is 50 nanometers to 100 nanometers, such as 50, 55, 60, 65, 70, 75. , 80, 85, 90, 95 or 100 nanometers, and the wire length is 5 to 50 microns, such as 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 microns.

In some embodiments, the electroluminescent fiber 100 further includes a protective layer 150 covering the transparent conductive layer 140. In some embodiments, the protective layer 150 includes polyethylene vinyl acetate (EVA) or polyvinyl acetate (PVAC), but is not limited thereto. The protective layer 150 may be a transparent protective layer to protect the transparent conductive layer 140 and avoid damage to the transparent conductive layer 140 during use. However, the present invention is not limited to this, and in other embodiments, the protective layer 150 may also be omitted. In some embodiments, the electroluminescent fiber 100 has flexibility. The flexibility of the electroluminescent fiber 100 can be adjusted by adding a crosslinking agent to the resin material. The flexible electroluminescent fiber 100 can be applied to various types of electroluminescent objects, such as wires, cloth, advertising box backlights, etc.

In some embodiments, the manufacturing method of the electroluminescent fiber 100 may include sequentially forming the dielectric layer 120, the electroluminescent layer 130, and the transparent conductive layer 140 in a wet or dry coating manner, and then using a wire-rolling method. The above The film layer is disposed on the linear center electrode 110.

FIG. 2 is a schematic cross-sectional view of the electroluminescent fiber 100 according to various embodiments of the present invention. Please refer to Figure 2. In various embodiments, the wire diameter D1 of the electroluminescent fiber 100 is in the range of 300 micrometers to 700 micrometers, such as 300, 350, 400, 450, 500, 550, 600, 650, or 700 micrometers. In some embodiments, the thickness T1 of the dielectric layer 120 is in the range of 20 microns to 50 microns, such as 20, 25, 30, 35, 40, 45, or 50 microns. In some embodiments, the thickness T2 of the electroluminescent layer 130 is in the range of 25 to 40 microns, such as 25, 30, 35, or 40 microns.

FIG. 3 is a three-dimensional exploded schematic diagram of a thin film electroluminescent device 200 according to another embodiment of the present invention. Referring to FIG. 3, the thin film electroluminescent device 200 includes a conductive layer 210, a dielectric layer 220, an electroluminescent layer 230, and a transparent conductive layer 240.

In some embodiments, the conductive layer 210 may be a silver paste conductive layer, and the thickness of the conductive layer 210 may be in the range of 20 μm to 30 μm, for example, 20, 25, or 30 μm.

The dielectric layer 220 is located between the conductive layer 210 and the electroluminescent layer 230 and separates them. In some embodiments, the materials of the dielectric layer 220 and the electroluminescent layer 230 may be the same as or similar to the dielectric layer 120 and the electroluminescent layer 130 of the electroluminescent fiber 100 mentioned above, so they will not be described again. In some embodiments, the thickness of the dielectric layer 220 ranges from 35 microns to 45 microns, such as 35, 40, or 45 microns. In some embodiments, the thickness of the electroluminescent layer 230 ranges from 25 microns to 50 microns, such as 25, 30, 35, 40, 45 or 50 microns.

In some embodiments, the material of the transparent conductive layer 240 may be the same as or similar to the transparent conductive layer 140 of the electroluminescent fiber 100, for example, including indium tin oxide (ITO) conductive glass, but is not limited thereto. In some embodiments, the transparent conductive layer 240 is, for example, indium tin oxide (ITO) conductive glass with a light transmittance of about 89%.

As shown in FIG. 3, the conductive layer 210 and the transparent conductive layer 240 can be used as electrodes in the thin film electroluminescence device 200, and are connected to an external power source (not shown) through wires 250 and 260, respectively.

In some embodiments, the electroluminescent layer 230, the dielectric layer 220, and the conductive layer 210 are sequentially arranged on the transparent conductive layer 240 by wet bar coating to form the thin film electroluminescent device 200.

The following examples are used to describe specific aspects of the present invention and enable those with ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. However, the following examples should not be used to limit the present invention.

Experimental example 1: Brightness test of electroluminescent fiber

In this experimental example, the manufacturing method of the electroluminescent fiber of Example 1 and Comparative Example 1 please refer to the manufacturing method of the aforementioned electroluminescent fiber 100, so it will not be repeated. The difference between Example 1 and Comparative Example 1 is that they have different electroluminescent layers, and the solid content of each component in the electroluminescent layer is shown in Table 1 below. In this experimental example, the linear center electrode is a copper wire with a wire diameter of 160 microns and a length of 10 cm; the dielectric layer is a formula of PU resin/water/barium titanate with a weight ratio of 12/4/15. The thickness and density are 40 microns and 4.68g/mL respectively; and the transparent conductive layer is 2/3 by weight The formula of PU resin/silver glue is dried and formed, and its thickness and density are 23 microns and 6.69g/mL.

Using an absolute brightness meter (model: BM-7A, purchased from TOPCON Co.), the electroluminescent fiber of Example 1 and Comparative Example 1 was tested with an alternating current of 160 volts and 11 kHz. Refer to Table 1 below. The difference between Example 1 and Comparative Example 1 is that the electroluminescent layer of Example 1 contains zinc oxide. It can be seen from Table 1 that compared with Comparative Example 1, in Example 1, the brightness of the electroluminescent fiber can be increased by about 34.9% by using the electroluminescent layer of zinc oxide mixed with copper zinc sulfide luminescent powder.

Experimental example 2: Comparison of the mixed concentration of zinc oxide and the brightness of thin film electroluminescent devices

In this experimental example, the manufacturing methods of the thin film electroluminescent device of Comparative Examples 2 and 3 and Examples 2 to 4 refer to the manufacturing method of the thin film electroluminescent device 200 described above, so the details are not repeated here.

In this experimental example, comparative examples two and three and examples two to four The electroluminescent layer is mixed with different weight parts of zinc oxide, and the solid content of each component in the electroluminescent layer is shown in Table 2 below. In addition, in this experimental example, an ITO glass substrate with a surface resistance of 7Ω/sq was used as the transparent conductive layer. The size of the thin-film electroluminescent device of Comparative Example 2 and Example 2 was 1.5cm×2.5cm. Comparative Example 3 and The size of the thin film electroluminescence device of Examples 3 and 4 is 0.7 cm×2.0 cm. A formula of PU resin/water/barium titanate with a weight ratio of 4/4/15 was used to dry to form a dielectric layer with a thickness of 40 microns, and a silver paste layer with a thickness of 23 microns was used.

Using a luminance meter (model: TES-137, purchased from Taishi Electronics Industry Co., Ltd.), the thin-film electroluminescent devices of Comparative Examples 2 and 3 and Examples 2 to 4 were tested for luminance at 160 volts and 11 kHz alternating current, and Compare the brightness changes, and see the results in Table 2 below.

It can be seen from Table 2 that compared to Comparative Example 2, in Example 2, by using zinc oxide mixed with copper-containing zinc sulfide luminescent powder, the brightness can be increased by about 8.4%. Compared with Comparative Example 3, Examples 3 and 4 can increase the brightness by about 47.5% and 8.3% respectively by using zinc oxide mixed with copper-containing zinc sulfide luminescent powder.

Experimental example 3: Comparison of the concentration of doped titanium dioxide and the brightness of thin-film electroluminescent devices

In this experimental example, the thin-film electroluminescent device manufacturing methods, materials, and brightness test methods of Comparative Example 4 and Examples 5-10 are similar to Experimental Example 2, and only the differences from Phase Experimental Example 2 are described below.

In this experimental example, the electroluminescent layers of Comparative Example 4 and Examples 5 to 10 were mixed with different weight parts of titanium dioxide, and the solid content of each component in the electroluminescent layer is shown in Table 3 below. In this experimental example, the size of the thin-film electroluminescence device is 0.7 cm×2.0 cm. A formula with a weight ratio of PU resin/water/barium titanate of 12/4/15 was used and dried to form a dielectric layer with a thickness of 40 microns.

It can be seen from Table 3 that compared with Comparative Example 4, Examples 5 to 9 use titanium dioxide mixed with copper-containing zinc sulfide luminescent powder, which can increase the brightness by about 24.4%, 30.8%, 22.3%, 19.1%, 13.8%, respectively. . However, in the tenth embodiment, the excessively high concentration of titanium dioxide caused a 23.4% decrease in brightness.

Experimental example 4: Comparison of the concentration of doped barium titanate and the brightness of thin film electroluminescent device

In this experimental example, the thin-film electroluminescent device manufacturing methods, materials and brightness test methods of Examples 11-14 are similar to those of Experimental Example 3. The difference is that the electroluminescent devices of Examples 11-14 The light-emitting layer is mixed with different weight parts of barium titanate, and the solid content of each component in the electroluminescent layer is shown in Table 4 below.

It can be seen from Table 4 that compared with Comparative Example 4, Examples 11 to 13 can increase the brightness by about 22.3%, 29.8%, and 19.9% respectively by using barium titanate mixed with copper-containing zinc sulfide luminescent powder. However, the use of excessively high concentration of barium titanate in Example 14 resulted in a 4.3% decrease in brightness.

Experimental example 5: Comparison of the concentration of doped manganese dioxide and the brightness of thin film electroluminescent devices

In this experimental example, the thin-film electroluminescent device manufacturing methods, materials and brightness test methods of Examples 15-17 are similar to those of Experimental Example 3. The difference is that the electroluminescent devices of Examples 15-17 The light-emitting layer is mixed with different weight parts of manganese dioxide, and the solid content of each component in the electroluminescent layer is shown in Table 5 below.

It can be seen from Table 5 that compared with Comparative Example 4, in Examples 15 to 16 by using manganese dioxide mixed with copper-containing zinc sulfide luminescent powder, the brightness can be increased by about 17.0% and 13.8%, respectively. However, the use of excessively high concentration of barium titanate in Example 17 resulted in a 27.7% decrease in brightness.

Experimental example 6: The influence of amine alcohol compounds and alkali metal carbonate types on brightness

In this experimental example, please refer to Comparative Example 3 for the manufacturing methods, materials, and brightness test methods of thin-film electroluminescent devices in Examples 18 and 19. The difference between Examples 18 and 19 and Comparative Example 3 is that the electroluminescent layer of Example 18 is doped with 0.5 parts by weight of zinc oxide, and diethanolamine is substituted for ethylene glycol; the electroluminescence of Example 19 The layer is doped with 0.5 parts by weight of zinc oxide, and cesium carbonate is substituted for potassium carbonate. The solid content of each component in the electroluminescent layer is shown in Table 6 below.

It can be seen from Table 6 that the brightness of Example 18 is improved by 38.3% under the conditions of doping zinc oxide and replacing ethylene glycol with diethanolamine. In Example 19, under the condition of doping with zinc oxide and replacing potassium carbonate with cesium carbonate, the brightness increased by 16.3%.

In summary, the present disclosure provides an electroluminescent fiber. By doping the electroluminescent layer of the electroluminescent fiber with a metal oxide, such as zinc oxide, titanium dioxide, barium titanate or manganese dioxide, the brightness of the electroluminescent fiber can be improved without the need for additional The functional layer can reduce the wire diameter of the electroluminescent fiber and simplify the manufacturing process. In addition, the electroluminescent fiber of the present disclosure has high brightness without applying a high voltage, so it can be applied to various types of electroluminescent objects.

Although the present invention has been disclosed as above in the embodiments, it is not intended to limit the present invention. Anyone who is familiar with this skill can make various modifications and retouching without departing from the spirit and scope of the present invention, so the protection of the present invention The scope shall be deemed as defined by the scope of the attached patent application.

100‧‧‧Electroluminescent fiber

110‧‧‧Linear center electrode

120‧‧‧Dielectric layer

130‧‧‧Electroluminescent layer

140‧‧‧Transparent conductive layer

150‧‧‧Protection layer

Claims (10)

An electroluminescent fiber comprising: a linear central electrode; a dielectric layer covering the linear central electrode; an electroluminescent layer covering the dielectric layer, and the electroluminescent layer comprises: 3 weights Parts to 7 parts by weight of copper-containing zinc sulfide luminescent powder; 0.05 parts by weight to 0.8 parts by weight of metal oxides including zinc oxide (ZnO), titanium dioxide (TiO ₂ ), and barium titanate (BaTiO ₃ ) , Manganese dioxide (MnO ₂ ) or a combination thereof; 0.1 parts by weight to 0.7 parts by weight of amine alcohol compounds; 0.095 parts by weight to 0.24 parts by weight of alkali metal carbonates; and 2.0 parts by weight to 2.5 parts by weight of PU resin; And a transparent conductive layer covering the electroluminescent layer. The electroluminescent fiber according to claim 1, wherein the thickness of the electroluminescent layer is in the range of 25 to 40 microns. The electroluminescent fiber according to claim 1, wherein the wire diameter of the electroluminescent fiber is in the range of 300 micrometers to 700 micrometers. The electroluminescent fiber according to claim 1, wherein the thickness of the dielectric layer is in the range of 20 microns to 50 microns. The electroluminescent fiber according to claim 1, further comprising a protective layer covering the transparent conductive layer, wherein the protective layer includes polyethylene vinyl acetate (EVA) or polyvinyl acetate (PVAC). The electroluminescent fiber according to claim 1, wherein the transparent conductive layer includes a plurality of silver nanowires, and the wire diameter of each silver nanowire is 50 nm to 100 nm, and the wire length It is 5 microns to 50 microns. The electroluminescent fiber according to claim 1, wherein the metal oxide is 0.1 to 0.8 parts by weight of zinc oxide (ZnO). The electroluminescent fiber according to claim 1, wherein the metal oxide is 0.05 to 0.3 parts by weight of titanium dioxide (TiO ₂ ). The electroluminescent fiber according to claim 1, wherein the metal oxide is 0.24 parts by weight to 0.75 parts by weight of barium titanate (BaTiO ₃ ). The electroluminescent fiber according to claim 1, wherein the metal oxide is 0.05 to 0.10 parts by weight of manganese dioxide (MnO ₂ ).

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