KR100258029B1 - Red-fluo resent material used in an active dynamic lcd - Google Patents

Abstract

PURPOSE: A red color phosphor is to improve its luminance and property of matter by adding appropriate amount of (K5-XNaX)EU2.5(WO4)6.25 based phosphor to a (ZnCd)S based phosphor having a property which is excited by a low speed electronic beam and emits light. CONSTITUTION: In a red color phosphor which is excited and emitted to a deep blue color light having a range of 380 to 420 nanometer, a (ZnCd)S based phosphor is prepared as a compound A while a (K5-XNaX)EU2.5(WO4)6.25 based phosphor is prepared as a compound B. The compound An is formed by mixing 12.3 parts of Zn with 60.5 parts of Cd. The X ranges between 0.5 and 1.5 and preferably equals 1 in the compound B. These compounds An and B are mixed at a normal temperature in a proportion of 4:1 to obtain a desired phosphor. Alternatively, the compounds An and B are mixed in a proportion of 1:1. An obtained red color phosphor exhibits excellent brilliance compared to a conventional (ZnCd)S based phosphor.

Description

Red phosphor suitable for active light emitting liquid crystal display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a red phosphor, and more particularly, to a red phosphor having improved luminance to be suitable for an active light emitting liquid crystal display device.

In the active light emitting liquid crystal display device, the light emitted from the rear light source passes through the polarizer and passes through the liquid crystal layer, and the liquid crystal layer functions to block or prevent the back light from passing through the rear light. The back light is to form a predetermined display form, and the back light passing through the liquid crystal layer is configured to display an image through the windshield by exciting the corresponding phosphor.

The active light-emitting type liquid crystal display device as described above has advantages in that the structure is simpler and easier to manufacture than the conventional color liquid crystal display device. However, among the fluorescent materials employed, the red phosphor has low luminance emitted in the near-ultraviolet region and thus is not practical. It is evaluated. In other words, the green and blue phosphors have a characteristic that the excitation spectrum is shifted to the long side even when the excitation source is a long wavelength, but in the case of the red phosphor, a suitable substance is recommended. Accordingly, attempts have been made to improve the characteristics of the red phosphor toward high luminance in the near ultraviolet region, but until recently, satisfactory results have not been obtained.

As a red phosphor of an active light emitting liquid crystal display device, the (ZnCd) S system is known as an inorganic phosphor. This has the characteristic that the emission color varies depending on the mixing ratio of Zn and Cd. For example, when the amount of Zn is increased, the color is converted into deep red-red-yellow. Therefore, the position of the main peak can be changed in accordance with the amount of Zn and Cd, and thus, low-speed electron beams are mainly used in devices in which excitation sources are used as in fluorescent display tubes. For this reason, the (ZnCd) S-based phosphor may be used for phosphors excited in red in the near ultraviolet region, but deterioration due to electron irradiation may be remarkable, and thus the improvement may be preceded for practical use.

In general, fluorescent display tubes are doped with Ag and Al in high concentrations to (ZnCd) S to stabilize physical properties. However, this method does not show sufficient luminance due to the small energy source in an active light emitting liquid crystal display device using a long wavelength such as near ultraviolet ray as an excitation source.

Accordingly, an object of the present invention is to provide a red phosphor that can be suitably used in an active light emitting liquid crystal display device by improving the physical properties of the red phosphor mainly containing (ZnCd) S.

The present invention, which realizes the above object, is a red phosphor which is excited by deep blue light in the 380-420 nm region, and is a mixture of (ZnCd) S and (K _5-x Na _x ) Eu _2.5 (WO ₄ ) _6.25 It consists of a red phosphor.

The above X is 0.5 to 1.5, preferably 1, and the mixing can be carried out by a ball mill or the like at room temperature, and a suitable mixing ratio is (ZnCd) S 1 to 4 to (K _5-x Na _x ) Eu _2.5 (WO). ₄ ) Let _6.25 be the ratio of 1.

Since the red phosphor according to the present invention has a main peak at 640 nm, it is optimal as a red phosphor of an active light emitting liquid crystal display device.

1 is a graph showing a luminance relationship for each wavelength of a phosphor of the present invention and a conventional (ZnCd) S-based phosphor.

When the present invention described above in detail as a preferred embodiment as follows.

Example 1

(ZnCd) S-based phosphors were prepared as mixture A and (K _5-x Na _x ) Eu _2.5 (WO ₄ ) _6.25- based phosphors as mixture B, respectively, wherein mixture A was mixed with Zn 12.3 and Cd 60.5. And X = 1 in the mixture B, and these were mixed in a ball mill at a ratio of A: B = 4: 1 at room temperature to obtain a desired phosphor.

Example 2

A mixture of Cd 53.4 and Zn 17.7 was employed as the mixture A. Otherwise, the desired phosphor was obtained in the same manner as in the above example.

Comparative Example 1

Under the same conditions as in Example 1, the mixture was mixed at a ratio of A: B = 1: 1 to obtain a desired phosphor.

Comparative Example 2

Under the same conditions as in Example 2, the mixture was mixed at a ratio of A: B = 1: 1 to obtain a desired phosphor.

The main peaks of the red phosphor obtained through Example 1 and the conventional (ZnCd) S-based phosphor were measured as shown in FIG. 1.

Since the main peak of the phosphor of the present invention is sharply shown at 640 nm in the graph of FIG.

In addition, the results of measuring the luminance and color coordinates of the red phosphor obtained through the above Examples and Comparative Examples 1 and 2 and the (ZnCd) S-based phosphor were as shown in the following [Table].

(ZnCd) S Example 1 Example 2 Comparative Example 1 Comparative Example 2 Whee 2.87 2.97 2.9 2.72 2.6 Color coordinates (X) 0.6187 0.6214 0.6218 0.6225 0.6234 Color coordinates (Y) 0.3742 0.3721 0.3711 0.3724 0.3731

As can be seen from Table 1, the red phosphor of the present invention can be seen that the luminance is improved compared to the conventional (ZnCd) S-based red inorganic phosphor. In the present invention, the (K _5-x Na _x ) Eu _2.5 (WO ₄ ) _6.25- based phosphor appeared to have a lower luminance when the amount exceeded a certain level.

As described above, the present invention is a red phosphor suitable for an active light emitting liquid crystal display device, and (K _5-x Na _x ) Eu _2.5 (WO ₄ ) _{6.25 is} applied to a (ZnCd) S-based phosphor having the property of being excited by a low speed electron beam The addition of an appropriate amount of the phosphor has an effect of improving the weakness of the brightness and physical properties.

Claims (2)

A red phosphor that is excited by deep blue light in the 380-420 nm region, and is suitable for an active light-emitting liquid crystal display device comprising a mixture of (ZnCd) S and (K _5-x Na _x ) Eu _2.5 (WO ₄ ) _6.25 . Phosphor. [Wherein X is 0.5 to 1.5 and preferably 1] The active light emitting liquid crystal display device according to claim 1, wherein the mixing ratio of the mixture is (ZnCd) S 1 to 4 and (K _5-x Na _x ) Eu _2.5 (WO ₄ ) _6.25 is 1. Red phosphor suitable for.

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