KR19980046669A - Red phosphor for active light emitting liquid crystal display - Google Patents

Abstract

K was synthesized through solid chemical reaction by combining potassium (K), europium (Eu) and tungsten (W) in an appropriate ratio to provide a new high-brightness red light-emitting phosphor that can realize the structure of an active light-emitting liquid crystal display. ₅ Eu _x (WO ₄ ) Phosphor having a composition of _{2.5 + 1.5x} (x = 1.5 ~ 3.0) is a red luminescent phosphor of 380 ~ 420nm which is excited at the composition near x = 2.0 ~ 2.5 and 3.5 excited MgO0.5MgF ₂ GeO ₂ : Mn It is a phosphor whose brightness is increased by 200% or more compared with the deep red phosphor, and by appropriately mixing the tungsten phosphor with the deep red phosphor, the color coordinate and luminance can be freely adjusted and the range of color reproduction can be expanded.

Description

Red phosphor for active light emitting liquid crystal display

The present invention relates to a red phosphor for an active light-emitting liquid crystal display, and more particularly, to develop a new red phosphor for use in an active light-emitting liquid crystal display using a phosphor and to form a novel potassium europium tungsten salt as a matrix. A red phosphor for an active light emitting liquid crystal display which is a phosphor.

All information displays perform their functions by utilizing the ability to control the light. Regardless of the complexity of the display, the basic operating principle of the display is to control the light in the pixels of the display. This is done by two methods, one type which gives each pixel the ability to generate light, called an active display, and a good example is a cathode ray tube. The screen of the cathode ray tube has a phosphor that emits light when the electron beam collides. Each pixel is made to generate light only by impinging on an electron beam.

In addition, the second form of the display does not generate light, but controls the amount of light reflected or transmitted by the display, called a passive display. Representative examples of passive displays include liquid crystal displays. The liquid crystal display is extremely thin and thin. It does not consume much power to generate light and use the light that exists around it, so it is operated at low cost and low power consumption. It is also well integrated with integrated circuits. Its size can be arbitrarily used for battery-powered equipment such as wristwatches, portable radios and tape players, and portable computers. Is expanding. Such a liquid crystal display has already been put to practical use in the size of 2 to 12.1 inches and is currently being studied for the enlargement of 12.1 inches or more.

The liquid crystal display is generally configured to control the arrangement of liquid crystal molecules by applying an electric field through a driving integrated circuit by making a liquid crystal layer having a thickness of several micrometers to several tens of micrometers between glass plates coated with two thin conductive films. have. When the electric field is applied, the arrangement state of the liquid crystal molecules is parallel to the electric field or rearranged in the vertical direction. When the electric field is removed or weakened, the liquid crystal molecules are returned to the original state by the thinly oriented alignment layer on the conductive film.

The method of applying an electric field to the liquid crystal layer is classified into active driving, which is an active driving method for each liquid crystal display pixel, and passive driving, which is a passive driving method. It is closely related to the display characteristics of the liquid crystal display such as crosstalk, contrast, flickering of the screen, view angle, and large screen.

The reason why the thin liquid crystal layer can electrically control the amount of light transmitted is that the liquid crystal molecules have optical anisotropy, that is, the refractive index is not constant or different depending on the difference between the light propagation direction and the liquid crystal molecule direction. The advantage of a liquid crystal display is that such optical properties can be obtained sufficiently with a liquid crystal layer only a few μm thick and the corresponding electric field strength is very low, with only a few volts of voltage.

Currently, the liquid crystal display is a red and green on the lower substrate formed with a thin film transistor (TFT), which is an individual switching element, that is, a TFT substrate and a liquid crystal layer and a black matrix layer having a predetermined repetitive pattern. ), And a blue colored layer is composed of an upper substrate, that is, a color filter substrate, which is repeatedly arranged to colorize.

When manufacturing the conventional color filter substrate for liquid crystal displays, it generally goes through the following processes.

First, a light blocking black matrix layer for preventing degradation of a thin film transistor is formed on a glass substrate by using a sputtering method of chromium (Cr) to a thickness of 1000 to 2000 μs. Subsequently, a negative photoresist having optimized spectral characteristics such as pigmented photosensitive resist resin in which pigments were dispersed was applied onto a glass substrate on which a black matrix layer was formed, and then a predetermined time was applied on a hot plate at 60 to 120 ° C. Soft bake, followed by development for 2 to 3 minutes with developer, followed by rinsing with deionized water for 1 to 2 minutes to form a red pattern, which is the first color filter layer with optimized red spectral characteristics. do. In the same manner as the first color filter layer, the pattern is formed such that the green pattern, which is the second color filter layer, and the blue pattern, which is the third color filter layer, are sequentially overlapped with the black matrix between each black matrix. Next, an indium tin oxide (ITO) transparent electrode film having a thickness of about 500 to 1800 μs is formed on the black matrix and the color filter layer to complete the color filter substrate as the upper substrate.

However, when manufacturing a liquid crystal display using a conventional color filter substrate manufactured as described above, the common electrode of the color filter substrate should be connected to the thin film transistor array substrate at several short points. In this case, the transparent conductive material used as the common electrode has a high specific resistance of the sheet resistance of several hundred ohms, and thus it is difficult to maintain a uniform voltage, and the common signal may be distorted, thereby causing interference. In order to prevent this, four or more short-circuit points are required, and therefore, an additional process is required and a complicated process must be added.

In order to solve the problem of the color substrate described above, an active light emitting liquid crystal display as shown in FIG. 1 has been developed. As shown in FIG. 1, this active light-emitting liquid crystal display is an electrode including liquid crystals 15 in which ultraviolet rays scanned from the rear light source pass between two polarizing plates 13 and pass through ultraviolet rays scanned from the rear light source 11. When the ultraviolet rays passed through collide with the ultraviolet-excited phosphors R, G, and B of the black matrix film 19 formed on the windshield 17, the phosphors emit light to reproduce colors. This active light emitting liquid crystal display improves the narrow reagent angle of the conventional liquid crystal display.

Phosphor which is used in the active light-emitting type liquid crystal display is a commercial fluorescent substance capable of emitting light from the back light 380 ~ 420nm excitation area has been widely used currently developed for the 5-wavelength lamp 3.5MgO0.5MgF ₂ GeO _2: Mn red core The phosphor is one of the phosphors emitting light in the above excitation region. However, since the phosphor emits deep red light at 650 nm, the phosphor has excellent color purity but low luminance. In addition, Na ₅ Eu (Wo ₄ ) _{4, which} is a self-luminous phosphor, has a problem in that it has low luminance due to insufficient light emission in the 380 to 420 nm region. Therefore, it is essential to develop a red phosphor in which the emission position where the luminance is not lowered while maintaining the color purity moves toward the shorter wavelength than 3.5MgO0.5MgF ₂ GeO ₂ : Mn and is excited in the wavelength range of 380 to 420 nm.

The present invention has been made to solve the above problems of the prior art, an object of the present invention is to produce a new high-luminance red light-emitting phosphor for an active light-emitting liquid crystal display of an active light-emitting liquid crystal display having a color CRT-level image quality It is to enable the realization.

1 is a cross-sectional view showing the structure of an active light emitting liquid crystal display.

2 is an excitation spectrum showing the relative intensity of PLE according to the wavelength at 612 nm of the K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor prepared in Example 1 of the present invention.

3 is an emission spectrum of the K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor prepared in Example 1 of the present invention at a wavelength of 394 nm in an excitation source.

4A and 4B are graphs showing the relative brightness of phosphors according to the composition ratio of x at K ₅ Eu _X (WO ₄ ) _{2.5 + 1.25x} and Na ₅ Eu _x (WO ₄ ) _{2.5 + 1.25x} .

5 is a SEM photograph of the K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor prepared in Example 1 of the present invention.

* Description of the symbols for the main parts of the drawings *

11: back light source 13: polarizing plate

15: liquid crystal 17: front glass

19: Black matrix film R, G, B: UV-excited RGB phosphor

The present invention has the following configuration to achieve the above object of the present invention.

In the present invention, there is provided a red phosphor for an active light-emitting liquid crystal display in which _x is represented by K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} having a value in the range of 1.5 to 3.0.

The x is 2.0 ~ 2.5 and the phosphor is preferably prepared through a solid chemical reaction.

In the present invention, the phosphor raw materials of K ₂ CO ₃ , Eu ₂ O ₃ and WO ₃ are mixed, and the mixed phosphor raw materials are calcined at a temperature of 800 to 1000 ° C. for 3 to 6 hours, and the calcined phosphor raw materials are obtained. Provided is a method of manufacturing a red phosphor for an active light-emitting liquid crystal display, including the step of washing.

In the above production method, it is preferable that K ₂ CO ₃ is 10 to 25% by weight, Eu ₂ O ₃ is 10 to 25% by weight, and WO ₃ is 60 to 70% by weight.

In the present invention, a red light emitting phosphor represented by K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} having a value in the range of 1.5 to 3.0 and a red light emitting phosphor represented by 3.5MgO0.5MgF ₂ GeO ₂ : Mn. It provides a red mixed phosphor for an active emission type liquid crystal display comprising a.

The x is preferably from 2.0 to 2.5 and the red light emitting phosphor represented by K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} having a value in the range of 1.5 to 3.0 _x 1-100% by weight and 3.5MgO0.5MgF ₂ The red light-emitting phosphor represented by GeO ₂ : Mn is preferably 1 to 99% by weight.

As a phosphor used in an active light emitting liquid crystal display, Na ₅ Eu (Wo ₄ ) _{4, which} is a self-luminous phosphor developed in the process of developing a commercial phosphor capable of emitting light at an excitation region of 380 to 420 nm as a back light, is 380 ~. In the 420nm region, although it does not generate sufficient light emission, it is very useful to develop a host light-emitting phosphor containing Eu ³⁺ ions by using this property because the absorption spectral band of Eu ³⁺ ions itself is around 380 ~ 420nm. It can be seen.

The present invention is a high-brightness red phosphor developed using the above characteristics, and has a new structure phosphor containing self-emissive Eu ³⁺ ions, and combines potassium, europium, and tungsten in an appropriate proportion to K ₅ Eu _x (WO ₄ ) A phosphor having a composition of _{2.5 + 1.5x} (x = 1.5 ~ 3.0) is synthesized through solid chemical reaction.

In the present invention, by mixing appropriately the phosphor developed as described above and commercially developed 3.5MgO0.5MgF ₂ GeO ₂ : Mn deep red phosphor as a phosphor for the lamp by adjusting the brightness and color purity according to the amount appropriately mixed phosphor Manufacture. Therefore, after the slurry is prepared from the red phosphor developed according to the present invention, a film is formed by photolithography, thereby realizing an active light-emitting full color liquid crystal display.

The following presents a preferred embodiment to aid the understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

EXAMPLE

Example 1

The synthesis of the K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor in the phosphor having a composition of K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} (x = 1.0 to 3.0) was prepared using a solid phase reaction method of solid chemistry. 102.7 g K ₂ CO ₃ , 126.1 g Eu ₂ O _{3, and} 430.9 g WO ₃ were mixed for 2 to 4 hours using a V-mixer or mortar. The well mixed phosphor material was placed in an alumina reaction vessel and calcined at 800-1100 ° C. for 3-6 hours. After firing, the phosphor was washed 2 ~ 3 times with warm water, and the finished product was produced by filtration.

Example 2

70 wt% of K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor prepared in Example 1 and 30 wt% of 3.5MgO0.5MgF ₂ GeO ₂ : Mn deep red phosphor were mixed to prepare a mixed phosphor.

Example 3

50 wt% of K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor prepared in Example 1 and 50 wt% of 3.5MgO0.5MgF ₂ GeO ₂ : Mn deep red phosphor were mixed to prepare a mixed phosphor.

Example 4

30 wt% of K ₅ Eu _2.5 (WO ₄ ) _6.25 phosphor prepared in Example 1 and 70 wt% of 3.5MgO0.5MgF ₂ GeO ₂ : Mn deep red phosphor were mixed to prepare a mixed phosphor.

[Comparative Example]

Only 100% by weight of the phosphor for 3.5MgO0.5MgF ₂ GeO ₂ : Mn lamp was used as a control.

The relative luminance and color coordinate values according to the composition ratios of the phosphors and the mixed phosphors prepared in Examples 1 to 4 and Comparative Examples were measured and shown in Table 1. By properly mixing the phosphor of the present invention and the deep red phosphor, excellent relative luminance and color coordinates are obtained, and thus a desired display color can be obtained.

The particles of the phosphors and the mixed phosphors prepared in Examples and Comparative Examples can be seen that the particle size and particle size are suitable for forming the fluorescent film by the SEM photograph of FIG. 5.

Excitation spectra of wavelengths of 340 to 500 nm of the phosphor having a composition of K ₅ Eu _2.5 (WO ₄ ) _6.25 synthesized in Example 1 of the present invention are shown in FIG. 2. Phosphor according to the present invention is not shown in Figure 2 but usually has a charge transfer band (charge transfer band) below 300nm, it can be seen that the self-absorption band of Eu ³⁺ ion is present at 380 ~ 420nm. Therefore, it can be said that this phosphor is suitable for realizing an active light emitting liquid crystal display having the structure of FIG. Figure 3 shows the emission spectrum of the phosphor according to the present invention when the excitation light is 394nm. 3, it can be confirmed that the red light-emitting phosphor is observed by observing that there is a considerably strong light emission band at a wavelength near 612 nm. Therefore, the phosphor according to the present invention can be said to be a phosphor suitable for realizing the active light emitting liquid crystal display of FIG. 1 even in the emission spectrum. In addition, Figure 4a shows the change in the relative luminance value of the phosphor as the composition ratio of x in the composition of K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} . As the amount of x increases, the luminance increases and shows the maximum value of relative luminance near x = 2.0 ~ 2.5. These results show that the _{Na 5 Eu x (WO 4)} 2.5 + 1.5x (x = 1.0 ~ 2.5) with the result of very different aspects of Figure 4b represents the highest luminance in the _{Na 5 Eu (WO 4) 4} .

The K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} (x = 1.0-3.0) phosphor of the present invention is a new phosphor and exhibits the most stable structure at an excitation source of 380-420 nm in a composition near x = 2.0-2.5. . Na ₅ Eu (WO ₄ ) ₄ phosphors have a known crystal structure, whereas K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} (x = 1.0-3.0) phosphors have no known structure.

In addition, the present phosphor can be appropriately mixed with the 3.5MgO0.5MgF ₂ GeO ₂ : Mn tri-red phosphor to adjust the color coordinates and the luminance.

The K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} (x = 1.0-3.0) phosphor of the present invention is a new high-brightness red luminescent phosphor that is excited at 380-420 nm in a composition near x = 2.0-2.5 and is excited by existing ultraviolet rays. Compared with the 3.5MgO0.5MgF ₂ GeO ₂ : Mn deep red phosphor, the luminance is increased by 200% or more.

In addition, in the present invention, the tungsten phosphor is properly mixed with the tri-red phosphor to enable color coordinate adjustment and luminance adjustment, and extend the color reproduction range to realize the structure of an active light emitting liquid crystal display.

Claims (8)

Red phosphor for an active light-emitting liquid crystal display in which _x is represented by K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} having a value in the range of 1.5 to 3.0. The red phosphor of claim 1, wherein x is 2.0 to 2.5. The red phosphor of claim 1, wherein the phosphor is prepared through a solid chemical reaction. Mixing phosphor raw materials of K ₂ CO ₃ , Eu ₂ O ₃ and WO ₃ ; Firing the mixed phosphor material at a temperature of 800 to 1000 ° C. for 3 to 6 hours; Washing the fired phosphor raw material; A method for producing a red phosphor for an active light emitting liquid crystal display comprising the step. The method of manufacturing a red phosphor for an active light-emitting liquid crystal display according to claim 4, wherein K ₂ CO ₃ is 10-25 wt%, Eu ₂ O ₃ is 10-25 wt%, and WO ₃ is 60-70 wt%. a red light-emitting phosphor represented by K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} in which _x has a value ranging from 1.5 to 3.0; A red light-emitting phosphor represented by 3.5 MgO 0.5 MgF ₂ GeO ₂ : Mn; Red mixed phosphor for active light-emitting liquid crystal display containing. 7. The red mixed phosphor of claim 6, wherein x is 2.0 to 2.5. The red light-emitting phosphor represented by K ₅ Eu _x (WO ₄ ) _{2.5 + 1.5x} having a value in the range of 1.5-3.0, and 3.5MgO0.5MgF ₂ GeO ₂ : Mn. The red light-emitting phosphor represented by 1 to 99% by weight of the red mixed phosphor for an active light-emitting liquid crystal display.